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Sample records for aqueous corrosion behavior

  1. Aqueous Corrosion Behavior of Iron aluminide Intermetallics

    Science.gov (United States)

    Sharma, Garima; Singh, P. R.; Sharma, R. K.; Gaonkar, K. B.; Ramanujan, R. V.

    2007-12-01

    Iron aluminide intermetallics based on DO3 ordered structure are being developed for use as structural materials and cladding material for conventional engineering alloys. Aqueous corrosion behavior of iron aluminides has been studied extensively by electrochemical techniques. Studies were carried out on pure Fe (99.9%), Fe-28Al (at.%), Fe-28Al-3Cr (at.%), and AISI SS 304 so as to compare and contrast their behavior in same experimental condition. Polarization behavior under different pH conditions was examined to evaluate their performance in acidic, basic, and neutral solutions. Pitting behavior was also studied in solution containing Cl-1 ions. The stability of the passive film formed was studied by current time transients and potential decay profiles. The presence of 3 at.% Cr in iron aluminides was found to improve the aqueous corrosion resistance and makes it comparable to AISI SS 304.

  2. Aqueous corrosion behavior of uranium-molybdenum alloys

    Science.gov (United States)

    Gardner, Levi D.

    Nuclear fuel characterization requires understanding of the various conditions to which materials are exposed in-reactor. One of these important conditions is corrosion, particularly that of fuel constituents. Therefore, corrosion behavior is of special interest and an essential part of nuclear materials characterization efforts. In support of the Office of Material Management and Minimization's Reactor Conversion Program, monolithic uranium-10 wt% molybdenum alloy (U-Mo) is being investigated as a low enriched uranium alternative to highly enriched uranium dispersion fuel currently used in domestic high performance research reactors. The aqueous corrosion behavior of U-Mo is being examined at Pacific Northwest National Laboratory (PNNL) as part of U-Mo fuel fabrication capability activity. No prior study adequately represents this behavior given the current state of alloy composition and thermomechanical processing methods, and research reactor water chemistry. Two main measurement techniques were employed to evaluate U-Mo corrosion behavior. Low-temperature corrosion rate values were determined by means of U-Mo immersion testing and subsequent mass-loss measurements. The electrochemical behavior of each processing condition was also qualitatively examined using the techniques of corrosion potential and anodic potentiodynamic polarization. Scanning electron microscopy (SEM) and optical metallography (OM) imagery and hardness measurements provided supplemental corrosion analysis in an effort to relate material corrosion behavior to processing. The processing effects investigated as part of this were those of homogenization heat treatment (employed to mitigate the effects of coring in castings) and sub-eutectoid heat treatment, meant to represent additional steps in fabrication (such as hot isostatic pressing) performed at similar temperatures. Immersion mass loss measurements and electrochemical results both showed very little appreciable difference between

  3. Corrosion behavior of bulk metallic glasses in different aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The corrosion behavior of as-cast fully amorphous, structural relaxed amorphous and crystallized Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glasses (BMGs) in NaCl, HCl and NaOH solutions was investigated by electrochemical polarization and immersion methods. X-ray photoelectron spectroscopy measurements was used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The corrosion resistance of the Fe65.5Cr4Mo4Ga4P12C5B5.5 BMG was better than its structural relaxation/crystallization counterparts and common alloys (such as stainless steel, carbonized steel, and steel) in the selected aqueous solutions. The high corrosion resistance of this alloy in corrosive solutions leads to the formation of Fe-, Cr- and Mo-enriched protective thin surface films.

  4. Corrosion behavior of Mg/graphene composite in aqueous electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Selvam, M. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saminathan, K., E-mail: ksaminath@gmail.com [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Siva, P. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India); Saha, P. [Department of Ceramic Engineering, National Institute of Technology, Rourkela, India-769008 (India); Rajendran, V. [Centre for Nano Science and Technology, KS Rangasamy College of Technology, Tiruchengode, 637215, Tamil Nadu (India)

    2016-04-01

    In the present work, the electrochemical corrosion behavior of magnesium (Mg) and thin layer graphene coated Mg (Mg/graphene) are studied in different salt electrolyte such as NaCl, KCl and Na{sub 2}SO{sub 4}. The phase structure, crystallinity, and surface morphology of the samples are investigated using X-ray diffraction (XRD) analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDAX), and Raman spectroscopy techniques. The electrochemical corrosion behavior of the Mg and graphene coated Mg are also investigated using Electrochemical Impedance Spectroscopy (EIS) analysis. The tafel plot reveals that the corrosion of Mg drastically drops when coated with thin layer graphene (Mg/graphene) compared to Mg in KCl electrolyte. Moreover, the EIS confirms that Mg/graphene sample shows improve corrosion resistance and lower corrosion rate in KCl solution compare to all other electrolytes studied in the present system. - Highlights: • The corrosion behavior of magnesium alloy (AZ91) was investigated in three different electrolyte solution. • To study the anti-corrosion behavior of graphene coated with magnesium alloy. • To improve the corrosion resistance for magnesium alloy. • Nyquist plots confirms that MgG shows better corrosion resistance and lower corrosion rate in KCl solution.

  5. EFFECT OF CERIUM ION IMPLANTATION ON THE AQUEOUS CORROSION BEHAVIOR OF ZIRCONIUM

    Institute of Scientific and Technical Information of China (English)

    D.Q. Peng; X.D. Bai; Q.G. Zhou; X.W. Chen; R.H. Yu; X.Y. Liu

    2004-01-01

    In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by cerium ions with a dosage range from 1 ×1016 to 1 ×1017 ions/cm2 at about 150℃, using MEWA source at an acceler ative voltage of 40kV. The valence of the surface layer was analyzed by X-ray photoelectron spectroscopy (XPS); Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 0.5mol/L H2SO4 solution. It was found that a remarkable decline in the aqueous corrosion behavior of zirconium implanted with cerium ions compared with that of the as-received zirconium. Finally, the mechanism of the corrosion resistance decline of the cerium-implanted zirconium is discussed.

  6. Effect of silty sand with different sizes on corrosion behavior of 3Cr steel in CO2 aqueous environment

    Science.gov (United States)

    Liu, Wei; Lu, Songle; Zhang, Peng; Dou, Juanjuan; Zhao, Qinghe

    2016-08-01

    Corrosion behavior of 3Cr steel in CO2 aqueous environment containing silty sand was investigated by immersion test. The results show that CO2 corrosion rate and morphology of 3Cr steel were obviously affected by the size of silty sand. 5000 mesh silty sand mixed with corrosion products, forming compact Cr-rich corrosion scale and resulting in low corrosion rate and uniform corrosion. 1000 mesh silty sand mixed with corrosion products, forming porous corrosion scale without Cr enrichment and resulting in high corrosion rate and pitting corrosion. 5000 mesh silty sand enhanced Cr enrichment in corrosion scale, leading to low anodic current. However, 1000 mesh silty sand deteriorated Cr enrichment in corrosion scale, leading to high anodic current. Cathodic current was reduced by silty sand, but was not affected by two sizes of silty sand. Cr enrichment in corrosion scale of 3Cr steel was obviously affected by separation effect of silty sand.

  7. Corrosion behavior of technetium waste forms exposed to various aqueous environments

    Energy Technology Data Exchange (ETDEWEB)

    Kolman, David Gary [Los Alamos National Laboratory; Jarvinen, Gordon [Los Alamos National Laboratory; Mausolf, Edward [UNIV OF NEVADA; Czerwinski, Ken [UNIV OF NEVADA; Poineau, Frederic [UNIV OF NEVADA

    2009-01-01

    Technetium is a long-lived beta emitter produced in high yields from uranium as a waste product in spent nuclear fuel and has a high degree of environmental mobility as pertechnetate. It has been proposed that Tc be immobilized into various metallic waste forms to prevent Tc mobility while producing a material that can withstand corrosion exposed to various aqueous medias to prevent the leachability of Tc to the environment over long periods of time. This study investigates the corrosion behavior of Tc and Tc alloyed with 316 stainless steel and Zr exposed to a variety of aqueous media. To date, there is little investigative work related to Tc corrosion behavior and less related to potential Tc containing waste forms. Results indicate that immobilizing Tc into stainless steel-zirconium alloys can be a promising technique to store Tc for long periods of time while reducing the need to separately store used nuclear fuel cladding. Initial results indicate that metallic Tc and its alloys actively corrode in all media. We present preliminary corrosion rates of 100% Tc, 10% Tc - 90% SS{sub 85%}Zr{sub 15%}, and 2% Tc - 98% SS{sub 85%}Zr{sub 15%} in varying concentrations of nitric acid and pH 10 NaOH using the resistance polarization method while observing the trend that higher concentrations of Tc alloyed to the sample tested lowers the corrosion rate of the proposed waste package.

  8. Stress Corrosion Cracking Behavior of Alloy 22 in Multi-Ionic Aqueous Environments

    Energy Technology Data Exchange (ETDEWEB)

    K.J. King; J.C. Estill; R.B. Rebak

    2002-07-15

    The US Department of Energy is characterizing a potential repository site for nuclear waste in Yucca Mountain (NV). In its current design, the nuclear waste containers consist of a double metallic layer. The external layer would be made of NO6022 or Alloy 22 (Ni-22Cr-13Mo-3W-3Fe). Since over their lifetime, the containers may be exposed to multi-ionic aqueous environments, a potential degradation mode of the outer layer could be environmentally assisted cracking (EAC) or stress corrosion cracking (SCC). In general, Alloy 22 is extremely resistant to SCC, especially in concentrated chloride solutions. Current results obtained through slow strain rate testing (SSRT) shows that Alloy 22 may suffer SCC in simulated concentrated water (SCW) at applied potentials approximately 400 mV more anodic than the corrosion potential (E{sub rr}).

  9. Corrosion problems with aqueous coolants, final report

    Energy Technology Data Exchange (ETDEWEB)

    Diegle, R B; Beavers, J A; Clifford, J E

    1980-04-11

    The results of a one year program to characterize corrosion of solar collector alloys in aqueous heat-transfer media are summarized. The program involved a literature review and a laboratory investigation of corrosion in uninhibited solutions. It consisted of three separate tasks, as follows: review of the state-of-the-art of solar collector corrosion processes; study of corrosion in multimetallic systems; and determination of interaction between different waters and chemical antifreeze additives. Task 1 involved a comprehensive review of published literature concerning corrosion under solar collector operating conditions. The reivew also incorporated data from related technologies, specifically, from research performed on automotive cooling systems, cooling towers, and heat exchangers. Task 2 consisted of determining the corrosion behavior of candidate alloys of construction for solar collectors in different types of aqueous coolants containing various concentrations of corrosive ionic species. Task 3 involved measuring the degradation rates of glycol-based heat-transfer media, and also evaluating the effects of degradation on the corrosion behavior of metallic collector materials.

  10. Effect of surface condition on the aqueous corrosion behavior of iron aluminies

    Energy Technology Data Exchange (ETDEWEB)

    Buchanan, R.A.; Perrin, R.L. [Univ. of Tennessee, Knoxville, TN (United States)

    1995-08-01

    The effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion characteristics of Fe-Al-based alloys were evaluated by electrochemical methods. Cyclic anodic polarization evaluations were conducted at room temperature in a mild acid-chloride solution (pH = 4,200 ppm Cl{sup {minus}}) on the Fe{sub 3}Al-based iron aluminides, FA-84 (Fe-28Al-2Cr-0.05B, at %), FA-129 (Fe-28Al-5Cr-0.5Nb-0.2C, at %), and FAL-Mo (Fe-28Al-5Cr-1Mo-0.04B-0.08Zr, at %), on the FeAl-based iron aluminide, FA-385 (Fe-35.65Al-0.20Mo-0.05Zr-0.11C, at %). The surface conditions evaluated were: As received (i.e. with the retained high-temperature oxides), mechanically cleaned (ground through 600-grit SiC paper), and chemically cleaned (10% HNO{sub 3}, 2%HF, at 43 {degree}C). The principal electrochemical parameter of interest was the critical putting potential with lower values indicating less resistance to chloride-induced localized corrosion. For all materials evaluated, the critical pitting potential was found to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. Mechanisms responsible for the detrimental high-temperature-oxide effect are under study.

  11. Aqueous Corrosion Rates for Waste Package Materials

    Energy Technology Data Exchange (ETDEWEB)

    S. Arthur

    2004-10-08

    The purpose of this analysis, as directed by ''Technical Work Plan for: Regulatory Integration Modeling and Analysis of the Waste Form and Waste Package'' (BSC 2004 [DIRS 171583]), is to compile applicable corrosion data from the literature (journal articles, engineering documents, materials handbooks, or standards, and national laboratory reports), evaluate the quality of these data, and use these to perform statistical analyses and distributions for aqueous corrosion rates of waste package materials. The purpose of this report is not to describe the performance of engineered barriers for the TSPA-LA. Instead, the analysis provides simple statistics on aqueous corrosion rates of steels and alloys. These rates are limited by various aqueous parameters such as temperature (up to 100 C), water type (i.e., fresh versus saline), and pH. Corrosion data of materials at pH extremes (below 4 and above 9) are not included in this analysis, as materials commonly display different corrosion behaviors under these conditions. The exception is highly corrosion-resistant materials (Inconel Alloys) for which rate data from corrosion tests at a pH of approximately 3 were included. The waste package materials investigated are those from the long and short 5-DHLW waste packages, 2-MCO/2-DHLW waste package, and the 21-PWR commercial waste package. This analysis also contains rate data for some of the materials present inside the fuel canisters for the following fuel types: U-Mo (Fermi U-10%Mo), MOX (FFTF), Thorium Carbide and Th/U Carbide (Fort Saint Vrain [FSVR]), Th/U Oxide (Shippingport LWBR), U-metal (N Reactor), Intact U-Oxide (Shippingport PWR, Commercial), aluminum-based, and U-Zr-H (TRIGA). Analysis of corrosion rates for Alloy 22, spent nuclear fuel, defense high level waste (DHLW) glass, and Titanium Grade 7 can be found in other analysis or model reports.

  12. Corrosion Behavior of Novel Mg-9Li-7Al-1Sn and Mg-9Li-5Al-3Sn-1Zn Alloys in NaCl Aqueous Solution

    Science.gov (United States)

    Kumar, Vinod; Shekhar, Rajiv; Balani, Kantesh

    2015-10-01

    Corrosion behavior of two multiphase Mg-Li-Al-based alloys in 0.6 M NaCl aqueous solution is investigated by hydrogen gas evolution measurement and electrochemical test. This paper reports, for the first time, the comparison of hydrogen evolution and Tafel extrapolation results of Mg-Li-Al-based alloys. The corrosion rate of Mg-9Li-7Al-1Sn is observed to be reasonably higher when compared to that of Mg-9Li-5Al-3Sn-1Zn, and both the alloys have shown higher corrosion rate than that of Mg-3Al-1Zn alloy (AZ31B). The micro-galvanic corrosion of primary precipitates and hcp α-phase (Mg-rich) is not as severe as was observed in case of the secondary precipitates and bcc β-phase (Li-rich). Corrosion mechanism of multiphase Mg-Li-Al-based alloys in chloride solution, which has not been adequately reported in the literature, is lucidly articulated based on the early stages of corrosion, film morphology, and in situ hydrogen bubble study.

  13. Inhibition of Mild Steel Corrosion in Acidic Medium by Aqueous Extract of Tridax procumbens L.

    OpenAIRE

    Ilayaraja, G.; Sasieekhumar, A. R.; Dhanakodi, P.

    2011-01-01

    The inhibition efficiency (IE) of an aqueous extract of Tridax procumbens L. in controlling corrosion of mild steel has been investigated by weight loss method in the absence and presence of corrosion inhibitor at different time interval at room temperature. The result showed that the corrosion inhibition efficiency of these compounds was found to vary with different time interval and different acid concentration. Also, it was found that the corrosion inhibition behavior of Tridax procumbens ...

  14. Corrosion inhibitor for aqueous ammonia absorption system

    Science.gov (United States)

    Phillips, Benjamin A.; Whitlow, Eugene P.

    1998-09-22

    A method of inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425.degree. F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25.degree. C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425.degree. F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer.

  15. Electrochemical preparation of NiAl intermetallic compound from solid oxides in molten CaCl{sub 2} and its corrosion behaviors in NaCl aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Yin Huayi; Yu Tang; Tang Diyong; Ruan Xuefeng; Zhu Hua [School of Resource and Environmental Science, Wuhan University, Wuhan 430072 (China); Wang Dihua, E-mail: wangdh@whu.edu.cn [School of Resource and Environmental Science, Wuhan University, Wuhan 430072 (China); State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Stoichiometric NiAl powder was prepared by one-step electrolysis of solid NiO-NiAl{sub 2}O{sub 4} in molten CaCl{sub 2}. Black-Right-Pointing-Pointer The energy consumption was as low as 6.1 kWh (kg-NiAl){sup -1}. Black-Right-Pointing-Pointer Uniform distribution and co-reduction of Ni and Al oxide played key role for Al retaining. Black-Right-Pointing-Pointer Electrolytic NiAl powder was made into dense NiAl rod by spark plasma sintering (SPS). Black-Right-Pointing-Pointer Obtained NiAl rod was self-passivated in NaCl solution and show very high corrosion resistance. - Abstract: Nickel aluminide powders were prepared by direct electrochemical reduction of solid mixture of NiO-NiAl{sub 2}O{sub 4} (Ni:Al = 1:1 in mol) precursor in molten CaCl{sub 2} at 850 Degree-Sign C. The reduction process of the solid oxide cathode was investigated by analyzing the intermediate products using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It reveals that nickel is preferentially reduced and it benefits to prevent aluminum leaving from the cathode. The products obtained at the constant cell voltage electrolysis of 3.0 V for more than 4 h were stoichiometric NiAl. The energy consumption could be as low as 6.1 kWh (kg-NiAl){sup -1} based on the applied cell voltage and the consumed electrolysis charge. Furthermore, the NiAl powders were made into a dense rod by spark plasma sintering (SPS) technique. The corrosion behaviors of the NiAl rod in 0.5 mol L{sup -1} NaCl aqueous solution at room temperature were investigated by polarization curve and ac impedance measurements. It was found that the NiAl rod had satisfactory anti-corrosion ability in the solution.

  16. Modelling aqueous corrosion of nuclear waste phosphate glass

    Science.gov (United States)

    Poluektov, Pavel P.; Schmidt, Olga V.; Kascheev, Vladimir A.; Ojovan, Michael I.

    2017-02-01

    A model is presented on nuclear sodium alumina phosphate (NAP) glass aqueous corrosion accounting for dissolution of radioactive glass and formation of corrosion products surface layer on the glass contacting ground water of a disposal environment. Modelling is used to process available experimental data demonstrating the generic inhibiting role of corrosion products on the NAP glass surface.

  17. Corrosion behavior of duplex coatings

    Directory of Open Access Journals (Sweden)

    K. Raghu Ram Mohan Reddy

    2016-07-01

    Full Text Available The titanium alloys are used in defense, aerospace, automobile, chemical plants and biomedical applications due to their very high strength and lightweight properties. However, corrosion is a life-limiting factor when Ti alloys are exposed to different chemical environments at high temperatures. In the present paper, duplex NiCrAlY/WC–Co coating is coated onto Ti6Al4V substrate to investigate the corrosion behavior of both coated samples and the substrate. The duplex coating was performed with NiCrAlY as the intermediate coat of 200 μm thickness deposited by HVOF process and WC–Co ceramic top coat with varying thicknesses of 250 μm, 350 μm and 450 μm deposited by DS process. Potentiodynamic polarization tests were employed to investigate the corrosion performance of duplex coated samples and substrate in Ringer’s solution at 37 °C and pH value was set to 5.7. Finally the results reveal that 350 μm thick coated samples showed highest corrosion resistance compared to 250 μm thick samples as well as bare substrate. However, the 450 μm thick coated sample showed poor corrosion resistance compared to the substrate. The scale formed on the samples upon corrosion was characterized by using SEM analysis to understand the degree of corrosion behavior.

  18. Corrosion resistance of amorphous and crystalline Pd40Ni40P20 alloys in aqueous solutions

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Chu, J.;

    2006-01-01

    The corrosion behaviors of amorphous and crystalline Pd40Ni40P20 alloys in various aqueous solutions are reported in this paper. The corrosion resistance of crystalline (annealed) Pd40Ni40P20 is better than that of amorphous Pd40Ni40P20 in various corrosive solutions, due to crystalline Pd40Ni40P20...... and mainly consists of inert Pd5P2, NI3P, Ni2Pd2P and noble Pd phases. These inert and noble properties result in a higher corrosion resistance in crystalline Pd40Ni40P20....

  19. Inhibition of Mild Steel Corrosion in Acidic Medium by Aqueous Extract of Tridax procumbens L.

    Directory of Open Access Journals (Sweden)

    G. Ilayaraja

    2011-01-01

    Full Text Available The inhibition efficiency (IE of an aqueous extract of Tridax procumbens L. in controlling corrosion of mild steel has been investigated by weight loss method in the absence and presence of corrosion inhibitor at different time interval at room temperature. The result showed that the corrosion inhibition efficiency of these compounds was found to vary with different time interval and different acid concentration. Also, it was found that the corrosion inhibition behavior of Tridax procumbens L. is greater in sulphuric acid than hydrochloric acid medium. So Tridax procumbens L. can be used as a good inhibitor for preventing mild steel material.

  20. Corrosion behaviors and effects of corrosion products of plasma electrolytic oxidation coated AZ31 magnesium alloy under the salt spray corrosion test

    Science.gov (United States)

    Wang, Yan; Huang, Zhiquan; Yan, Qin; Liu, Chen; Liu, Peng; Zhang, Yi; Guo, Changhong; Jiang, Guirong; Shen, Dejiu

    2016-08-01

    The effects of corrosion products on corrosion behaviors of AZ31 magnesium alloy with a plasma electrolytic oxidation (PEO) coating were investigated under the salt spray corrosion test (SSCT). The surface morphology, cross-sectional microstructure, chemical and phase compositions of the PEO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD), respectively. Further, the corrosion process of the samples under the SSCT was examined in a non-aqueous electrolyte (methanol) using electrochemical impedance spectroscopy (EIS) coupled with equivalent circuit. The results show that the inner layer of the coating was destroyed firstly and the corrosion products have significant effects on the corrosion behaviors of the coating. The results above are discussed and an electrochemical corrosion model is proposed in the paper.

  1. Corrosion penetration monitoring of advanced ceramics in hot aqueous fluids

    Directory of Open Access Journals (Sweden)

    Klaus G. Nickel

    2004-03-01

    Full Text Available Advanced ceramics are considered as components in energy related systems, because they are known to be strong, wear and corrosion resistant in many environments, even at temperatures well exceeding 1000 °C. However, the presence of additives or impurities in important ceramics, for example those based on Silicon Nitride (Si3N4 or Al2O3 makes them vulnerable to the corrosion by hot aqueous fluids. The temperatures in this type of corrosion range from several tens of centigrade to hydrothermal conditions above 100 °C. The corrosion processes in such media depend on both pH and temperature and include often partial leaching of the ceramics, which cannot be monitored easily by classical gravimetric or electrochemical methods. Successful corrosion penetration depth monitoring by polarized reflected light optical microscopy (color changes, Micro Raman Spectroscopy (luminescence changes and SEM (porosity changes will be outlined. The corrosion process and its kinetics are monitored best by microanalysis of cross sections, Raman spectroscopy and eluate chemistry changes in addition to mass changes. Direct cross-calibrations between corrosion penetration and mechanical strength is only possible for severe corrosion. The methods outlined should be applicable to any ceramics corrosion process with partial leaching by fluids, melts or slags.

  2. Passive Corrosion Behavior of Alloy 22

    Energy Technology Data Exchange (ETDEWEB)

    Rebak, R B; Payer, J H

    2006-01-10

    Alloy 22 (N06022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nanometers per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.

  3. Effects of surface condition on aqueous corrosion and environmental embrittlement of iron aluminides

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, R.L.; Buchanan, R.A. [Univ. of Tennessee, Knoxville, TN (United States)

    1996-08-01

    Effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion and environmental-embrittlement characteristics of Fe{sub 3}Al-based iron aluminides (FA-84, FA-129 and FAL-Mo), a FeAl-based iron aluminide (FA-385), and a disordered low-aluminum Fe-Al alloy (FAPY) were evaluated. All tests were conducted at room temperature in a mild acid-chloride solution. In cyclic-anodic-polarization testing for aqueous-corrosion behavior, the surface conditions examined were: as-received (i.e., with the retained high-temperature oxides), mechanically cleaned and chemically cleaned. For all materials, the polarization tests showed the critical pitting potentials to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. These results indicate detrimental effects of the retained high-temperature oxides in terms of increased susceptibilities to localized corrosion. In 200-hour U-bend stress-corrosion-cracking tests for environmental-embrittlement behavior, conducted at open-circuit corrosion potentials and at a hydrogen-charging potential of {minus}1500 mV (SHE), the above materials (except FA-385) were examined with retained oxides and with mechanically cleaned surfaces. At the open-circuit corrosion potentials, none of the materials in either surface condition underwent cracking. At the hydrogen-charging potential, none of the materials with retained oxides underwent cracking, but FA-84, FA-129 and FAL-Mo in the mechanically cleaned condition did undergo cracking. These results suggest beneficial effects of the retained high-temperature oxides in terms of increased resistance to environmental hydrogen embrittlement.

  4. Corrosion of metastable iron alloys in aqueous solutions

    Science.gov (United States)

    Wolf, Gerhard K.; Ferber, H.

    1983-05-01

    There exist some examples showing that metastable surface alloys can modify the corrision properties of a substrate in the same way as stable alloys do. In the present paper the corrosion behaviour of metastable surface alloys obtained by implanting gold, lead and mercury in iron was studied in aqueous solution of pH = 5.6. Potentiodynamic current density-potential curves were recorded of the implanted samples without further treatment and after isothermal annealing to temperatures up to 800°C. The results were compared with structural information on the alloys obtained by Turos et al. with α-backscattering and channeling experiments. Gold implantation turned out to enhance the active corrosion rate of iron, while lead and mercury had an impeding effect. The annealing experiments showed that the surface alloying facilitated the passivation of iron as long as the substitutional solid solution was "(meta)stable". After the breakdown at higher annealing temperatures leading to surface migration and clustering of the implanted elements a significant increase of the critical current density for passivation took place. This indicates passivation difficulties caused by the heterogeneous distribution of the "alloying" particles. In general the results suggest that substitutional metastable iron alloys cause in a systematic way corrosion inhibition or enhancement. However, their corrosion properties may change completely for non-substitutional distribution of the alloying elements as originating from annealing at higher temperatures.

  5. Corrosion behavior of Al6061 alloy weldment produced by friction stir welding process

    OpenAIRE

    Farhad Gharavi; Khamirul Amin Matori; Robiah Yunus; Norinsan Kamil Othman; Firouz Fadaeifard

    2015-01-01

    In this work, the corrosion behavior of welded lap joints of AA6061-T6 aluminum alloy produced by friction stir welding process has been investigated. Corrosion properties of welded lap joints were studied by cyclic polarization and electrochemical impedance spectroscopy tests. All tests were performed in an aerated 0.6 mol L−1 NaCl aqueous solution with pH = 6.5 at a temperature of 30 °C to characterize corrosion morphology and realize corrosion features of weld regions as opposed to the par...

  6. Corrosion behavior in heat pipe

    Directory of Open Access Journals (Sweden)

    Anurak Rodbumrung

    2016-01-01

    Full Text Available The aim of this study was to perform life testing and determine the effect of working fluid on the corrosion of a heat pipe with a sintered wick. The heat pipe was made from a copper tube. The inner heat pipe was filled with 99.97% pure copper powder as a dendritic for the sintering process. The heat pipe had an outer diameter of 6 mm with a length of 200 mm, and distilled water and ethanol were the working fluids. The operating temperature at the evaporator was 125°C. The analysis consisted of using a scanning electron microscope, energy dispersive X-ray spectrometry and atomic absorption spectroscopy. The results of the scanning electron microscope and energy dispersive X-ray spectrometry analysis showed that the corrosion of the heat pipe was uniform. The result of the atomic absorption spectroscopy indicated that the concentration of the copper in the ethanol as the working fluid was greater than in the distilled water as the working fluid, and the highest concentration of copper particles in the ethanol was 22.7499 ppm or 0.0409 mg after testing for 3000 h. The concentration of copper was higher when the length of the life test increased due to corrosion of the heat pipe.

  7. Evaluation of Iron Nickel Oxide Nanopowder as Corrosion Inhibitor: Effect of Metallic Cations on Carbon Steel in Aqueous NaCl

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhry, A. U.; Mishra, Brajendra [Colorado School of Mines, Denver (United States); Mittal, Vikas [The Petroleum Institute, Abu Dhabi (United Arab Emirates)

    2016-01-15

    The aim of this study was to evaluate the use of iron-nickel oxide (Fe{sub 2}O{sub 3}.NiO) nanopowder (FeNi) as an anti-corrosion pigment for a different application. The corrosion protection ability and the mechanism involved was determined using aqueous solution of FeNi prepared in a corrosive solution containing 3.5 wt.% NaCl. Anti-corrosion abilities of aqueous solution were determined using electrochemical impedance spectroscopy (EIS) on line pipe steel (API 5L X-80). The protection mechanism involved the adsorption of metallic cations on the steel surface forming a protective film. Analysis of EIS spectra revealed that corrosion inhibition occurred at low concentration, whereas higher concentration of aqueous solution produced induction behavior.

  8. Corrosion behavior of magnesium and magnesium alloys

    Institute of Scientific and Technical Information of China (English)

    I.M.Baghni; WU Yin-shun(吴荫顺); LI Jiu-qing(李久青); ZHANG Wei(张巍)

    2004-01-01

    The automotive industry has crossed the threshold from using magnesium alloys in interior applications such as instrument panels and steering wheels to unprotected environment such as oil pan, cylinder head and wheels. The expanding territory of magnesium leads to new challenges: mainly environmental degradation of the alloys used and how they can be protected. The present critical review is aimed at understanding the corrosion behavior of magnesium and magnesium alloys in industrial and marine environments, and the effect of microstructure, additive elements and inhibitors on the corrosion mechanism.

  9. Electrochemical corrosion behavior of carbon steel with bulk coating holidays

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    With epoxy coal tar as the coating material, the electrochemical corrosion behavior of Q235 with different kinds of bulk coating holidays has been investigated with EIS (Electrochemical Impedance Spectroscopy) in a 3.5vol% NaCl aqueous solution.The area ratio of bulk coating holiday to total coating area of steel is 4.91%. The experimental results showed that at free corrosionpotential, the corrosion of carbon steel with disbonded coating holiday is heavier than that with broken holiday and disbonded & broken holiday with time; Moreover, the effectiveness of Cathodic Protection (CP) of carbon steel with broken holiday is better than that with disbonded holiday and disbonded & broken holiday on CP potential -850 mV (vs CSE). Further analysis indicated that the two main reasons for corrosion are electrolyte solution slowly penetrating the coating, and crevice corrosion at steel/coating interface near holidays. The ratio of impedance amplitude (Z) of different frequency to minimum frequency is defined as K value. The change rate of K with frequency is related to the type of coating holiday.

  10. Dilute condition corrosion behavior of glass-ceramic waste form

    Science.gov (United States)

    Crum, Jarrod V.; Neeway, James J.; Riley, Brian J.; Zhu, Zihua; Olszta, Matthew J.; Tang, Ming

    2016-12-01

    Borosilicate glass-ceramics are being developed to immobilize high-level waste generated by aqueous reprocessing into a stable waste form. The corrosion behavior of this multiphase waste form is expected to be complicated by multiple phases and crystal-glass interfaces. A modified single-pass flow-through test was performed on polished monolithic coupons at a neutral pH (25 °C) and 90 °C for 33 d. The measured glass corrosion rates by micro analysis in the samples ranged from 0.019 to 0.29 g m-2 d-1 at a flow rate per surface area = 1.73 × 10-6 m s-1. The crystal phases (oxyapatite and Ca-rich powellite) corroded below quantifiable rates, by micro analysis. While, Ba-rich powellite corroded considerably in O10 sample. The corrosion rates of C1 and its replicate C20 were elevated an order of magnitude by mechanical stresses at crystal-glass interface caused by thermal expansion mismatch during cooling and unique morphology (oxyapatite clustering).

  11. Corrosion behavior of Al6061 alloy weldment produced by friction stir welding process

    Directory of Open Access Journals (Sweden)

    Farhad Gharavi

    2015-07-01

    Full Text Available In this work, the corrosion behavior of welded lap joints of AA6061-T6 aluminum alloy produced by friction stir welding process has been investigated. Corrosion properties of welded lap joints were studied by cyclic polarization and electrochemical impedance spectroscopy tests. All tests were performed in an aerated 0.6 mol L−1 NaCl aqueous solution with pH = 6.5 at a temperature of 30 °C to characterize corrosion morphology and realize corrosion features of weld regions as opposed to the parent alloy. The microstructure of weld nugget (WN, heated affected zone (HAZ, and parent alloy were analyzed using scanning electron microscopy and energy dispersive spectroscopy. The experimental results indicated that the welding process has a major effect on the corrosion resistance, which possibly associated to the break-down and dissolution of intermetallic particles. It is supposed that an increasing in intermetallic distributed throughout the matrix of weld regions increases the galvanic corrosion couples. Furthermore, by decreasing the grain size in the weld regions, the susceptibility to corrosion is enhanced. The pitting corrosion and intergranular attack are the dominant corrosion types in the weld regions and the parent alloy.

  12. Corrosion behavior of WE54 magnesium alloy in 3.5%NaCl solution

    Institute of Scientific and Technical Information of China (English)

    LI Zhuo-qun; SHAN Da-yong; CHEN Rong-shi; KE Wei; HAN En-hou

    2006-01-01

    The corrosion behavior of WE54 magnesium alloy was investigated in 3.5%NaCl aqueous solution. The electrochemical study shows that the value of corrosion potential of WE54 magnesium was -1.8V(vs SCE). In the initial stage of immersion, a kind of visible thin film, which has the appearance of artificial conversion coating by microscopy observation, formed on the surface of WE54 alloy. Through the comparison of corrosion behavior between WE54 and AZ91D, it is shown that the value of corrosion potential of WE54 is approximately 200 mV lower than that of AZ91D, and the corrosion rate of WE54 was one order smaller than that of AZ91D. After 72 h constant immersion and corrosion products removal, deeper grooves along grain boundaries was revealed but lighter corrosion was apparent on the matrix of WE54 alloy. As far as AZ91D alloy was concerned, severe localized corrosion was dominant and network-bone-like structure was remained.

  13. Study of the corrosion behavior of magnesium alloy weddings in NaCl solutions by gravimetric tests

    Energy Technology Data Exchange (ETDEWEB)

    Segarra, J. A.; Calderon, B.; Portoles, A.

    2015-07-01

    In this article, the corrosion behavior of commercial AZ31 welded plates in aqueous chloride media was investigated by means of gravimetric techniques and Neutral Salt Spray tests (NSS). The AZ31 samples tested were welded using Gas Tugsten Arc Welding (GTAW) and different filler materials. Material microstructures were investigated by optical microscopy to stablish the influence of those microstructures in the corrosion behavior. Gravimetric and NSS tests indicate that the use of more noble filler alloys for the sample welding, preventing the reduction of aluminum content in weld beads, does not imply a better corrosion behavior. (Author)

  14. Investigation of Corrosion Behavior of Wrought Stellite Alloys

    Science.gov (United States)

    Zhang, Xiaozhou

    The corrosion behavior of two wrought Stellite alloys, Stellite 6B and Stellite 6K, is studied under polarization test and immersion test. Two types of corrosive media, 3.5 wt% sodium chloride (NaCl) aqueous solution and Green Death solution, are used in the polarization test. Both potentiodynamic polarization and cyclic polarization testes are performed to investigate general and localized corrosion resistance of these alloys. Immersion tests of the two alloys are conducted in Green Death solution to determine Critical Pitting Temperature (CPT), mass loss, thickness change and the Extreme Value (minimum thickness) of the Extreme Value Analysis (EVA) model which derived from the Gumbel Distribution. The minimum thickness for Stellite 6B and Stellite 6K that is required for an assumed service time is predicted. Maximum pit depths, which are the input of the EVA model, are measured using a surface texture and contour measuring instrument. A Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDX) spectrum is utilized to analyze the chemical composition of the corrosion products (pits). The CPTs of Stellite 6B and Stellite 6K in Green Death solution are determined to be all 60°C. The experimental results demonstrate that Stellite 6B and Stellite 6K have good general and localized corrosion resistance by forming the protective Cr-oxide film. However, the presence of carbides generates potential in the electrochemical reaction, causing corrosion of the alloys in the solution. The larger the carbide volume fraction is, the more the pits are forming in the alloy. Carbide size affects maximum pit depths; the larger the carbide size is, the bigger and deeper the pits are. The EDX analysis results of pits show large amount of oxygen in the carbide phase and small amount of oxygen in the solid solution phase. The Cr-rich carbides react with oxygen forming Cr-rich carbonates which are easily brittle, loose and broken, while Cr in the solid solution reacts with

  15. Ecological and corrosion behavior of depleted uranium

    Directory of Open Access Journals (Sweden)

    Stojanović Mirjana D.

    2015-01-01

    Full Text Available Environmental pollution with radionuclides, particularly uranium and its decay products is a serious global problem. The current scientific studies estimated that the contamination originating from TENORM, caused by nuclear and non-nuclear technologies, has significantly increased natural level of radioactivity in the last thirty years. During the last decades all the more were talking about the "new pollutant" - depleted uranium (DU, which has been used in anti-tank penetrators because of its high density, penetration and pyrophoric properties. It is estimated that during the Gulf War, the war in Bosnia and Yugoslavia and during the invasion of Iraq, 1.4 million missiles with depleted uranium was fired. During the NATO aggression against the ex Yugoslavia in 1999., 112 locations in Kosovo and Metohija, 12 locations in southern Serbia and two locations in Montenegro were bombed. On this occasion, approximately 10 tons of depleted uranium were entered into the environment, mainly on land, where the degree of contamination ranged from 200 Bq / kg to 235 000 Bq/kg, which is up to 1000 times higher than the natural level. Fourteen years ago there was very little information about the behavior of ecological systems damaged by DU penetrators fired. Today, unfortunately, we are increasingly faced with the ―invisible threat" of depleted uranium, which has a strong radioactive and hemotoxic impact on human health. Present paper provides a detailed overview of the current understanding of corrosion and corrosion behavior of DU and environmental factors that control corrosion, together with indicators of environmental impact in order to highlight areas that need further attention in developing remediation programs.

  16. Pitting Corrosion Behavior of Stainless Steel 304 in Carbon Dioxide Environments

    Institute of Scientific and Technical Information of China (English)

    LI Guo-min; GUO Xing-peng; ZHENG Jia-shen

    2004-01-01

    The pitting corrosion behavior of stainless steel (SS) 304 in aqueous CO2-H2S-Cl- environment was investigated by potentiodynamic cyclic anodic polarization and electron probe microanalysis (EPMA). The experimental results show that the pitting corrosion susceptivity of SS 304 increases with the increase of temperature. Chlorine ion is the prerequisite for pitting corrosion of SS 304 in H2S-CO2 environments. There is a linear relationship between the pitting corrosion potential (Eb-100) and chlorine ion concentration, and Eb-100 becomes noble with increasing pH value of the solution with or without H2S. pH value has little effect on the protection potential with the presence of H2S. H2S increases strongly the pitting corrosion susceptivity and deteriorates the pitting corrosion resistance of SS 304 in CO2 environments. The observations by EPMA show that SS 304 in CO2-saturated NaCl solution (3 %) with H2S suffers pitting corrosion accompanied with intergranular corrosion.

  17. The Corrosion and Corrosion Fatigue Behavior of Nickel Based Alloy Weld Overlay and Coextruded Claddings

    Science.gov (United States)

    Stockdale, Andrew

    The use of low NOx boilers in coal fired power plants has resulted in sulfidizing corrosive conditions within the boilers and a reduction in the service lifetime of the waterwall tubes. As a solution to this problem, Ni-based weld overlays are used to provide the necessary corrosion resistance however; they are susceptible to corrosion fatigue. There are several metallurgical factors which give rise to corrosion fatigue that are associated with the localized melting and solidification of the weld overlay process. Coextruded coatings offer the potential for improved corrosion fatigue resistance since coextrusion is a solid state coating process. The corrosion and corrosion fatigue behavior of alloy 622 weld overlays and coextruded claddings was investigated using a Gleeble thermo-mechanical simulator retrofitted with a retort. The experiments were conducted at a constant temperature of 600°C using a simulated combustion gas of N2-10%CO-5%CO2-0.12%H 2S. An alternating stress profile was used with a minimum tensile stress of 0 MPa and a maximum tensile stress of 300 MPa (ten minute fatigue cycles). The results have demonstrated that the Gleeble can be used to successfully simulate the known corrosion fatigue cracking mechanism of Ni-based weld overlays in service. Multilayer corrosion scales developed on each of the claddings that consisted of inner and outer corrosion layers. The scales formed by the outward diffusion of cations and the inward diffusion of sulfur and oxygen anions. The corrosion fatigue behavior was influenced by the surface finish and the crack interactions. The initiation of a large number of corrosion fatigue cracks was not necessarily detrimental to the corrosion fatigue resistance. Finally, the as-received coextruded cladding exhibited the best corrosion fatigue resistance.

  18. Corrosion behavior of corrosion resistant alloys in stimulation acids

    Energy Technology Data Exchange (ETDEWEB)

    Cheldi, Tiziana [ENI E and P Division, 20097 San Donato Milanese Milano (Italy); Piccolo, Eugenio Lo; Scoppio, Lucrezia [Centro Sviluppo Materiali, via Castel Romano 100, 00128 Rome (Italy)

    2004-07-01

    In the oil and gas industry, selection of CRAs for downhole tubulars is generally based on resistance to corrosive species in the production environment containing CO{sub 2}, H{sub 2}S, chloride and in some case elemental sulphur. However, there are non-production environments to which these materials must also be resistant for either short term or prolonged duration; these environments include stimulation acids, brine and completion fluids. This paper reports the main results of a laboratory study performed to evaluate the corrosion and stress corrosion behaviour to the acidizing treatments of the most used CRAs for production tubing and casing. Laboratory tests were performed to simulate both 'active' and 'spent' acids operative phases, selecting various environmental conditions. The selected steel pipes were a low alloyed steel, martensitic, super-martensitic, duplex 22 Cr, superduplex 25 Cr and super-austenitic stainless steels (25 Cr 35 Ni). Results obtained in the 'active' acid environments over the temperature range of 100-140 deg. C, showed that the blend acids with HCl at high concentration and HCl + HF represented too much severe conditions, where preventing high general corrosion and heavy localised corrosion by inhibition package becomes very difficult, especially for duplex steel pipe, where, in some case, the specimens were completely dissolved into the solution. On the contrary, all steels pipes were successfully protected by inhibitor when organic acid solution (HCOOH + CH{sub 3}COOH) were used. Furthermore, different effectiveness on corrosion protection was showed by the tested inhibitors packages: e.g. in the 90% HCl at 12% + 10 CH{sub 3}COOH acid blend. In 'spent' acid environments, all steel pipes showed to be less susceptible to the localised and general corrosion attack. Moreover, no Sulphide Stress Corrosion Cracking (SSC) was observed. Only one super-austenitic stainless steel U-bend specimen showed

  19. Tribological and corrosion behaviors of carburized AISI 4340 steel

    Science.gov (United States)

    Thong-on, Atcharawadi; Boonruang, Chatdanai

    2016-01-01

    AISI 4340 steel is widely used in automotive and aircraft industries as gear components. In such applications, surface hardening processes such as carburizing are required in order to improve the life time of the components. There are many studies showing the tribological behavior of the carburized steel, but the corrosion behavior has not yet been clarified. This paper reports on both tribological and corrosion behaviors of the carburized AISI 4340 steel. Factor associated with carburizing, such as the quantities of deposited carbon, dissolved carbon, and formed Cr23C6 and Fe3C, affect the tribological and corrosion behaviors of the steel by improving hardness, friction, lubrication, and wear resistance; but corrosion resistance is reduced. The dissolved carbon affects the formation of the oxide layer of the carburized steel, by obstructing the continuous oxide layer formation and by decreasing the chromium content of the steel, leading to the decrease in the corrosion resistance of the steel.

  20. Electrochemical corrosion behavior of arc sprayed Zn-Al coatings

    Institute of Scientific and Technical Information of China (English)

    LIU Yan; ZHU Zi-xin; CHEN Yong-xiong; XU Bin-shi; MA Shi-ning; LI Zhuo-xin

    2004-01-01

    Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coatings were studied with potentiodynamic measurement in 5 % NaCl solution. Compared with pure Zn, pure Al and Zn-15Al coatings, Zn-26Al coatings show a higher corrosion resistance in salt solution. The potentiodynamic polarization tests show that the corrosion resistance of Zn-Al coatings increases as Al content is raised. Pure Al coating exhibits different electrochemical behaviors with other coatings. The corrosion initiated at the micro-pores of the coating and the underlying corrosion mechanism is very similar to that of the pitting corrosion.

  1. The corrosion behavior of nanocrystalline nickel based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Danışman, Murat, E-mail: muratdan@gmail.com

    2016-03-01

    In this study, the effect of Cr addition on corrosion behavior of Ni thin films were investigated. Ni thin films and Ni films with three different Cr content were deposited on glass substrates by magnetron sputtering. After deposition process, thin films with different Cr content were thermally treated in a rapid thermal process system. Phase analysis and grain size calculations of the samples were carried out by X-ray diffraction analysis. In order to reveal corrosion properties, potentiodynamic tests were conducted on samples. Analysis revealed that, although Cr addition to pure-Ni thin films improved their corrosion resistance, occurrence of σ-Cr{sub 3}Ni{sub 2} phase at higher Cr contents increased corrosion rate. The corrosion properties of the samples were also investigated by electrochemical impedance spectroscopy and surface related parameters caused by corrosion reactions were calculated. The analysis revealed that at 55% wt. Cr, rapid ion exchange occurred and highest corrosion current, 23.4 nA cm{sup −2} was observed. - Highlights: • Thin film Ni–Cr samples were deposited on glass substrate. • Effect of Cr addition on corrosion behavior of Ni thin films were investigated. • Potentiodynamic tests and electrochemical impedance spectroscopy methods were used. • Cr content in Ni thin films plays and important role on corrosion. • Up to a certain Cr content, Cr addition reduces corrosion rate.

  2. Corrosion behavior of tantalum and its nitride in alkali solution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Deyuan; LIN Qin; FEI Qinyong; ZHAO Haomin; KANG Guangyu; GENG Man

    2003-01-01

    The corrosion behavior of tantalum and its nitrides in stirring NaOH solutions was researched by potenfiostatic method, cyclic voltammetry and XPS. The results showed that the corrosion products were composed of Ta2O5 and NaTaO3.The corrosion reaction formula of tantalum and its nitrides was written according to cyclic volt-ampere curves. The electric charge transfer coefficient and the electric charge transfer number were calculated.

  3. Corrosion behavior of Ti–39Nb alloy for dentistry

    Energy Technology Data Exchange (ETDEWEB)

    Fojt, Jaroslav, E-mail: fojtj@vscht.cz [Institute of Chemical Technology, Technicka 5, 166 28 Prague (Czech Republic); Joska, Ludek [Institute of Chemical Technology, Technicka 5, 166 28 Prague (Czech Republic); Malek, Jaroslav [UJP Praha, Nad Kamínkou 1345, 156 10 Prague-Zbraslav (Czech Republic); Sefl, Vaclav [Institute of Chemical Technology, Technicka 5, 166 28 Prague (Czech Republic)

    2015-11-01

    To increase an orthopedic implant's lifetime, researchers are now concerned on the development of new titanium alloys with suitable mechanical properties (low elastic modulus–high fatigue strength), corrosion resistance and good workability. Corrosion resistance of the newly developed titanium alloys should be comparable with that of pure titanium. The effect of medical preparations containing fluoride ions represents a specific problem related to the use of titanium based materials in dentistry. The aim of this study was to determine the corrosion behavior of β titanium alloy Ti–39Nb in physiological saline solution and in physiological solution containing fluoride ions. Corrosion behavior was studied using standard electrochemical techniques and X-ray photoelectron spectroscopy. It was found that corrosion properties of the studied alloy were comparable with the properties of titanium grade 2. The passive layer was based on the oxides of titanium and niobium in several oxidation states. Alloying with niobium, which was the important part of the alloy passive layer, resulted in no significant changes of corrosion behavior. In the presence of fluoride ions, the corrosion resistance was higher than the resistance of titanium. - Highlights: • Alloy Ti–39Nb shows excellent corrosion resistance in physiological solution. • Corrosion resistance of Ti–39Nb alloy is significantly higher than that of titanium in the presence of fluoride ions. • The electrochemical impedance spectroscopy indicates a porous passive layer. • Passive layer of the alloy is enriched by niobium.

  4. Aqueous sodium chloride induced intergranular corrosion of Al-Li-Cu alloys

    Science.gov (United States)

    Pizzo, P. P.; Daeschner, D. L.

    1986-01-01

    Two methods have been explored to assess the susceptibility of Al-Li-Cu alloys to intergranular corrosion in aqueous sodium chloride solution. They are: (1) constant extension rate testing with and without alternate-immersion preexposure and (2) metallographic examination after exposure to a NaCl-H2O2 corrosive solution per Mil-H-6088F. Intergranular corrosion was found to occur in both powder and ingot metallurgy alloys of similar composition, using both methods. Underaging rendered the alloys most susceptible. The results correlate to stress-corrosion data generated in conventional time-to-failure and crack growth-rate tests. Alternate-immersion preexposure may be a reliable means to assess stress corrosion susceptibility of Al-Li-Cu alloys.

  5. Corrosion Behavior of Titanium in Artificial Saliva by Lactic Acid

    Directory of Open Access Journals (Sweden)

    Qing Qu

    2014-07-01

    Full Text Available As one of the main products produced by oral microorganisms, the role of lactic acid in the corrosion of titanium is very important. In this study, the corrosion behavior of titanium in artificial saliva with and without lactic acid were investigated by open-circuit potentials (OCPs, polarization curves and electrochemical impedance spectroscopy (EIS. OCP firstly increased with the amount of lactic acid from 0 to 3.2 g/L and then tended to decrease from 3.2 to 5.0 g/L. The corrosion of titanium was distinctly affected by lactic acid, and the corrosion rate increased with increasing the amount of lactic acid. At each concentration of lactic acid, the corrosion rate clearly increased with increasing the immersing time. Results of scanning electron microscopy (SEM also indicated that lactic acid accelerated the pitting corrosion in artificial saliva. A probable mechanism was also proposed to explain the experimental results.

  6. Electrochemical corrosion behavior of steel wires in a coalmine with a corrosive medium

    Institute of Scientific and Technical Information of China (English)

    Wang Songquan; Zhang Dekun; Wang Dagang; Zhang Zefeng

    2011-01-01

    A 6 × 19 point-contact hoisting cable was used as our research object to examine the progress of corrosion of steel wires in a laboratory, simulating the actual working conditions in a coalmine. An electrochemical method was used to investigate the corrosion behavior of steel wires with different surface treatments of a corrosive acid solution. The results show that anode activation of steel wire mainly occurs during pre-corrosion, where the anode activation process of bare steel wires is the fastest as is their corresponding corrosion speed, while the anode activation process of oil coated steel wires and their corresponding corrosion speed are the lowest. During the intermediate and late immersion periods,a passive film is generated on the surface of steel wires, which are gradually damaged with the passage of time. Local pitting corrosion occurs easily on the surface of steel wires with a high-polarization potential.Suitable equivalent circuits were chosen to fit the electrochemical impedance spectroscopy (EIS) of steel wires over various corrosive times and different surface treatments, which indicate good fitting results.The double electrical layer charge-transfer resistance increases in the sequence: bare steel wire,untreated steel wire and oil coated steel wire and their corrosion resistance decreases in turn, which is consistent with their polarization curves. The oil layer provides a certain protective effect on untreated steel wires, but its effect is not entirely clear.

  7. Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion

    OpenAIRE

    Xuming Zhang; Guosong Wu; Xiang Peng; Limin Li; Hongqing Feng; Biao Gao; Kaifu Huo; Chu, Paul K.

    2015-01-01

    Rapid corrosion of magnesium alloys is undesirable in structural and biomedical applications and a general way to control corrosion is to form a surface barrier layer isolating the bulk materials from the external environment. Herein, based on the insights gained from the anticorrosion behavior of corrosion products, a special way to mitigate aqueous corrosion is described. The concept is based on pre-corrosion by a hydrothermal treatment of Al-enriched Mg alloys in water. A uniform surface c...

  8. CEMS study of corrosion products formed by NaCl aqueous solution

    Science.gov (United States)

    Nakanishi, A.

    2012-03-01

    Conversion electron Mössbauer spectroscopy was used to study corrosion products by NaCl aqueous solution. A drop of the solution is put on an iron foil and the foil is left at RT. During the evaporation of the solution, corrosion products are formed. Conversion electron Mössbauer spectra were taken at temperatures between 15 K and room temperature (RT). In the Mössbauer spectra a ferric doublet is observed at RT, but sextets are found at 15 K. These results show that the corrosion product mainly consists of γ - FeOOH and a small amount of β - FeOOH is noticed. As NaCl concentration increases, the corrosion layer becomes thick and β- FeOOH / γ - FeOOH ratio increases slightly. Consequently, it has been concluded that the produced amount of β- FeOOH increases more rapidly than that of γ - FeOOH with increasing NaCl concentration.

  9. Corrosion behavior of Ti-39Nb alloy for dentistry.

    Science.gov (United States)

    Fojt, Jaroslav; Joska, Ludek; Malek, Jaroslav; Sefl, Vaclav

    2015-11-01

    To increase an orthopedic implant's lifetime, researchers are now concerned on the development of new titanium alloys with suitable mechanical properties (low elastic modulus-high fatigue strength), corrosion resistance and good workability. Corrosion resistance of the newly developed titanium alloys should be comparable with that of pure titanium. The effect of medical preparations containing fluoride ions represents a specific problem related to the use of titanium based materials in dentistry. The aim of this study was to determine the corrosion behavior of β titanium alloy Ti-39Nb in physiological saline solution and in physiological solution containing fluoride ions. Corrosion behavior was studied using standard electrochemical techniques and X-ray photoelectron spectroscopy. It was found that corrosion properties of the studied alloy were comparable with the properties of titanium grade 2. The passive layer was based on the oxides of titanium and niobium in several oxidation states. Alloying with niobium, which was the important part of the alloy passive layer, resulted in no significant changes of corrosion behavior. In the presence of fluoride ions, the corrosion resistance was higher than the resistance of titanium.

  10. Corrosion electrochemical behavior of brass tubes in circulating cooling seawater

    Institute of Scientific and Technical Information of China (English)

    LU Yu-zhuo; SONG Shi-zhe; YIN Li-hui

    2005-01-01

    Electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) were used to study the corrosion electrochemical behavior of brass tubes in circulating cooling seawater using the developed sensor. EIS study shows that the inhibitor can lead to the formation of corrosion products on metal surface, which will then inhibit the corrosion process. When the flow rate of the seawater increases, the diffusion of oxygen speeds up and the action of filming on HAl77-2 tube accelerates, resulting in decrease of corrosion rate. EN analysis shows that the flow rate of the seawater has little effect on pitting susceptivity of HSn70-1 tube; however the pitting susceptivity of HAl77-2 tube increases with increasing flow rate. Good agreement is observed between the spectral noise resistance Rsn (f) calculated from EN data and the modulus of impedance. It is shown that the electrochemical noise technique can be used in corrosion monitoring.

  11. Corrosion Behavior of Commercial Magnetic Refrigerant Gadolinium in Water

    Institute of Scientific and Technical Information of China (English)

    Zhang Zeyu; Long Yi; Wen Da; Ye Rongchang; Wan Farong

    2004-01-01

    Gadolinium(Gd) used as magnetic refrigerant always works in water environment.However, its poor corrosion resistance is serious impediment against wider application of Gd.In this paper, the corrosion behavior of two types of commercial Gd ( A, B both are 98.9 at.% pure) with the same oxygen content has been studied.The results show that the corrosion rate of A is 3.226 times higher than that of B in deionized water and 6.039 times in tap water.According to SEM, the different corrosion rate is because of the different distribution of impurity in matrix.In addition,NaOH solution was chosen as inhibitor to prevent Gd from being corroded successfully.No pitting corrosion and weight loss were observed for commercial Gd even after immersion for nearly 2000 h in NaOH solution.

  12. Corrosion behavior of construction materials for ionic liquid hydrogen compressor

    DEFF Research Database (Denmark)

    Arjomand Kermani, Nasrin; Petrushina, Irina; Nikiforov, Aleksey Valerievich

    2016-01-01

    The corrosion behavior of various commercially available stainless steels and nickel-based alloys as possible construction materials for components which are in direct contact with one of five different ionic liquids was evaluated. The ionic liquids, namely: 1-ethyl-3-methylimidazolium triflate, 1...... liquid hydrogen compressor. An electrochemical cell was specially designed, and steady-state cyclic voltammetry was used to measure the corrosion resistance of the alloys in the ionic liquids at 23 °C, under atmospheric pressure. The results showed a very high corrosion resistance and high stability...... for all the alloys tested. The two stainless steels, AISI 316L and AISI 347 showed higher corrosion resistance compared to AISI 321 in all the ionic liquids tested. It was observed that small addition of molybdenum, tantalum, and niobium to the alloys increased the corrosion stability in the ionic liquids...

  13. Polarization-corrosion behavior of commercial gold- and silver-base casting alloys in Fusayama solution.

    Science.gov (United States)

    Johnson, D L; Rinne, V W; Bleich, L L

    1983-12-01

    Based on polarization measurements, high Au alloys are highly corrosion-resistant and exhibit the lowest corrosion rates; intermediate Au, Ag, and Pd alloys with Cu are passive but exhibit higher corrosion rates. Twenty weight percent (w/o) In-Ag alloys exhibit active corrosion behavior at potentials only 100 mV noble to the corrosion potential.

  14. Corrosive wear behavior of 2014 and 6061 aluminum alloy composites

    Energy Technology Data Exchange (ETDEWEB)

    Varma, S.K.; Andrews, S.; Vasquez, G. [Univ. of Texas, El Paso, TX (United States). Dept. of Metallurgical and Materials Engineering

    1999-02-01

    Alloys of 2014 and 6061 aluminum reinforced with 0.1 volume fraction of alumina particles (VFAP) were subjected to impact scratching during a corrosive wear process. The transient currents generated due to the impact were measured in the two composites as well as in their respective monoliths. The effect of solutionizing time on the transient currents was correlated to the near surface microstructures, scratch morphology, concentration of quenched-in vacancies, and changes in grain sizes. It was observed that the transient current values increase with an increase in solutionizing time, indicating that the corrosive wear behavior is not strongly affected by the grain boundaries. However, a combination of pitting and the galvanic corrosion may account for the typical corrosive wear behavior exhibited by the alloys and the composites of this study.

  15. In situ soft X-ray absorption spectroscopy investigation of electrochemical corrosion of copper in aqueous NaHCO3 solution

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Peng; Chen, Jeng-Lung; Borondics, Ferenc; Glans, Per-Anders; West, Mark W.; Chang, Ching-Lin; Salmeron, Miquel; Guo, Jinghua

    2010-03-31

    A novel electrochemical setup has been developed for soft x-ray absorption studies of the electronic structure of electrode materials during electrochemical cycling. In this communication we illustrate the operation of the cell with a study of the corrosion behavior of copper in aqueous NaHCO3 solution via the electrochemically induced changes of its electronic structure. This development opens the way for in situ investigations of electrochemical processes, photovoltaics, batteries, fuel cells, water splitting, corrosion, electrodeposition, and a variety of important biological processes.

  16. Corrosion and mechanical behavior of materials for coal gasification applications

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.

    1980-05-01

    A state-of-the-art review is presented on the corrosion and mechanical behavior of materials at elevated temperatures in coal-gasification environments. The gas atmosphere in coal-conversion processes are, in general, complex mixtures which contain sulfur-bearing components (H/sub 2/S, SO/sub 2/, and COS) as well as oxidants (CO/sub 2//CO and H/sub 2/O/H/sub 2/). The information developed over the last five years clearly shows sulfidation to be the major mode of material degradation in these environments. The corrosion behavior of structural materials in complex gas environments is examined to evaluate the interrelationships between gas chemistry, alloy chemistry, temperature, and pressure. Thermodynamic aspects of high-temperature corrosion processes that pertain to coal conversion are discussed, and kinetic data are used to compare the behavior of different commercial materials of interest. The influence of complex gas environments on the mechanical properties such as tensile, stress-rupture, and impact on selected alloys is presented. The data have been analyzed, wherever possible, to examine the role of environment on the property variation. The results from ongoing programs on char effects on corrosion and on alloy protection via coatings, cladding, and weld overlay are presented. Areas of additional research with particular emphasis on the development of a better understanding of corrosion processes in complex environments and on alloy design for improved corrosion resistance are discussed. 54 references, 65 figures, 24 tables.

  17. Corrosion Inhibition of Mild Steel in Citric Acid by Aqueous Extract of Piper Nigrum L.

    Directory of Open Access Journals (Sweden)

    P. Matheswaran

    2012-01-01

    Full Text Available The inhibition efficiency (IE of an aqueous extract of Piper Nigrum L. in controlling corrosion of mild steel at pH 12 has been evaluated by weight loss method in the absence and presence of inhibitor in citric acid medium at different concentration. The result showed that the corrosion inhibition efficiency of these compounds was found to vary with the different concentration at two hour time interval at room temperature. Also, it was found that the corrosion inhibition behaviour of Piper Nigrum L. is greater in 2 N Citric acid than 1 N Citric acid medium. So Piper Nigrum L. can be used has a good inhibitor for preventing mild steel material which is used in many construction purpose.

  18. Aromatic quinoxaline as corrosion inhibitor for bronze in aqueous chloride solution

    Indian Academy of Sciences (India)

    N Saoudi; A Bellaouchou; A Guenbour; A Ben Bachir; E M Essassi; M El Achouri

    2010-06-01

    A new corrosion inhibitor, viz. 3-ethyl-6-méthyl-quinoxalin-2-one, 1-benzyl-6-methyl-quinoxalin- 2-one, 2-benzyloxy-3,6-dimethyl-quinoxaline, 1-benzyl-3-methyl-quinoxalin-2-one, were synthesized in the laboratory. Their influence on the inhibition on corrosion of bronze in aqueous chloride solution (3% NaCl) was studied by electrochemical polarization methods and weight-loss measurements. The impact of temperature on the effectiveness of the substances mentioned above has been determined between 20 and 60°C. The results showed that the corrosion resistance was greatly enhanced in the presence of inhibitor and that the effectiveness depends on some physicochemical properties of the molecule, related to its functional groups. These compounds act through the formation of a protective film on the surface of the alloy.

  19. Evaluation of alternative descriptions of PWR cladding corrosion behavior

    Energy Technology Data Exchange (ETDEWEB)

    Quecedo, M.; Serna, J. J.; Weiner, R. A.; Kersting, P. J.

    1999-05-15

    A statistical procedure has been used to evaluate several alternative descriptions of pressurized water reactor (PWR) cladding corrosion behavior, using an extensive database of Improved (low tin) Zr-4 cladding corrosion measurements from fuel irradiated in commercial PWRs. The in-reactor corrosion enhancement factors considered in the model development are based on a comprehensive review of the current literature for PWR cladding corrosion phenomenology and models. In addition, because prediction of PWR cladding corrosion behavior is very sensitive to the values used for the oxide surface temperatures, several models for the forced convection and sub-cooled nucleate boiling (SNB) coolant heat transfer under PWR conditions have also been evaluated. This evaluation determined that the choice of the forced convection heat transfer has the greatest impact on the ability to fit the data. In addition, the SNB heat transfer model used must account for a continuous transition from forced convection conditions to fully developed SNB conditions. With these choices for the heat transfer models, the evaluation determined that the significant in-reactor corrosion enhancement factors are related to the formation of a hydride rim at the cladding outer diameter, the coolant lithium concentration, and the fast neutron fluence (author) (ml)

  20. Corrosion behavior on aluminum alloy LY12 in simulated atmospheric corrosion process

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen-yao; MA Teng; HAN Wei; YU Guo-cai

    2007-01-01

    The corrosion behavior of typical high-strength aluminum alloy LY12 was studied by accelerated corrosion tests of cyclic wet-dry-immersion containing media of NaHSO3 and NaCl to simulate the corrosion process in different atmosphere environment, and the corrosion mechanism was also discussed. The main experimental techniques include mass loss, morphological check, analysis of corrosion products and electrochemical measurement. The result shows that the mass loss of LY12, with or without cladding, has linear relationship with test time in the three kinds of chemical media, 0.02 mol/L NaHSO3, 0.006 mol/L NaCl and 0.02 mol/L NaHSO3+0.006 mol/L NaCl, respectively. A layer of cladding on high-strength aluminum alloy can raise evidently the resistance of atmospheric corrosion. Cl- can promote pitting generation on the oxide film of LY12 when HOS3- exists, LY12 can react much intensely with HOS3- derived from anions.

  1. Crevice and pitting corrosion behavior of stainless steels in seawater

    Energy Technology Data Exchange (ETDEWEB)

    Zaragoza-Ayala, A.E.; Orozco-Cruz, R. [Univ. Autonoma de Campeche (Mexico). Programa de Corrosion del Golfo de Mexico

    1999-11-01

    Pitting and crevice corrosion tests in natural seawater were performed on a series of stainless steels (i.e., S31603, N08904, S32304, S31803, S32520, N08925 and S31266) in order to determine their resistance to these types of localized corrosion. Open circuit potential (OCP) measurements for these alloys show for short exposure times an ennoblement in the OCP. After a certain time, occasional fall and rise in the OCP values was observed, which can be related to nucleation and repassivation of pits and/or crevices on the metal surface. Analysis of the electrochemical behavior and microscopic observations shows that only S31603 and S32304 alloys were susceptible to crevice and pitting corrosion, whereas the remaining alloys exhibited good resistance. Pitting potentials determined by the potentiodynamic technique also show S3 1603 and S32304 are susceptible to pitting corrosion under the experimental conditions used in this work.

  2. Oxidation and Hot Corrosion Behavior of a Composite Coating System

    Institute of Scientific and Technical Information of China (English)

    Dongbai XIE; Fuhui WANG

    2003-01-01

    The oxidation and hot corrosion behavior of Co-Ni-Cr-Al-Ta-Y coating produced by magnetron sputtering with and without enamel coating has been investigated in air at 900℃ and in molten 75 wt pct NaCl+25 wt pct Na2SO4at 850℃. The results show that the enamel coating possesses good hot corrosion resistance in the molten salts, in comparison with the sputtered Co-Ni-Cr-Al-Ta-Y coating. In the hot corrosion test, breakaway corrosion did not occur on the samples with enamel coating and the composition of enamel coating did not significantly change either. The oxidation resistance of the sputtered coating, which offers good adhesion, can be improved by the enamel coating.

  3. Effect of heat treatment on corrosion behavior of duplex coatings

    Directory of Open Access Journals (Sweden)

    K. Raghu Ram Mohan Reddy

    2017-01-01

    Full Text Available In the present paper, duplex WC-Co/NiCrAlY coating is coated onto Ti6Al4V substrate and vacuum heat treatment is employed to investigate the corrosion behavior of heat treated samples as well as Ti6Al4V substrate for comparison. In this duplex coating system, High Velocity Oxy Fuel (HVOF process is used to deposit NiCrAlY interlayer with a constant thickness of 200 μm and WC-Co ceramic top layer with varying thickness of 250 μm, 350 μm and 450 μm deposited by Detonation Spray (DS process. Different heat treatment temperatures (600–1150 °C were employed for the coated samples to study the microstructure and the effect on corrosion resistance of the duplex coatings. Potentiodynamic polarization tests were carried to investigate the corrosion performance of duplex coated heat treated samples and the substrate in Ringer’s solution at 37 °C and prepared the pH to 5.7. The microstructure upon corrosion after heat treatment was characterized by SEM analysis to understand the corrosion behavior. The results disclosed that at all heat treatment temperatures, all the coated samples exhibited better corrosion resistance than the base substrate. However, during 950 °C and 1150 °C heat treatment temperatures, it was observed highest corrosion potential than 600 °C and 800 °C. The 350 μm thickness, coated sample exhibited highest corrosion resistance compared to other two coated samples and the substrate at all heat treatment temperatures.

  4. Al-MoSi2 Composite Materials: Analysis of Microstructure, Sliding Wear, Solid Particle Erosion, and Aqueous Corrosion

    Science.gov (United States)

    Gousia, V.; Tsioukis, A.; Lekatou, A.; Karantzalis, A. E.

    2016-08-01

    In this effort, AMCs reinforced with new intermetallic phases, were produced through casting and compared as far as their microstructure, sliding wear, solid particle erosion, and aqueous corrosion response. Casting was selected as a production method based on the concept: (a) ease-to-handle and low cost production route and (b) optimum homogeneity of the reinforcing phase distribution. The MoSi2 phase was produced through vacuum arc melting and the resulting drops were milled for 30 h to produce fine powder, the characteristics of which were ascertained through SEM-EDS and XRD analysis. MoSi2 was used as precursor source for the final reinforcing phase. The powder material was incorporated in molten Al1050 alloy to additions of 2, 5 and 10 vol.% respectively. Extensive reactivity between the molten Al and the MoSi2 particles was observed, leading to the formation of new reinforcing phases mainly of the Al-Mo system. In all cases, a uniform particle distribution was observed, mainly characterized by isolated intermetallic phases and few intermetallic phase clusters. Sliding wear showed a beneficial action of the reinforcing phase on the wear of the composites. Surface oxidation, plastic deformation, crack formation, and debris abrasive action were the main degradation features. The results of solid particle erosion showed that the mechanism is different as the impact angle and the vol.% change. Regarding the corrosion, the analysis revealed localized corrosion effects. The composite behavior was not altered significantly compared to that of the monolithic matrix.

  5. Corrosion characteristics of seven metals in three aqueous environments for forensic applications

    Science.gov (United States)

    Tong, Tianqi

    Corrosion characteristics of seven varieties of metals---zinc, brass C260, stainless steel 302, stainless steel 316, stainless steel 420, stainless steel 430, and stainless steel 440---in three aqueous media---Atlantic Ocean, Charles River, and deionized waters---were assessed via mass loss methods over 32 weeks, with supplemental data in the form of photomicrographic records. Concurrently, tests were conducted to determine the degree of measurement error resulting from the analytical scale used during corrosion assessment. This was accomplished by using reference samples of each type of metal and a glass vial as the container that held the metal and water samples. These error tests indicated that while the mass error associated with the metal samples was low, the error in mass associated with the vial displayed error margins two orders of magnitude larger than the error margins for the smaller metal samples. Further, control tests and statistical analysis indicated that this variation was the result of some quality inherent to the vial. The metal samples involved in the corrosion assessment experiment generally displayed corrosion characteristics in agreement with trends reported in the literature. Zinc produced the greatest quantity of corrosion residues out of all the metals studied. Brass C260 also developed visible corrosion. For example, brass C260 developed dark green/brown adherent residue and whitish blue-tinted nonadherent residue in Atlantic Ocean water, faint greenish tarnishing and some dark green spots and dots over time in Charles River water, and only faint greenish tarnish in deionized water. In contrast with zinc and brass C260, the stainless steels did not exhibit signs of significant corrosion rates excepting stainless steel 420 (SS420), which displayed pitted features surrounded by multi-colored rings on all of its Atlantic Ocean immersion samples and 25% of its Charles River immersion samples. Atlantic Ocean water generally caused the greatest

  6. Mechanical Properties and Corrosion Behavior of Low Carbon Steel Weldments

    Directory of Open Access Journals (Sweden)

    Mohamed Mahdy

    2013-01-01

    Full Text Available This research involves studying the mechanical properties and corrosion behavior of “low carbon steel” (0.077wt% C before and after welding using Arc, MIG and TIG welding. The mechanical properties include testing of microhardness, tensile strength, the results indicate that microhardness of TIG, MIG welding is more than arc welding, while tensile strength in arc welding more than TIG and MIG.The corrosion behavior of low carbon weldments was performed by potentiostat at scan rate 3mV.sec-1 in 3.5% NaCl to show the polarization resistance and calculate the corrosion rate from data of linear polarization by “Tafel extrapolation method”. The results indicate that the TIG welding increase the corrosion current density and anodic Tafel slop, while decrease the polarization resistance compared with unwelded low carbon steel. Cyclic polarization were measured to show resistance of specimens to pitting corrosion and to calculate the forward and reveres potentials. The results show shifting the forward, reverse and pitting potentials toward active direction for weldments samples compared with unwelded sample.

  7. Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels

    Institute of Scientific and Technical Information of China (English)

    Hua-bing Li; Zhou-hua Jiang; Yan Yang; Yang Cao; Zu-rui Zhang

    2009-01-01

    Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels (HNSS) were investigated by electrochemical and immersion testing methods in chloride solution, respectively. The chemical constitution and composition in the depth of passive films formed on HNSS were analyzed by X-ray photoelectron spectrum (XPS). HNSS has excellent pitting and crevice corrosion resistance compared to 316L stainless steel. With increasing the nitrogen content in steels, pitting potentials and critical pitting temperature (CPT) increase, and the maximum, average pit depths and average weight loss decrease. The CPT of HNSS is correlated with the alloying element content through the measure of alloying for resistance to corrosion (MARC). The MARC can be expressed as an equation of CPT=2.55MARC-29. XPS results show that HNSS exhibiting excellent corrosion resis-tance is attributed to the enrichment of nitrogen on the surface of passive films, which forms ammonium ions increasing the local pH value and facilitating repassivation, and the synergistic effects of molybdenum and nitrogen.

  8. Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na{sub 3}PO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Liu Song [Department of Applied Chemistry, South China University of Technology, Wushan 1, Guangzhou 510640 (China)], E-mail: chsliu@scut.edu.cn; Xu Nannan; Duan Jinmei; Zeng Zhenou [Department of Applied Chemistry, South China University of Technology, Wushan 1, Guangzhou 510640 (China); Feng Ziping; Xiao Rui [Guangzhou Institute of Energy Conversion, CAS, Guangzhou 510640 (China)

    2009-06-15

    The corrosion inhibition behavior of benzotriazole, Na{sub 3}PO{sub 4} and their mixture on carbon steel in 20 wt.% (0.628 mol l{sup -1}) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l{sup -1} BTA and 2 g l{sup -1} SP showed optimum enhanced inhibition compared with their individual effects.

  9. Influence of Aluminum Ions Implantation on Corrosion Behavior of Zircaloy-2 Alloy in 1 M H2SO4

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The specimens were implanted with aluminum ions with fluence ranging from 1×1016 to 1×1017 ions/cm2 to study the effect of aluminum ion implantation on the aqueous corrosion behavior of zircaloy-2 by metal vapor vacuum arc source (MEWA) at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Transmission electron microscopy (TEM) was used to examine the microstructure of the aluminum-implanted samples. Glancing angle X-ray diffraction (GAXRD)was employed to examine the phase transformation due to the aluminum ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircaloy-2 in a 1 M H2SO4 solution. It is found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-2 implanted with aluminum ions. Finally, the mechanism of the corrosion behavior of aluminum-implanted zircaloy-2 was discussed.

  10. CO2 Corrosion and Grooving Corrosion Behavior of the ERW Joint of the Q125 Grade Tube Steel

    Institute of Scientific and Technical Information of China (English)

    Li-dong WANG; Feng-lei LIU; Qing-yun ZHAO; Hui-bin WU

    2015-01-01

    In order to investigate the CO2 corrosion behavior and the grooving corrosion susceptibility of electric resistance welded tubes of the Q125 grade, the high temperature and high pressure autoclave was employed to conduct CO2 corrosion experiments for the welded joint. The mechanisms of grooving corrosion and the factors inlfuencing grooving corrosion susceptibility were identiifed by electrochemical measurement, microstructure observation, residual stress examination, micro-region composition and orientation analysis. The CO2 corrosion results show that the corrosion resistance of the base material is the best, followed by heat-affected zone and the welded seam is the worst. The grooving corrosion occurred in the welded seam, and the grooving corrosion susceptibility of welded seam is relativity high. The dominated reason for the grooving corrosion of the electric resistance welded jointis the notable inclusions consisting of MnS as the main content in the welded seam.The proportion of high-angle grain bound-aries in the welding zone is higher than that of base metal and the heat affected zone, which plays an important role in the corrosion behavior of the welded seam.

  11. Corrosion behaviour of galvanized steel and electroplating steel in aqueous solution: AC impedance study and XPS

    Energy Technology Data Exchange (ETDEWEB)

    Lebrini, M.; Fontaine, G. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Gengembre, L. [Unite de Catalyse et Chimie du solide UMR 8181 Bat C3, USTL, F-59655 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France)], E-mail: Michel.Traisnel@ensc-lille.fr; Lerasle, O.; Genet, N. [TOTAL France, Centre de Recherche de Solaize, Chemin du canal, BP 22, F-69360 Solaize (France)

    2008-08-30

    The efficiency of a new triazole derivative, namely, 2-{l_brace}(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl]amino{r_brace} ethanol (TTA) has been studied for corrosion inhibition of galvanized steel and electroplating steel in aqueous solution. Corrosion inhibition was studied using electrochemical impedance spectroscopy (EIS). These studies have shown that TTA was a very good inhibitor. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour of galvanized steel and electroplating steel in aqueous solution was also investigated in the presence of 4-methyl-1H-benzotriazole (TTA unsubstituted) by EIS. These studies have shown that the ability of the molecule to adsorb on the steel surface was dependent on the group in triazole ring substituent. X-ray photoelectron spectroscopy surface analysis with TTA shows that it chemisorbed on surface of galvanized steel and electroplating steel.

  12. Inhibition behavior for copper corrosion by photoelectrochemical methods

    Institute of Scientific and Technical Information of China (English)

    徐群杰; 周国定

    2003-01-01

    The application of photoelectrochemical methods in the inhibition effects for copper corrosion was described. The methods include cyclic voltammetry photocurrent measurements, intensity modulated photocurrent spectrum(IMPS) and laser-scanning photoelectrochemical microscopic method(PEM) which have been applied to the evaluation of inhibitors and inhibition behavior. The inhibition effect of BTA for copper corrosion is better than that of 4CBTA, 5CBTA, CBT-1, PTD, BT-250, CBTME and CBTBE at the same concentration. The inhibition mechanism of the derivatives of BTA with-COOH group(4CBTA, 5CBTA, CBT-1) is different from those with estergroup(CBTME, CBTBE).

  13. Sonoelectrochemical Synthesis of PPy-MWCNTs-Chitosan Nanocomposite Coatings: Characterization and Corrosion Behavior

    Science.gov (United States)

    Ashassi-Sorkhabi, Habib; Bagheri, Robabeh; Rezaei-moghadam, Babak

    2015-01-01

    This study investigated the effect of co-incorporation of a kind of nanomaterials and organic additives in a polymer matrix coating on corrosion performance of St-12 steel. We synthesized sonoelectrochemically the polypyrrole (PPy), polypyrrole/chitosan (PPy-chitosan), polypyrrole/multiwalled carbon nanotubes (PPy/MWCNTs), and polypyrrole/MWCNTs/chitosan (PPy-MWCNTs-chitosan) films on the base alloy. In-situ polymerization carried out in a solution containing 0.1 mol/L oxalic acid, 100 mg/L dodecylbenzen sulfonic acid, and 0.1 mol/L pyrrole in the absence and presence of a certain amount of MWCNTs and chitosan. The corrosion protection behavior of the synthesized coatings in 3.5% NaCl aqueous solution was studied by the evolution of the open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. The results revealed that PPy-MWCNTs-chitosan nanocomposite coating exhibits significantly better corrosion protection than others. The PPy-MWCNTs-chitosan film acts as a physical barrier against the corrosive species, because it has a very dense and more compact structure. The surface morphology was investigated by scanning electron microscopy.

  14. Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal

    Directory of Open Access Journals (Sweden)

    A. Nikitin

    2017-01-01

    Full Text Available Arc brazing has, in comparison to arc welding, the advantage of less heat input while joining galvanized sheet metals. The evaporation of zinc is reduced in the areas adjacent to the joint and improved corrosion protection is achieved. In the automotive industry, lightweight design is a key technology against the background of the weight and environment protection. Structured sheet metals have higher stiffness compared to typical automobile sheet metals and therefore they can play an important role in lightweight structures. In the present paper, three arc brazing variants of galvanized structured sheet metals were validated in terms of the corrosion behavior. The standard gas metal arc brazing, the pulsed arc brazing, and the cold metal transfer (CMT® in combination with a pulsed cycle were investigated. In experimental climate change tests, the influence of the brazing processes on the corrosion behavior of galvanized structured sheet metals was investigated. After that, the corrosion behavior of brazed structured and flat sheet metals was compared. Because of the selected lap joint, the valuation of damage between sheet metals was conducted. The pulsed CMT brazing has been derived from the results as the best brazing method for the joining process of galvanized structured sheet metals.

  15. Behavior of aspartic acid as a corrosion inhibitor for steel

    Energy Technology Data Exchange (ETDEWEB)

    Kalota, D.J.; Silverman, D.C. (Monsanto Co., St. Louis, MO (United States))

    1994-02-01

    Corrosion inhibition of steel by aspartic acid (C[sub 4]H[sub 7]NO[sub 4]), an amino acid of low molecular weight, was found to depend strongly on pH. At a pH less than the ionization constant at [approximately]9.5 to 10 (measured at 25 C), C[sub 4]H[sub 7]NO[sub 4] appeared to accelerate corrosion. Above the pH, it acted as a corrosion inhibitor for steel. A specially constructed potential-pH diagram for iron (Fe) that incorporated C[sub 4]H[sub 7]NO[sub 4] showed the change in behavior was accompanied by the most stable thermodynamic state changing from an iron aspartate complex to iron oxide. Polymerized C[sub 4]H[sub 7]NO[sub 4] (polyaspartic acid) behaved in a similar manner. Some other amino acids of low molecular weight behaved similarly.

  16. Corrosion behavior of boride layers evaluated by the EIS technique

    Energy Technology Data Exchange (ETDEWEB)

    Campos, I. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico)], E-mail: icampos@ipn.mx; Palomar-Pardave, M. [Universidad Autonoma Metropolitana-Azcapotzalco, Materials Department, Avenue San Pablo 180 Col. Reynosa Tamaulipas, Mexico D.F. 02200 (Mexico); Amador, A. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico); VillaVelazquez, C. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico); Hadad, J. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico)

    2007-09-30

    The corrosion behavior of boride layers at the AISI 304 steel surface is evaluated in the present study. Electrochemical impedance spectroscopy (EIS) technique was used for the evaluation of the polarization resistance at the steel surface, with the aid of AUTOLAB potentiostat. Samples were treated with boron paste thickness of 4 and 5 mm, in the range of temperatures 1123 {<=} T {<=} 1273 K and exposed time of 4 and 6 h. The electrochemical technique employed 10 mV AC with a frequency scan range from 8 kHz to 3 mHz in deaerated 0.1 M NaCl solution. Nyquist diagrams show that the highest values of corrosion resistance are present in the samples borided at the temperature of 1273 K, with treatment time of 4 h and 4 mm of boron paste thickness. The values of corrosion resistance on borided steels are compared with the porosity exhibited in the layers.

  17. Corrosion Behaviors of Steel A3 Exposed to Thiobacillus Ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    Jianhua LIU; Xin LIANG; Songmei LI

    2008-01-01

    The corrosion behaviors of steel A3 in synergistic action of Thiobacillus ferrooxidans (T.f) and electrochemically accelerated corrosion were studied by electrochemical, microbiology and surface analysis methods. The open circuit potential (Eocp) and electrochemical impedance spectroscopy (EIS) of the steel A3 electrodes were measured in leathen culture medium without and with T.f (simply called T.f solution in the following paper)in immersion electrode way at the time of the 2nd, 5th, 10th, 20th and 30th days, respectively. It was found that Eocp of the electrode for immersion in leathen culture medium shifted negatively with the immersion time while that for immersion in T.f solutions shifted negatively, then positively and finally negatively. On the 20th day, the corrosion of steel A3 for immersion in culture medium was in pitting initiation stage while that for immersion in T.f solutions was in pitting growth stage. It was found that the corrosion of steel A3 was accelerated by T.f. The morphology of corrosion product of steel A3 immersion in T.f solutions observed through scanning electron microscopy (SEM) transformed from solid globules to tabular plates and to spongy globules and plates.

  18. Failure behavior of protective organic coatings under corrosive conditions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xian-cheng; XU Bin-shi; WANG Hai-dou; WU Yi-xiong

    2004-01-01

    Recent research activities on the formation of micro-defects and porosity in organic coatings were reviewed. The mechanisms of aggressive ionic conduction through organic coatings were analyzed. The micro-mechanisms for the failure behavior of coatings under corrosive environments were discussed in detail. These mechanisms included blistering (i. e. osmotic blistering, anodic blistering and cathodic blistering) in the coating, wet-adhesion loss at the substrate/coating interface, cathodic delamination of coating from the substrate. Based on these researches, it was found that the failure behavior of organic coatings is closely related to the micro-defects in coatings, regardless of the failure mode. Additionally, the general failure mode of a coating system was proposed to interpret the failure behavior of organic in corrosion environments. The topics discussed can provide some insights into the development of a methodology for designing fail-safe coating systems.

  19. The evaporation behavior of sessile droplets from aqueous saline solutions.

    Science.gov (United States)

    Soulié, Virginie; Karpitschka, Stefan; Lequien, Florence; Prené, Philippe; Zemb, Thomas; Moehwald, Helmuth; Riegler, Hans

    2015-09-14

    Quantitative experiments on the evaporation from sessile droplets of aqueous saline (NaCl) solutions show a strong dependence on salt concentration and droplet shape. The experiments were performed with seven decades of initial NaCl concentrations, with various droplet sizes and with different contact angles. The evaporation rate is significantly lower for high salt concentrations and small contact angles than what is expected from the well-accepted diffusion-controlled evaporation scenario for sessile droplets, even if the change of the vapor pressure due to the salt is taken into account. Particle tracking velocimetry reveals that this modification of the evaporation behavior is caused by marangoni flows that are induced by surface tension gradients originating from the local evaporative peripheral salt enrichment. In addition it is found that already very low salt concentrations lead to a pinning of the three phase contact line. Whereas droplets with concentration ≥10(-6) M NaCl are pinned as soon as evaporation starts, droplets with lower salt concentration do evaporate in a constant contact angle mode. Aside from new, fundamental insights the findings are also relevant for a better understanding of the widespread phenomenon of corrosion initiated by sessile droplets.

  20. Corrosion

    Science.gov (United States)

    Slabaugh, W. H.

    1974-01-01

    Presents some materials for use in demonstration and experimentation of corrosion processes, including corrosion stimulation and inhibition. Indicates that basic concepts of electrochemistry, crystal structure, and kinetics can be extended to practical chemistry through corrosion explanation. (CC)

  1. Superhydrophobic copper surfaces fabricated by fatty acid soaps in aqueous solution for excellent corrosion resistance

    Science.gov (United States)

    Xu, Wenlong; Hu, Yuanyuan; Bao, Wenda; Xie, Xiaoyu; Liu, Yiran; Song, Aixin; Hao, Jingcheng

    2017-03-01

    A simple and safe one-step immersion method was developed to obtain the stable superhydrophobic copper surfaces with excellent corrosion resistance ability using fatty acids in water-medium instead of ethanol. An organic alkali, N,N-dimethylcyclohexylamine (DMCHA), was chosen to solve the poor solubility of fatty acids in water and the high Krafft point of carboxylate salts with inorganic counterions. The superhydrophobic property can be realized in a much quicker process (7.5 min) in aqueous solution than in ethanol (more than 2 d), which is universally feasible for the fabrication of superhydrophobic metal surfaces in industry scale, thereby greatly increasing the safety in industrial manufacture.

  2. Intergranular stress corrosion cracking of welded ferritic stainless steels in high temperature aqueous environments

    Energy Technology Data Exchange (ETDEWEB)

    Fukuzuka, Toshio; Shimogori, Kazutoshi; Fujiwara, Kazuo; Tomari, Haruo (Kobe Steel Ltd. (Japan). Central Research and Development Lab.); Kanda, Masao

    1982-07-01

    In considering the application of ferritic stainless steels to heat exchanger tubing materials for moisture separator-reheaters in LWRs, the effects of environmental conditions (temperature, chloride, dissolved oxygen, pH), thermal history, and steel composition (content of C, N, Cr and Ti) on the Inter-Granular Stress Corrosion Cracking (IGSCC) in high temperature aqueous environments, were studied. The IGSCC was proved to depend on steel composition and thermal history rather than environment. From these results, a steel was designed to prevent IGSCC of the welding HAZ for 18Cr and 13Cr steels.

  3. Corrosion Fatigue Behavior of 316LN SS in Acidified Sodium Chloride Solution at Applied Potential

    Science.gov (United States)

    Poonguzhali, A.; Pujar, M. G.; Mallika, C.; Mudali, U. Kamachi

    2015-05-01

    The influence of acidified 1 M NaCl solution by addition of 2 ml/L of HCl on the cyclic plastic deformation of AISI Type 316LN SS containing 0.07 wt.% and 0.22 wt.% N was investigated as a function of the applied potentials. The corrosion fatigue (CF) behavior of stainless steel (SS) was explained vis-a-vis the dislocation behavior, the propensity to form microcracks, and the evolution of the current transients based on the studies carried out at both room-temperature and boiling conditions. CF experiments were conducted using round tensile specimens at a stress ratio of 0.5 and a frequency of 0.1 Hz. Two different kinds of damage mechanisms were observed (I) the damage mechanism in the stable-passive state was correlated with the localization of the anodic dissolution due to a depassivation-repassivation process, whereas (II) the cyclic stress induced pitting corrosion in the metastable pitting state, which resulted in formation of microcracks. The study of the microcracking process and its evolution is a key to the physical mechanism by which the fatigue life of stainless steels would be affected in an aqueous corrosive solution under the applied potential.

  4. Corrosion behavior of Mg and Mg-Zn alloys in simulated body fluid

    Institute of Scientific and Technical Information of China (English)

    GAO Jia-cheng; WU Sha; QIAO Li-ying; WANG Yong

    2008-01-01

    The corrosion behavior of Mg and Mg-Zn in simulated body fluid was studied.The mass loss of pure Mg,Mg-Zn-Zr and Mg-Zn-Zr-Y in simulated body fluid was measured using photovoltaic scale meter.Corrosion rate was determined through electrochemical tests.Finally,the corrosion mechanism was tbermodynamically studied.The results show that the corrosion rate decreases with the lapse of time for both pure Mg and Mg alloys.The purer the alloy,the borer the corrosion resistance exhibits.The corrosion behavior of Mg alloy is improved by the addition of trace Y.

  5. Corrosion Behavior of Alloys in Molten Fluoride Salts

    Science.gov (United States)

    Zheng, Guiqiu

    The molten fluoride salt-cooled high-temperature nuclear reactor (FHR) has been proposed as a candidate Generation IV nuclear reactor. This reactor combines the latest nuclear technology with the use of molten fluoride salt as coolant to significantly enhance safety and efficiency. However, an important challenge in FHR development is the corrosion of structural materials in high-temperature molten fluoride salt. The structural alloys' degradation, particularly in terms of chromium depletion, and the molten salt chemistry are key factors that impact the lifetime of nuclear reactors and the development of future FHR designs. In support of materials development for the FHR, the nickel base alloy of Hastelloy N and iron-chromium base alloy 316 stainless steel are being actively considered as critical structural alloys. Enriched 27LiF-BeF2 (named as FLiBe) is a promising coolant for the FHR because of its neutronic properties and heat transfer characteristics while operating at atmospheric pressure. In this study, the corrosion behavior of Ni-5Cr and Ni-20Cr binary model alloys, and Hastelloy N and 316 stainless steel in molten FLiBe with and without graphite were investigated through various microstructural analyses. Based on the understanding of the corrosion behavior and data of above four alloys in molten FLiBe, a long-term corrosion prediction model has been developed that is applicable specifically for these four materials in FLiBe at 700ºC. The model uses Cr concentration profile C(x, t) as a function of corrosion distance in the materials and duration fundamentally derived from the Fick's diffusion laws. This model was validated with reasonable accuracy for the four alloys by fitting the calculated profiles with experimental data and can be applied to evaluate corrosion attack depth over the long-term. The critical constant of the overall diffusion coefficient (Deff) in this model can be quickly calculated from the experimental measurement of alloys' weight

  6. Effects of 1000 C oxide surfaces on room temperature aqueous corrosion and environmental embrittlement of iron aluminides

    Energy Technology Data Exchange (ETDEWEB)

    Buchanan, R.A.; Perrin, R.L. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering

    1997-12-01

    Results of electrochemical aqueous-corrosion studies at room temperature indicate that retained in-service-type high-temperature surface oxides (1000 C in air for 24 hours) on FA-129, FAL and FAL-Mo iron aluminides cause major reductions in pitting corrosion resistance in a mild acid-chloride solution designed to simulate aggressive atmospheric corrosion. Removal of the oxides by mechanical grinding restores the corrosion resistance. In a more aggressive sodium tetrathionate solution, designed to simulate an aqueous environment contaminated by sulfur-bearing combustion products, only active corrosion occurs for both the 1000 C oxide and mechanically cleaned surfaces at FAL. Results of slow-strain-rate stress-corrosion-cracking tests on FA-129, FAL and FAL-Mo at free-corrosion and hydrogen-charging potentials in the mild acid chloride solution indicate somewhat higher ductilities (on the order of 50%) for the 1000 C oxides retard the penetration of hydrogen into the metal substrates and, consequently, are beneficial in terms of improving resistance to environmental embrittlement. In the aggressive sodium tetrathionate solution, no differences are observed in the ductilities produced by the 1000 C oxide and mechanically cleaned surfaces for FAL.

  7. Influence of alkali, silicate, and sulfate content of carbonated concrete pore solution on mild steel corrosion behavior

    Energy Technology Data Exchange (ETDEWEB)

    L' Hostis, V. [CEA Saclay, DEN, DPC, SCCME, Lab Etud Comportement Betons and Argiles, F-91191 Gif Sur Yvette (France); Huet, B. [Schlumberger Riboud Prod Ctr, Schlumberger Carbon Serv, F-92142 Clamart (France); Tricheux, L. [CEBTP SOLEN, F-78990 Elancourt (France); Idrissi, H. [CNRS, Lab MATEIS UMR 5510, Equipe RI2S, Dept Sci and Genie Mat, F-69621 Villeurbanne (France)

    2010-07-01

    The increase in the rebar corrosion rate due to the concrete carbonation is the major cause of reinforced concrete degradation. The aim of this study was to investigate the corrosion behavior of mild steel rebars in simulated carbonated concrete solution. For this purpose, thermodynamic calculations, electrochemical techniques, gravimetric measurements, and surface analyses were used. Thermodynamic investigations of the nature of the interstitial solution provides an estimation of the influence of sulfate (SO{sub 4}{sup 2-}) and alkali (Na{sup +}, K{sup +}) content on carbonate alkalinity of the CO{sub 2}/H{sub 2}O open system (pCO{sub 2}=0. 3 mbar). in this system, calcium-silicate hydrates (C-S-H) remain thermodynamically unstable and amorphous silica controls silicate aqueous content at 100 ppm. Electrochemical results highlight a decrease in the corrosion rate with increasing carbonate alkalinity and the introduction of silicate. The introduction of sulfate at fixed carbonate alkalinity shows a dual effect: at high carbonate alkalinity, the corrosion rate is increased whereas at low carbonate alkalinity, corrosion rate is decreased. Those results are supported by surface analysis. Authors conclude that silicate and sulfate release from cement hydrates and fixation of alkali on carbonated hydrates are key parameters to estimate mild steel corrosion in carbonated concrete. (authors)

  8. Influence of alkali, silicate, and sulfate content of carbonated concrete pore solution on mild steel corrosion behavior

    Energy Technology Data Exchange (ETDEWEB)

    Huet, B. [Schlumberger Carbon Services, Schlumberger Riboud Product Center, Clamart (France); L' Hostis, V. [CEA, DEN, DPC, SCCME, Laboratoire d' Etude du Comportement des Betons et des Argiles, Gif-sur-Yvette, (France); Tricheux, L. [CEBTP-SOLEN, Elancourt, (France); Idrissi, H. [Laboratoire MATEIS UMR CNRS, Equipe RI2S, Department Science et Genie des Materiaux, Villeurbanne, (France)

    2010-02-15

    The increase in the rebar corrosion rate due to the concrete carbonation is the major cause of reinforced concrete degradation. The aim of this study was to investigate the corrosion behavior of mild steel rebars in simulated carbonated concrete solution. For this purpose, thermodynamic calculations, electrochemical techniques, gravimetric measurements, and surface analyses were used. Thermodynamic investigations of the nature of the interstitial solution provides an estimation of the influence of sulfate (SO{sub 4}{sup 2} {sup -}) and alkali (Na{sup +}, K{sup +}) content on carbonate alkalinity of the CO{sub 2}/H{sub 2}O open system (pCO{sub 2} = 0.3 mbar). In this system, calcium-silicate hydrates (C-S-H) remain thermodynamically unstable and amorphous silica controls silicate aqueous content at 100 ppm. Electrochemical results highlight a decrease in the corrosion rate with increasing carbonate alkalinity and the introduction of silicate. The introduction of sulfate at fixed carbonate alkalinity shows a dual effect: at high carbonate alkalinity, the corrosion rate is increased whereas at low carbonate alkalinity, corrosion rate is decreased. Those results are supported by surface analysis. Authors conclude that silicate and sulfate release from cement hydrates and fixation of alkali on carbonated hydrates are key parameters to estimate mild steel corrosion in carbonated concrete. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  9. Corrosion Behavior of Nickel Alloys in Wet Hydrofluoric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Rebak, R B

    2004-02-06

    Hydrofluoric acid is a water solution of hydrogen fluoride (HF). Hydrofluoric acid is used widely in diverse types of industrial applications; traditionally, it is used in pickling solutions in the metal industry, in the fabrication of chlorofluorocarbon compounds, as an alkylation agent for gasoline and as an etching agent in the industry of glass. In recent years, hydrofluoric acid has extensively been used in the manufacture of semiconductors and microelectronics during the wet chemical cleaning of silicon wafers. Hydrofluoric acid can be considered a reducing acid and although it is chemically classified as weaker than, for example, sulfuric or hydrochloric acids, it is extremely corrosive. This acid is also particularly toxic and poses greater health hazard than most other acids. The corrosion behavior of metals in hydrofluoric acid has not been as systematic studied in the laboratory as for other common inorganic acids. This is largely because tests using hydrofluoric acid cannot be run in standard equipment and because of the toxic nature of this acid. Moreover, short-term weight loss laboratory corrosion tests in hydrofluoric acid can be frustrating since the results are not as highly reproducible as in the case of other acids such as sulfuric or hydrochloric. One of the reasons is because hydrofluoric acid commonly attacks the coupons used for testing in a non-uniform manner. That is, the corrosive power of this acid is not aimed to uniform thinning but mostly to localized penetration below the skin of the metal in the form of thin cracks, voids, pits, trenches and sometimes intergranular attack. Figure 1 shows the cross section of a coupon of Alloy 600 (N06600) exposed for 336 h to the vapor phase of a solution of 20% HF at 93 C. In cases where internal penetration occurs such as in Figure 1, it may not be recommended to use corrosion rates based on weight loss for material selection.

  10. Growth and corrosion behavior of molybdate passivation film on hot dip galvanized steel

    Institute of Scientific and Technical Information of China (English)

    卢锦堂; 孔纲; 陈锦虹; 许乔瑜; 眭润舟

    2003-01-01

    Hot dip galvanized steel sheets were passivated by molybdate aqueous solution containing 10 g/LNa2 MoO4 @ 2H2O, and the growth behavior and corrosion resistance of the passivation film were investigated. Inthe initial stage of passivation, the mass gain of film increases with passivation time proportionally. The film growsup more quickly and is apt to cracking at grain boundaries of zinc, then the cracks spread gradually on the whole sur-face of the film, and eventually the film will flake off with the increasing of film thickness. XPS results indicate thatMo compounds are present in Mo(Ⅵ) state on the surface of the film, and Mo(Ⅵ) and Mo(Ⅳ ) states inside thefilm. NSS test shows that, the corrosion resistance of the passivation film decreases as the cracks occur, but inAASS test, the thicker the film is, the better the corrosion resistance is, the cracks of film have little effect on thecorrosion resistance.

  11. Effect of microstructure on the corrosion and deformation behavior of a newly developed 6Mn-5Cr-1.5Cu corrosion-resistant white iron

    Science.gov (United States)

    Rao, P. N. V. R. S. S. V. Prasada; Patwardhan, A. K.; Jain, N. C.

    1993-02-01

    An experimental study has been made of the effect of heat treatment on the transformation behavior of a 4.8 pct Cr white iron, alloyed with 6 pct Mn and 1.5 pct Cu, by employing optical metallography, X-ray diffractometry, and differential thermal analysis (DTA) techniques, with a view to assess the suitability of the different microstructures in resisting aqueous corrosion. The matrix microstructure in the as-cast condition, comprising pearlite + bainite/martensite, transformed to austenite on heat-treating at all the temperatures between 900 °C and 1050 °C. Increasing the soaking period at each of the heat-treating temperatures led to an increase in the volume fraction and stability of austenite. M3C was the dominant carbide present in the as-cast condition. On heat-treating, different carbides formed: M23C6 carbide was present on heat-treating at 900 °C and 950 °C; on heat-treating at 1000 °C, M7C3 formed and persisted even on heattreating at 1050 °C. The possible formation of M5C2 carbide in the as-cast and heat-treated conditions (900 °C and 950 °C) is also indicated. Dispersed carbides (DC), present in austenite up to 950 °C, mostly comprised M3C and M5C2. On stress relieving of the heat-treated samples, M7C3-type DC also formed. The hardness changes were found to be consistent with the micro-structural changes occurring on heat-treating. The as-cast state was characterized by a reasonable resistance to corrosion in 5 pct NaCl solution. On heat-treating, the corrosion resistance improved over that in the as-cast state. After 4 hours soaking, increasing the temperature from 900 °C to 1050 °C led to an improvement in corrosion resistance. However, after 10 hours soaking, corrosion resistance decreased on increasing the temperature from 900 °C to 950 °C and improved thereafter on increasing the heat-treating temperature. Deformation behavior responded to the microstructure on similar lines as the corrosion behavior. Although in an early stage of

  12. Flow-induced corrosion behavior of absorbable magnesium-based stents.

    Science.gov (United States)

    Wang, Juan; Giridharan, Venkataraman; Shanov, Vesselin; Xu, Zhigang; Collins, Boyce; White, Leon; Jang, Yongseok; Sankar, Jagannathan; Huang, Nan; Yun, Yeoheung

    2014-12-01

    The aim of this work was to study corrosion behavior of magnesium (Mg) alloys (MgZnCa plates and AZ31 stents) under varied fluid flow conditions representative of the vascular environment. Experiments revealed that fluid hydrodynamics, fluid flow velocity and shear stress play essential roles in the corrosion behavior of absorbable magnesium-based stent devices. Flow-induced shear stress (FISS) accelerates the overall corrosion (including localized, uniform, pitting and erosion corrosions) due to the increased mass transfer and mechanical force. FISS increased the average uniform corrosion rate, the localized corrosion coverage ratios and depths and the removal rate of corrosion products inside the corrosion pits. For MgZnCa plates, an increase of FISS results in an increased pitting factor but saturates at an FISS of ∼0.15Pa. For AZ31 stents, the volume loss ratio (31%) at 0.056Pa was nearly twice that (17%) at 0Pa before and after corrosion. Flow direction has a significant impact on corrosion behavior as more severe pitting and erosion corrosion was observed on the back ends of the MgZnCa plates, and the corrosion product layer facing the flow direction peeled off from the AZ31 stent struts. This study demonstrates that flow-induced corrosion needs be understood so that Mg-based stents in vascular environments can be effectively designed.

  13. Atmosphere corrosion behavior of plasma sprayed and laser remelted coatings on copper

    Institute of Scientific and Technical Information of China (English)

    Gongying Liang; T. T. Wong; Geng An; J. M. K. MacAlpine

    2006-01-01

    Nickel and chromium coatings were produced using plasma spraying and laser remelting on the copper sheet. The corrosion test was carried out in an acidic atmosphere, and the corrosive behaviors of both coatings and original copper samples were investigated by using an impedance comparison method. Experimental results show that nickel and chromium coatings display better corrosion resistance properties relative to the original pure copper sample. The corrosion rate of chromium coating is less than that of nickel coating, and corrosion resistances of laser remelted nickel and chromium samples are better thanthose of plasma sprayed samples. The corrosion deposit film of copper is loose compared with nickel and chromium.

  14. Effect of Ca2+ and Mg2+ on CO2 Corrosion Behavior of Tube Steel

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guo-xian; LI Jian-ping; HAO Shi-ming; L(U) Xiang-hong; LI He-lin

    2005-01-01

    Effects of Ca2+ and Mg2+ on the CO2 corrosion behaviors of tube steel were studied in simulated oil-fieldenvironment. The influence of Ca2+ and Mg2+ on the corrosion rate and morphologies of corrosion product layerwas determined by scanning electron microscope and measuring mass loss. Potentiodynamic polarization and im-pedance spectroscopy were used to investigate the change of electrochemical characteristic parameters of corrosionproduct layer and corrosion dynamic process. The results show that with Ca2+ and Mg2+ in electrolyte, the mor-phologies and microstructures of corrosion product layer changed obviously, thus affecting the corrosion process.

  15. Kinetics of Corrosion Process in H2SO4 and HNO3 Aqueous Solutions of Lead Free Sn-Ag-Cu Solder Alloys

    OpenAIRE

    Guśpiel J.; Wierzbicka-Miernik A.; Reczyński W.

    2016-01-01

    This paper presents the results of the corrosion resistance of Sn-Ag-Cu alloys in air-saturated aqueous solutions containing NO3-, SO42- ions, whose concentration was equivalent to their contents in acid rains and in concentrations 10 - 100 times higher. The Ag, Cu and Sn concentrations in the corrosive media were determined using the Atomic Absorption Spectrometry. The specific dissolution rate and corrosion current were derived using the a rotating disc technique. The corrosion rate of Sn- ...

  16. Comparison of corrosion behavior of ZL104 alloy at as-cast and heat treatment states

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The corrosion behavior of ZL 104 alloy at different states (as-cast and heat treatment) in salt spray corrosion (SSC) was studied. The results show that the sample treated after refinement and modification has the least corrosive resistance compared with the sample bearing as-cast structure at the beginning of the corrosion. As the corrosion process continued, however, the trend reversed itself. After 44 h continuous corrosion, the corrosive rates of all samples tend to be stable. After experiments, the sample bearing as-cast structure had the most corrosive products on the surface whereas the sample being refined and modified had the least products. The Fourier transformation infrared spectroscopy (FTIR)analyses of the corrosion products show that these products are composed of hydroxyl-containing substances.

  17. Corrosion Behavior of Au, Hastelloy C-276 Alloy and Monel 400 Alloy in Molten Lithium Fluoride

    Institute of Scientific and Technical Information of China (English)

    WANG; Chang-shui; GUO; Jun-kang

    2013-01-01

    For searching better corrosion-resistant material in high temperature,we investigated the corrosion behavior of Au,Haynes C-276 alloy and Monel 400 alloy in molten lithium fluoride at 950℃.The corrosion products and fine structures of the corroded specimens were characterized by inductively coupled plasma mass spectrometry(ICP-MS),scanning electron microscope(SEM),energy dispersive

  18. Some problems on the aqueous corrosion of structural materials in nuclear engineering; Problemes de corrosion aqueuse de materiaux de structure dans les constructions nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Coriou, H.; Grall, L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    The purpose of this report is to give a comprehensive view of some aqueous corrosion studies which have been carried out with various materials for utilization either in nuclear reactors or in irradiated fuel treatment plants. The various subjects are listed below. Austenitic Fe-Ni-Cr alloys: the behaviour of austenitic Fe-Ni-Cr alloys in nitric medium and in the presence of hexavalent chromium; the stress corrosion of austenitic alloys in alkaline media at high temperatures; the stress corrosion of austenitic Fe-Ni-Cr alloys in 650 C steam. Ferritic steels: corrosion of low alloy steels in water at 25 and 360 C; zirconium alloys; the behaviour of ultrapure zirconium in water and steam at high temperature. (authors) [French] On presente un ensemble d'etudes de corrosion en milieu aqueux effectuees sur des materiaux utilises, soit dans la construction des reacteurs soit pour la realisation des usines de traitement des combustibles irradies. Les differents sujets etudies sont les suivants. Les alliages austenitiques Fer-Nickel-Chrome: comportement d'alliages austenitiques fer-nickel-chrome en milieu nitrique en presence de chrome hexavalent; Corrosion sous contrainte d'alliages austenitiques dans les milieux alcalins a haute temperature; Corrosion sous contrainte dans la vapeur a 650 C d'alliages austenitiques fer-nickel-chrome. Les aciers ferritiques; Corrosion d'aciers faiblement allies dans l'eau a 25 et 360 C; le zirconium et ses alliages; Comportement du zirconium tres pur dans l'eau et la vapeur a haute temperature. (auteurs)

  19. STUDY ON THE EROSION-CORROSION BEHAVIOR OF STEELS AND THERMAL SPRAYED COATINGS

    Institute of Scientific and Technical Information of China (English)

    ChenHuahui; ZhaoHuiyou; ShooHesheng; ZhaoShanzhon

    1996-01-01

    16Mn steel, 1Cr18Ni9 stainless steel, thermal sprayed Al2O3-TiO2 ceramic coating and nylonl010-5%Al2O3 coating were tested with an erosion-corrosion tester.The effects of pH values and slurry velocities on the erosion-corrosion behavior of the materials tested were determined. The erosion-corrosion behavior of the materials tested changes with pH values and presents different change tendencies. The erosion-corrosion rates of the materials are increased with slurry velocities. The erosion-corrosion mechanisms for the steels and the coatings are considerably different.

  20. Notch Corrosion Fatigue Behavior of Ti-6Al-4V

    Directory of Open Access Journals (Sweden)

    Sergio Baragetti

    2014-06-01

    Full Text Available The aim of this paper is to map the corrosion fatigue characteristics of Ti-6Al-4V alloy through the evaluation of the corrosion fatigue initiation and failure mechanisms. The study included the effect of the stress concentration factor at very high Kt values and the role of different inert or corrosive environments. This alloy is widely used in naval-structures and aero-engine communities and the outcomes of the work will have direct relevance to industrial service operations. Axial fatigue tests (R = 0.1; 2 × 105 cycles; f = 10 Hz were carried out on smooth and high notched (Ktmax = 18.65 flat specimens in laboratory air, paraffin oil, laboratory air + beeswax coating, recirculated 3.5% NaCl solution. The step loading procedure was used to perform the fatigue tests and the surface replica method and crack propagation gages were used to check crack nucleation and propagation until failure. Log-Log plots of σmax vs. Kt showed a bilinear behavior and enabled the demonstration of the presence of a threshold stress intensity factor (Kt = 8–9, after which the environment has no effect on the fatigue damage for all the tested environments.

  1. Laser beam welding of Waspaloy: Characterization and corrosion behavior evaluation

    Science.gov (United States)

    Shoja Razavi, Reza

    2016-08-01

    In this work, a study on Nd:YAG laser welding of Waspaloy sheets has been made. Microstructures, phase changes and hardness of the laser joint were investigated using optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and vickers microhardness (HV0.3). Corrosion behavior of the weldment at low temperature in 3.5%wt NaCl solution at room temperature was also investigated using open circuit potential and cyclic potentiodynamic polarization tests. Hot corrosion studies were conducted on samples in the molten salt environment (Na2SO4-60%V2O5) at 900 °C for 50 h. Results indicated that the microstructure of weld zone was mainly dendritic grown epitaxially in the direction perpendicular to the weld boundary and heat transfer. Moreover, the Ti-Mo carbide particles were observed in the structure of the weld zone and base metal. The average size of carbides formed in the base metal (2.97±0.5 μm) was larger than that of the weld zone (0.95±0.2 μm). XRD patterns of the weld zone and base metal showed that the laser welding did not alter the phase structure of the weld zone, being in γ-Ni(Cr) single phase. Microhardness profile showed that the hardness values of the weld zone (210-261 HV) were lower than that of the base metal (323-330 HV). Electrochemical and hot corrosion tests indicated that the corrosion resistance of the weld metal was greater than the base metal in both room and high temperatures.

  2. Effect of copper ions implantation on the corrosion behavior of ZIRLO alloy in 1 mol/L H2SO4

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to study the effect of copper ion implantation on the aqueous corrosion behavior of ZIRLO alloy, specimens were implanted with copper ions with fluences ranging from l×l016 to 1×1017 ions/cm2, using a metal vapor vacuum arc source (MEVVA) at an extraction voltage of 40 kV.The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively.Glancing angle X-ray diffraction(GAXRD) was employed to examine the phase transformation due to the copper ion implantation.The potentiodynamic polarization technique was used to evaluate the aqueous corrosion resistance of implanted ZIRLO alloy in a l mol/L H2SO4 solution.It was found that a significant improvement was achieved in the aqueous corrosion resistance of ZIRLO alloy implanted with copper ions when the fluence is 5×1016 ions/cm2.When the fluence is l×l016 or l×l017 ions/cm2, the corrosion resistance of implanted samples was bad..Finally, the mechanism of the corrosion behavior of copper-implanted ZIRLO alloy was discussed.

  3. Corrosion behavior of Zn-Ni-Al2O3 composite coating

    Institute of Scientific and Technical Information of China (English)

    ZHENG Huanyu; AN Maozhong; LU Junfeng

    2006-01-01

    The corrosion behavior and anti-corrosion mechanism of the Zn-Ni-Al2O3 composite coating were investigated by SEM, EDS and XPS.The results indicate that the corrosion type of the Zn-Ni-Al2O3 coatings in neutral 5 wt.% NaCl solution is uniform corrosion.The presence of compact and uniformly dispersed nano alumina particles substantially inhibits the corrosion of Zn-Ni-Al2O3 composite coatings.In the initial corrosion stage, the corrosive products of Zn-Ni matrix form a compact ZnCl2·4Zn(OH)2 layer.With the development of corrosion, some nano alumina particles are embedded and form a Ni enrichment layer.In Ni enrichment layer, Ni presents as Ni and NiO.

  4. Corrosion behavior of NiCrBSi coatings deposited by HVOF spraying

    Institute of Scientific and Technical Information of China (English)

    赵卫民; 王勇; 吴开源; 薛锦

    2003-01-01

    The corrosion resistance of NiCrBSi coating deposited on steel substrate by HVOF was examined using electrochemical tests and immersion tests so as to offer an experimental basis to expand a promising applied field of HVOF in aqueous medium, comparing with those of coatings deposited by oxyacetylene flame spraying and flame cladding. The results show that the general corrosion rate of HVOF sprayed coatings is quite bigger than that of clad coatings, but it is less sensitive to local corrosion. There is less and smaller porosity in the coatings deposited by HVOF than that in flame sprayed coatings. The effects of porosity on the corrosion current density was indistinctive, but the existence of large amount of defects in the coatings damaged the cohesion of the coatings, causing the metallic particles drop off from the coatings under the influence of corrosive medium. Improving the quality and reducing the porosity of coatings is the key to get the coatings with high corrosion resistance.

  5. Corrosion Behavior of Low-Alloy Pipeline Steel Exposed to H2S/CO2-Saturated Saline Solution

    Science.gov (United States)

    Liu, Zhenguang; Gao, Xiuhua; Du, Linxiu; Li, Jianping; Li, Ping; Bai, Xiaolei; Misra, R. D. K.

    2017-02-01

    Immersion experiments were carried out to study H2S/CO2 corrosion behavior of low-alloy pipeline steel in terms of microstructure, corrosion kinetics, corrosion phases, microscopic surface morphology, cross-sectional morphology and elemental distribution. The experimental results indicated that the microstructure of designed steel was tempered martensite. The corrosion rate followed exponential behavior. H2S corrosion dominated the corrosion process, and the corrosion products were mackinawite, greigite and troilite. The corrosion products changed from mackinawite/greigite to mackinawite/troilite, and mackinawite dominated the corrosion phases. The corrosion products became more compact with immersion time, which led to decrease in corrosion rate. The chromium and molybdenum content in the corrosion product was higher than that in the steel substrate.

  6. Nitinol: Tubing versus sputtered film - microcleanliness and corrosion behavior.

    Science.gov (United States)

    Wohlschlögel, Markus; Lima de Miranda, Rodrigo; Schüßler, Andreas; Quandt, Eckhard

    2016-08-01

    Corrosion behavior and microcleanliness of medical-device grade Nitinol tubing (Nix Ti1- x , x = 0.51; outer diameter 7 mm, wall thickness 0.5 mm), drawn from various ingot qualities, are compared to the characteristics of sputtered Nitinol film material (Nix Ti1- x , x = 0.51; thickness 50 µm). Electropolished tubing half-shell samples are tested versus as-received sputtered film samples. Inclusion size distributions are assessed using quantitative metallography and corrosion behavior is investigated by potentiodynamic polarization testing in phosphate-buffered saline at body temperature. For the sputtered film samples, the surface chemistry is additionally analyzed employing Auger Electron Spectroscopy (AES) composition-depth profiling. Results show that the fraction of breakdowns in the potentiodynamic polarization test correlates with number and size of the inclusions in the material. For the sputtered Nitinol film material no inclusions were detectable by light microscopy on the one hand and no breakdowns were found in the potentiodynamic polarization test on the other hand. As for electropolished Nitinol, the sputtered Nitinol film material reveals Nickel depletion and an Oxygen-to-Titanium intensity ratio of ∼2:1 in the surface oxide layer, as measured by AES. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1176-1181, 2016.

  7. The corrosion and stress corrosion cracking behavior of a novel alumina-forming austenitic stainless steel in supercritical water

    Science.gov (United States)

    Sun, Hongying; Yang, Haijie; Wang, Man; Giron-Palomares, Benjamin; Zhou, Zhangjian; Zhang, Lefu; Zhang, Guangming

    2017-02-01

    The general corrosion and stress corrosion behavior of Fe-27Ni-15Cr-5Al-2Mo-0.4Nb alumina-forming austenitic (AFA) steel were investigated in supercritical water under different conditions. A double layer oxide structure was formed: a Fe-rich outer layer (Fe2O3 and Fe3O4) and an Al-Cr-rich inner layer. And the inner layer has a low growth rate with exposing time, which is good for improvement of corrosion resistance. Additionally, some internal nodular Al-Cr-rich oxides were also observed, which resulted in a local absence of inner layer. Stress corrosion specimens exhibited a combination of high strength, good ductility and low susceptibility. The stress strength and elongation was reduced by increasing temperature and amount of dissolved oxygen. In addition, the corresponding susceptibility was increased with decreased temperatures and increased oxygen contents.

  8. Corrosion behavior of zirconia in acidulated phosphate fluoride

    Directory of Open Access Journals (Sweden)

    Anie Thomas

    2016-02-01

    Full Text Available ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM. Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study.

  9. Corrosion-erosion resistance of Zn-Al co-cementation coatings on carbon steels in aqueous media

    Institute of Scientific and Technical Information of China (English)

    李德志; 何业东; 王德仁; 张召恩; 齐慧滨; 高唯

    2002-01-01

    A novel Zn-Al co-cementation coating was obtained by a pack cementation method. This coating possesses a two-layered structure. The outer layer is mainly composed of Fe2Al5 and FeAl intermetallics with a small amount of Zn, and the inner layer consists of Zn, Fe and a small amount of Al. The corrosion-erosion resistance of Zn-Al co-cementation coatings on carbon steel was studied by a rotary corrosion method in various NaCl and H2S containing solutions and relevant SiO2 containing media. The experimental results are compared with those of carbon steels and the sherardizing and aluminizing coatings, showing that the Zn-Al co-cementation coatings have excellent corrosion-erosion resistance in various aqueous media.

  10. Behavior of Stress Corrosion Cracking in a Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    SONG Renguo; YANG Fanger; BLAWERT Carsten; DIETZEL Wolfgang

    2009-01-01

    Slow strain rate testing (SSRT) was employed to study the stress corrosion cracking (SCC) behavior of ZE41 magnesium alloy in 0.01 M NaCl solution. Smooth tensile specimens with different thicknesses were strained dynamically in both longitudinal and transverse direction under permanent immersions at a strain rate of 10-6 s-1. It is found that ZE41 magnesium alloy is susceptible to SCC in 0.01 M NaCl solution. The SCC susceptibility of the thinner specimen is lower than that of the thicker specimen. Also, the longitudinal specimens are slightly more susceptible to SCC than the transverse specimens. The SCC mechanism of magnesium alloy is attributed to the combination of anodic dissolution with hydrogen embrittlement.

  11. Study of the corrosion behavior of magnesium alloy weldings in NaCl solutions by gravimetric tests

    Directory of Open Access Journals (Sweden)

    Segarra, José A.

    2015-09-01

    Full Text Available In this article, the corrosion behavior of commercial AZ31 welded plates in aqueous chloride media was investigated by means of gravimetric techniques and Neutral Salt Spray tests (NSS. The AZ31 samples tested were welded using Gas Tugsten Arc Welding (GTAW and different filler materials. Material microstructures were investigated by optical microscopy to stablish the influence of those microstructures in the corrosion behavior. Gravimetric and NSS tests indicate that the use of more noble filler alloys for the sample welding, preventing the reduction of aluminum content in weld beads, does not imply a better corrosion behavior.En este artículo se ha investigado el comportamiento frente a la corrosión en medios acuosos salinos de chapas soldadas de aleación AZ31 mediante técnicas gravimétricas y ensayo en cámara de niebla salina. Las muestras estudiadas han sido soldadas mediante soldadura TIG (Tungsten Inert Gas y con diferentes materiales de aporte. En el estudio se ha empleado microscopía óptica para analizar la microestructura. Los ensayos de gravimetría y los ensayos de niebla salina indican que el empleo de materiales de aporte más nobles para soldar las muestras evitando la disminución del contenido en aluminio en los cordones, no implica un mejor comportamiento frente a la corrosión.

  12. Electrochemical corrosion behavior of steam turbine materials for geothermal power plants in simulated geothermal waters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Haofeng [Shinshu Univ. (Japan). Graduate School; Niu Libin; Oishi, Shuji [Shinshu Univ. (Japan). Faculty of Engineering; Takaku, Hiroshi [Shinshu Univ. (Japan). Faculty of Engineering; Naigai Chemical Products Co. (Japan); Shiokawa, Kunio; Yamashita, Mitsuo; Sakai, Yoshihiro [Fuji Electric Advanced Technology Co., Ltd. (Japan)

    2007-08-15

    In order to evaluate the influence of chloride, sulfate and carbon dioxide in water on the electrochemical corrosion behavior of geothermal steam turbine materials, measurements of the anodic polarization and the pitting corrosion potential were conducted in simulated geothermal waters. The corrosion resistance of all materials tested was lowered by an increasing carbon dioxide content in the simulated geothermal waters. Higher chloride concentrations in the waters induced lower corrosion resistance and also lower pitting corrosion potentials for materials with higher chromium contents, suggesting the corrosion behavior was mainly controlled by the chromium content of the materials. The corrosion resistance of 9CrMoV and 13Cr steels was also influenced by the concentration of sulfate in the water. The improved heat-treated 16Cr-4Ni material for turbine blades showed excellent corrosion resistance. In the presence of sulfate, the corrosion reactions are mitigated due to a decreasing concentration of chloride (due to the presence of sulfate) in corrosion pits. (orig.)

  13. The corrosion behavior of hafnium in high-temperature-water environments

    Energy Technology Data Exchange (ETDEWEB)

    Rishel, D.M.; Smee, J.D.; Kammenzind, B.F.

    1999-10-01

    The high-temperature-water corrosion performance of hafnium is evaluated. Corrosion kinetic data are used to develop correlations that are a function of time and temperature. The evaluation is based on corrosion tests conducted in out-of-pile autoclaves and in out-of-flux locations of the Advanced Test Reactor (ATR) at temperatures ranging from 288 to 360 C. Similar to the corrosion behavior of unalloyed zirconium, the high-temperature-water corrosion response of hafnium exhibits three corrosion regimes: pretransition, posttransition, and spalling. In the pretransition regime, cubic corrosion kinetics are exhibited, whereas in the posttransition regime, linear corrosion kinetics are exhibited. Because of the scatter in the spalling regime data, it is not reasonable to use a best fit of the data to describe spalling regime corrosion. Data also show that neutron irradiation does not alter the corrosion performance of hafnium. Finally, the data illustrate that the corrosion rate of hafnium is significantly less than that of Zircaloy-2 and Zircaloy-4.

  14. Corrosion behavior of F82H exposed to high temperature pressurized water with a rotating apparatus

    Science.gov (United States)

    Kanai, A.; Kasada, R.; Nakajima, M.; Hirose, T.; Tanigawa, H.; Enoeda, M.; Konishi, S.

    2014-12-01

    The present study reports the corrosion behavior of a reduced-activation ferritic martensitic steel F82H exposed to high temperature pressurized water for 28 and 100 h using a rotating disk apparatus at rotation speeds of 500 and 1000 rpm at a temperature of 573 K under a water pressure of 15 MPa with corrosion and/or flow-accelerated corrosion of F82H under the rotating condition.

  15. Quantitative analysis of hydrogen gas formed by aqueous corrosion of metallic uranium

    Energy Technology Data Exchange (ETDEWEB)

    Fonnesbeck, J.

    2000-03-20

    Three unirradiated EBR-II blanket fuel samples containing depleted uranium metal were corrosion tested in simulated J-13 well water at 90 C. The corrosion rate of the blanket uranium metal was then determined relative to H{sub 2} formation. Corrosion of one of the samples was interrupted prior to complete oxidation of the uranium metal and the solid corrosion product was analyzed for UO{sub 2} and UH{sub 3}.

  16. The stress-corrosion behavior of Al-Li-Cu alloys: A comparison of test methods

    Science.gov (United States)

    Rizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1982-01-01

    Two powder metallurgy processed (Al-Li-Cu) alloys with and without Mg addition were studied in aqueous 3.5% NaCl solution during the alternate immersion testing of tuning fork specimens, slow crack growth tests using fracture mechanics specimens, and the slow strain rate testing of straining electrode specimens. Scanning electron microscopy and optical metallography were used to demonstrate the character of the interaction between the Al-Li-Cu alloys and the selected environment. Both alloys are susceptible to SC in an aqueous 3.5% NaCl solution under the right electrochemical and microstructural conditions. Each test method yields important information on the character of the SC behavior. Under all conditions investigated, second phase particles strung out in rows along the extrusion direction in the alloys were rapidly attacked, and played principal role in the SC process. With time, larger pits developed from these rows of smaller pits and under certain electrochemical conditions surface cracks initiated from the larger pits and contributed directly to the fracture process. Evidence to support slow crack growth was observed in both the slow strain rate tests and the sustained immersion tests of precracked fracture mechanics specimens. The possible role of H2 in the stress corrosion cracking process is suggested.

  17. Corrosion Behavior of S450EW Low-alloy Weathering Steel in Cyclically Alternate Corrosion Environments

    Institute of Scientific and Technical Information of China (English)

    Jun-shan WANG; Pei-yang SHI; Cheng-jun LIU; Mao-fa JIANG

    2015-01-01

    Weathering steel is widely used in various ifelds due to its excellent mechanical properties and high corrosion resistance. The effect of chromium content on the S450EW weathering steel in cyclic immersion test was studied. The results indicated that the corrosion resistance of S450EW weathering steel is closely related to chromium content. The addition of chromium signiif-cantly inhibited the weathering steel corrosion. The corrosion rate of experimental steel after 96 h immersion was 1.101 g·m−2·h−1. The rust of S450EW weathering steel was mainly constituted of FeOOH and Fe3O4 phase, and the elevation of chromium content promoted the formation of α-FeOOH. The ifne precipitates of the two phases contributed to the formation of dense dust layer of test steel. Furthermore, the increase of chromium is beneifcial for the cure of original defects and cracks of the rust layer via the enrich-ment of chromium. The corrosion potential and the resistance of corrosion process were thus increased, protecting the experimental steel from further corrosion. A S450EW steel with corrosion resistance more than 1.5 times of Q450NQR1 steel was prepared.

  18. Effect of microstructure on corrosion behavior of Ag-30Cu-27Sn alloy in vitro media

    Energy Technology Data Exchange (ETDEWEB)

    Salehisaki, Mehdi, E-mail: mehdisasaki@ut.ac.ir [Department of Materials Science and Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Aryana, Maryam, E-mail: maryam.aryana@yahoo.com [AGSP Engineering Company, Biomaterial Research Unit, R.N: 12786 Kerman (Iran, Islamic Republic of)

    2014-04-01

    Highlights: • High cooling rates decrease the number of Ag intermetallic particles in Cu-rich phase. • Increasing cooling rate improves corrosion behavior of Ag-30Cu-27Sn dental alloy. • Cathode/anode ratio in Cu-rich phases determines the corrosion behavior of alloy. - Abstract: In the present work, three simple heat treatment cycles were used to study the effects of microstructure on electrochemical corrosion behavior of Ag-30Cu-27Sn dental alloy. The electrochemical impedance spectroscopy (EIS) measurements and potentiodynamic polarization tests were carried out to investigate the corrosion behavior of as-cast and heat treated samples in synthetic saliva solution. The presence of intermetallic compounds were studied by X-ray diffraction method (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray detector (EDAX). The microstructural observations and electrochemical corrosion results revealed that, increasing the cooling rate improves the corrosion behavior of under investigation samples. Improvement of the corrosion behavior is attributed to reducing the area of fine distributed Ag{sub 3}Sn islands in the Cu-rich matrix which decrease the cathode/anode ratio of microgalvanic cells.

  19. Investigation of the Corrosion Behavior of Electroless Ni-P Coating in Flue Gas Condensate

    Directory of Open Access Journals (Sweden)

    Hejie Yang

    2017-01-01

    Full Text Available The corrosion behavior of Ni-P coating deposited on 3003 aluminum alloy in flue gas condensate was investigated by electrochemical approaches. The results indicated that nitrite acted as a corrosion inhibitor. The inhibiting effect of nitrite was reduced in solutions containing sulfate or nitrate. Chloride and sulfate accelerated the corrosion of Ni-P coatings greatly. This can provide important information for the researchers to develop special Ni-P coatings with high corrosion resistance in the flue gas condensate.

  20. Influence of sulfide concentration on the corrosion behavior of pure copper in synthetic seawater

    Science.gov (United States)

    Taniguchi, Naoki; Kawasaki, Manabu

    2008-09-01

    Corrosion rate and stress corrosion cracking (SCC) behavior of pure copper under anaerobic conditions were studied by immersion tests and slow strain rate tests (SSRT) in synthetic seawater containing Na 2S. The corrosion rate was increased with sulfide concentration both in simple saline solution and in bentnite-sand mixture. The results of SSRT showed that copper was susceptible to intergranular attack; selective dissolution at lower sulfide concentration (less than 0.005 M) and SCC at higher sulfide concentration (0.01 M). It was expected that if the sulfide concentration in groundwater is less than 0.001 M, pure copper is possible to exhibit superior corrosion resistance under anaerobic condition evident by very low corrosion rates and immunity to SCC. In such a low sulfide environment, copper overpack has the potential to achieve super-long lifetimes exceeding several tens of thousands years according to long-term simulations of corrosion based on diffusion of sulfide in buffer material.

  1. Effect of Sulfate Reduced Bacterium on Corrosion Behavior of 10CrMoAl Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Hua; LIANG Cheng-hao

    2007-01-01

    The effects of sulfate reduced bacterium (SRB) on the corrosion behavior of 10CrMoAl steel in seawater were studied by chemical immersion, potentiodynamic polarization, electrochemical impedance spectroscopy measurement, and scanning electron microscope techniques. The results show that the content of element sulfur in the corrosion product of 10CrMoAl steel in seawater with SRB is up to 9.23%, which is higher than that of the same in sterile seawater. X-ray diffraction demonstrates that the main corrosion product is FeS. SRB increases the corrosion rate by anodic depolarization of the metabolized sulfide product. SEM observation indicates that the corrosion product is not distributed continuously; in addition, bacilliform sulfate-reduced bacterium accumulates on the local surface of 10CrMoAl steel. Hence, SRB enhances sensitivity to the localized corrosion of 10CrMoAl steel in seawater.

  2. Corrosion Behaviors of PI 10 Steel and Chromium Coating in CO2-saturated Simulated Oilfield Brine

    Institute of Scientific and Technical Information of China (English)

    LIN Naiming; XIE Faqin; ZHOU Jun; WU Xiangqing; TIAN Wei

    2011-01-01

    The protective chromium coating was prepared on P110 steel by employing pack cementation. The corrosion behaviors of P110 steel and the obtained coating in CO2-saturated simulated oilfield brine were studied by static complete immersion tests and electrochemical measurements.The corrosion attacks of the samples were determined by mass loss, corroded surface morphologies,corrosion products, and results of electrochemical measurements. The experimental results showed that the coating was uniform, continuous and compact. The chromium coating was slightly corroded,and the mass loss and corrosion rate of the coating were far lower than those of P110 steel. Chromium coating has higher self-corroding potential and lower corrosion current density than P110 steel in accordance with the electrochemical tests results. Taken as a whole, chromizing treatment has significantly improved the corrosion resistance of P110 steel.

  3. Corrosion-wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

    Science.gov (United States)

    Fu, Li-cai; Qin, Wen; Yang, Jun; Liu, Wei-min; Zhou, Ling-ping

    2017-01-01

    The corrosion-wear behavior of a nanocrystalline Fe88Si12 alloy disc coupled with a Si3N4 ball was investigated in acid (pH 3) and alkaline (pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe88Si12 alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe88Si12 alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe88Si12 alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si3N4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe88Si12 alloy in the pH 9 aqueous solution.

  4. Evaluating the Hot Corrosion Behavior of High-Temperature Alloys for Gas Turbine Engine Components

    Science.gov (United States)

    Deodeshmukh, V. P.

    2015-11-01

    The hot corrosion behavior of high-temperature alloys is critically important for gas turbine engine components operating near the marine environments. The two test methods—Two-Zone and Burner-Rig—used to evaluate the hot corrosion performance of high-temperature alloys are illustrated by comparing the Type I hot corrosion behavior of selected high-temperature alloys. Although the ranking of the alloys is quite comparable, it is evident that the two-zone hot corrosion test is significantly more aggressive than the burner-rig test. The effect of long-term exposures and the factors that influence the hot corrosion performance of high-temperature alloys are briefly discussed.

  5. Preparation and corrosion behavior evaluation of amalgam/titania nano composite

    Directory of Open Access Journals (Sweden)

    Neda Bahremandi Tolou

    2011-01-01

    Conclusion: By adding nano particles of titania and preparing amalgam/titania nano composite as a dental amalgam, corrosion behavior and mercury release during the 2 st h after preparation could be improved.

  6. Corrosion behavior of construction materials for intermediate temperature steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Jensen, Jens Oluf

    2013-01-01

    was measured under simulated conditions (molten KH2PO4) corresponding to the proton-conducting solid acids or transition metal phosphates as electrolytes. It was shown that, unlike at temperatures below 200 °C, gold is unstable with respect to corrosion in molten KH2PO4. Platinum demonstrated high corrosion...

  7. Corrosion Behavior of Pure Cr, Ni, and Fe Exposed to Molten Salts at High Temperature

    Directory of Open Access Journals (Sweden)

    O. Sotelo-Mazón

    2014-01-01

    Full Text Available Corrosion resistance of pure Fe, Cr, and Ni materials exposed in NaVO3 molten salt at 700°C was evaluated in static air during 100 hours. The corrosion resistance was determined using potentiodynamic polarization, open circuit potential, and lineal polarization resistance. The conventional weight loss method (WLM was also used during 100 hours. The electrochemical results showed that Fe and Cr have a poor corrosion resistance, whereas pure Ni showed the best corrosion performance, which was supported by the passive layer of NiO formed on the metallic surface and the formation of Ni3V2O8 during the corrosion processes, which is a refractory compound with a higher melting point than that of NaVO3, which reduces the corrosivity of the molten salt. Also, the behavior of these materials was associated with the way in which their corresponding oxides were dissolved together with their type of corrosion attack. Through this study, it was confirmed that when materials suffer corrosion by a localized processes such as pitting, the WLM is not reliable, since a certain amount of corrosion products can be kept inside the pits. The corroded samples were analyzed through scanning electron microscopy.

  8. Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

    Institute of Scientific and Technical Information of China (English)

    LIN Bi-lan; LU Xin-ying; LI Long

    2009-01-01

    Three kinds of single layer coatings of Zn,Zn15Al,316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion.The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization,electrochemical impedance spectroscopy (EIS) and natural immersion tests.The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn,Zn15Al,Zn+316L and Zn15Al+316L coatings.The corrosion rate value of Zn15Al coated samples is negative.The corrosion products on Zn and Zn15Al coated samples are compact and firm.The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time,and the latter are more outstanding than the former.But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time.When the coatings are sealed with epoxy resin,the corrosion resistance of the coatings will be enhanced significantly.

  9. Corrosion Behavior of Welded Joints for Cargo Oil Tanks of Crude Oil Carrier

    Institute of Scientific and Technical Information of China (English)

    Jin-shan WEI; Yan-chang QI; Zhi-ling TIAN; Yun PENG

    2016-01-01

    E32 grade corrosion resistant steel was welded with welding wires with three different S contents.The mi-crostructure,mechanical properties,inclusions,and corrosion behavior of welded joint were investigated.The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environ-ment of the inner bottom plates of cargo oil tanks.The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus.The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite,ferrite side-plate and proeutectoid ferrite.The micro-structure of heat-affected zone is composed predominantly of bainite.Joint welded with low S filler wire has good me-chanical properties.S can decrease free corrosion potential and increase the corrosion tendency.The pitting initiation is oxide inclusion or sulfide-oxide inclusion complex.S can induce the formation of occluded area and promote the corrosion propagation.The chemical compositions of weld metal is similar to base metal,which can limit the galvanic corrosion between weld metal and base metal,and avoid formation of corrosion step.

  10. The effect of heat treatment and test parameters on the aqueous stress corrosion cracking of D6AC steel

    Science.gov (United States)

    Gilbreath, W. P.; Adamson, M. J.

    1974-01-01

    The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history and test technique, under sustained load in natural seawater, 3.3 percent NaCl solution, distilled water, and high humidity air was investigated. Reported investigations of D6AC were considered with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, threshold, and the extension of corrosion fatigue data to sustained load conditions. Stress history effects were found to be most important in that they controlled incubation period, initial crack growth rates, and apparent threshold.

  11. Transport and Corrosion Behavior of Cracked Reinforced Concrete

    DEFF Research Database (Denmark)

    Pease, Bradley Justin

    to enter the concrete. This is, among others, important in the corrosion of reinforcing steel. When cracks protrude to the depth of reinforcing steel, liquids containing aggressive ions (i.e. chlorides associated with salts and sea water) may rapidly access and initiate corrosion of the reinforcing...... structures. These models currently lack some of the scientific validity to fully represent actual field structures, i.e. structures containing cracks. Further understanding, therefore is needed on the effect cracks have on transport and corrosion in reinforced concrete. The fundamental mechanisms...... of transport and corrosion in cracked, reinforced concrete are not yet fully understood. The scope of this study therefore is to develop a link between concrete cracks and the relevant transport mechanism(s) under particular environmental conditions. It is envisioned that a finite element model...

  12. Erosion-Corrosion Behavior of Power Plant Pipe Caused by Hot Feed Water

    Energy Technology Data Exchange (ETDEWEB)

    Bang, Sungho; Lee, Jinwon; Kim, Taewon [Hanyang Univ., Seoul (Korea, Republic of)

    2013-06-15

    In this study, we tried to define the erosion-corrosion behavior together with the resulting effects on a pipe that is a part of a feed water circulation system according to the pipe size and hot feed water environment. An erosion corrosion analysis was performed through the Hayduk and Minas model based on the chemical reaction between iron and oxygen, an essential corrosive factor. The erosion-corrosion rate against the pipe diameter and feed water temperature was then evaluated by means of finite element analysis using Abacus. As shown in the results, the feed water temperature was the main factor influencing the erosion-corrosion rate; in particular, it was expected that the thickness of 316 stainless steel would decrease by 2.59 {mu}m every year in a hot water environment at 290 .deg. C.

  13. Effects of High Magnetic Field on Solidification and Corrosion Behaviors of Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The solidification behaviors of AZ61 magnesium alloy under a high magnetic field were studied. The corrosion property of AZ61 alloy was investigated in a solution of 3.5 mol/L NaCl by measuring electrochemical polarization. The results show that the high magnetic field can refine microstructure and benefit aluminum transfer.The crystal of α-Mg is induced to orient with their c-axis parallel to the magnetic field. The corrosion studies indicate that different crystal plane of magnesium has different corrosion property. The passivating films on the a- and b-planes have higher corrosion resistance than that on the c-plane. Aligned structure affects the corrosion property of AZ61 magnesium alloy.

  14. Corrosion behavior of 907 steel under thin electrolyte layers of artificial seawater

    Institute of Scientific and Technical Information of China (English)

    王慧萍; 丁少春; 朱娟; 张昭; 张鉴清; 曹楚南

    2015-01-01

    The corrosion behavior of 907 steel under thin electrolyte layer (TEL) has been investigated by means of cathodic polarization curve measurement, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The results show that the cathodic diffusion current density presents the variation trend of initial increase and subsequent decrease with the decrease of TEL thickness, and the maximum deposits at 58 μm. The cotangent-hyperbolic impedance (O) is rationally first introduced to study the diffusion process of the reactants through the corrosion products layer with many permeable holes. The initial corrosion rate of 907 steel under different TEL thickness increases with the decrease of TEL thickness except that of 104 μm, whereas the corrosion rate after long time corrosion can be ranked as 104μm﹥402μm﹥198μm﹥301μm﹥bulk solution.

  15. Corrosion behavior of pure aluminum in FeCl3 solution

    Institute of Scientific and Technical Information of China (English)

    QU Jun-e; GUO Xing-peng; WANG Hai-ren; HUANG Jin-ying

    2006-01-01

    The corrosion behavior of pure aluminum in FeCl3 solution was investigated mainly by in-situ AFM (Atomic Force Microscopy). The results of combined researches of AFM, SEM(Scanning Electron Microscopy) and EDAX(Energy Dispersive Analysis of X-ray) show that in addition to uniform attack, pitting corrosion takes place also on pure aluminum surface in FeCl3solution at open-circuit potential, and impurity elements Fe and Cu are found enriched in corrosion product. In-situ AFM was also used to examine the initiation and development of pitting corrosion of pure aluminum induced by potentiodynamic sweep, and the repassivation of an active pit is observed. AFM tip scratching technique was used to produce a physical defect on metal surface,which is traced by in-situ AFM and it is found that the defect is likely to be preferentially attacked and evolve to pitting corrosion.

  16. Corrosion behavior of niobium coated 304 stainless steel in acid solution

    Science.gov (United States)

    Pan, T. J.; Chen, Y.; Zhang, B.; Hu, J.; Li, C.

    2016-04-01

    The niobium coating is fabricated on the surface of AISI Type 304 stainless steel (304SS) by using a high energy micro arc alloying technique in order to improvecorrosion resistance of the steel against acidic environments. The electrochemical corrosion resistance of the niobium coating in 0.7 M sulfuric acid solutions is evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and the open circuit potential versus time. Electrochemical measurements indicate that the niobium coating increases the free corrosion potential of the substrate by 110 mV and a reduction in the corrosion rate by two orders of magnitude compared to the substrate alone. The niobium coating maintains large impedance and effectively offers good protection for the substrate during the long-term exposure tests, which is mainly ascribed to the niobium coating acting inhibiting permeation of corrosive species. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion resistance behavior of the niobium coating in acid solutions.

  17. Corrosion Behavior of Carbon Steel in Synthetically Produced Oil Field Seawater

    Directory of Open Access Journals (Sweden)

    Subir Paul

    2014-01-01

    Full Text Available The life of offshore steel structure in the oil production units is decided by the huge corrosive degradation due to SO42-, S2−, and Cl−, which normally present in the oil field seawater. Variation in pH and temperature further adds to the rate of degradation on steel. Corrosion behavior of mild steel is investigated through polarization, EIS, XRD, and optical and SEM microscopy. The effect of all 3 species is huge material degradation with FeSx and FeCl3 and their complex as corrosion products. EIS data match the model of Randle circuit with Warburg resistance. Addition of more corrosion species decreases impedance and increases capacitance values of the Randle circuit at the interface. The attack is found to be at the grain boundary as well as grain body with very prominent sulphide corrosion crack.

  18. Corrosion Behavior of Alloy 22 in Chloride Solutions Containing Organic Acids

    Energy Technology Data Exchange (ETDEWEB)

    Carranza, R M; Giordano, C M; Rodr?guez, M A; Rebak, R B

    2005-11-04

    Alloy 22 (N06022) is a nickel based alloy containing alloying elements such as chromium, molybdenum and tungsten. It is highly corrosion resistant both under reducing and under oxidizing conditions. Electrochemical studies such as electrochemical impedance spectroscopy (EIS) were performed to determine the corrosion behavior of Alloy 22 in 1M NaCl solutions at various pH values from acidic to neutral at 90 C. Tests were also carried out in NaCl solutions containing oxalic acid or acetic acid. It is shown that the corrosion rate of Alloy 22 was higher in a solution containing oxalic acid than in a solution of the same pH acidified with HCl. Acetic acid was not corrosive to Alloy 22. The corrosivity of oxalic acid was attributed to its capacity to form stable complex species with metallic cations from Alloy 22.

  19. Study on the hot corrosion behavior of a cast Ni-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.; Guo, J.T.; Zhang, J.; Yuan, C.; Zhou, L.Z.; Hu, Z.Q. [Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research

    2010-07-01

    Hot corrosion behavior of Nickel-base cast superalloy K447 in 90% Na{sub 2}SO{sub 4} + 10% NaCl melting salt at 850 C and 900 C was studied. The hot corrosion kinetic of the alloy follows parabolic rate law under the experimental conditions. The external layer is mainly Cr{sub 2}O{sub 3} scale which is protective to the alloy, the intermediate layer is the Ti-rich phase, and the internal layer is mainly the international oxides and sulfides. With increased corrosion time and temperature, the oxide scales are gradually dissolved in the molten salt and then precipitate as a thick and non-protective scale. Chlorides cause the formation of volatile species, which makes the oxide scale disintegrate and break off. The corrosion kinetics and morphology examinations tend to support the basic dissolution model for hot corrosion mechanisms. (orig.)

  20. Solid-like mechanical behaviors of ovalbumin aqueous solutions.

    Science.gov (United States)

    Ikeda, S; Nishinari, K

    2001-04-12

    Flow and dynamic mechanical properties of ovalbumin (OVA) aqueous solutions were investigated. OVA solutions exhibited relatively large zero-shear viscosity values under steady shear flow and solid-like mechanical responses against oscillating small shear strains, that is, the storage modulus was always larger than the loss modulus in the examined frequency range (0.1--100 rad s(-1)). These results suggest that dispersed OVA molecules arranged into a colloidal crystal like array stabilized by large interparticle repulsive forces. However, marked solid-like mechanical behaviors were detected even when electrostatic repulsive forces among protein molecules were virtually absent, which could not be explained solely on the basis of conventional Derjaguin--Landau--Verwey--Overbeek (DLVO) theory. Large non-DLVO repulsive forces seem to stabilize native OVA aqueous solutions.

  1. Effects of cold working on the pitting corrosion behavior s of AISI 304 stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Kee Min; Kim, Jong Soo; Kim, Young Jun; Kwon, Houk Sang [KAIST, Daejon (Korea, Republic of)

    2015-12-15

    These microstructural changes by cold working can lead improvement of mechanical properties, however from a corrosion resistant point of view, the effects of cold working on the corrosion resistance of stainless steel have been argued. Several studies has been focused on the influence of cold working on the localized corrosion resistance of stainless steels. However, the opinions about the role of cold working on the localized corrosion resistance are highly in consistence. Some studies report that the pitting potential of austenitic stainless steels decreased with cold working level, on the other hands, other studies claimed that the pitting resistance was increased by cold working. Therefore it is necessary to verify how cold working affects pitting corrosion behavior of austenitic stainless steels. In the present work, the influence of cold working on the localized corrosion of AISI 304stainless steel in the neutral chloride solution was studied based on point defect model (PDM). The fraction of deformation-induced martensite was linearly increased with cold rolling level. Through cold rolling, the pitting potential was decreased, the metastable pitting event density was significantly increased and the repassivation potential was decreased. The overall localized corrosion resistance was decreased with cold working, however cold working level increased from 30 % to 50 %, localized corrosion resistance was recovered. The accumulated cation vacancy generates a void at metal/film interface, therefore film breakdown accelerates for cold worked alloys.

  2. Sodium corrosion behavior of austenitic alloys and selective dissolution of chromium and nickel

    Science.gov (United States)

    Suzuki, T.; Mutoh, I.; Yagi, T.; Ikenaga, Y.

    1986-06-01

    The corrosion behavior of six austenitic alloys and reference Type 316 stainless steel (SS) has been examined in a flowing sodium environment at 700°C for up to about 4000 h. The alloys with a range of nickel content between ~ 15 and 43 wt% were designed and manufactured with an expectation of improved swelling resistance during fast neutron irradiation, compared to reference Type 316 SS. The corrosion loss of the alloys at zero downstream position and the concentrations of chromium, nickel and iron in the surface region were determined as a function of corrosion time. The selective dissolution of nickel and chromium played an important role in sodium corrosion of the alloys. During the initial period, accelerated corrosion took place and selective dissolution of chromium and nickel proceeded at a rapid rate. During the subsequent period, the overall corrosion rate and depletion of chromium and nickel decreased with increasing time until the corrosion rate and the surface concentrations of chromium, nickel and iron, which depended on composition of the alloys, reached the steady-state after about 2000 h. Also, the corrosion rate increased with increasing original nickel content of the alloys. Microstructural examination revealed surface attack of the alloys with higher nickel contents, in particular for the two precipitation strengthened Fe-Ni alloys. The alloys showed a trend of increasing carbon and nitrogen contents.

  3. In -Vitro: Evaluation of Corrosion Behavior of Orthodontic Stainless Steel Brackets to Salad Dressing

    Directory of Open Access Journals (Sweden)

    S.F.Hussain

    2016-11-01

    Full Text Available The objectives of this study were to investigate the corrosion behavior of conventional and self-ligating stainless steel brackets and the surface structural changes in response to salad dressing. Damon, In-Ovation,Smart clip, Discovery, OMNI and Masel brackets were all included in the study. For the control group, the brackets were placed in Petri dishes with Potassium Ferrocyanide (Fe [CN]6K4 and distilled water. Whereasas for the experimental group, the brackets were incorporated into the same reagent mixed with Oil-based - Kraft Classic French Oil and Water-based-Salad Magic, Herb and Garlic Dressing. The released ferrous ion concentrations were measured by spectrophotometer after 24 and 48 hours. Scanning electron microscope was used to analyze surface changes of the brackets. All types of brackets demonstrated signs of corrosion. Generally, self-ligating brackets were more susceptible to corrosion than the conventional ones the most extensive corrosion was seen in In-Ovation R™. Meanwhile, Masel was the most corroded brackets for conventional brackets.The oil-based salad dressing illustrated the most extensive corrosion in all brackets. Self-ligating brackets, Inovation R™ showed pitting corrosion on the wings. Smart clip showed surfaces corrosion only. The commonly ingested fluids aggravate the corrosive process, and this is related to sodium chloride content.

  4. Effect of Sulfate-reducing Bacteria on Corrosion Behavior of Mild Steel in Sea Mud

    Institute of Scientific and Technical Information of China (English)

    Xiaodong ZHAO; Jizhou DUAN; Baorong HOU; Suru WU

    2007-01-01

    Microbiologically influenced corrosion (MIC) is very severe corrosion for constructions buried under sea mud environment. Therefore it is of great importance to carry out the investigation of the corrosion behavior of marine steel in sea mud. In this paper, the effect of sulfate-reducing bacteria (SRB) on corrosion behavior of mild steel in sea mud was studied by weight loss, dual-compartment cell, electronic probe microanalysis (EPMA), transmission electron microscopy (TEM) combined with energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The results showed that corrosion rate and galvanic current were influenced by the metabolic activity of SRB. In the environment of sea mud containing SRB, the original corrosion products, ferric (oxyhydr) oxide, transformed to iron sulfide. With the excess of the dissolved H2S, the composition of the protective layer formed of FeS transformed to FeS2 or other non-stoichiometric polysulphide, which changed the state of the former layer and accelerated the corrosion process.

  5. Hot corrosion behavior of the spray-formed nickel-based superalloy

    Science.gov (United States)

    Xia, Min; Gu, Tian-Fu; Jia, Chong-Lin; Ge, Chang-Chun

    2016-12-01

    An investigation of low temperature hot corrosion is carried out on a spray-formed nickel-based superalloy FGH100 pre-coated with Na2SO4-NaCl at 700 °C for 100 h. Mass gain measurement, x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy are used to study the corrosion behavior. Results reveal that corrosion behavior follows a sequence, that is, first rapidly proceeding, then gradually slowing down, and finally forming an outer layer composed of different types of oxides and an inner layer mainly comprised of sulfides. In-depth analysis reveals that the hot corrosion of FGH100 is a combined effect of oxidation-sulfidation and transfer of oxides.

  6. Corrosion and Runoff Behavior of Carbon Steel in Simulated Acid Rain

    Institute of Scientific and Technical Information of China (English)

    Baigang AN; Xueyuan ZHANG; Enhou HAN; Honxi LI

    2004-01-01

    Under the condition of simulated rain precipitation in the laboratory, with ElS and SEM observation, the effects of pH value of simulated rain on corrosion and runoff behavior of carbon steel A3 were studied. The corrosion rate of A3 steel increased and runoff action of rain precipitation on A3 steel surface was intensified with decreasing pH value, of simulated rainwater.The runoff and corrosion traces were formed along the flowing direction of rainwater, which appeared more apparently with decreasing pH value.

  7. Effect of Nitrite Inhibitor on the Macrocell Corrosion Behavior of Reinforcing Steel

    Directory of Open Access Journals (Sweden)

    Zhonglu Cao

    2015-01-01

    Full Text Available The effect of nitrite ions on the macrocell corrosion behavior of reinforcing steel embedded in cement mortar was investigated by comparing and analyzing the macrocell corrosion current, macrocell polarization ratios, and slopes of anodic and cathodic steels. Based on the experimental results, the relationship between macrocell potential difference and macrocell current density was analyzed, and the mechanism of macrocell corrosion affected by nitrite ions was proposed. The results indicated that nitrite ions had significant impact on the macrocell polarization ratios of cathode and anode. The presence of nitrite could reduce the macrocell current by decreasing the macrocell potential difference and increasing the macrocell polarization resistance of the anode.

  8. Strength and corrosion behavior of SiC - based ceramics in hot coal combustion environments

    Energy Technology Data Exchange (ETDEWEB)

    Breder, K.; Parten, R.J. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    As part of an effort to evaluate the use of advanced ceramics in a new generation of coal-fired power plants, four SiC-based ceramics have been exposed to corrosive coal slag in a laboratory furnace and two pilot scale combustors. Initial results indicate that the laboratory experiments are valuable additions to more expensive pilot plant experiments. The results show increased corrosive attack with increased temperature, and that only slight changes in temperature may significantly alter the degree of strength degradation due to corrosive attack. The present results are part of a larger experimental matrix evaluating the behavior of ceramics in the coal combustion environment.

  9. Corrosion Behavior of Reverse-Pulse Electrodeposited Zn-Ni Alloys in Saline Environment

    Science.gov (United States)

    Boonyongmaneerat, Yuttanant; Saengkiettiyut, Kanokwan; Saenapitak, Sawalee; Sangsuk, Supin

    2014-01-01

    The study investigates the relationship of the reverse-pulse electrodeposited zinc-nickel alloy coatings' characteristics and their corrosion behaviors in a saline environment, using both anodic polarization and electrochemical impedance analysis. The introduction of anodic pulsation gives deposits of more refined grain sizes and increased nickel contents, resulting in improvement of the corrosion resistance. High anodic current densities employed in the reverse-pulse electrodeposition, however, modulate crystallographic orientations of the grains, introduce porosity to the structure, and hence adversely affect the corrosion resistance of the coating deposits.

  10. Effect of lanthanum addition on microstructure and corrosion behavior of AI-Sn-Bi anodes

    Institute of Scientific and Technical Information of China (English)

    HOU Delong; LI Defu; HAN Li; JI Lianqin

    2011-01-01

    Novel Al-Sn-Bi anodes with and without lanthanum (La) were prepared. To evaluate the corrosion properties of the anodes, constant current and dynamic loop tests were carried out to determine its efficiency and corrosion rote. Optical microscopy (OM), transmission electron microscopy (TEM) and energy spectrum analysis techniques were used to examine and analyze microstructure and corrosion behavior of the specimens. The result showed that the Al-Sn-Bi anodes with La additions revealed higher current efficiency and anticorrosion in artificial environment. Segregation phase of anodes with La additions got more homogenous than that without La additions. Its grains were fined and the amount of segregation Fe-phase was reduced.

  11. THE ELECTROCHEMICAL BEHAVIOR OF OCEANIC MICROBIOLOGICAL INFLUENCED CORROSION ON CARBON STEEL

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.

  12. RHEOLOGICAL BEHAVIOR OF ERWINIA GUM IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Li-na Zhang; Mei Zhang; Jing-hua Chen; Hideki Iijima; Hiromichi Tsuchiya

    1999-01-01

    Erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose and glucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and a rotational viscometer. Its weight-average molecular weight Mw and intrinsic viscosity [η] in 0.2 mol/L NaCl aqueous solution were measured by light scattering method at 35℃ and viscometry at 25℃ and found to be 1.06 × 106 g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gel permeation chromatography (GPC). These results indicated that E gum in water has exceedingly high viscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreased with increasing temperature, and the turning point appeared at 38℃ for dilute solution and 80℃ for concentrated solution suggesting that the aggregates of E gum in water started to disaggregate under these temperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimental results indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.

  13. Localized Corrosion Behavior of Al-Si-Mg Alloys Used for Fabrication of Aluminum Matrix Composites

    Science.gov (United States)

    Pech-Canul, M. A.; Giridharagopal, R.; Pech-Canul, M. I.; Coral-Escobar, E. E.

    2013-12-01

    The relationship between microstructure and localized corrosion behavior in neutral aerated chloride solutions was investigated with SEM/EDAX, conventional electrochemical techniques, and with scanning Kelvin probe force microscopy (SKPFM) for two custom-made alloys with Si/Mg molar ratios of 0.12 and 0.49. In this order, Al3Fe, Al3Mg2, and Mg2Si intermetallics were identified in the first alloy and Al(FeMn)Si and Mg2Si particles in the second one. Anodic polarization curves and corrosion morphology showed that the alloy with higher Si/Mg molar ratio exhibited a better corrosion performance and evidence was shown that it had a more corrosion-resistant passive film. The corrosion process for both alloys in aerated 0.1 M NaCl solutions was localized around the Fe-rich intermetallics. They acted as local cathodes and produced dissolution of the aluminum matrix surrounding such particles. Mg2Si and Al3Mg2 exhibited anodic behavior. SKPFM was successfully used to map the Volta potential distribution of main intermetallics. The localized corrosion behavior was correlated with a large Volta potential difference between the Fe-rich intermetallics and the matrix. After immersion in the chloride solution, such Volta potential difference decreased.

  14. EFFECT OF NANOCRYSTALLINE AND TWIN BOUNDARIES ON CORROSION BEHAVIOR OF 316L STAINLESS STEEL USING SMAT

    Institute of Scientific and Technical Information of China (English)

    A.Q. Lü; Y. Zhang; Y. Li; G. Liu; Q.H. Zang; C.M. Liu

    2006-01-01

    By means of surface mechanical attrition treatment (SMAT), the grain size with a diameter of about 60nm formed at about 20μm depth and numerous mechanical twins at about 50μm depth from the treated surface were synthesized in 316L stainless steel because of the different distributions of strain and strain rate along depth orientation. For instance the maximum strain rate reached103-104s-1 on the top surface. The relationship between the microstructure and the corrosion property was studied in 0. 05M H2SO4+ 0.25M Na2SO4 aqueous solution, and the results show an extreme improvement of corrosion resistance owing to the appearance of twin boundaries and the obvious reduction in corrosion resistance attributed to the presence of nanocrystaline boundaries.

  15. Electrochemical corrosion behavior of Ni-containing hypoeutectic Al-Si alloy

    Directory of Open Access Journals (Sweden)

    Abul Hossain

    2015-12-01

    Full Text Available Electrochemical corrosion characteristics of the thermally treated 2 wt % Ni-containing Al-6Si-0.5Mg alloy were studied in NaCl solutions. The corrosion behavior of thermally treated (T6 Al-6Si-0.5Mg (-2Ni alloys in 0.1 M NaCl solution was investigated by electrochemical potentiodynamic polarization technique consisting of linear polarization method using the fit of Tafel plot and electrochemical impedance spectroscopy (EIS techniques. Generally, linear polarization experiments revealed a decrease of the corrosion rate at thermal treated Al-6Si-0.5Mg-2Ni alloy. The EIS test results showed that there is no significant change in charge transfer resistance (Rct after addition of Ni to Al-6Si-0.5Mg alloy. The magnitude of the positive shift in the open circuit potential (OCP, corrosion potential (Ecorr and pitting corrosion potential (Epit increased with the addition of Ni to Al-6Si-0.5Mg alloy. The forms of corrosion in the studied Al-6Si-0.5Mg alloy (except Al-6Si-0.5Mg-2Ni alloy are pitting corrosion as obtained from the scanning electron microscopy (SEM study.

  16. Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM

    Directory of Open Access Journals (Sweden)

    Armen Kvryan

    2016-04-01

    Full Text Available The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy (SKPFM was used to map the Volta potential differences. Co-localization of SKPFM with Energy Dispersive Spectroscopy (EDS measurements enabled spatially resolved correlation of potential differences with composition and subsequent galvanic corrosion behavior. Following exposure to the aggressive solution, corrosion damage morphology was characterized to determine the mode of attack and likely initiation areas. When exposed to 0.6 M NaCl, corrosion occurred at the braze-316L interface preceded by preferential dissolution of the Cu-rich phase within the braze alloy. Braze corrosion was driven by galvanic couples between the braze alloys and stainless steel as well as between different phases within the braze microstructure. Microgalvanic corrosion between phases of the braze alloys was investigated via SKPFM to determine how corrosion of the brazed joints developed.

  17. Corrosion Behavior of Ti-6Al-4V Alloy in Different Media

    Directory of Open Access Journals (Sweden)

    Slafa I. Ibrahim

    2010-01-01

    Full Text Available In this work the corrosion behavior of Ti-6Al-4V alloy was studied by using galvanostatic measurements at room temperature in different media which includ sodium chloride (food salt, sodium tartrate (presence in jellies, margarine, and sausage casings,etc., sodium oxalate (presence in fruits, vegetables,etc., acetic acid (presence in vinegar, phosphoric acid (presence in drink, sodium carbonate (presence in 7up drink,etc., and sodium hydroxide in order to compare. Corrosion parameters were interpreted in these media which involve corrosion potential( Ecorr and corrosion current density (icorr, since the results of (Ecorr indicate that Oxalate ions are more corrosive than other materials while the results of (icorr indicate that NaCl is more corrosive than other materials. Cathodic and Anodic Tafel slopes that were used to calculate the polarization resistance (Rp to know which materials effect on Ti-6Al-4V alloy uses in dental materials and the results of (Rp were: Na2CO3 >Oxalate >H3PO4 >CH3COOH >NaOH >Tartrate >NaCl. The change in free energy (∆G and rate of corrosion in (mpy were calculated, and the results of rate indicate that increasing in the following sequences: NaCl>Tartrate >NaOH >Oxalate> CH3COOH> H3PO4> Na2CO3.

  18. Corrosion behavior of titanium wires: An in vitro study

    Directory of Open Access Journals (Sweden)

    Thakur Prasad Chaturvedi

    2012-01-01

    Results: The results showed degradation of titanium wires by electrochemical attack when they were placed in the hostile electrolytic environments provided in the experiments. Surface analysis of titanium wires showed pitting and localized attacks on the surface. Pitting corrosion was found in the titanium wires.

  19. Corrosion behavior of nickel-containing alloys in artificial sweat.

    Science.gov (United States)

    Randin, J P

    1988-07-01

    The corrosion resistance of various nickel-containing alloys was measured in artificial sweat (perspiration) using the Tafel extrapolation method. It was found that Ni, CuNi 25 (coin alloy), NiAl (colored intermetallic compounds), WC + Ni (hard metal), white gold (jewelry alloy), FN42 and Nilo Alby K (controlled expansion alloys), and NiP (electroless nickel coating) are in an active state and dissolve readily in oxygenated artificial sweat. By contrast, austenitic stainless steels, TiC + Mo2C + Ni (hard metal), NiTi (shape-memory alloy), Hastelloy X (superalloy), Phydur (precipitation hardening alloy), PdNi and SnNi (nickel-containing coatings) are in a passive state but may pit under certain conditions. Cobalt, Cr, Ti, and some of their alloys were also investigated for the purpose of comparison. Cobalt and its alloys have poor corrosion resistance except for Stellite 20. Chromium and high-chromium ferritic stainless steels have a high pitting potential but the latter are susceptible to crevice corrosion. Ti has a pitting potential greater than 3 V. Comparison between the in vitro measurements of the corrosion rate of nickel-based alloys and the clinical observation of the occurrence of contact dermatitis is discussed.

  20. Galvanic corrosion behavior of titanium implants coupled to dental alloys.

    Science.gov (United States)

    Cortada, M; Giner, L; Costa, S; Gil, F J; Rodríguez, D; Planell, J A

    2000-05-01

    The corrosion of five materials for implant suprastructures (cast-titanium, machined-titanium, gold alloy, silver-palladium alloy and chromium-nickel alloy), was investigated in vitro, the materials being galvanically coupled to a titanium implant. Various electrochemical parameters E(CORR), i(CORR) Evans diagrams, polarization resistance and Tafel slopes) were analyzed. The microstructure of the different dental materials was observed before and after corrosion processes by optical and electron microscopy. Besides, the metallic ions released in the saliva environment were quantified during the corrosion process by means of inductively coupled plasma-mass spectrometry technique (ICP-MS). The cast and machined titanium had the most passive current density at a given potential and chromium-nickel alloy had the most active critical current density values. The high gold content alloys have excellent resistance corrosion, although this decreases when the gold content is lower in the alloy. The palladium alloy had a low critical current density due to the presence of gallium in this composition but a selective dissolution of copper-rich phases was observed through energy dispersive X-ray analysis.

  1. Investigation of hexagonal boron nitride as an atomically thin corrosion passivation coating in aqueous solution

    Science.gov (United States)

    Zhang, Jing; Yang, Yingchao; Lou, Jun

    2016-09-01

    Hexagonal boron nitride (h-BN) atomic layers were utilized as a passivation coating in this study. A large-area continuous h-BN thin film was grown on nickel foil using a chemical vapor deposition method and then transferred onto sputtered copper as a corrosion passivation coating. The corrosion passivation performance in a Na2SO4 solution of bare and coated copper was investigated by electrochemical methods including cyclic voltammetry (CV), Tafel polarization and electrochemical impedance spectroscopy (EIS). CV and Tafel analysis indicate that the h-BN coating could effectively suppress the anodic dissolution of copper. The EIS fitting result suggests that defects are the dominant leakage source on h-BN films, and improved anti-corrosion performances could be achieved by further passivating these defects.

  2. A prediction method for the general corrosion behavior of Alloy 690 steam generator tube using eddy current testing

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hee-Sang; Choi, Myung Sik; Lee, Deok Hyun; Hur, Do Haeng, E-mail: dhhur@kaeri.re.kr

    2016-02-15

    Highlights: • A corrosion test for the tubes with different levels of eddy current noise was conducted. • A relationship between the corrosion rate and the eddy current noise of tubes was explored. • Corrosion rate was closely correlated to the tube noise of a rotating pancake probe. • Corrosion rate was not related to the tube noise measured using a bobbin probe. - Abstract: The purpose of this work is to develop an eddy current testing method to predict the general corrosion behavior of Alloy 690 steam generator tubes. A corrosion test was conducted for tubes with different levels of eddy current noise in simulated primary water at 330 °C, and their corrosion behavior was correlated with the tube noise measured using bobbin and rotating probes. The corrosion behavior was closely correlated with the tube noise measured using a rotating probe. However, there was no correlation between the corrosion behavior and the tube noise measured using a bobbin probe. The tube noise value measured using a rotating pancake coil probe is suggested to be a significant parameter in estimating the general corrosion behavior of tubes.

  3. Pitting and galvanic corrosion behavior of stainless steel with weld in wet-dry environment containing Cl-

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Accelerated corrosion test of stainless steel with weld was carried out to investigate the corrosion behavior under the wetdry cyclic condition in the atmosphere containing Cl-. In the surface morphology, corrosion products were analyzed by metallographic observation, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the damage to stainless steel with weld in the atmosphere containing Cl- is due to localized corrosion, especially pitting and galvanic corrosion.Weld acts as the anode, whereas matrix acts as the cathode in the corrosion process. The pitting corrosion, including the nucleation and growth of a stable pit, is promoted by the presence of wet-dry cycles, especially during the drying stage. Pits centralizing in weld are found to be grouped together like colonies, with a number of smaller pits surrounding a larger pit. The composition of the corrosion products is Fe2O3, Cr2O3, Fe3O4, NiCrO4, etc.

  4. Initial corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition was investigated.The results show that corrosion potential shifts positively and the corrosion current density decreases at low wet-dry cyclic time.Further increase of the cyclic time results in the negative movement of corrosion potential and the increase of current density.SEM observation indicates that corrosion Occurs only in αphase,βphase is inert in corrosive medium,and the corrosion of AZ91 magnesium appears in uniform characteristic.XPS analysis suggests that the corrosion product is mainly composed of oxide and hydroxide of magnesium and aluminum,and a small amount of sulfate is also contained in the film.

  5. A Revisit to the Corrosion Inhibition of Aluminum in Aqueous Alkaline Solutions by Water-Soluble Alginates and Pectates as Anionic Polyelectrolyte Inhibitors

    Directory of Open Access Journals (Sweden)

    Refat Hassan

    2013-01-01

    Full Text Available The corrosion behavior of aluminum (Al in alkaline media in presence of some natural polymer inhibitors has been reinvestigated. The inhibition action of the tested inhibitors was found to obey both Langmuir and Freundlich isotherms models. The inhibition efficiency was found to increase with increasing the inhibitors concentration and decrease with increasing the temperature, suggesting physical adsorption mechanism. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated, and a suitable corrosion mechanism consistent with the kinetic results obtained is suggested and discussed.

  6. Corrosion behavior of tempered dual-phase steel embedded in concrete

    Institute of Scientific and Technical Information of China (English)

    O(g)uzhan Kelestemur; Mustafa Aksoy; Servet Yddtz

    2009-01-01

    Dual-phase (DP) steels with different martensite contents were obtained by appropriate heat treatment of an SAE1010 structural carbon steel,which was cheap and widely used in the construction industry.The corrosion behavior of DP steels in con-crete was investigated under various tempering conditions.Intercritical annealing heat treatment was applied to the reinforcing steel to obtain DP steels with different contents of martensite.These DP steels were tempered at 200,300,and 400℃ for 45 min and then cooled to room temperature.Corrosion experiments were conducted in two stages.In the first stage,the corrosion potential of DP steels embedded in concrete was measured every day for a period of 30 d based on the ASTM C 876 standard.In the second stage,the anodic and cathodic polarization values of these steels were obtained and subsequently the corrosion currents were determined with the aid of cathodic polarization curves.It was observed that the amount of second phase had a definite effect on the corrosion behavior of the DP steel embedded in concrete.As a result of this study,it is found that the corrosion rate of the DP steel increases with an increase in the amount ofmartensite.

  7. Corrosion Behavior of Alloy 22 in Oxalic Acid and Sodium Chloride Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Day, S D; Whalen, M T; King, K J; Hust, G A; Wong, L L; Estill, J C; Rebak, R B

    2003-06-24

    Nickel based Alloy 22 (NO6022) is extensively used in aggressive industrial applications, especially due to its resistance to localized corrosion and stress corrosion cracking in high chloride environments. The purpose of this work was to characterize the anodic behavior of Alloy 22 in oxalic acid solution and to compare its behavior to sodium chloride (NaCl) solutions. Standard electrochemical tests such as polarization resistance and cyclic polarization were used. Results show that the corrosion rate of Alloy 22 in oxalic acid solutions increased rapidly as the temperature and the acid concentration increased. Extrapolation studies show that even at a concentration of 10{sup -4}M oxalic acid, the corrosion rate of Alloy 22 would be higher in oxalic acid than in 1 M NaCl solution. Alloy 22 was not susceptible to localized corrosion in oxalic acid solutions. Cyclic polarization tests in 1 M NaCl showed that Alloy 22 was susceptible to crevice corrosion at 90 C but was not susceptible at 60 C.

  8. Effect of hydrogen on the corrosion behavior of the Mg–xZn alloys

    Directory of Open Access Journals (Sweden)

    Yingwei Song

    2014-09-01

    Full Text Available Hydrogen evolution reaction is inevitable during the corrosion of Mg alloys. The effect of hydrogen on the corrosion behavior of the Mg–2Zn and Mg–5Zn alloys is investigated by charging hydrogen treatment. The surface morphologies of the samples after charging hydrogen were observed using a scanning electron microscopy (SEM and the corrosion resistance was evaluated by polarization curves. It is found that there are oxide films formed on the surface of the charged hydrogen samples. The low hydrogen evolution rate is helpful to improve the corrosion resistance of Mg alloys, while the high hydrogen evolution rate can increases the defects in the films and further deteriorates their protection ability. Also, the charging hydrogen effect is greatly associated with the microstructure of Mg substrate.

  9. Hot corrosion behavior of NiAl coatings on AISI 403 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahimian, M. [Iranian Surface Research and Engineering Centre, Isfahan (Iran, Islamic Republic of); Moradi, M.; Partovi Rad, M.; Ashrafizadeh, F. [Isfahan Univ. of Technology, Dept. of Materials Engineering, Isfahan (Iran, Islamic Republic of)

    2003-07-01

    The present paper reports the hot corrosion behavior of Nickel-aluminized coatings and Ni-Al plasma sprayed coatings on stainless steel type 403 as a substrate material. Evaluation of corrosion resistance was achieved by furnace tests on both uncoated and coated specimens. Aluminizing and plasma spraying processes were used for deposition and formation of Ni-Al intermetallic coatings on the specimens. Before aluminizing, a layer of nickel, about 40 {mu}m, was deposited on specimens by electroplating. Various techniques including SEM, EDAX, optical microscopy and micro-hardness testing were employed to investigate the coatings before and after corrosion tests. Nickel-aluminides produced by two stage; plating-aluminizing, treatment with NiAl on the surface displayed better performance in hot corrosion tests compared with plasma sprayed coatings. (author)

  10. Effect of Secondary Phase Precipitation on the Corrosion Behavior of Duplex Stainless Steels

    Directory of Open Access Journals (Sweden)

    Kai Wang Chan

    2014-07-01

    Full Text Available Duplex stainless steels (DSSs with austenitic and ferritic phases have been increasingly used for many industrial applications due to their good mechanical properties and corrosion resistance in acidic, caustic and marine environments. However, DSSs are susceptible to intergranular, pitting and stress corrosion in corrosive environments due to the formation of secondary phases. Such phases are induced in DSSs during the fabrication, improper heat treatment, welding process and prolonged exposure to high temperatures during their service lives. These include the precipitation of sigma and chi phases at 700–900 °C and spinodal decomposition of ferritic grains into Cr-rich and Cr-poor phases at 350–550 °C, respectively. This article gives the state-of the-art review on the microstructural evolution of secondary phase formation and their effects on the corrosion behavior of DSSs.

  11. The corrosion behavior of Nd2Fe14B and SmCo5 magnets.

    Science.gov (United States)

    Kitsugi, A; Okuno, O; Nakano, T; Hamanaka, H; Kuroda, T

    1992-12-01

    Rare earth magnets have corrosive problems associated with their use in prostheses in various fields including orthodontics. The purpose of this study is to investigate the corrosion behavior of an Nd2Fe14B magnet and a SmCo5 magnet in an oral environment. The relations among the attractive force changes, the released elements, the weight changes and the anodic polarization measurements of the magnets were examined under immersions in 1% NaCl, 1% lactic acid, 0.05% HCl, 0.1% Na2S and Greenwood's artificial saliva at 37 degrees C for forty-two days. The results showed that the rare earth magnets underwent high corrosive assaults and large attractive force reductions by the immersions in 1% lactic acid and 0.05% HCl. The problem of corrosion of the magnets could be overcome by sealing them within laser-welded stainless steel capsules.

  12. Corrosion Behavior of 110S Tube Steel in Environments of High H2S and CO2 Content

    Institute of Scientific and Technical Information of China (English)

    LI W en-fei; ZHOU Yan-jun; XUE Yan

    2012-01-01

    The corrosion behavior of the 110S tube steel in the environments of high H2 S and CO2 content was inves- tigated by using a high-temperature and high-pressure autoclave, and the corrosion products were characterized by scanning electron microscopy and X ray diffraction technique. The results showed that all of the corrosion products under the test conditions mainly consisted of different types of iron sulfides such as pyrrhotite of Fe0.95 S, mackinaw- ite of FeS0.9, Fe0. 985 S and FeS, and the absence of iron carbonate in the corrosion scales indicated that the corrosion process was controlled by H2S corrosion. The corrosion rate of the 110S steel decreased firstly and then increased with the rising of temperature. The minimum corrosion rate occurred at 110 ℃. When the H2 S partial pressure PH2s below 9 MPa, the corrosion rate declined with the increase of PH2s. While over 9 MPa, a higher PH2s resulted in a faster corrosion process. With the increasing of the CO2 partial pressure, the corrosion rate had an increasing trend. The morphologies of the corrosion scales had a good accordance with the corrosion rates.

  13. The effect of surface treatment and position of the dental restoration on amalgam corrosion behavior

    Energy Technology Data Exchange (ETDEWEB)

    Mortazavi, V. [Isfahan Univ. of Medical Sciences, Faculty of Dentistry, Isfahan (Iran, Islamic Republic of); Fathi, M.H. [Isfahan Univ. of Technology, Materials Engineering Dept., Isfahan (Iran, Islamic Republic of)

    2003-07-01

    The aim of this research was to evaluate the effect of surface treatment, clinical operations and the condition and position of the dental restoration on amalgam corrosion behavior. Commercial amalgam alloy namely Oralloy was selected. Twenty-one amalgam samples were prepared. After triturating and condensation, the samples were divided into three groups and each group was finished by using one of three surface clinical procedures; carving, carving-burnishing, carving-burnishing-polishing. A special cylindrical mold was used in order to simulation of the interproximal areas and proximal surfaces of the dental restorations. Stainless steel matrix band was laid on the internal mold surfaces and amalgam paste was compacted in the mold. Electrochemical potentiodynamic tests were performed at a temperature of 37{+-}1 {sup o}C in physiological solution in order to determine and compare the corrosion behavior of dental amalgam samples, as an indication of biocompatibility. The results showed statistically significant differences between the mean corrosion current density values of three different groups of dental amalgam (P<0.05). The polished group possesses the lowest and the carved group shows the highest corrosion current density. The carved group shows more corrosion resistance in compare with the sample near the matrix band as an index of the proximal surfaces of restorations. It was concluded that even a simple clinical operation could effect on dental amalgam corrosion resistance. The proximal surfaces of the class II restorations are not only susceptible to concentration cell corrosion but also possess less corrosion resistance because dentist could perform no clinical surface treatment. (author)

  14. Corrosion-Resistant High-Entropy Alloys: A Review

    Directory of Open Access Journals (Sweden)

    Yunzhu Shi

    2017-02-01

    Full Text Available Corrosion destroys more than three percent of the world’s gross domestic product. Therefore, the design of highly corrosion-resistant materials is urgently needed. By breaking the classical alloy-design philosophy, high-entropy alloys (HEAs possess unique microstructures, which are solid solutions with random arrangements of multiple elements. The particular locally-disordered chemical environment is expected to lead to unique corrosion-resistant properties. In this review, the studies of the corrosion-resistant HEAs during the last decade are summarized. The corrosion-resistant properties of HEAs in various aqueous environments and the corrosion behavior of HEA coatings are presented. The effects of environments, alloying elements, and processing methods on the corrosion resistance are analyzed in detail. Furthermore, the possible directions of future work regarding the corrosion behavior of HEAs are suggested.

  15. The Corrosion Behavior of Carburized Aluminum Using DC Plasma

    Directory of Open Access Journals (Sweden)

    Somayeh Pirizadhejrandoost

    2012-01-01

    Full Text Available Because of the outstanding properties of aluminum, it is widely used in today's advanced technological world. However, its insufficient wear resistance limits its use for commercial and industrial applications. In this study, we performed DC diode plasma carburizing of aluminum in the gas composition of CH4–H2 (20–80% and at a temperature of about 350°C for 4 and 8 hours. The corrosion properties of the untreated and plasma-carburized samples were evaluated using anodic polarization tests in 3 N HCl solution according to ASTM: G5-94. The metallurgical characteristics were then investigated using XRD and SEM. The results showed that the carburizing process improves the corrosion resistance of treated specimens at low temperature.

  16. Tensile Behavior of Alloy 718 in Hot Corrosive Environment

    Science.gov (United States)

    Mahobia, G. S.; Paulose, Neeta; Mannan, S. L.; Chattopadhyay, K.; Santhi Srinivas, N. C.; Singh, Vakil

    2013-12-01

    Nickel-iron-based alloy 718 was thermally exposed in peak-aged condition at 550 and 650 °C, from 5 to 100 h, with and without salt coatings and was tested in tension at room temperature and elevated temperatures. Standard tensile specimens were coated with three different salts (in wt.%): NaCl(100), Na2SO4 + NaCl (75/25), and Na2SO4 + NaCl + V2O5 (90/5/5). Exposure of salt-coated specimens at 550 and 650 °C revealed formation of scales and corrosion pits. Tensile deformation resulted in cracking of the surface oxide/corrosion scale. The uncoated specimens showed formation of oxide scales on the surface, without any cracking whereas the salt-coated specimens showed surface cracking and pitting at some places. However, tensile properties were not degraded due to salt coatings.

  17. Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal

    OpenAIRE

    Nikitin, A.; L. Schleuss; R. Ossenbrink; V. Michailov

    2017-01-01

    Arc brazing has, in comparison to arc welding, the advantage of less heat input while joining galvanized sheet metals. The evaporation of zinc is reduced in the areas adjacent to the joint and improved corrosion protection is achieved. In the automotive industry, lightweight design is a key technology against the background of the weight and environment protection. Structured sheet metals have higher stiffness compared to typical automobile sheet metals and therefore they can play an importan...

  18. Panel report on corrosion in energy systems

    Energy Technology Data Exchange (ETDEWEB)

    None

    1979-06-01

    Corrosion problems in high-temperature (non aqueous) energy systems, corrosion in aqueous energy systems and institutional problems inhibiting the development of corrosion science and engineering are discussed. (FS)

  19. Corrosion Behavior of Titanium Grade 7 in Fluoride-Containing NaCl Brines

    Energy Technology Data Exchange (ETDEWEB)

    Lian, T; Whalen, M T; Wong, L

    2004-10-25

    The effects of fluoride on the corrosion behavior of Titanium Grade 7 (0.12-0.25% Pd) have been investigated. Up to 0.1 mol/L fluoride was added to the NaCl brines at 95 C, and three pH values of 4, 8, and 11 were selected for studying pH dependence of fluoride effects. It was observed that fluoride significantly altered the anodic polarization behavior, at all three pH values of 4, 8, and 11. Under acidic condition fluoride caused active corrosion. The corrosion of Titanium grade 7 was increased by three orders of magnitude when a 0.1 mol/L fluoride was added to the NaCl brines at pH 4, and the Pd ennoblement effect was not observed in acidic fluoride-containing environments. The effects of fluoride were reduced significantly when pH was increased to 8 and above.

  20. Investigation of Corrosion Behavior of Bioactive Coverings on Commercially Pure Titanium and its Alloys

    Directory of Open Access Journals (Sweden)

    M.Yu. Gazizova

    2015-12-01

    Full Text Available A microporous and macroporous bioactive coatings on boimedical titanium alloys (VT1-0, VT6, Ti-6Al-7Nb were formed by a micro-arc oxidation method. The effect of the phase composition of microporous and macroporous coatings on corrosion behavior titanium and its alloys was investigated. The results show that phase composition of the coatings microporous presented only titanium oxides: anatase and rutile, at that the phase composition macroporous coatings consists of anatase, rutile and calcium phosphate compounds: tricalcium phosphate (TCP α-Ca3(PO42 and calcium deficient hydroxyapatite Ca9HPO4(PO45OH. Corrosion behavior of MAO coatings was investigated in solution 0.9 % NaCl using potentiodynamic polarization tests. The microporous coatings exhibited a more highest corrosion resistance than macroporous coatings, it is connected with containing calcium phosphate compounds in macroporous coatings.

  1. Tungstate as a synergist to phosphonate-based formulation for corrosion control of carbon steel in nearly neutral aqueous environment

    Indian Academy of Sciences (India)

    B V Appa Rao; M Venkateswara Rao; S Srinivasa Rao; B Sreedhar

    2010-07-01

    Synergistic inhibition of corrosion of carbon steel in low chloride aqueous medium using tungstate as a synergist in combination with ,-(phosphonomethyl) glycine (BPMG) and zinc ions is presented. The synergistic action of tungstate has been established through the present studies. The new ternary inhibitor formulation is effective in neutral and slightly acidic as well as slightly alkaline media. Potentiodynamic polarisation studies inferred that the formulation functions as a mixed inhibitor. Impedance studies of the metal/solution interface revealed that the surface film is highly protective. Characterisation by X-ray photoelectron spectroscopy (XPS) of the surface film formed in presence of the inhibitor revealed the presence of iron, phosphorus, nitrogen, oxygen, carbon, zinc and tungsten in the surface film. The chemical shifts in the binding energies of these elements inferred that the surface film is composed of iron oxides/hydroxides, zinc hydroxide, heteropolynuclear complex [Fe(III), Zn(II)-BPMG] and WO3. Reflection absorption FTIR spectroscopic studies also supported the presence of these compounds in the surface film. Morphological features of the metal surface studied in the absence and presence of the inhibitor by scanning electron microscopy (SEM) are also presented. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.

  2. Synchrotron-based in situ soft X-ray microscopy of Ag corrosion in aqueous chloride solution

    Science.gov (United States)

    Bozzini, B.; D'Urzo, L.; Gianoncelli, A.; Kaulich, B.; Kiskinova, M.; Prasciolu, M.; Tadjeddine, A.

    2009-09-01

    In this paper we report an in situ X-ray microscopy study of a model metal electrochemistry system, incorporating faradaic reactivity: the anodic corrosion and cathodic electrodeposition of Ag in aqueous systems. The information at sub-μm scale about morpho-chemical evolution of the electrified interface, provided by this novel electroanalytical approach fosters fundamental understanding of important issues concerning material fabrication and stability, which are crucial in developing the next generation electrochemical technologies, such as fuel cells and biosensors. The key methodology challenge faced in this pilot electrochemical experiments is combining a three-electrode configuration and wet environment, which required metal electrodes suitable for transmitting soft X-rays and a sealed cell allowing working in high vacuum. This has been solved via lithographic fabrication route fabricating 75 nm thick Ag electrodes and using Si3N4 membranes as X-ray windows and electrode support. Imaging in the STXM mode with phase contrast allowed us to monitor the corrosion morphologies and metal outgrowth features. Localised thickness variation and the build-up of reaction products of electron density different from that of the starting material have been detected with high sensitivity.

  3. Synchrotron-based in situ soft X-ray microscopy of Ag corrosion in aqueous chloride solution

    Energy Technology Data Exchange (ETDEWEB)

    Bozzini, B; D' Urzo, L [Dipartimento di Ingegneria dell' Innovazione, Universita del Salento, via Monteroni, 73100 Lecce (Italy); Gianoncelli, A; Kaulich, B; Kiskinova, M [Sincrotrone Trieste S.C.p.A., ELETTRA, s.s. 14 km 163.5 in Area Science Park, 34012 Basovizza, Trieste (Italy); Prasciolu, M [CNR-INFM TASC National Laboratory S.S.14 Km 163.5, Area Science Park, 34012 Basovizza, Trieste (Italy); Tadjeddine, A, E-mail: alessandra.gianoncelli@elettra.trieste.i [3UDIL/CNRS, BP34 91898 Orsay Cedex (France)

    2009-09-01

    In this paper we report an in situ X-ray microscopy study of a model metal electrochemistry system, incorporating faradaic reactivity: the anodic corrosion and cathodic electrodeposition of Ag in aqueous systems. The information at sub-{mu}m scale about morpho-chemical evolution of the electrified interface, provided by this novel electroanalytical approach fosters fundamental understanding of important issues concerning material fabrication and stability, which are crucial in developing the next generation electrochemical technologies, such as fuel cells and biosensors. The key methodology challenge faced in this pilot electrochemical experiments is combining a three-electrode configuration and wet environment, which required metal electrodes suitable for transmitting soft X-rays and a sealed cell allowing working in high vacuum. This has been solved via lithographic fabrication route fabricating 75 nm thick Ag electrodes and using Si{sub 3}N{sub 4} membranes as X-ray windows and electrode support. Imaging in the STXM mode with phase contrast allowed us to monitor the corrosion morphologies and metal outgrowth features. Localised thickness variation and the build-up of reaction products of electron density different from that of the starting material have been detected with high sensitivity.

  4. Effect of Heat Treatment on Corrosion Behaviors of Mg-5Y-1.5Nd Alloys

    Directory of Open Access Journals (Sweden)

    Xiumin Ma

    2016-01-01

    Full Text Available Corrosion behavior of Mg-5Y-1.5Nd alloy was investigated after heat treatment. The microstructure and precipitation were studied by scanning electron microscope (SEM and energy dispersive spectrometer (EDS. The weight loss rates of different samples were arranged as T6-24 h>T6-6 h>T6-14 h>as-cast>T4. The open circuit potential (OCP showed that T4 sample had a more positive potential than that of other samples. The potentiodynamic polarization curves showed that the T6-24 h sample had the highest corrosion current density of 245.362 μA·cm−2, whereas the T4 sample had the lowest at 52.164 μA·cm−2. The EIS results confirmed that the heat treatment reduced the corrosion resistance for Mg-5Y-1.5Nd alloy, because the precipitations acted as the cathode of electrochemical reactions to accelerate the corrosion process. The corrosion rates of different samples were mainly determined by the amount and distribution of the precipitations. The precipitations played dual roles that depended on the amount and distribution. The presence of the phase in the alloys could deteriorate the corrosion performance as it could act as an effective galvanic cathode. Otherwise, a fine and homogeneous phase appeared to be a better anticorrosion barrier.

  5. EFFECT OF CORROSION ON BOND BEHAVIOR AND BENDING STRENGTH OF REINFORCED CONCRETE BEAMS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There is growing concern for corrosion damage in reinforced concrete structures with several decades' service. Pullout tests and beam tests were carried out to study the effect of reinforcement corrosion on the bond behavior and bending strength of reinforced concrete beams. The bond strength of plain bars and concrete initially increases with increasing corrosion, then declines. The turning point depends on the cracking of the concrete cover. The bond strength of deformed bars and concrete increases with corrosion up to a certain amount, but with progressive increase in corrosion, the bond strength decreases, and the cracking of the concrete cover seems to have no effect on the bond strength. On the basis of test data, the bond strength coefficient recommended here, which, together with the bond strength of uncorroded steel bars and concrete, can be used to easily calculate the bond strength of corroded steel bars and concrete. The bond strength coefficient proposed in this paper can be used to study the bond stress-slip relationship of corroded steel bars and concrete. The bending strength of corroded reinforced concrete beams declines with increasing reinforcement corrosion. Decreased bending strength of corroded RC beam is due to reduction in steel bar cross section, reduction of yield strength of steel bar, and reduction of bond capacity between steel bar and concrete.

  6. Understanding the high temperature corrosion behavior of modified 13%Cr martensitic OCTG

    Energy Technology Data Exchange (ETDEWEB)

    Felton, P.; Schofield, M.J. [Cortest Labs., Sheffield (United Kingdom)

    1998-12-31

    Recent efforts by manufacturers of OCTG have led to the development of several new grades of modified or `supermartensitic` tubulars. The main feature of these products is improved corrosion performance at high temperatures (above 13O C), i.e. in conditions which standard 13Cr, based on type 420 chemistry, corrodes at a rate too high to permit its use. In order to study these new materials, laboratory corrosion tests have been conducted, in conditions in which the standard 13Cr (API 5CT L80) suffers severe corrosion. The H{sub 2}S partial pressure in these tests was in the range 0.01---0.1 bar (1--10 kPa). It was found that the general corrosion rate of the modified alloy was approximately one-tenth of that of the standard 13Cr, and the pitting rate was reduced by a factor of 3--4. Observation of the samples after test revealed the presence of colored interference films on the modified materials, whereas the standard 13Cr was different in having a corrosion product on its surface. This was less adherent and protective than the film on the modified martensitics. Electrochemical testing has confirmed that the corrosion behavior of the modified martensitics falls between that of the standard 13Cr (which tends to corrode generally) and that of 22Cr duplex in the same conditions (which is fully passive).

  7. The corrosion behavior of nano-meter embedded phase in Ti implanted H13 steel

    Institute of Scientific and Technical Information of China (English)

    张通和; 吴瑜光; 邓志威; 马芙蓉; 王晓妍; 梁宏; 周固; 赵渭江; 薛建明

    1999-01-01

    On the SEM micrographs of Ti implanted H13 steel, a tree-branch-like structure can be observed. Further investigation with TEM shows that the newly tormed composition is a formation of nann-meter FeTi2 phase in Ti implanted layer. The layer with a relatively high corrosion resistance has been formed in Ti implanted H13 steel with this structure.The results of electrochemical measurement show that the corrosion current density decreases obviously with an increase of ion dose. The corrosion current density in Ti implanted steel with a dose of 1.3×1018/cm2 is 8-20 times less than that of Ti implanted steel with a dose of 6×1017/cm2. The corrosion behavior of Ti implanted steel with a dose of 6×1017/cm2 could be further improved as the sample was annealed at 500℃ for 20 min and the corrosion current density decreases by 48-80 times compared to that of non-implanted samples. The corrosion trace was not observed on the annealing sample by SEM, after multi-sweep cyclic voltammetry of 40 cycles

  8. Influence of rare earth elements on corrosion behavior of Al-brass in marine water

    Institute of Scientific and Technical Information of China (English)

    LIN Gaoyong; ZHOU Yuxiong; ZENG Juhua; ZOU Yanming; LIU Jian; SUN Liping

    2011-01-01

    The corrosion behaviors of Al-brass in stagnant and flowing marine water as a function of combinative rare earths (Ce and La) addition were investigated by electrochemical techniques,X-ray diffraction (XRD) and scanning electron microscopy (SEM).It was demonstrated that RE elements could make the corrosion product layer more protective and strengthen the cohesion between the film and matrix in stagnant seawater.The electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) analysis confirmed that a duplex layer,which was mainly composed of an inner A12O3 with trace amounts of RE compounds and an outer basic chloride of copper or zinc like (Cu,Zn)2Cl(OH)3,Cu(OH)Cl and CuCl2·3Cu(OH)2 layer was formed on RE-contained Al-brass surface and that the inner layer was responsible for the good corrosion resistance of the alloy.While only a porous and non-protective corrosion product layer was formed on the Al-brass alloy without RE addition,which made small values of the corrosion resistance.Additionally,in flowing marine water with velocity about 2 m/s,pitting corrosion occurred on the M-brass surface and RE addition could availably decrease pitting sensitivity of the alloy.

  9. Preparation of Aluminum Coatings by Atmospheric Plasma Spraying and Dry-Ice Blasting and Their Corrosion Behavior

    Science.gov (United States)

    Dong, Shu-Juan; Song, Bo; Zhou, Gen-Shu; Li, Chang-Jiu; Hansz, Bernard; Liao, Han-Lin; Coddet, Christian

    2013-10-01

    Aluminum coating, as an example of spray coating material with low hardness, was deposited by atmospheric plasma spraying while dry-ice blasting was applied during the deposition process. The deposited coatings were characterized in terms of microstructure, porosity, phase composition, and the valence states. The results show that the APS aluminum coatings with dry-ice blasting present a porosity of 0.35 ± 0.02%, which is comparable to the bulk material formed by the mechanical compaction. In addition, no evident oxide has been detected, except for the very thin and impervious oxide layer at the outermost layer. Compared to plasma-sprayed Al coatings without dry-ice blasting, the adhesion increased by 52% for Al substrate using dry-ice blasting, while 25% for steel substrate. Corrosion behavior of coated samples was evaluated in 3.5 wt.% NaCl aqueous using electrochemistry measurements. The electrochemical results indicated that APS Al coating with dry-ice blasting was more resistant to pitting corrosion than the conventional plasma-sprayed Al coating.

  10. Different immersion periods and aqueous solutions effects upon the corrosion resistance of zinc and aluminium specimens

    Directory of Open Access Journals (Sweden)

    Osório, W. R.

    2005-12-01

    Full Text Available Several metallic materials form spontaneously an oxide film at the surface when is exposed in a corrosive environment. It is well known that the type of corrosive media may develop different results at the material corrosion resistance. The aim of the present paper is to investigate the influence of immersion periods and different solutions upon the corrosion resistance of pure Zn and Al specimens presenting different grain morphologies. The specimens were monitored for several periods in a 3 % NaCl solution at room temperature. Tests were also performed with variations of the 3 % NaCl solution modified by additions of acid and alkaline components. Both the electrochemical impedance spectroscopy (EIS and polarization methods were applied.

    Algunos materiales metálicos, cuando se encuentran en un entorno corrosivo, forman espontáneamente una película de óxido en su superficie. Se sabe que los medios corrosivos pueden dar resultados diferentes, según sea la resistencia a la corrosión del material. El propósito del siguiente trabajo es investigar la influencia de los períodos de inmersión en diferentes soluciones sobre la resistencia a la corrosión de probetas de cinc y aluminio puros, con morfologías de grano diferentes. Las probetas fueron ensayadas durante varios períodos de tiempo en soluciones de NaCl 3 % y también con adiciones de ácidos y bases. Se utilizaron las técnicas de espectrometría de impedancia electroquímica (EIS y de polarización.

  11. Corrosion behavior of magnetic refrigeration material La-Fe-Co-Si in distilled water

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Min, E-mail: zhmn9459@gmail.com [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 XueYuan Road, Haidian District, Beijing 100083 (China); Long Yi; Ye Rongchang; Chang Yongqin [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 XueYuan Road, Haidian District, Beijing 100083 (China)

    2011-02-24

    Research highlights: > In this paper, we study the corrosion behavior of La(Fe{sub 0.94}Co{sub 0.06}){sub 11.7}Si{sub 1.3} compound in distilled water and report an unexpected discovery that corrosion occurs at matrix phase rather than rare earth rich phase, which is different from other rare earth materials. The corrosion has decreased the maximum magnetic entropy change of the compound. - Abstract: The corrosion behavior of magnetic refrigeration material La(Fe{sub 0.94}Co{sub 0.06}){sub 11.7}Si{sub 1.3} in distilled water has been studied using X-ray diffraction analysis, weight loss method, scanning electron microscopy and X-ray photoelectron spectroscopy. Results show that La(Fe{sub 0.94}Co{sub 0.06}){sub 11.7}Si{sub 1.3} compound suffers electrochemical preferential corrosion in distilled water. La(Fe{sub 0.94}Co{sub 0.06}){sub 11.7}Si{sub 1.3} compound contains three phases which are matrix phase, a small amount of {alpha}-Fe phase and La-rich phase. The matrix phase with NaZn{sub 13} structure works as anode to be corroded. The final corrosion products on sample surface are La{sub 2}O{sub 3}, {gamma}-Fe(OOH), Co(OH){sub 2} and H{sub 2}SiO{sub 3}, respectively. Corrosion has decreased the maximum magnetic entropy change of the compound.

  12. Corrosion of used nuclear fuel in aqueous perchlorate and carbonate solutions

    Science.gov (United States)

    Shoesmith, D. W.; Sunder, S.; Bailey, M. G.; Miller, N. H.

    1996-01-01

    The corrosion of used fuel was investigated using electrodes constructed from fuel pins discharged from the Pickering, Bruce and Darlington CANDU reactors, and compared to the corrosion behaviour observed on unirradiated UO 2 and SIMFUEL. Experiments were carried out in solutions of NaClO 4 (pH˜ 9.5) in the presence and absence of (a) substantial concentrations of sodium carbonate, and (b) additional external gamma fields. Used fuel electrodes reached oxidizing corrosion potentials ( ECORR) rapidly compared with unirradiated UO 2 electrodes. However, optical and SEM examinations showed no evidence for rapid oxidative dissolution. This reaction, expected to be fast since high values of ECORR are observed, appears to be blocked by the accumulation of secondary phases in grain boundaries. The oxidation and dissolution behaviour of used fuel is determined predominantly by (i) the dose rate in solution near the fuel surface, (ii) the extent of burnup (which determines the degree of fission product doping), and (iii) the degree of non-stoichiometry.

  13. Impact of high dose Kr+ ion irradiation on the corrosion behavior and microstructure of Zircaloy-4

    Institute of Scientific and Technical Information of China (English)

    Qian Wan; Xinde Bai; Xiaoyang Liu

    2005-01-01

    In order to investigate the ion irradiation effect on the corrosion behavior and microstructure of Zircaloy-4, the Zircaloy-4 film were prepared by electron beam deposition on the Zircaloy-4 specimen surface and irradiated by Kr ions using an accelerator at an energy of 300 keV with the dose from 1×1015 to 3×1016ions/cm2. The post-irradiation corrosion tests were conducted to rank the corrosion resistance of the resulting specimens by potentiodynamic polarization curve measurements in a 0.5 mol/L H2SO4 water solution at room temperature. Transmission electron microscopy (TEM) was employed to examine the microstructural change in the surface. The potentiodynamic tests show that with the irradiation dose increasing, the passive current density, closely related to the surface corrosion resistance, decreases firstly and increases subsequently. The mechanism of the corrosion behavior transformation is due to the amorphous phase formation firstly and the amorphous phase destruction and the polycrystalline structure formation in the irradiated surface subsequently.

  14. Properties, weldability and corrosion behavior of supermartensitic stainless steels for on- and offshore applications

    Energy Technology Data Exchange (ETDEWEB)

    Taban, Emel; Kaluc, Erdinc; Ojo, Olatunji Oladimeji [Kocaeli Univ. (Turkey). Welding Research, Education and Training Center

    2016-08-01

    Stimulated material-environment interactions inside and around flowlines of deep or ultra deep wells during oil and gas exploration, and fabrication economy of pipelines have been the major challenges facing the oil and gas industries. Presumably, an extensive focus on high integrity, performance and material economy of flowlines have realistically made supermartensitic stainless steels (SMSS) efficient and effective material choices for fabricating onshore and offshore pipelines. Supermartensitic stainless steels exhibit high strength, good low temperature toughness, sufficient corrosion resistance in sweet and mildly sour environments, and good quality weldability with both conventional welding processes and modern welding methods such as laser beam welding, electron beam welding and hybrid welding approaches. In terms of economy, supermartensitic stainless steels are cheaper and they are major replacements for more expensive duplex stainless steels required for tubing applications in the oil and gas industry. However, weld areas of SMSS pipes are exposed to sulphide stress cracking (SSC), so intergranular stress corrosion cracking (IGSCC) or stress corrosion cracking can occur. In order to circumvent this risk of cracking, a post-weld heat treatment (PWHT) for 5 minutes at about 650 C is recommended. This paper provides detailed literature perusal on supermartensitic stainless steels, their weldability and corrosion behaviors. It also highlights a major research area that has not been thoroughly expounded in literature; fatigue loading behaviors of welded SMSS under different corrosive environments have not been thoroughly detailed in literature.

  15. Electrochemical corrosion behavior of AZ91D alloy in ethylene glycol

    Energy Technology Data Exchange (ETDEWEB)

    Fekry, A.M. [Chemistry Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)], E-mail: hham4@hotmail.com; Fatayerji, M.Z. [Chemistry Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2009-11-01

    The effect of concentration on the corrosion behavior of Mg-based alloy AZ91D was investigated in ethylene glycol-water solutions using electrochemical techniques i.e. potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. This can provide a basis for developing new coolants for magnesium alloy engine blocks. Corrosion behavior of AZ91D alloy by coolant is important in the automotive industry. It was found that the corrosion rate of AZ91D alloy decreased with increasing concentration of ethylene glycol. For AZ91D alloy in chloride >0.05 M or fluoride <0.05 M containing 30% ethylene glycol solution, they are more corrosive than the blank (30% ethylene glycol-70% water). However, at concentrations <0.05 for chloride or >0.05 M for fluoride containing ethylene glycol solution, some inhibition effect has been observed. The corrosion of AZ91D alloy in the blank can be effectively inhibited by addition of 0.05 mM paracetamol that reacts with AZ91D alloy and forms a protective film on the surface at this concentration as confirmed by surface examination.

  16. Influence of the casting processing route on the corrosion behavior of dental alloys.

    Science.gov (United States)

    Galo, Rodrigo; Rocha, Luis Augusto; Faria, Adriana Claudia; Silveira, Renata Rodrigues; Ribeiro, Ricardo Faria; de Mattos, Maria da Gloria Chiarello

    2014-12-01

    Casting in the presence of oxygen may result in an improvement of the corrosion performance of most alloys. However, the effect of corrosion on the casting without oxygen for dental materials remains unknown. The aim of this study was to investigate the influence of the casting technique and atmosphere (argon or oxygen) on the corrosion behavior response of six different dental casting alloys. The corrosion behavior was evaluated by electrochemical measurements performed in artificial saliva for the different alloys cast in two different conditions: arc melting in argon and oxygen-gas flame centrifugal casting. A slight decrease in open-circuit potential for most alloys was observed during immersion, meaning that the corrosion tendency of the materials increases due to the contact with the solution. Exceptions were the Co-based alloys prepared by plasma, and the Co-Cr-Mo and Ni-Cr-4Ti alloys processed by oxidized flame, in which an increase in potential was observed. The amount of metallic ions released into the artificial saliva solution during immersion was similar for all specimens. Considering the pitting potential, a parameter of high importance when considering the fluctuating conditions of the oral environment, Co-based alloys show the best performance in comparison with the Ni-based alloys, independent of the processing route.

  17. INFLUENCE OF SO2-4 AND Cl- ON THE CORROSION BEHAVIOR OF COPPER TUBE IN AIR-CONDITIONING SYSTEM

    Institute of Scientific and Technical Information of China (English)

    C.S. Wu; Z. Zhang; F.H. Cao; J.Q. Zhang; J.M. Wang; C.N. Cao

    2004-01-01

    The influence of chloride or sulphur dioxide on the corrosion behavior of copper tube in the air-conditioning system was studied using scanning electron microscope (SEM),energy dispersion spectrometer (EDS) and cyclic polarization techniques. The results showed that the corrosion of copper tube are mainly caused by the SO2-4- and Cl- ions in the circulating water, and the former is mainly responsible for the general corrosion of the copper tube whilst the latter for the pitting corrosion. The different influences of SO2-4- and Cl- ions on the corrosion type of copper tube may be attributed to that the radius of SO2-4- ion is much larger than that of Cl- ion. Meanwhile the results also indicated that SO2-4- inhibits the pitting corrosion caused by Cl- and Cl- inhibits the general corrosion initiated by SO2-4- due to their competitive adsorption on the copper matrix.

  18. Corrosion and wear behaviors of Al-bronzes in 5.0% H2SO4 solution

    Institute of Scientific and Technical Information of China (English)

    LI Wen-sheng; WANG Zhi-ping; LU Yang; YUAN Li-hua; XIAO Rong-zhen; ZHAO Xu-dong

    2009-01-01

    Steady-state corrosion and wear behaviors of two Al-bronzes, Cu-14Al-X and QAl9-4, in 5.0% H2SO4 solution were investigated. It is found that wear loss of bronzes in 5.0% H2SO4 solution is lower than that in water or in air, namely, it exhibits negative synergy between corrosion and wear. Further analysis shows that corrosive solution plays an important role in cooling of specimen during the sliding wear to prevent the reduction of the surface hardness of specimen, induced by frictional heat. On the other hand, the bronzes suffer a de-alloying corrosion, and a noble copper subsurface and patina form on the specimen surface in corrosive solution, which has a passive function for further corrosion. The noble copper subsurface experiences strain hardening during the corrosion and wear, resulting in the increase of the surface hardness thus the increase in wear resistance.

  19. Corrosion behavior of the friction-stir-welded joints of 2A14-T6 aluminum alloy

    Science.gov (United States)

    Qin, Hai-long; Zhang, Hua; Sun, Da-tong; Zhuang, Qian-yu

    2015-06-01

    The corrosion behavior of friction-stir-welded 2A14-T6 aluminum alloy was investigated by immersion testing in immersion exfoliation corrosion (EXCO) solution. Electrochemical measurements (open circuit potential, potentiodynamic polarization curves, and electrochemical impedance spectroscopy), scanning electron microscopy, and energy dispersive spectroscopy were employed for analyzing the corrosion mechanism. The results show that, compared to the base material, the corrosion resistance of the friction-stir welds is greatly improved, and the weld nugget has the highest corrosion resistance. The pitting susceptibility originates from the edge of Al-Cu-Fe-Mn-Si phase particles as the cathode compared to the matrix due to their high self-corrosion potential. No corrosion activity is observed around the θ phase (Al2Cu) after 2 h of immersion in EXCO solution.

  20. The study of corrosion behavior of laser induced surface improvement (LISI) on steel and aluminum substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lindsey, N.; Vasanth, K.L.

    1999-07-01

    Laser Induced Surface Improvement (LISI) is a new process developed by University of Tennessee Space Institute (UTSI) which employs lasers to melt precursor coatings and portions of the substrate to form a durable corrosion resistant surface. The LISI surface can be tailored to yield a composition that provides minimum impact to the base substrate material while giving good corrosion characteristics. The LISI surface treatment of tungsten carbide was applied on 7075 and 6061 aluminum alloys. The LISI treatment uses a chromium/nickel mixture and a stainless steel type mixture (pseudo stainless steel of 18 wt% chromium, 8 wt% nickel and a trace amount of manganese and silicon) on steel alloy 1010. The corrosion characteristics of these samples were determined in 3.5 wt% NaCl aqueous solution using linear polarization resistance technique. Potentiodynamic scans were run to determine the corrosion rates and optical microscopy was used to examine pitting characteristics of the different surface coatings. The effectiveness of the LISI modified surfaces to protect both steel and aluminum substrates is discussed.

  1. Investigation of Electrochemical Charging Behaviors of "Naked" Gold Nanoparticles Ensembles in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    CHENG,Wen-Long(程文龙); HAN,Xiao-Jun(韩晓军); PENG,Zhang-Quan(彭章泉); DOGN,Shao-Jun(董绍俊); WANG,Er-Kang(汪尔康)

    2002-01-01

    Gold nanoparticles were immobilized onto the electrode surface by simple self-assembly technique. Interestingly, the ensmbles of these nanoparticles exhibit quantized charging behaviors in aqueous solution. Possible mechanism for such behaviors was proposed.

  2. Investigation of Electrochemical Charging Behaviors of“Naked” Gold Nanoparticles Ensembles in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    程文龙; 韩晓军; 彭章泉; 董绍俊; 汪尔康

    2002-01-01

    Gold nanoparticles were imnoobilized onto the electrode surface by simple self-assembly technique.Interestingly,the ensembles of these nanoparticles exhibit quantized charging behaviors in aqueous solution.Possible mechanism for such behaviors was proposed.

  3. Modeling corrosion behavior of gas tungsten arc welded titanium alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained.Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of problems associated with the development of titanium alloy welding. The preferred welding process of titanium alloy is frequently gas tungsten arc(GTA) welding due to its comparatively easier applicability and better economy. In the case of single pass GTA welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. The benefit of the process is utilized to obtain better quality titanium weldments. Four factors, five levels, central composite, rotatable design matrix are used to optimize the required number of experiments. The mathematical models have been developed by response surface method(RSM). The results reveal that the titanium alloy can form a protective scale in marine environment and is resistant to pitting corrosion. Experimental results are provided to illustrate the proposed approach.

  4. Corrosion Inhibition and Adsorption Behavior of Clove Oil on Iron in Acidic Medium

    Directory of Open Access Journals (Sweden)

    Archana Saxena

    2012-01-01

    Full Text Available Corrosion behavior of iron in hydrochloric acid solution was studied using weight loss as well Scanning electron microscopy study without and with clove oil. The percentage inhibition efficiency increases with increasing clove oil concentration. All the data revel that the oil acts as an excellent inhibitor for the corrosion of iron in HCl solution. Thermodynamic, kinetic parameters and equilibrium constant for adsorption process were calculated from the experimental data. The adsorption of clove oil on experimental metals was found to follow the Langmuir adsorption isotherm at all the concentration studies. Scanning electron microscope (SEM, investigations also indicate that clove oil greatly lowers the dissolution currents.

  5. Tuning the Corrosion Behavior of Rapidly Solidified and Thermally-annealed Fe-Ti-Pd Alloys

    OpenAIRE

    Gonzalez Sanchez, Sergio; Sort, Jordi

    2014-01-01

    The corrosion behavior of rapidly solidified Fe(91-x)Ti9Pdx (x=0, 1, 3 5) alloys (wt. %), both in the as-cast and thermally annealed (i.e., slowly cooled) states, has been investigated by means of electrochemical potentiodynamic polarization and immersion tests. Addition of Pd shifts the corrosion potential towards more anodic values than in the Fe91Ti9 alloy, both in the as-cast and annealed samples. In turn, the processing route (rapid cooling vs. thermal annealing) has a strong influence i...

  6. Corrosion behavior of oxide dispersion strengthened ferritic steels in supercritical water

    Science.gov (United States)

    Gao, Wenhua; Guo, Xianglong; Shen, Zhao; Zhang, Lefu

    2017-04-01

    The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer.

  7. Effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings

    OpenAIRE

    Yu Mei; Liu Yuxing; Liu Jianhua; Li Songmei; Xue Bing; Zhang You; Yin Xiaolin

    2015-01-01

    The present work examines the effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings. The Si–Zr hybrid sol–gel coatings on a 2A12 aluminum substrate were prepared through hydrolysis and condensation of glycidoxypropyl-trimethoxy-silane (GTMS) and zirconium(IV) n-propoxide (TPOZ). Used as inhibitors for corrosion, three types of cerium salts (Ce(NO3)3, CeCl3, and Ce(CH3COO)3) were doped into the sol–gel coatings. Fourier transform infrared (FTIR) and scanning electron ...

  8. Corrosion behavior of two heat treatment Al-Zn-Mg-Cu alloys in different intergranular corrosion solution

    Institute of Scientific and Technical Information of China (English)

    曹发和; 张昭; 李劲风; 程英亮; 张鉴清; 曹楚南

    2004-01-01

    The electrochemical behavior of two kinds of artificial aged Al-Zn-Mg-Cu alloys in two intergranular corrosion (IGC) solutions were studied using electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) at steady-state. EDAX result indicates that different artificial ageing methods change the composition and content of Cu and Zn in different zones. Zn/Cu depleted precipitation-free zone that plays a very important role in IGC is formed by heating the solubilized Al alloy for 135 ℃ at 16 h. All impedance spectra of the two alloys in two IGC solutions can be divided into three types. The two different states Al alloys takes on one time constant and two capacitive arcs at high-mediate frequency and low frequency in the NaCl+(NH4 )2 SO4 solution respectively; but in the NaCl+HCl solution, impedance displays one capacitive arc at the high-mediate frequency and an inductive loop at low frequency. OCP results show that more micro-galvanic cells in the NaCl+ (NH4)2SO4 solution than that in the NaCl+HCl solution results in more potential fluctuation amplitude, and long-term drift of OCP is due to the long-term variation of the cathodic and anodic corrosion processes.

  9. Dissolution and Protection of Aluminium Oxide in Corrosive Aqueous Media - An Ellipsometry and Reflectometry Study

    NARCIS (Netherlands)

    Karlsson, P.M.; Postmus, B.R.; Palmqvist, A.E.C.

    2009-01-01

    Dissolution of alumina has been studied from wafers in aqueous solution by means of ellipsometry and reflectometry. It was discovered that the dissolution of aluminium oxide is promoted by ethanol amines like N,N-bis(2-hydroxyethyl)glycine and triethanolamine, and that this dissolution is retarded b

  10. The Activity of Trace Metals in Aqueous Systems and the Effect of Corrosion Control Inhibitors

    Science.gov (United States)

    1975-10-01

    corrosion product on metallic zinc 49 Uncombined slilica as quartz or cristobalite forms by the hydrothermal alteration of solid zilicates or by direct...175ml vol. pH K, umhos/cm 8. Polymer JB **Stein, Hall, and Co., 0.05 g 6.83 12.3 Inc; 3-D gel formation which plugs or diverts addati ves. 9. Polymer F...it aids in the formation of acids (Eq. 31) or it may oxidize any metallic material pre- sent in solution. 3. Water Correction. The proper method of

  11. Corrosion Behavior of Commercial Aluminum Alloy Processed by Equal Channel Angular Pressing

    Directory of Open Access Journals (Sweden)

    Atef Korchef

    2013-01-01

    Full Text Available A commercial aluminum alloy was subjected to severe plastic deformation through equal channel angular pressing (ECAP. The alloy contains a low volume fraction of α-AlFeSi located essentially at the grain boundaries. The corrosion behavior of the ECAP’ed alloy was investigated in NaCl solution using potentiodynamic polarization and immersion tests. The effects of scan rate and NaCl concentration on the alloy susceptibility to corrosion were also studied. The results obtained were compared with those of the nonpressed alloy. ECAP leads to an intensive grain refinement accompanied by an increased dislocation density. All electrochemical tests confirm that corrosion resistance of the alloy remarkably diminished with increasing the ECAP number of passes. This is presumably due to the breakdown of the α-AlFeSi after ECAP leading to higher number of galvanic cells and enhanced dissolution of the aluminum matrix.

  12. Corrosion behavior of CuCrNiAl alloy in HCl solutions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The corrosion behavior of a CuCrNiAl alloy in HCl solutions was studied by means of metallograph, XRD, SEM/EDX and TEM methods. The results show that in low concentration of HCl solutions, Cu of CuCrNiAl alloy is more easily subject to corrsion than Cr; the dechromisation of the CuCrNiAl alloy occurs at a certain concentration of HCl solutions, at the same time Al of CuCrNiAl alloy is subject to corrosion also. The dechromisation corrosion occurs initially at the interface between Cr phase and Cu phase, then it gradually extends Cr phase until Cr phase is dissolved completely. It is also revealed that the tendency of dechromisaion of the CuCrNiAl alloy increases with the increase in concentration and temperature of HCl solutions.

  13. Effect of niobium element on the electrochemical corrosion behavior of depleted uranium

    Science.gov (United States)

    Wu, Yanping; Wu, Quanwen; Zhu, Shengfa; Pu, Zhen; Zhang, Yanzhi; Wang, Qinguo; Lang, Dingmu; Zhang, Yuping

    2016-09-01

    Depleted uranium (DU) has many military and civilian uses. However, its high chemical reactivity limits its application. The effect of Nb content on corrosion behavior of DU is evaluated by scanning Kelvin probe and electrochemical corrosion measurements. The Volta potential value of DU and U-2.5 wt% Nb is about the same level, the Volta potential value of U-5.7 wt% Nb has a rise of 370mVSHE in comparison with DU. The polarization current of U-5.7 wt% Nb alloy is about an order of magnitude of that of DU. The Nb2O5 is the protective layer for the U-Nb alloys. The negative potential of Nb-depleted α phase is the main reason of the poor corrosion resistance of DU and U-2.5 wt% Nb alloy.

  14. Effect of Harmonic Microstructure on the Corrosion Behavior of SUS304L Austenitic Stainless Steel

    Science.gov (United States)

    Rai, Prabhat K.; Shekhar, S.; Nakatani, M.; Ota, M.; Vajpai, S. K.; Ameyama, K.; Mondal, K.

    2016-12-01

    Corrosion behavior of a harmonic structured SUS304L austenitic stainless steel was examined and compared with nonharmonic structured SUS304L stainless steel and conventional 304 stainless steel in 3.5 pct NaCl solution. The study was performed using linear polarization, potentiodynamic polarization, cyclic polarization, and a salt fog exposure test for 30 days. Characterization was accomplished using a scanning electron microscope, an electron probe microanalyzer, and Raman spectroscopy. Improved pitting corrosion resistance was found in the case of the harmonic structured steel as compared to that of the nonharmonic and the conventional 304 stainless steel. Harmonically distributed fine-grained structure, less porosity, and higher fraction of passive α-FeOOH are attributed to the improvement in corrosion resistance of the harmonic structured steel.

  15. CORROSION BEHAVIOR OF A CONVERSION COATING BASED ON ZIRCONIUM AND COLORANTS ON GALVANIZED STEEL BY ELECTRODEPOSITION

    Directory of Open Access Journals (Sweden)

    Josiane Soares Costa

    2015-06-01

    Full Text Available Corrosion performance of Zr-based coating on substrates obtained by zinc electrodeposition in an alkaline bath is compared to chromate coatings (Cr III and Cr VI. The “nano Zr” is a conversion coating formed by immersion in a hexafluorozirconic acid solution. Since the “nano Zr” coating is transparent, the addiction of a colorant provides color to the surface. In this case, the colorant, when applied after the conversion coating, conferred the yellow color to the surface. The coating produced improves the corrosion protection of the substrate. For this study the samples were analyzed by electrochemical impedance spectroscopy (EIS and accelerated corrosion test in a humidity chamber. The results showed similar behaviors between the “nano Zr”, colorant and the chromate (Cr III coating. Therefore this kind of conversion coating is a promising substitute for chromate coatings.

  16. Corrosion behavior of steel in concrete made with slag-blended cement

    Energy Technology Data Exchange (ETDEWEB)

    Dehghanian, C. [Univ. of Technology, Isfahan (Iran, Islamic Republic of). Dept. of Chemical Engineering

    1999-03-01

    Concretes formulated with slag as a partial replacement for cement were used to evaluate the corrosion behavior of steel embedded in concrete, resistivity, and the compressive strength of the concrete. Corrosion rates and pitting corrosion of steel in concrete with up to 30% slag and exposed to sodium chloride (NaCl) solutions decreased. Slag-blended cement concrete increased concrete resistivity. A water-to-cement ratio <0.55 and submersion in water for a period of 18 days gave the best chloride (Cl{sup {minus}}) diffusion resistance from the external salt solutions. Compressive strength of the concrete decreased with addition of slag in the early ages of the concrete. After 5 months of age, compressive strength of the concrete increased with addition of slag. This trend continued with up to 30% slag addition.

  17. Corrosion behavior of rebar for intermittent cathodic protection of coastal bridges

    Energy Technology Data Exchange (ETDEWEB)

    Ziomek-Moroz, M. | Cramer, S.D. | Covino, B.S., Jr. | Bullard, S.J. | Holcomb, G.R. | Russell, J.H. | Windisch, Jr., C.F. (PNNL)

    2001-02-01

    A number of reinforced concrete bridges on the Oregon coast are protected against chloride-induced corrosion damage by means of impressed current cathodic protection (ICCP). Thermal-sprayed Zn serves as the anode in these systems. Rebar in the concrete can remain passive and protected for some period of time after the CP system is turned off. The active-passive corrosion behavior of rebar in simulated pore solution (SPS) was investigated as a function of pH and Cl- concentration as part of a study of intermittent ICCP operation. Rebar corrosion rates in SPS were determined from polarization curves by fitting the Butler-Volmer equation and the linear polarization equation. Analysis of the passive film in SPS by x-ray diffraction and surface enhanced Raman spectroscopy showed it to be largely Fe3O4. However, the Fe(OH)2 content increased with cathodic polarization time.

  18. EFFECT OF COPPER ON PASSIVITY AND CORROSION BEHAVIOR OF FE-XC-5CU ALLOY

    Directory of Open Access Journals (Sweden)

    M. Ferhat

    2014-06-01

    Full Text Available The correlation between corrosion behavior rate of annealed Fe-xC-5Cu alloys and their microstructure and phase composition is presented. The metallurgical analyses, including, X-Ray diffraction (XRD, the scanning electron microscopy (SEM with energy dispersive analysis (EDX, and induction hardening characterization are conducted to study the Fe-C-Cu alloys. Corrosion parameters in H2SO4 1N solution have been established by carrying out electrochemical studies such as potentiodynamic (Tafel polarization and linear polarization, LP and electrochemical impedance spectroscopy (EIS. The coupled effect copper/microstructure is discussed. Alloying Cu showed a beneficial effect on hypoeutectoid steel and harmful effect on hypereutectoid steel. The improved corrosion resistance is related to cementite morphology and by a copper dissolution/re-deposition process.

  19. EFFECT OF COPPER ON PASSIVITY AND CORROSION BEHAVIOR OF FE-XC-5CU ALLOY

    Directory of Open Access Journals (Sweden)

    M. Ferhat

    2015-07-01

    Full Text Available The correlation between corrosion behavior rate of annealed Fe-xC-5Cu alloys and their microstructure and phase composition is presented. The metallurgical analyses, including, X-Ray diffraction (XRD, the scanning electron microscopy (SEM with energy dispersive analysis (EDX, and induction hardening characterization are conducted to study the Fe-C-Cu alloys. Corrosion parameters in H2SO4 1N solution have been established by carrying out electrochemical studies such as potentiodynamic (Tafel polarization and linear polarization, LP and electrochemical impedance spectroscopy (EIS. The coupled effect copper/microstructure is discussed. Alloying Cu showed a beneficial effect on hypoeutectoid steel and harmful effect on hypereutectoid steel. The improved corrosion resistance is related to cementite morphology and by a copper dissolution/re-deposition process.

  20. Study of Pitting Corrosion Behavior of FSW weldments of AA6101- T6 Aluminium Alloy

    Directory of Open Access Journals (Sweden)

    L.V. Kamble

    2015-09-01

    Full Text Available Friction Stir Welding (FSW is a promising solid state joining process widely used generally for Al alloys, especially in aerospace, marine and automobile applications. In present work, the microstructure and corrosion behavior of friction stir welded AA6101 T6 Al alloy is studied. The friction stir welding was carried using vertical milling machine with different tool rotational speeds and welding speeds. The microstructure at weld nugget or stir zone (SN, thermo-mechanically affected zone (TMAZ, heat affected zone (HAZ and base metal were observed using optical microscopy. The corrosion tests of base alloy and welded joints were carried out in 3.5% NaCl solution at temperature of 30º C. Corrosion rate and emf were determined using cyclic polarization measurement.

  1. Microstructure and corrosion behavior of binary titanium alloys with beta-stabilizing elements.

    Science.gov (United States)

    Takada, Y; Nakajima, H; Okuno, O; Okabe, T

    2001-03-01

    Binary titanium alloys with the beta-stabilizing elements of Co, Cr, Cu, Fe, Mn and Pd (up to 30%) and Ag (up to 45%) were examined through metallographic observation and X-ray diffractometry to determine whether beta phases that are advantageous for dental use could be retained. Corrosion behavior was also investigated electrochemically and discussed thermodynamically. Some cast alloys with Co, Cr, Fe, Mn, and Pd retained the beta phase, whereas those with Ag and Cu had no beta phase. In some alloys, an intermetallic compound formed, based on information from the phase diagram. The corrosion resistance deteriorated in the TiAg alloys because Ti2Ag and/or TiAg intermetallic compounds preferentially dissolved in 0.9% NaCl solution. On the other hand, the remaining titanium alloys became easily passive and revealed good corrosion resistance similar to pure titanium since their matrices seemed to thermodynamically form titanium oxides as did pure titanium.

  2. Corrosion behavior of a 14Cr-ODS steel in supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Hu, H.L. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhou, Z.J., E-mail: zhouzhangjianustb@163.com [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liao, L. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, L.F. [School of Nuclear Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China); Wang, M.; Li, S.F.; Ge, C.C. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2013-06-15

    The corrosion behavior of a 14Cr-ODS steel in the supercritical water was investigated using a variety of characterization techniques. Compared with 316L austenitic steel, the 14Cr-ODS steel had better corrosion resistant property. As the increasing of the exposure time, the weight gain increased, but the corrosion rates decreased. The curve of weight gain as a function of time followed a parabolic law. The general weight gain was 0.3476 mg/(dm{sup 2} h). A triple layer was observed which consisted of an outer layer, an inner layer and a diffusion layer. The outer layer was iron rich and contained Fe{sub 3}O{sub 4}, on which pores were observed. The inner layer and diffusion layer contained mainly (Fe,Cr{sub 2})O{sub 4}. The oxidation mechanism was also discussed.

  3. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Institute of Scientific and Technical Information of China (English)

    Qin Chunling; Xiao Tongna; Li Yongyan; Wang Zhifeng; Liu Li; Xiong Hanqing; Zhao Weimin

    2014-01-01

    The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous al oys in simulated body fluids (SBF) were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 ºC for different times were observed under scanning electron microscope (SEM). Results show that the corrosion resistance of Mg-based al oys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microal oying Nd element to the al oys leads to an ennoblement in the open circuit potentials of the al oys and a decrease in the anodic current density in SBF, especial y for the Mg66-xZn30Ca4Ndx al oys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the al oys immersed in SBF change with the Nd addition. A flake-like structure paral el to the al oy substrate formed on the surface of 1.0at.% Nd-containing al oy immersed in SBF for 7 days improves the corrosion resistance of the amorphous al oys by blocking the corrosion liquid from attacking the al oys.

  4. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Directory of Open Access Journals (Sweden)

    Qin Chunling

    2014-11-01

    Full Text Available The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body fluids (SBF were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 篊 for different times were observed under scanning electron microscope (SEM. Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A flake-like structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.

  5. Corrosion behavior of pristine and added MgB2 in Phosphate Buffered Saline Solution

    Science.gov (United States)

    Batalu, D.; Bojin, D.; Ghiban, B.; Aldica, G.; Badica, P.

    2012-09-01

    We have obtained by Spark Plasma Sintering (SPS), dense samples of MgB2 added with Ho2O3. Starting composition was (MgB2)0.975(HoO1.5)0.025 and we used addition powders with an average particle size below and above 100 nm. For Mg, pristine and added MgB2 samples we measured potentiodynamic polarization curves in Phosphate Buffered Saline (PBS) solution media at room temperature. MgB2 based composites show corrosion/ degradation effects. This behavior is in principle similar to Mg based alloys in the same media. Our work suggests that the different morphologies and phase compositions of the SPS-ed samples influence the interaction with corrosion medium; hence additions can play an important role in controlling the corrosion rate. Pristine MgB2 show a significant improvement of the corrosion resistance, if compared with Mg. The best corrosion resistance is obtained for pristine MgB2, followed by MgB2 with nano-Ho2O3 and μ-Ho2O3 additions.

  6. Electrochemical corrosion behavior of the carburized porous TiAl alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Cuijiao [Hunan University of Technology, Zhuzhou, Hunan 412000 (China); Yang, Junsheng [Wuhan Polytechnic University, Wuhan, Hubei 430023 (China); He, Yuehui, E-mail: yuehui@mail.csu.edu.cn [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Ming, XingZu [Hunan University of Technology, Zhuzhou, Hunan 412000 (China)

    2015-01-15

    Highlights: • Ti{sub 2}AlC phase forms on porous TiAl alloy in a carburizing atmosphere. • The carburized sample at 1203 K for 10 h has continuous carburized layers. • Carburization can improve corrosion resistance of the porous TiAl alloy. • The passive film of the carburized sample at 1203 K for 10 h is very stable. - Abstract: Carburization was carried out to improve corrosion resistance of porous Ti–46.5 Al (at.%) intermetallic compound. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to analyze the carburized layers. Electrochemical corrosion behavior of the untreated and the carburized samples were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and open circuit potential. The results reveal that the continuous and thick carburized layers form after carburization treatment at 1203 K for 10 h, whose main phase is a functional complex ceramic phase, Ti{sub 2}AlC. Carburization can improve corrosion resistance of the porous TiAl alloy. Among the carburized samples, the carburized one at 1203 K for 10 h presents the highest corrosion resistance and has the most stable oxide film.

  7. Microstructure and corrosion behavior of laser processed NiTi alloy.

    Science.gov (United States)

    Marattukalam, Jithin J; Singh, Amit Kumar; Datta, Susmit; Das, Mitun; Balla, Vamsi Krishna; Bontha, Srikanth; Kalpathy, Sreeram K

    2015-12-01

    Laser Engineered Net Shaping (LENS™), a commercially available additive manufacturing technology, has been used to fabricate dense equiatomic NiTi alloy components. The primary aim of this work is to study the effect of laser power and scan speed on microstructure, phase constituents, hardness and corrosion behavior of laser processed NiTi alloy. The results showed retention of large amount of high-temperature austenite phase at room temperature due to high cooling rates associated with laser processing. The high amount of austenite in these samples increased the hardness. The grain size and corrosion resistance were found to increase with laser power. The surface energy of NiTi alloy, calculated using contact angles, decreased from 61 mN/m to 56 mN/m with increase in laser energy density from 20 J/mm(2) to 80 J/mm(2). The decrease in surface energy shifted the corrosion potentials to nobler direction and decreased the corrosion current. Under present experimental conditions the laser power found to have strong influence on microstructure, phase constituents and corrosion resistance of NiTi alloy.

  8. Surface properties and corrosion behavior of Co-Cr alloy fabricated with selective laser melting technique.

    Science.gov (United States)

    Xin, Xian-zhen; Chen, Jie; Xiang, Nan; Wei, Bin

    2013-01-01

    We sought to study the corrosion behavior and surface properties of a commercial cobalt-chromium (Co-Cr) alloy which was fabricated with selective laser melting (SLM) technique. For this purpose, specimens were fabricated using different techniques, such as SLM system and casting methods. Surface hardness testing, microstructure observation, surface analysis using X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test were carried out to evaluate the corrosion properties and surface properties of the specimens. We found that microstructure of SLM specimens was more homogeneous than that of cast specimens. The mean surface hardness values of SLM and cast specimens were 458.3 and 384.8, respectively; SLM specimens showed higher values than cast ones in hardness. Both specimens exhibited no differences in their electrochemical corrosion properties in the artificial saliva through potentiodynamic curves and EIS, and no significant difference via XPS. Therefore, we concluded that within the scope of this study, SLM-fabricated restorations revealed good surface properties, such as proper hardness, homogeneous microstructure, and also showed sufficient corrosion resistance which could meet the needs of dental clinics.

  9. Electrochemical Corrosion Behavior of Nd-Fe-B Sintered Magnets in Different Acid Solutions

    Institute of Scientific and Technical Information of China (English)

    Zheng Jingwu; Jiang Liqiang; Chen Qiaoling

    2006-01-01

    Electrochemical corrosion behavior of Nd-Fe-B sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied.Potentiodynamic polarization curves and immersion time dependence of corrosion rates of Nd-Fe-B sintered magnets in different acid solutions were tested.Microstructures of corroded Nd-Fe-B sintered magnets were investigated by means of SEM and AFM.The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl>H2SO4>HNO3 solution and Nd-Fe-B sintered magnets are passivated in phosphate acid and oxalic acid.Within 25 min, the corrosion rates of Nd-Fe-B sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising.And in H2C2O4 solution, weight of the magnets increases.The brim of Nd-Fe-B sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid.The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.

  10. Effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings

    Directory of Open Access Journals (Sweden)

    Yu Mei

    2015-04-01

    Full Text Available The present work examines the effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings. The Si–Zr hybrid sol–gel coatings on a 2A12 aluminum substrate were prepared through hydrolysis and condensation of glycidoxypropyl-trimethoxy-silane (GTMS and zirconium(IV n-propoxide (TPOZ. Used as inhibitors for corrosion, three types of cerium salts (Ce(NO33, CeCl3, and Ce(CH3COO3 were doped into the sol–gel coatings. Fourier transform infrared (FTIR and scanning electron microscopy (SEM were employed to investigate the structures and morphologies of various coatings, and the corrosion resistances of the coatings were evaluated by electrochemical methods and neutral salt spray tests. Experimental results indicate that the addition of cerium salts can hinder the process of corrosion due to their self-healing abilities. Furthermore, the sol–gel coating doped with Ce(CH3COO3 has the best corrosion resistance because of the promotions of hydrolysis and condensation provided by CH3COO−.

  11. In vitro corrosion behavior and cellular response of thermally oxidized Zr-3Sn alloy

    Science.gov (United States)

    Zhou, F. Y.; Wang, B. L.; Qiu, K. J.; Li, H. F.; Li, L.; Zheng, Y. F.; Han, Y.

    2013-01-01

    In this study, ZrSn alloy was thermally oxidized at 600 °C for 3 h and its morphological and structural characteristics, corrosion behavior, ion release and in vitro cytocompatibility were studied to evaluate the feasibility of applying it as dental implant. After oxidation, a dense black oxide layer formed on ZrSn alloy surface, which consisted of predominant monoclinic zirconia and a few non-stoichiometric oxides. The scratching and water contact angle test results demonstrated that the oxide layer exhibited good adhesion strength and similar hydrophilicity to zirconia. The oxidized ZrSn alloy showed higher corrosion resistance, as indicated by far lower corrosion current density and passive current density compared to pure Ti and untreated ZrSn alloy in artificial saliva with and without H2O2. The amount of ions released from the oxidized ZrSn alloy was much lower than that dissolved from pure Ti in simulated corrosive oral mediums. Moreover, the oxidized ZrSn alloy did not present any significant toxic effect to both osteoblast-like cells and fibroblast cells, and osteoblast-like cells could adhere well onto the surface and exhibited a good proliferative pattern. The combination of improved surface properties, superior corrosion resistance and good biocompatibility made the oxidized ZrSn alloy promising for oral implantology application.

  12. On the corrosion behavior and biocompatibility of palladium-based dental alloys

    Science.gov (United States)

    Sun, Desheng

    Palladium-based alloys have been used as dental restorative materials for about two decades with good clinical history. But there have been clinical case reports showing possible allergy effects from these alloys. The aim of this study was to characterize the corrosion behavior and mechanisms of several palladium-based dental alloys by potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), and scanning Kelvin probe force microscopy/atomic force microscopy (SKPFM/AFM), and to evaluate their biocompatibility by a cell culture technique and an animal model. Using SKPFM/AFM and scanning electron microscopy, the Ru-enriched phase from the use of ruthenium as a grain-refining element was identified as being slightly more noble than the palladium solid solution matrix in a high-palladium alloy. Other secondary precipitates that exist in the microstructures of these high-palladium alloys have minimal differences in Volta potential compared to the matrix. For high-palladium alloys, corrosion is generally uniform due to the predominant palladium content in the different phases. Potentiodynamic polarization and EIS have shown that representative palladium-silver alloys have low corrosion tendency and high corrosion resistance, which are equivalent to a well-known high-noble gold-palladium alloy in simulated body fluid and oral environments. The palladium-silver alloys tested are resistant to chloride ion corrosion. Passivation and dealloying have been identified for all of the tested palladium-silver alloys. The great similarity in corrosion behavior among the palladium-silver alloys is attributed to their similar chemical compositions. The variation in microstructures of palladium-silver alloys tested does not cause significant difference in corrosion behavior. The corrosion resistance of these palladium-silver alloys at elevated potentials relevant to oral environment is still satisfactory. The release of elements from representative dental

  13. Corrosion Behavior of Bi2Te3-Based Thermoelectric Materials Fabricated by Melting Method

    Science.gov (United States)

    Kohri, Hitoshi; Yagasaki, Takayoshi

    2016-11-01

    Bi2Te3-based compounds are used practically as thermoelectric cooling materials. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudobinary system compounds are usually applied as p- or n-type material, respectively. Atmospheric water may condense on the surface of thermoelectric materials constituting Peltier modules, depending on their operating environment. Very few studies on the corrosion resistance of Bi2Te3-based compounds have been reported in literature. Moreover, the detailed corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the corrosion behavior of cleavage planes of Bi2Te3-based compounds fabricated by a melting method has been investigated. Bi2Te3, Sb2Te3, and Bi2Se3 were prepared by the vertical Bridgman method, respectively. Their electrochemical properties evaluated at room temperature by cyclic voltammetry in a standard three-electrode cell with naturally aerated 0.6 mass% or 3.0 mass% NaCl solution as working electrolyte. The c-planes of Bi2Te3 and Sb2Te3 exhibited similar corrosion potential. The corrosion potential of c-plane of Bi2Se3 was more cathodic compared with that of the telluride. The passive current density of the Bi2Te3-based compounds was single or double digit lower than that of stainless steel. X-ray photoelectron spectroscopy results for the electrolyte after testing indicated the possibility that a corrosion product diffuses to the environment including NaCl for Sb2Te3 and Bi2Se3.

  14. Influence of turbulent flow on the corrosion kinetics of API X52 pipeline steel in aqueous solutions containing H{sub 2}S

    Energy Technology Data Exchange (ETDEWEB)

    Galvan-Martinez, Ricardo; Genesca-Llongueras, Juan [Departamento Ingenieria Metalurgica, Facultad Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Ciudad Universitaria, 04510 Mexico D.F. (Mexico); Mendoza-Flores, Juan; Duran-Romero, Ruben [Corrosion, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico)

    2004-07-01

    A corrosion process can be influenced by the relative movement between the corroding environment and the metal. This relative movement could increase the heat transfer and the mass transfer of reactants towards and from the surface of the corroding metal, with a consequent increase in the corrosion rate. Also, if solid particles are present, removal of protective films, erosion and wear can occur on the metallic surface. Many industrial processes involve the movement of corrosive liquids in close contact to metallic structures. Therefore, the influence of flow on the corrosion processes is an important issue to be considered in the design and operation of industrial equipment. This influence is complex and many variables are involved. Several observations of flow-accelerated corrosion problems have been documented, particularly in the oil and gas industries, where the combined effect of flow and dissolved gases, such as hydrogen sulphide (H{sub 2}S) and carbon dioxide (CO{sub 2}), is important. Turbulent flow conditions are commonly found in industrial processes. However, few corrosion studies in controlled turbulent flow conditions are available. With the increasing necessity to describe the corrosion of metals in turbulent flow conditions some laboratory hydrodynamic systems have been used with different degrees of success. The use of the rotating cylinder electrode (RCE), as a laboratory hydrodynamic test system, has gained popularity in corrosion studies. This popularity is due to its characteristics, such as, its operation mainly at turbulent flow conditions; its well understood mass transfer properties and its easiness of construction and operation. The aim of the present work is to explore the effect that turbulent flow conditions have on the electrochemical kinetics of steel samples immersed in aqueous environments containing H{sub 2}S. In order to control the turbulent flow conditions in the laboratory, a rotating cylinder electrode (RCE) was used. In

  15. Electrochemical corrosion testing of metal waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Abraham, D. P.; Peterson, J. J.; Katyal, H. K.; Keiser, D. D.; Hilton, B. A.

    1999-12-14

    Electrochemical corrosion tests have been conducted on simulated stainless steel-zirconium (SS-Zr) metal waste form (MWF) samples. The uniform aqueous corrosion behavior of the samples in various test solutions was measured by the polarization resistance technique. The data show that the MWF corrosion rates are very low in groundwaters representative of the proposed Yucca Mountain repository. Galvanic corrosion measurements were also conducted on MWF samples that were coupled to an alloy that has been proposed for the inner lining of the high-level nuclear waste container. The experiments show that the steady-state galvanic corrosion currents are small. Galvanic corrosion will, hence, not be an important mechanism of radionuclide release from the MWF alloys.

  16. An aqueous, polymer-based redox-flow battery using non-corrosive, safe, and low-cost materials

    Science.gov (United States)

    Janoschka, Tobias; Martin, Norbert; Martin, Udo; Friebe, Christian; Morgenstern, Sabine; Hiller, Hannes; Hager, Martin D.; Schubert, Ulrich S.

    2015-11-01

    For renewable energy sources such as solar, wind, and hydroelectric to be effectively used in the grid of the future, flexible and scalable energy-storage solutions are necessary to mitigate output fluctuations. Redox-flow batteries (RFBs) were first built in the 1940s and are considered a promising large-scale energy-storage technology. A limited number of redox-active materials--mainly metal salts, corrosive halogens, and low-molar-mass organic compounds--have been investigated as active materials, and only a few membrane materials, such as Nafion, have been considered for RFBs. However, for systems that are intended for both domestic and large-scale use, safety and cost must be taken into account as well as energy density and capacity, particularly regarding long-term access to metal resources, which places limits on the lithium-ion-based and vanadium-based RFB development. Here we describe an affordable, safe, and scalable battery system, which uses organic polymers as the charge-storage material in combination with inexpensive dialysis membranes, which separate the anode and the cathode by the retention of the non-metallic, active (macro-molecular) species, and an aqueous sodium chloride solution as the electrolyte. This water- and polymer-based RFB has an energy density of 10 watt hours per litre, current densities of up to 100 milliamperes per square centimetre, and stable long-term cycling capability. The polymer-based RFB we present uses an environmentally benign sodium chloride solution and cheap, commercially available filter membranes instead of highly corrosive acid electrolytes and expensive membrane materials.

  17. Nanoscale surface characterization of aqueous copper corrosion: Effects of immersion interval and orthophosphate concentration

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, Stephanie L. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); United States Environmental Protection Agency, National Risk Management Research Laboratory (NRMRL), Water Supply and Water Resource Division (WSWRD), Cincinnati, OH 45268 (United States); Sprunger, Phillip T. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Center for Advanced Microstructures and Devices, Synchrotron Radiation Facility of Louisiana State University, Baton Rouge, LA 70803 (United States); Kizilkaya, Orhan [Center for Advanced Microstructures and Devices, Synchrotron Radiation Facility of Louisiana State University, Baton Rouge, LA 70803 (United States); Lytle, Darren A. [United States Environmental Protection Agency, National Risk Management Research Laboratory (NRMRL), Water Supply and Water Resource Division (WSWRD), Cincinnati, OH 45268 (United States); Garno, Jayne C., E-mail: jgarno@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States)

    2013-11-15

    Morphology changes for copper surfaces exposed to different water parameters were investigated at the nanoscale with atomic force microscopy (AFM), as influenced by changes in pH and the levels of orthophosphate ions. Synthetic water samples were designed to mimic physiological chemistries for drinking water, both with and without addition of orthophosphate over a pH range 6.5–9. Copper surfaces treated with orthophosphate as a corrosion inhibitor after 6 and 24 h were evaluated. Tapping mode AFM images revealed dosing of the water with 6 mg/L of orthophosphate was beneficial in retarding the growth of copper by-products. The chemical composition and oxidation state of the surface deposits were characterized with X-ray diffraction (XRD), near edge X-ray absorption fine structure (NEXAFS) spectroscopy and Fourier transform infrared spectroscopy (FTIR).

  18. Galvanic corrosion behavior of die cast AZ91D magnesium alloy in chloride solution

    Institute of Scientific and Technical Information of China (English)

    Zhensong Tong; Wei Zhang; Jiuqing Li; Jin Gao; Jiquan He; Ji Zhou

    2004-01-01

    The galvanic corrosion behavior of die cast AZ91D magnesium alloy coupled with H62 brass, 316L stainless steel, A3steel and LY12 aluminum alloy of different areas in 3.5% NaC1 solution was studied. The free corrosion potentials, galvanic potentials and currents of these galvanic couples were measured. The galvanic effects were determined by the mass loss and regression method using three points. The results show that: (1) In these four kinds of couples AZ91D acts as the anode, whose galvanic corrosion behavior is mainly controlled by the cathodic polarization; (2) The free corrosion potentials of these four kinds of couples change a liffle with time and cathodic/anodic area ratio (CAAR); (3) The galvanic potential of AZ91D/LY12 moves positively with the increase of time and CAAR; (4) The galvanic currents increase with CAAR, but there is difference in the current change between different couples; (5) The anodic dissolution rate of the magnesium alloy increases by 2-3 orders after being coupled with these four kinds of metals and the galvanic effects of these couples have such a relation as γH62>γ316LS.S>γLY12 >γA3.

  19. Corrosion Behavior of Surface-treated Ferritic/Martensitic Steel in Liquid Sodium Environment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, JeongHyeon; Lee, Jung Ki; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Shin, Sang Hun [KAERI, Daejeon (Korea, Republic of)

    2015-10-15

    Their compatibility with sodium is one of issues especially dissolution, chemical reaction, and carbon transfer with impurities, which degraded the mechanical properties. The compatibility of cladding and structural materials with sodium has to be carefully investigated, as sodium could promote corrosion of cladding and structural materials in two ways. One is produced by the dissolution of alloy constituents into the sodium, and the other is produced through a chemical reaction with impurities (especially oxygen and carbon) in the sodium environment. Gr.92 is known as compatible in sodium environment because this steel possesses excellent properties. For instance, Gr.92 has high creep and tensile strength, low thermal expansion coefficient. In the Ultra-long Cycle Fast Reactor (UCFR) which is developed in UNIST, however, cladding is exposed long-term in high temperature liquid sodium environment. So, it is very important to investigate the corrosion-related behavior such as surface corrosion rate, carburization, decarburization and mechanical properties for its operation time. In this study, as-received and surface-treated Gr.92 specimen in the oxygen-saturated liquid sodium were examined at high temperature for 300h. The impedance results reveal the information for the corrosion behavior in liquid sodium. Also, microstructure results reveal the information for the maintenance of coating and role of coating.

  20. Corrosion fatigue behavior of fastening hole structure and virtual crack propagation tests

    Institute of Scientific and Technical Information of China (English)

    Youhong Zhang; Xinlong Chang; Guozhi Lv; Hui Wang; Zhong Li; Yueliang Cheng

    2008-01-01

    The fatigue crack propagation behavior of the LY12CZ aluminum alloy fastener involving a central hole in air or in 3.5wt% NaC1 solution was investigated. The experimental results indicated that the corrosion fatigue crack growth rate decreased with the increasing loading frequency, and in a corrosive environment, the crack growth rate was slightly larger than that in air.Based on the experimental results, the virtual corrosion fatigue crack propagation tests were investigated and the stochastic process method and the AFGROW simulation method were presented. The normal process and lognormal process were considered for the stochastic process method based on the numerically fitted Paris equation. The distribution of crack size and the corresponding prob-abilistic model of crack length distribution for a given number of cycles can be found by integrating the stochastic process over time.Using the AFGROW software, the virtual simulation was carried out to analyze the corrosion fatigue crack growth behavior and the predicted crack growth curve was in good agreement with the experimental results.

  1. Effect of aging on mechanical properties and localized corrosion behaviors of Al-Cu-Li alloy

    Institute of Scientific and Technical Information of China (English)

    JIANG Na; LI Jin-feng; ZHENG Zi-qiao; WEI Xiu-yu; LI Yan-fen

    2005-01-01

    The effects of aging on mechanical properties,intergranular corrosion and exfoliation corrosion behaviors of a 2197 type A1-Li alloy were investigated,and the mechanisms were studied through microstructure observation and electrochemical measurement of simulated bulk phase.The main strengthening precipitates of the alloy aged at175 ℃ and 160 ℃ are δ' and T1.T1 precipitation in the alloy aged at 160 ℃ is delayed,which results in its slower age strengthening and over-aging behavior than the alloy aged at 175 ℃.Meanwhile,aging temperature of 160 ℃causes more uniform distribution and finer size of T1,resulting in its better strengthening effect.As aging time and aging temperature are increased,the size of T1 at grain boundaries and the width of PFZ along grain boundaries are increased,leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion.It is suggested that better comprehensive properties can be obtained when the alloy is aged at 160 ℃.

  2. Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

    Science.gov (United States)

    Fu, Guangyan; Wu, Yongzhao; Liu, Qun; Li, Rongguang; Su, Yong

    2017-03-01

    The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating steel with Al-Si coating steel without any coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

  3. Magnesium-Based Corrosion Nano-Cells For Reductive Transformation Of Contaminants

    Science.gov (United States)

    Magnesium, with its potential to reduce a variety of aqueous contaminants, unique self-limiting corrosion behavior affording long active life times, natural abundance, low cost, and environmentally friendly nature, promises to be an effective technology. However, nanoparticles o...

  4. Corrosion behavior of a CuCrNiAl alloy in the presence of NaCl deposit

    Institute of Scientific and Technical Information of China (English)

    XU Tao; CHANG Limin; LIU Jianhua

    2006-01-01

    The corrosion behavior of a CuCrNiAl alloy with NaCl deposit at 700 and 900℃ was studied by means of metalloscope, XRD, SEM/EDX, and thermogravimetric analysis. The results indicated that the corrosion of the CuCrNiAl alloy beneath the NaCl deposit is severe; the corrosion production is loose and easy to scale off; the Cr phase is easier to erode than the Cu phase, and the contents of Cu and Cr decrease when the content of Ni increases in the matrix of the alloy beneath the corrosion region. The effects of distortion on the corrosion of the CuCrNiAl alloy were discussed, and the acceleration mechanisms of NaCl on the corrosion were also discussed.

  5. Effect of tempering temperature and Mo content on the corrosion behavior of 13Cr martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Jong Woo; Ahn, Yong Sik; Park, Hwa Soon [Pukyong National Univ., Busan (Korea, Republic of)

    1999-07-01

    Martensitic stainless steel has high strength and hardness in comparison with other stainless steels. But the toughness and corrosion resistance is lower. So lots of researches have been done in order to improve these properties. In the previous study the alloying element of Mo resulted in increasing the toughness at tempered condition of the steel. It has been investigated in this work how the Mo addition and tempering condition influence on the various types of corrosion behavior of 13% Cr martensitic stainless steel. Corrosion resistance was hardly changed by the tempering up to temperature of 500 .deg. C, but decreased at 600 .deg. C due to the formation of Cr carbide on the prior austenite boundary. However, the corrosion resistance increased again at 700 .deg. C, because Cr carbides were resolved and redistributed. Both general corrosion resistance and intergranular corrosion resistance of tempered steel are significantly improved with Mo content.

  6. Corrosion Behavior of Electrodepositing Ni/Al2O3 Composite Coatings under the Presence of NaCl Deposit

    Institute of Scientific and Technical Information of China (English)

    Xie Danyang; Liu Lin

    2007-01-01

    The morphology and corrosion behavior of Ni/Al2O3 composite coatings prepared using double-pulsed electrodepositing technique after oxidized under 800℃ NaCl deposit in air environment were analyzed by scanning electrical microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrum (EDS). The results showed that the corrosion of all composite coatings was accelerated under NaCl deposits, and the corrosion products were rather porous with poor adherence to the matrix. Al2)O3 particles in the coatings can refine the grain size and improve the high temperature corrosion resistance of the coatings. Within the test scope, the more Al2O3 particles in the coatings, the lower corrosion rates could be obtained, and the corrosion mechanism was also discussed.

  7. Aqueous oxidation reaction enabled layer-by-layer corrosion of semiconductor nanoplates into single-crystalline 2D nanocrystals with single layer accuracy and ionic surface capping.

    Science.gov (United States)

    Ji, Muwei; Xu, Meng; Zhang, Jun; Liu, Jiajia; Zhang, Jiatao

    2016-02-25

    A controllable aqueous oxidation reaction enabled layer-by-layer corrosion has been proposed to prepare high-quality two-dimensional (2D) semiconductor nanocrystals with single layer accuracy and well-retained hexagonal shapes. The appropriate oxidizing agent, such as H2O2, Fe(NO3)3, and HNO3, could not only corrode the layered-crystalline-structured Bi2Te3 nanoplates layer-by-layer to be a single quintuple layer, but also replace the organic barriers to be ionic ligands on the surface synergistically. AFM analysis was used to confirm the layer-by-layer exfoliation from the side to the center. Together with precise XRD, LRTEM and HRTEM characterizations, the controllable oxidation reaction enabled aqueous layer-by-layer corrosion mechanism has been studied.

  8. Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion

    Science.gov (United States)

    Zhang, Xuming; Wu, Guosong; Peng, Xiang; Li, Limin; Feng, Hongqing; Gao, Biao; Huo, Kaifu; Chu, Paul K.

    2015-11-01

    Rapid corrosion of magnesium alloys is undesirable in structural and biomedical applications and a general way to control corrosion is to form a surface barrier layer isolating the bulk materials from the external environment. Herein, based on the insights gained from the anticorrosion behavior of corrosion products, a special way to mitigate aqueous corrosion is described. The concept is based on pre-corrosion by a hydrothermal treatment of Al-enriched Mg alloys in water. A uniform surface composed of an inner compact layer and top Mg-Al layered double hydroxide (LDH) microsheet is produced on a large area using a one-step process and excellent corrosion resistance is achieved in saline solutions. Moreover, inspired by the super-hydrophobic phenomenon in nature such as the lotus leaves effect, the orientation of the top microsheet layer is tailored by adjusting the hydrothermal temperature, time, and pH to produce a water-repellent surface after modification with fluorinated silane. As a result of the trapped air pockets in the microstructure, the super-hydrophobic surface with the Cassie state shows better corrosion resistance in the immersion tests. The results reveal an economical and environmentally friendly means to control and use the pre-corrosion products on magnesium alloys.

  9. In vitro corrosion behavior and cellular response of thermally oxidized Zr-3Sn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F.Y.; Wang, B.L.; Qiu, K.J. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Li, H.F. [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Li, L. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Han, Y. [State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xian 710049 (China)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer A main monoclinic ZrO{sub 2} layer formed on ZrSn alloy after thermal oxidation. Black-Right-Pointing-Pointer Corrosion resistance of ZrSn alloy was improved with thermal oxidation. Black-Right-Pointing-Pointer The oxide layer inhibited the release of the ions into the mediums. Black-Right-Pointing-Pointer Oxidized ZrSn alloy exhibited an excellent in vitro biocompatibility. - Abstract: In this study, ZrSn alloy was thermally oxidized at 600 Degree-Sign C for 3 h and its morphological and structural characteristics, corrosion behavior, ion release and in vitro cytocompatibility were studied to evaluate the feasibility of applying it as dental implant. After oxidation, a dense black oxide layer formed on ZrSn alloy surface, which consisted of predominant monoclinic zirconia and a few non-stoichiometric oxides. The scratching and water contact angle test results demonstrated that the oxide layer exhibited good adhesion strength and similar hydrophilicity to zirconia. The oxidized ZrSn alloy showed higher corrosion resistance, as indicated by far lower corrosion current density and passive current density compared to pure Ti and untreated ZrSn alloy in artificial saliva with and without H{sub 2}O{sub 2}. The amount of ions released from the oxidized ZrSn alloy was much lower than that dissolved from pure Ti in simulated corrosive oral mediums. Moreover, the oxidized ZrSn alloy did not present any significant toxic effect to both osteoblast-like cells and fibroblast cells, and osteoblast-like cells could adhere well onto the surface and exhibited a good proliferative pattern. The combination of improved surface properties, superior corrosion resistance and good biocompatibility made the oxidized ZrSn alloy promising for oral implantology application.

  10. Corrosion Behavior of Cold Sprayed Titanium Coatings and Free Standing Deposits

    Science.gov (United States)

    Hussain, T.; McCartney, D. G.; Shipway, P. H.; Marrocco, T.

    2011-01-01

    Cold gas dynamic spraying can be used to deposit oxygen-sensitive materials, such as titanium, without significant chemical degradation of the powder. The process is thus believed to have potential for the deposition of corrosion-resistant barrier coatings. However, to be effective, a barrier coating must not allow ingress of a corrosive liquid and hence must not have interconnected porosity. This study investigated the effects of porosity on the corrosion behavior of cold sprayed titanium coatings onto carbon steel and also of free standing deposits. For comparative purposes, a set of free standing deposits was also vacuum heat-treated to further decrease porosity levels below those in the as-sprayed condition. Microstructures were examined by optical and scanning electron microscopy. Mercury intrusion porosimetry (MIP) was used to characterize the interconnected porosity over a size range of micrometers to nanometers. Open circuit potential (OCP) measurements and potentiodynamic polarization scans in 3.5 wt.% NaCl were used to evaluate the corrosion performance. The MIP results showed that in cold sprayed deposits a significant proportion of the porosity was sub-micron and so could not be reliably measured by optical microscope based image analysis. In the case of free standing deposits, a reduction in interconnected porosity resulted in a lower corrosion current density, a lower passive current density, and an increase in OCP closer to that of bulk titanium. For the lowest porosity level, ~1.8% achieved following vacuum heat treatment, the passive current density was identical to that of bulk titanium. However, electrochemical measurements of the coatings showed significant substrate influence when the interconnected porosity of the coating was 11.3 vol.% but a decreased substrate influence with a porosity level of 5.9 vol.%. In the latter case, the OCP was still around 250 mV below that of bulk Ti. Salt spray tests confirmed these electrochemical findings and

  11. Erosion-Corrosion Behaviors of High Velocity Arc Sprayed Fe-Al/Cr3C2 Coating

    Institute of Scientific and Technical Information of China (English)

    XU Weipu; XU Binshi; ZHANG Wei; WU Yixiong

    2006-01-01

    Iron aluminide intermetallic coatings were prepared from Fe-Al/Cr3C2 cored wires using High Velocity Arc Spraying (HVAS) technology. Erosion and corrosion properties of HVAS sprayed Fe-Al/Cr3C2 coatings were investigated. Results show that the erosion at impingement angle of 30° is more than that of 90°. The erosion resistance of coatings was enhanced with the increase of temperature. Coatings had a better erosion resistance than substrates. The erosion changed from ductile behaviors to brittle behaviors above 450 ℃. At high temperature, the erosion resistances were superior to those at low temperature and room temperature. Coatings had much higher corrosion properties than substrates. The temperature had a little effect on the corrosion resistance of coatings; The corrosion losing of coatings increased slowly with the increase of corrosion time. The HVAS-sprayed Fe-Al/Cr3C2 coatings exhibited a high bond strength and hardness.

  12. Corrosion Behavior of AlSi10Mg Alloy Produced by Additive Manufacturing (AM vs. Its Counterpart Gravity Cast Alloy

    Directory of Open Access Journals (Sweden)

    Avi Leon

    2016-06-01

    Full Text Available The attractiveness of additive manufacturing (AM relates to the ability of this technology to rapidly produce very complex components at affordable costs. However, the properties and corrosion behavior, in particular, of products produced by AM technology should at least match the properties obtained by conventional technologies. The present study aims at evaluating the corrosion behavior and corrosion fatigue endurance of AlSi10Mg alloy produced by selective laser melting (SLM in comparison with its conventional counterpart, gravity cast alloy. The results obtained indicate that the corrosion resistance of the printed and cast alloys was relatively similar, with a minor advantage to the printed alloy. The corrosion fatigue endurance of the printed alloy was relatively improved compared to the cast alloy. This was mainly attributed to the significant differences between the microstructure and defect characteristics of those two alloys.

  13. Effects of Copper and Austempering on Corrosion Behavior of Ductile Iron in 3.5 Pct Sodium Chloride

    Science.gov (United States)

    Hsu, Cheng-Hsun; Lin, Kuan-Ting

    2013-10-01

    Although alloying and heat treatments are common industrial practices to obtain ductile irons with desired mechanical properties, related information on how the two practices affect corrosion behavior is scarce. In this study, two ductile irons—with and without 1 wt pct copper addition—were austempered to obtain austempered ductile irons (ADIs). Polarization tests and salt spray tests were conducted to explore how both copper-alloying and austempering heat treatments influenced the corrosion behavior of ductile irons. The results showed that the corrosion resistance of 1 wt pct copper-alloyed ductile iron was better than that of the unalloyed one, while ADI had improved corrosion resistance compared with the as-cast. In particular, the ductile iron combined with the copper-alloying and austempering treatments increased the corrosion inhibition efficiency up to 84 pct as tested in 3.5 wt pct NaCl solution.

  14. Effects of Mg content on pore structure and electrochemical corrosion behaviors of porous Al-Mg alloys

    Institute of Scientific and Technical Information of China (English)

    何文远; 肖逸锋; 吴靓; 许艳飞; 钱锦文; 贺跃辉; 郑学军

    2016-01-01

    Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with X-ray diffractometer, scanning electron microscope and electrochemical analyzer. The volume expansion ratio, open porosity and corrosion resistance in 3.5% (mass fraction) NaCl aqueous solution of the alloys increase at first and then decrease with the increase of Mg content. The maxima of volume expansion ratio and open porosity are 18.3% and 28.1% for the porous Al-56%Mg (mass fraction) alloy, while there is the best corrosion resistance for the porous Al-37.5% Mg (mass fraction) alloy. The pore formation mechanism can be explained by Kirkendall effect, and the corrosion resistance can be mainly affected by the phase composition for the porous Al-Mg alloys. They would be of the potential application for filtration in the chloride environment.

  15. Corrosion Inhibition of Aluminum in 0.5 M HCl by Garlic aqueous extract

    Directory of Open Access Journals (Sweden)

    Saedah R. Al-Mhyawi

    2014-06-01

    Full Text Available The inhibition efficiency of extract of Garlic on aluminium in hydrochloric acid solutions has been evaluated by weight loss techniques. Values of inhibition efficiency obtained are dependent upon the concentration of inhibitor and temperature. Generally, inhibition was found to increase with inhibitor concentration, half-life, activation energy but decrease with temperature and first-order rate constant at the temperatures studied. Physical adsorption mechanism has been proposed for the inhibition and Langmuir , Temkin adsorption isotherm was obeyed. Garlic is an inhibitor of aluminium corrosion in 0.5 M hydrochloric acid solution.The values of standard free energy of adsorption suggest that the adsorption of inhibitor on aluminium surface occurred by physisorption mechanism. the negative sign of the Free Energy of adsorption indicates that the adsorption of the inhibitors on the aluminum surface was a spontaneous process.the negative values of enthalpy of adsorption (ΔH suggest that the chemical reaction involved in the adsorption of the inhibitors on the metal surface is an exothermic process, hence increase in the reaction temperature of the medium will decrease the inhibition efficiency.

  16. Preparation and corrosion behavior evaluation of amalgam/titania nano composite

    OpenAIRE

    Neda Bahremandi Tolou; Mohammadhossein Fathi; Ahmad Monshi; Vajihesadat Mortazavi; Farzaneh Shirani

    2011-01-01

    Background: Many attempts have been performed and continued for improvement of dental amalgam properties during last decades. The aim of present research was fabrication and characterization of amalgam/titania nano composite and evaluation of its corrosion behavior. Materials and Methods: In this experimental research, nano particles of titania were added to initial amalgam alloy powder and then, dental amalgam was prepared. In order to investigate the effect of nano particle amounts on p...

  17. Kinetics of Corrosion Process in H2SO4 and HNO3 Aqueous Solutions of Lead Free Sn-Ag-Cu Solder Alloys

    Directory of Open Access Journals (Sweden)

    Guśpiel J.

    2016-06-01

    Full Text Available This paper presents the results of the corrosion resistance of Sn-Ag-Cu alloys in air-saturated aqueous solutions containing NO3-, SO42- ions, whose concentration was equivalent to their contents in acid rains and in concentrations 10 - 100 times higher. The Ag, Cu and Sn concentrations in the corrosive media were determined using the Atomic Absorption Spectrometry. The specific dissolution rate and corrosion current were derived using the a rotating disc technique. The corrosion rate of Sn- Ag-Cu alloys depends on pH of the examined solutions and on the concentration of oxygen near the phase boundary. In the whole range of concentrations of the applied H2SO4 + HNO3 mixtures of acids, the pure Sn was more corrosion resistant than eutectic alloy as well as the near eutectic one, following the sequence: Sn>Sn3.66Ag0.91Cu>3.8Ag0.7Cu.

  18. Corrosion Behavior of the Stressed Sensitized Austenitic Stainless Steels of High Nitrogen Content in Seawater

    Directory of Open Access Journals (Sweden)

    A. Almubarak

    2013-01-01

    Full Text Available The purpose of this paper is to study the effect of high nitrogen content on corrosion behavior of austenitic stainless steels in seawater under severe conditions such as tensile stresses and existence of sensitization in the structure. A constant tensile stress has been applied to sensitized specimens types 304, 316L, 304LN, 304NH, and 316NH stainless steels. Microstructure investigation revealed various degrees of stress corrosion cracking. SCC was severe in type 304, moderate in types 316L and 304LN, and very slight in types 304NH and 316NH. The electrochemical polarization curves showed an obvious second current peak for the sensitized alloys which indicated the existence of second phase in the structure and the presence of intergranular stress corrosion cracking. EPR test provided a rapid and efficient nondestructive testing method for showing passivity, degree of sensitization and determining IGSCC for stainless steels in seawater. A significant conclusion was obtained that austenitic stainless steels of high nitrogen content corrode at a much slower rate increase pitting resistance and offer an excellent resistance to stress corrosion cracking in seawater.

  19. Corrosion behavior of an Al-6Mg-Sc-Zr alloy

    Institute of Scientific and Technical Information of China (English)

    XU Guangxing; TAO Binwu; LIU Jianhua; LI Songmei

    2005-01-01

    The corrosion behavior of an Al-6Mg-Sc-Zr alloy was studied and compared with that of an Al-6Mg-Zr alloy.The addition of scandium into the Al-6Mg-Zr alloy reduced the susceptibility to exfoliation corrosion. By using the constant load tensile method in a 3.5 wt.% NaCl solution, the resistance to SCC of the Al-6Mg-Sc-Zr alloy was higher than that of the Al-6Mg-Zr alloy. When the specimens were not applied with an anodic current, the Al-6Mg-Sc-Zr alloy was resistance to SCC and no brittle cracking was found on the fracture surface. When an anodic current was applied, the Al-6Mg-Sc-Zr alloy specimens failed as a result of accelerated corrosion rather than SCC. It was believed that the addition of scandium resulted in (Al3Sc, Zr) particles that greatly refmed grains and promoted the formation of homogeneous discontinuous distribution of β-phase in the alloy base, which much contributed to good corrosion resistance of the Al-6Mg-Sc-Zr alloy.

  20. Grit blasting of medical stainless steel: implications on its corrosion behavior, ion release and biocompatibility.

    Science.gov (United States)

    Galván, J C; Saldaña, L; Multigner, M; Calzado-Martín, A; Larrea, M; Serra, C; Vilaboa, N; González-Carrasco, J L

    2012-03-01

    This study reports on the biocompatibility of 316 LVM steel blasted with small and rounded ZrO(2) particles or larger and angular shaped Al(2)O(3) particles. The effect of blasting on the in vitro corrosion behavior and the associated ion release is also considered. Surface of Al(2)O(3) blasted samples was rougher than that of ZrO(2) blasted samples, which was also manifested by a higher surface area. Compared to the polished alloy, blasted steels exhibited a lower corrosion resistance at the earlier stages of immersion, particularly when using Al(2)O(3) particles. With increasing immersion time, blasted samples experienced an improvement of the corrosion resistance, achieving impedance values typical of passive alloys. Blasting of the alloy led to an increase in Fe release and the leaching of Ni, Mn, Cr and Mo. On all surfaces, ion release is higher during the first 24 h exposure and tends to decrease during the subsequent exposure time. Despite the lower corrosion resistance and higher amount of ions released, blasted alloys exhibit a good biocompatibility, as demonstrated by culturing osteoblastic cells that attached and grew on the surfaces.

  1. Corrosion Behavior of Ultra-high Strength Steel 300M in Different Simulated Marine Environments

    Institute of Scientific and Technical Information of China (English)

    GUO Qiang; LIU Jianhua; YU Mei; LI Songmei

    2016-01-01

    Corrosion behavior of 300M in neutral corrosion environments containing NaCl simulated by total immersion (TI), salt spraying (SS) and periodic immersion (PI), was investigated by surface analysis techniques, corrosion weight-loss method, and electrochemical measurements. In total immersion environment, rust on the steel consisted of a porous outer rust layer with main constituent ofγ-FeOOH, and an inner rust layer of dense Fe3O4 iflm with network broad cracks. In salt spraying environment, outer rust with main composition ofγ-FeOOH/α-FeOOH/Fe3O4 was compact, and inner rust showed dense Fe3O4 iflm. Rust formed by periodic immersion exhibited a compact outer rust layer with constituent ofα-FeOOH/γ-FeOOH/Fe3O4 and an inner rust layer with composition ofα-FeOOH/α-Fe2O3; inner rust showed a ultra-dense iflm adherent to the steel. The corrosion rate showed a rule ofvs(salt spraying)>vti(total immersion)>>vpi(periodic immersion) in 0-240 h, andvss≈vti»vpiin 240-720 h. The rust formed by periodic immersion was dense and compact, with stable electrochemical properties, and had excellent protection on the steel. Humidity and oxygen concentration in all the environments played major roles in rust formation.

  2. Influence of sulfide concentration on the corrosion behavior of titanium in a simulated oral environment.

    Science.gov (United States)

    Harada, Rino; Takemoto, Shinji; Kinoshita, Hideaki; Yoshinari, Masao; Kawada, Eiji

    2016-05-01

    This study assessed the corrosion behavior of titanium in response to sulfide by determining the effects of sulfide concentration and pH over immersion period. Corrosion was evaluated through changes in color, glossiness, surface characterization, and titanium release. Sulfide solutions were prepared in 3 different concentrations with Na2S, each in pH unadjusted (sulfide-alkaline) and pH adjusted to 7.5 (sulfide-neutral). Titanium discoloration increased and glossiness decreased as sulfide concentration and immersion period increased in sulfide-alkaline solutions. Coral-like complexes were observed on the surface of these specimens, which became more pronounced as concentration increased. Small amounts of titanium release were detected in sulfide-alkaline solutions; however, this was not affected by immersion periods. Corrosion was indicated through considerable surface oxidation suggesting the formation of a thick oxide layer. No significant changes in color and glossiness, or titanium release were indicated for titanium specimens immersed in sulfide-neutral solutions indicating that pH had a significant effect on corrosion. Our findings suggest that a thick oxide layer on the titanium surface was formed in sulfide-alkaline solutions due to excessive oxidation.

  3. Effects of Cl- and SO2-4 Ions on Corrosion Behavior of X70 Steel

    Institute of Scientific and Technical Information of China (English)

    Junwei WU; Xiaogang LI; Cuiwei DU; Song WANG; Yiquan SONG

    2005-01-01

    Corrosion behaviors of X70 steel were studied by means of electrochemical experiments and morphology observation.First, through potentiodynamic polarization in solution of various Cl- ions concentration, it was found that Epit began to appear in solution of Cl- concentration above 0.1 mol/L, and there was a critical point of Cl- concentration between 0.05 mol/L and 0.1 mol/L, below which the extent of pitting and general corrosion were trivial, while in solution of Cl- concentration above 0.1 mol/L, general and pitting corrosion became greater as the increasing of Cl- concentration. All of them were confirmed by the SEM observations after anodic polarization. Second, via the potentiodynamic polarization curves of X70 steel in 0.5 mol/L Cl- solution with 0, 0.05, 0.5 and 1 mol/L SO42-ions, it was found SO42- ions were able to inhibit corrosion aroused from Cl- ions, accordingly a model was set up to describe the process. In addition, to further explore the inhibited effect of SO42- ions, EIS was used in solutions of different Cl- and SO42- concentrations, the results revealed that the e(ectrochemical resistance has a relation with the [SO42-]/[Cl-], that was, the bigger the value of [SO42-]/[Cl-], the greater the electrochemical resistance.

  4. Microstructure and corrosion behavior of electroless deposited Ni-P/CeO2 coating

    Institute of Scientific and Technical Information of China (English)

    Hui Ming Jin; Shi Hang Jiang; Lin Nan Zhang

    2008-01-01

    Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition,and its microstructure and corrosive property were compared with its CeO2-free counterpart.Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) spectrometer were used to examine surface morphology and structure of the as-plated coating.Differential scanning calorimeter (DSC) and transmission electronic microscopy (TEM) were used to study the coating's phase change at high temperature.The coating's corrosive behavior in 3%NaCI + 5%H2SO4 solution was also investigated.The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals,while the Ni-P/CeO2 coating had perfect amorphous structure.In high-temperature condition,Ni3P precipitation and Ni crystallization took place in both coatings but at different temperatures,while the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels.The anti-corrosion property was better in the CeO2-containing coating,and this was due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart.Ni-P/CeO2 coating's pure amorphous structure was the result of Ni's hindered crystal-typed deposition and P's promoted deposition.

  5. Aqueous corrosion of borosilicate glasses: experiments, modeling and Monte-Carlo simulations; Alteration par l'eau des verres borosilicates: experiences, modelisation et simulations Monte-Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Ledieu, A

    2004-10-01

    This work is concerned with the corrosion of borosilicate glasses with variable oxide contents. The originality of this study is the complementary use of experiments and numerical simulations. This study is expected to contribute to a better understanding of the corrosion of nuclear waste confinement glasses. First, the corrosion of glasses containing only silicon, boron and sodium oxides has been studied. The kinetics of leaching show that the rate of leaching and the final degree of corrosion sharply depend on the boron content through a percolation mechanism. For some glass contents and some conditions of leaching, the layer which appears at the glass surface stops the release of soluble species (boron and sodium). This altered layer (also called the gel layer) has been characterized with nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS) techniques. Second, additional elements have been included in the glass composition. It appears that calcium, zirconium or aluminum oxides strongly modify the final degree of corrosion so that the percolation properties of the boron sub-network is no more a sufficient explanation to account for the behavior of these glasses. Meanwhile, we have developed a theoretical model, based on the dissolution and the reprecipitation of the silicon. Kinetic Monte Carlo simulations have been used in order to test several concepts such as the boron percolation, the local reactivity of weakly soluble elements and the restructuring of the gel layer. This model has been fully validated by comparison with the results on the three oxide glasses. Then, it has been used as a comprehensive tool to investigate the paradoxical behavior of the aluminum and zirconium glasses: although these elements slow down the corrosion kinetics, they lead to a deeper final degree of corrosion. The main contribution of this work is that the final degree of corrosion of borosilicate glasses results from the competition of two opposite mechanisms

  6. Assessing the effect of cement-steel interface on well casing corrosion in aqueous CO2 environments

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jiabin [Los Alamos National Laboratory; Carey, James W [Los Alamos National Laboratory; Zhang, Jinsuo [Los Alamos National Laboratory

    2010-01-01

    CO{sub 2} leakage is a critical safety concern for geologic storage. In wellbore environments, important leakage paths include the rock-cement and cement-casing interfaces. If the cement-casing interface is filled with escaping CO{sub 2}, the well casing directly contacts the CO{sub 2}. This can cause severe corrosion in the presence of water. This paper studies the effect of steel-cement interface gaps, ranging from 1 mm to 0 um, on casing corrosion. Corrosion kinetics were measured employing electrochemical techniques including linear polarization resistance, open circuit potential and electrochemical impedance spectroscopy. The experimental results showed that the corrosion of steel is not significant where the gap between steel and cement is small ({le} 100 {micro}m). Corrosion rates are controlled by the diffusion of corrosive species (H{sub 2}CO{sub 3} and H{sup +}) along the interface. In contrast, steel corrosion is severe in a broad gap where the corrosion process is limited only by the reaction kinetics of steel and corrosive species. The threshold leading to severe corrosion in terms of the cement-steel interface size (100 {micro}m) was determined. Our research clarifies a corrosion scenario at the cement-steel interface. Casing steel corrosion is initiated when attacked by corrosive species at the cement-steel interface. For relatively tight interfaces, this results in a slow thinning of the casing and expansion of the interface width. If the gap increases beyond the critical threshold size, the corrosion rate increases significantly, and a potentially damaging cycle of corrosion and interface expansion is developed.

  7. Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control

    Institute of Scientific and Technical Information of China (English)

    FAN Xiaomeng; GUAN Xiaohong; MA Jun; AI Hengyu

    2009-01-01

    Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic and invariable pH conditions that was unsuitable for practical application.Without reaction conditions (dissolved oxygen or reaction pH) control, this study aimed at subjecting the kinetics of denitrification by microscale Fe0 (160-200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface.Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant.Additional test results showed that the reduction rate of nitrate increased with increasing Fe0 dosage.The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage.Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration.X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5.The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

  8. Thermodynamic simulation of the effect of slag chemistry on the corrosion behavior of alumina-chromia refractory

    Institute of Scientific and Technical Information of China (English)

    Shi-xian Zhao; Bin-li Cai; Hong-gang Sun; Gang Wang; Hong-xia Li; and Xiao-yan Song

    2016-01-01

    The corrosion behavior of alumina–chromia refractory against two kinds of industrial slags (coal slag and iron smelting slag) at 1550°C was investigated via thermodynamic simulations. In the proposed simulation model, the initial slag first attacks the matrix and sur-face aggregates and subsequently attacks the inner aggregates. The simulation results indicate that the slag chemistry strongly affects the phase formation and corrosion behavior of the refractory brick. Greater amounts of alumina were dissolved and spinel solid phases formed when the brick interacted with iron smelting slag. These phenomena, as well as the calculated lower viscosity, may lead to much deeper penetration than that exhibited by coal slag and to more severe corrosion compared to that induced by coal slag. The thermodynamic calcula-tions well match the experimental observations, demonstrating the efficiency of the proposed simulation model for evaluating the corrosion behavior of alumina–chromia refractory.

  9. Mechanisms of Copper Corrosion in Aqueous Environments. A report from the Swedish National Council for Nuclear Waste's scientific workshop, on November 16, 2009

    Energy Technology Data Exchange (ETDEWEB)

    2010-07-01

    In 2010 the Swedish Nuclear Fuel and Waste Management Company, SKB, plans to submit its license application for the final repository of spent nuclear fuel. The proposed method is the so-called KBS-3 method and implies placing the spent nuclear fuel in copper canisters, surrounded by a buffer of bentonite clay, at 500 m depth in the bedrock. The site selected by SKB to host the repository is located in the municipality of Oesthammar on the Swedish east coast. The copper canister plays a key role in the design of the repository for spent nuclear fuel in Sweden. The long-term physical and chemical stability of copper in aqueous environments is fundamental for the safety evolution of the proposed disposal concept. However, the corrosion resistance of copper has been questioned by results obtained under anoxic conditions in aqueous solution. These observations caused some head-lines in the Swedish newspapers as well as public and political concerns. Consequently, the Swedish National Council for Nuclear Waste organized a scientific workshop on the issue 'Mechanisms of Copper Corrosion in Aqueous Environments'. The purpose of the workshop was to address the fundamental understanding of the corrosion characteristics of copper regarding oxygen-free environments, and to identify what additional information is needed to assess the validity of the proposed corrosion mechanism and its implication on the containment of spent nuclear fuel in a copper canister. This seminar report is based on the presentations and discussions at the workshop. It also includes written statements by the members of the expert panel

  10. Effect of Aging Treatments on the Mechanical and Corrosive Behaviors of Spray-Formed 7075 Alloy

    Science.gov (United States)

    Su, Rui-ming; Qu, Ying-dong; Li, Rong-de

    2014-11-01

    Mechanical properties, microstructure, exfoliation corrosion (EXCO), and intergranular corrosion (IGC) behaviors of the spray-formed 7075 aluminum alloy after T6, T73, retrogression (R), and re-aging (RRA) treatment, respectively, were studied by using tensile tester, transmission electron microscope, and scanning electron microscope. The results show that the T6 process can increase the ultimate tensile strength (UTS) up to 760 MPa, while it decreases the elongation, the EXCO, and the IGC resistance of the alloy. The T73 process can improve elongation, the EXCO, and the IGC resistance of the alloy. The corrosion resistance of the alloy can also be improved by R and RRA processes with retrogression times increase. The tiny precipitated phases distributed homogeneously in the matrix can increase the UTS. The close-connected discrete grain boundary phases (GBP) and the narrow precipitate free zones (PFZ) will lower the elongation, the EXCO, and the IGC resistance of the alloy. Contrarily, the discrete GBP and wide PFZ can improve the elongation, the EXCO, and the IGC resistance of the alloy. The EXCO and the IGC behaviors for the spray-formed 7075 alloy after different aging treatments have been established according to the standards of ASTM G34-2001 (2007) and ASTM G110-1992 (2009).

  11. Erosion and Corrosion Behavior of Laser Cladded Stainless Steels with Tungsten Carbide

    Science.gov (United States)

    Singh, Raghuvir; Kumar, Mukesh; Kumar, Deepak; Mishra, Suman K.

    2012-11-01

    Laser cladding of tungsten carbide (WC) on stainless steels 13Cr-4Ni and AISI 304 substrates has been performed using high power diode laser. The cladded stainless steels were characterized for microstructural changes, hardness, solid particle erosion resistance and corrosion behavior. Resistance of the clad to solid particle erosion was evaluated using alumina particles according to ASTM G76 and corrosion behavior was studied by employing the anodic polarization and open circuit potential measurement in 3.5% NaCl solution and tap water. The hardness of laser cladded AISI 304 and 13Cr-4Ni stainless steel was increased up to 815 and 725Hv100 g, respectively. The erosion resistance of the modified surface was improved significantly such that the erosion rate of cladded AISI 304 (at 114 W/mm2) was observed ~0.74 mg/cm2/h as compared to ~1.16 and 0.97 mg/cm2/h for untreated AISI 304 and 13Cr-4Ni, respectively. Laser cladding of both the stainless steels, however, reduced the corrosion resistance in both NaCl and tap water.

  12. Wear and corrosion behavior of W/WC bilayers deposited by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, N.A. de [Excellence Center for Novel Materials, Universidad del Valle, Cali (Colombia); Jaramillo, H.E. [Science and Engineering of Materials Group, Department of Basic Science of Engineering, Universidad Autonoma de Occidente, Cali (Colombia); Department of Energetic and Mechanic, Universidad Autonoma de Occidente, Cali (Colombia); Bejarano, G. [Excellence Center for Novel Materials, Universidad del Valle, Cali (Colombia); Group for Engineering and Materials Development, CDT ASTIN-SENA, Cali (Colombia); Group of Corrosion and Protection, Antioquia University, Medellin (Colombia); Villamil, B.E.; Teran, G. [Richer Young, COLCIENCIAS, Cali (Colombia)

    2007-07-01

    WC/W coatings were deposited by reactive magnetron sputtering using 40%, 60% and 80% methane CH{sub 4} in the gas mixture. The bilayers were grown on to AISI 420 stainless-steel substrates in order to study the wear and corrosion behavior. Before growing the bilayers, one Ti monolayer was grown to improve the adherence of the coatings to the substrate. The wear resistance and the friction coefficient of the coatings were determined using a pin-on-disk tribometer. All coatings had a friction coefficient of about 0.5. The measured weight lost of the bilayers from each probe allowed the qualitative analysis of wear behavior all coatings. The bilayers grown with 80% methane showed the best abrasive wear resistance and adhesion without failure through the coating in the wear track for dry pin-on-disk sliding. Electrochemical corrosion test showed that the bilayers grown with 80% methane were more resistant to corrosion than the ones uncoated. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Effect of Indium Content on the Microstructure, Mechanical Properties and Corrosion Behavior of Titanium Alloys

    Directory of Open Access Journals (Sweden)

    Mi-Kyung Han

    2015-05-01

    Full Text Available Ti-xIn (x = 0, 5, 10, 15 and 20 wt% alloys were prepared to investigate the effect of indium on the microstructure, mechanical properties, and corrosion behavior of titanium with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xIn alloys. The Ti-xIn alloys exhibited a lamellar α-Ti structure at an indium content of up to 20 wt%. High-resolution TEM images of the Ti-xIn alloys revealed that all the systems contained a fine, acicular martensitic phase, which showed compositional fluctuations at the nanoscopic level. The mechanical properties and corrosion behavior of Ti-xIn alloys were sensitive to the indium content. The Vickers hardness increased as the In content increased because of solid solution strengthening. The Ti-xIn alloys exhibited superior oxidation resistance compared to commercially pure Ti (cp-Ti. Electrochemical results showed that the Ti-xIn alloys exhibited a similar corrosion resistance to cp-Ti. Among the alloys tested, Ti-10In showed a potential for use as a dental material.

  14. Adsorption Behavior and Inhibition Corrosion Effect of Sodium Carboxymethyl Cellulose on Mild Steel in Acidic Medium

    Institute of Scientific and Technical Information of China (English)

    BAYOL E; G(U)RTEN A.A; DURSUN M.; KAYAK(I)R(I)LMAZ K.

    2008-01-01

    The effect of sodium carboxymethyl cellulose (Na-CMC) on the corrosion behavior of mild steel in 1.0 mol· L-1 HC1 solution has been investigated by using weight loss (WL) measurement, potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods. These results showed that the inhibition efficiency of Na-CMC increased with increasing the inhibitor concentration. Potentiodynamic polarization studies revealed that the Na-CMC was a mixed type inhibitor in 1.0 mol·L-1 HC1. The adsorption of the inhibitor on mild steel surface has been found to obey the Langmuir isotherm. The effect of temperature on the corrosion behavior of mild steel in 1.0 mol ·L-1 HC1 with addition of 0.04% of Na-CMC has been studied in the temperature range of 298-328 K The associated apparent activation energy (E*a) of corrosion reaction has been determined. Scanning electron microscopy (SEM) has been applied to investigate the surface morphology of mild steel in the absence and presence of the inhibitor molecules.

  15. A Comparison of Corrosion Behavior of Copper and Its Alloy in Pongamia pinnata Oil at Different Conditions

    Directory of Open Access Journals (Sweden)

    Meenakshi H. N. Parameswaran

    2013-01-01

    Full Text Available Vegetable oils are promising substitutes for petrodiesel as they can be produced from numerous oil seed crops that can be cultivated anywhere and have high energy contents, exhibiting clean combustion behavior with zero CO2 emission and negligible SO2 generation. The impact of biofuel on the corrosion of various industrial metals is a challenge for using biofuel as automotive fuel. Fuel comes in contact with a wide variety of metallic materials under different temperatures, velocities, and loads thereby causing corrosion during storage and flow of fuel. Hence, the present investigation compares the corrosion rates of copper and brass in Pongamia pinnata oil (O100, 3% NaCl, and oil blend with NaCl (O99 obtained by static immersion test and using rotating cage. The corrosivity and conductivity of the test media are positively correlated. This study suggested that the corrosivity of copper is higher than brass in Pongamia pinnata oil (PO.

  16. Corrosion behavior of tantalum-coated cobalt-chromium modular necks compared to titanium modular necks in a simulator test.

    Science.gov (United States)

    Dorn, Ulrich; Neumann, Daniel; Frank, Mario

    2014-04-01

    This study compared the corrosion behavior of tantalum-coated cobalt-chromium modular necks with that of titanium alloy modular necks at their junction to titanium-alloy femoral stem. Tests were performed in a dry assembly and two wet assemblies, one contaminated with calf serum and the other contaminated with calf serum and bone particles. Whereas the titanium modular neck tested in the dry assembly showed no signs of corrosion, the titanium modular necks tested in both wet assemblies showed marked depositions and corrosive attacks. By contrast, the tantalum-coated cobalt-chromium modular necks showed no traces of corrosion or chemical attack in any of the three assemblies. This study confirms the protective effect of tantalum coating the taper region of cobalt-chromium modular neck components, suggesting that the use of tantalum may reduce the risk of implant failure due to corrosion.

  17. Electrochemical Study of Corrosion Behavior of Wrought Stellite Alloys in Sodium Chloride and Green Death Solutions

    Science.gov (United States)

    Zhang, X. Z.; Liu, R.; Chen, K. Y.; Yao, M. X.; Collier, R.

    2015-09-01

    Corrosion behavior of wrought Stellite 6B and Stellite 6K, which have similar chemical composition but contain different carbon content, in 3.5 wt.% NaCl solution and in Green Death solution is investigated using various electrochemical methods, including potentiodynamic polarization, cyclic polarization, and electrochemical impedance spectroscopy (EIS). The obtained potentiodynamic polarization curves, cyclic polarization curves, and EIS spectra for these alloys are in good agreement, showing that Stellite 6K with higher carbon content is easier corroded due to its larger volume fraction of carbides but the Cr2O3 film formed on this alloy is stronger and more stable than that on Stellite 6B. Further immersion tests on these alloys show that Stellite 6K has less resistance to pitting corrosion.

  18. High temperature corrosion behavior of arc-sprayed aluminum coatings on steel

    Institute of Scientific and Technical Information of China (English)

    SUN Jian-bo; WANG Yong; DONG Li-xian

    2004-01-01

    Aluminum coatings were sprayed on the substrate of steel Q235 by arc spraying. The test samples of Q235, Al coatings and Al coatings with seal coat were placed in box type electric resistance furnace at 400, 500,600, 650 ℃ when their oxidation behaviors were studied. And their oxidation kinetics curves were protracted. Microstructure, microhardness, bond strength and distribution of section elements were investigated by optical microscope(OM), Vickers microhardness instrument, electric tensile test machine and EPMA. Al coatings and Al coatings with seal coat can enhance the oxidation-resistance of substrate under 500 ℃. The latter has the best corrosion resistance. The coatings can't protect the substrate against oxidation above 600 ℃. After a long time corrosion there is enriched oxygen element at interface.

  19. Study on Marine Corrosion and Antifouling Behavior of Copper Alloys Exposed to Sea Areas in China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The relationship of corrosion resistance and antifouling behavior of 19 Cu alloys exposed to seawater of Qingdao ,Xiamen,Yulin sea areas in China for 1,2,4,8 year intervals was studied .The experiments were carried on by analyzing the composition of corrosion films formed on the surface of alloy specimens during the immersion time and by using OM,SEM,EDXA and AES experiment methods.The results verify the view point that it is the cuprous oxide film which played an important role in antifouling property of Cu alloys in seawater and throw a light on the view point in details further.The influence of different sea areas on the antifouling property of Cu alloys is also discussed.

  20. Effect of manganese on the microstructure, mechanical properties and corrosion behavior of titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-Woo; Hwang, Moon-Jin; Han, Mi-Kyung [Department of Dental Materials and MRC for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Kim, Yong-Geun [Department of Ophthalmic Optics, Dongkang College, Gwangju 500-714 (Korea, Republic of); Song, Ho-Jun [Department of Dental Materials and MRC for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Park, Yeong-Joon, E-mail: yjpark@jnu.ac.kr [Department of Dental Materials and MRC for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757 (Korea, Republic of)

    2016-09-01

    The phase/microstructure, mechanical properties and corrosion behavior of a series of binary Ti−Mn alloys with 5, 10, 15 and 20 wt% Mn were investigated in order to understand the effects of Mn content on mechanical properties, oxidation behavior, and electrochemical corrosion properties of Ti−Mn alloys. The phase/microstructure of Ti-xMn alloys was analyzed using X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. All examined properties of the Ti−Mn alloys were sensitive to the Mn content. The tested Ti-xMn alloys had α-Ti, β-Ti, and α-TiMn phases. Ti−Mn alloy containing 5 wt% Mn composed of α-Ti, β-Ti, α-TiMn, and isothermal ω phases. The proportion of α-Ti phase decreased and precipitation of β-Ti phase increased with increasing wt% of Mn. Cast Ti−Mn exhibited higher hardness and better oxidation protection than commercially pure Ti (cp-Ti). The tested Ti-xMn alloys showed better corrosion resistance than the cp-Ti. Ti−Mn alloy containing 5 wt% Mn had the highest hardness and lowest modulus, and is a good candidate for dental implant alloy. - Highlights: • Mechanical properties of Ti−Mn alloys were sensitive to the content of Mn. • As Mn content increased, α-Ti phase decreased and β-Ti phase increased. • Ti−Mn exhibited higher hardness and better oxidation protection ability. • Ti−Mn displayed superior corrosion resistance than commercially pure Ti. • Ti−Mn alloy with 5 wt% Mn is a good candidate for dental casting alloy.

  1. Corrosion Behavior in 3.5% NaCl Solutions of γ-TiAl Processed by Electron Beam Melting Process

    Directory of Open Access Journals (Sweden)

    Asiful Hossain Seikh

    2015-12-01

    Full Text Available In this work, the corrosion behavior of γ-TiAl alloy produced by electron beam melting (EBM process in 3.5% NaCl solution was reported. The study has been performed using potentiodynamic polarization resistance and electrochemical impedance spectroscopy techniques and complemented by scanning electron microscopy investigations. All measurements were carried out after different periods of alloy exposure in the chloride solutions and at different temperatures. The results showed that the EBM produced γ-TiAl alloy has excellent corrosion resistance confirmed by the high values of polarization resistance and the low values of corrosion current and corrosion rate. With increase in immersion time, the corrosion potential moved to a higher positive value with a decrease in corrosion current and corrosion rate, which suggests an improvement in corrosion resistance. On the other hand, the increase of temperature was found to significantly increase the corrosion of the processed γ-TiAl alloy.

  2. Influence of Freeze-Thaw Damage on the Steel Corrosion and Bond-Slip Behavior in the Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Fangzhi Zhu

    2016-01-01

    Full Text Available This paper mainly studies the behavior of steel corrosion in various reinforced concrete under freeze-thaw environment. The influence of thickness of concrete cover is also discussed. Additionally, the bond-slip behavior of the reinforced concrete after suffering the freeze-thaw damage and steel corrosion has also be presented. The results show that the freeze-thaw damage aggravates the steel corrosion in concrete, and the results become more obvious in the concrete after suffering serious freeze-thaw damage. Compared with the ordinary concrete, both air entrained concrete and waterproofing concrete possess better resistance to steel corrosion under the same freeze-thaw environment. Moreover, increasing the thicknesses of concrete cover is also an effective method of improving the resistance to steel corrosion. The bond-slip behavior of reinforced concrete with corroded steel decreases with the increase of freeze-thaw damage, especially for the concrete that suffered high freeze-thaw cycles. Moreover, there exists a good correlation between the parameters of bond-slip and freeze-thaw cycles. The steel corrosion and bond-slip behavior of reinforced concrete should be considered serious under freeze-thaw cycles environment, which significantly impact the durability and safety of concrete structure.

  3. Microstructural Characterization and Corrosion Behavior of Al 7075 Alloys Using X-ray Synchrotron Tomography

    Science.gov (United States)

    Singh, Sudhanshu Shekhar

    Al 7075 alloys are used in a variety of structural applications, such as aircraft wings, automotive components, fuselage, spacecraft, missiles, etc. The mechanical and corrosion behavior of these alloys are dependent on their microstructure and the environment. Therefore, a comprehensive study on microstructural characterization and stress-environment interaction is necessary. Traditionally, 2D techniques have been used to characterize microstructure, which are inaccurate and inadequate since the research has shown that the results obtained in the bulk are different from those obtained on the surface. There now exist several techniques in 3D, which can be used to characterize the microstructure. Al 7075 alloys contain second phase particles which can be classified as Fe-bearing inclusions, Si-bearing inclusions and precipitates. The variation in mechanical and corrosion properties of aluminum alloys has been attributed to the size, shape, distribution, corrosion properties and mechanical behavior of these precipitates and constituent particles. Therefore, in order to understand the performance of Al 7075 alloys, it is critical to investigate the size and distribution of inclusions and precipitates in the alloys along with their mechanical properties, such as Young's modulus, hardness and stress-strain behavior. X-ray tomography and FIB tomography were used to visualize and quantify the microstructure of constituent particles (inclusions) and precipitates, respectively. Microscale mechanical characterization techniques, such as nanoindentation and micropillar compression, were used to obtain mechanical properties of inclusions. Over the years, studies have used surface measurements to understand corrosion behavior of materials. More recently, in situ mechanical testing has become more attractive and advantageous, as it enables visualization and quantification of microstructural changes as a function of time (4D). In this study, in situ X-ray synchrotron tomography

  4. Effect of Stress Ratio and Loading Frequency on the Corrosion Fatigue Behavior of Smooth Steel Wire in Different Solutions

    Directory of Open Access Journals (Sweden)

    Songquan Wang

    2016-09-01

    Full Text Available In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more severe than that in neutral and alkaline solutions. With the extension of immersion time in acid solution, the cathodic reaction of steel wire gradually changed from the reduction of hydrogen ion to the reduction of oxygen, but was always the reduction of hydrogen ion in neutral and alkaline solutions. The corrosion kinetic parameters and equivalent circuits of steel wires were also obtained by simulating the Nyquist diagrams. In corrosion fatigue test, the effect of stress ratio and loading frequency on the crack initiation mechanism was emphasized. The strong corrosivity of acid solution could accelerate the nucleation of crack tip. The initiation mechanism of crack under different conditions was summarized according to the side and fracture surface morphologies. For the crack initiation mechanism of anodic dissolution, the stronger the corrosivity of solution was, the more easily the fatigue crack source formed, while, for the crack initiation mechanism of deformation activation, the lower stress ratio and higher frequency would accelerate the generation of corrosion fatigue crack source.

  5. Corrosion Behavior of Copper-Clad Steel Bars with Unclad Two-End Faces for Grounding Grids in the Red Clay Soil

    Science.gov (United States)

    Shao, Yupei; Mu, Miaomiao; Zhang, Bing; Nie, Kaibin; Liao, Qiangqiang

    2017-02-01

    Iron-aluminum oxides in the red soil have a significant impact on the corrosion behavior of the metal for grounding grids. Effects of iron-aluminum oxides on the corrosion behavior of the cross section of copper-clad steel in the red soil have been investigated using electrochemical impedance spectroscopy and Tafel polarization. All the data indicate that the iron-aluminum oxides can promote the corrosion of copper-clad steel in the red soil. The corrosivity of the red soil greatly increases after iron-aluminum oxides are added into the soil. Iron-aluminum oxides promote galvanic corrosion of copper-clad steel and increase the corrosion degree of the center steel layer. The iron-aluminum oxides stimulate corrosion process of copper-clad steel acting as a cathodic depolarizing agent. XRD results further validate that the corrosion products of the copper-clad steel bar mainly consist of Fe3O4 and Cu2O.

  6. Passivation and Corrosion Behavior of Modified Ferritic-Pearlitic Railway Axle Steels

    Science.gov (United States)

    Moon, A. P.; Sangal, S.; Srivastav, Simant; Gajbhiye, N. S.; Mondal, K.

    2015-01-01

    Electrochemical polarization behavior of two newly developed ferritic-pearlitic railway axle steels (MS3 and MS6) and the standard Indian conventional axle steel has been studied in sodium borate buffer solution of pH 8.4 with and without the presence of NaCl. The polarization behavior of both the new axle steels shows close resemblance, whereas, different polarization behavior has been observed for the conventional axle steel. Electrochemical impedance spectroscopy measurements have clearly reflected significantly improved passivation behavior for the newly developed steels compared to that of the conventional axle steel. NaCl salt fog exposure tests have also shown superior corrosion resistance of the newly developed axle steels as compared to the conventional axle steel. Higher surface roughness on the corroded conventional axle steel has also been observed compared to the smoother surface in case of the new axle steels. Higher corrosion resistance of the new axle steels has been attributed to their finer microstructure and strongly adherent protective rusts.

  7. Evaluating the effects of hydroxyapatite coating on the corrosion behavior of severely deformed 316Ti SS for surgical implants

    Energy Technology Data Exchange (ETDEWEB)

    Mhaede, Mansour, E-mail: mansour.mhaede@yahoo.com [Institute of Materials Science and Engineering, Clausthal University of Engineering, Agicolastr.6, 38678 Clausthal-Zellerfeld (Germany); Faculty of Engineering, Zagazig University, 44519 Zagazig (Egypt); Ahmed, Aymen; Wollmann, Manfred; Wagner, Lothar [Institute of Materials Science and Engineering, Clausthal University of Engineering, Agicolastr.6, 38678 Clausthal-Zellerfeld (Germany)

    2015-05-01

    The present work investigates the effects of severe plastic deformation by cold rolling on the microstructure, the mechanical properties and the corrosion behavior of austenitic stainless steel (SS) 316Ti. Hydroxyapatite coating (HA) was applied on the deformed material to improve their corrosion resistance. The martensitic transformation due to cold rolling was recorded by X-ray diffraction spectra. The effects of cold rolling on the corrosion behavior were studied using potentiodynamic polarization. The electrochemical tests were carried out in Ringer's solution at 37 ± 1 °C. Cold rolling markedly enhanced the mechanical properties while the electrochemical tests referred to a lower corrosion resistance of the deformed material. The best combination of both high strength and good corrosion resistance was achieved after applying hydroxyapatite coating. - Highlights: • Cold rolling markedly increases the hardness of SS 316Ti from 125 to 460 HV10. • Higher deformation degrees lead to lower corrosion resistance. • Application of HA-coating leads to significant improvement of the corrosion resistance.

  8. Effects of Alloying Element Ca on the Corrosion Behavior and Bioactivity of Anodic Films Formed on AM60 Mg Alloys

    Directory of Open Access Journals (Sweden)

    Anawati Anawati

    2016-12-01

    Full Text Available Effects of alloying element Ca on the corrosion behavior and bioactivity of films formed by plasma electrolytic oxidation (PEO on AM60 alloys were investigated. The corrosion behavior was studied by conducting electrochemical tests in 0.9% NaCl solution while the bioactivity was evaluated by soaking the specimens in simulated body fluid (SBF. Under identical anodization conditions, the PEO film thicknesses increased with increasing Ca content in the alloys, which enhanced the corrosion resistance in NaCl solution. Thicker apatite layers grew on the PEO films of Ca-containing alloys because Ca was incorporated into the PEO film and because Ca was present in the alloys. Improvement of corrosion resistance and bioactivity of the PEO-coated AM60 by alloying with Ca may be beneficial for biodegradable implant applications.

  9. Magnetically induced electrodeposition of Zn-Ni alloy coatings and their corrosion behaviors

    Science.gov (United States)

    Rao, Vaishaka R.; Bangera, Kasturi V.; Hegde, A. Chitharanjan

    2013-11-01

    The less magnetic features of Zn-Ni alloy compared to Fe-Ni and Fe-Co alloys made it interesting to develop them under the influence of applied magnetic field. In this regard, the effects of a magnetic field (B) applied in a direction parallel and perpendicular to the nominal current, during electrodeposition process of Zn-Ni alloy have been investigated by means of X-ray diffraction and EDX analysis. The modification of crystal orientation by superimposition of a varying magnetic field is studied for alloys of constant nickel content (8 a %.), deposited at optimal current density (j) of 3.0 A dm-2. The effect of magnetic field on crystallographic orientation and hence the corrosion behaviors of the coatings were studied. The preferential orientations (101) and (002) of the zinc phase and (330) γ-Ni5Zn21 phase are always favored to exist with parallel and perpendicular magnetic field. The preferential (321) γ-Ni5Zn21 orientation is found to be the characteristic of perpendicular magnetic field. Further, Zn (100) orientation is found to be non-responsive to the effect of parallel magnetic field. The coatings developed using perpendicular magnetic field is more corrosion resistant compare to that for parallel magnetic field. This is attributed to the additional (321) γ-Ni5Zn21 orientations. The changes in the phase structure of the coatings deposited at different magnetic field are attributed to the effect caused by the magnetic convection induced in the electrolytic solution, called MHD effect (magneto-hydrodynamic effect). The chemical composition of the alloy was found to be same in both natural and magnetically induced deposition due to constant Ni content in the bath. The variation in the surface morphology of the coatings was studied by scanning electron microscopy (SEM). The Zn-Ni alloy coating deposited at 0.8 T perpendicular B showed the highest corrosion resistance (with corrosion rate=0.26×10-2 mm y-1) compared to the one with no B (corrosion rate=14

  10. Effect of Carbide Distribution on Corrosion Behavior of the Deep Cryogenically Treated 1.2080 Steel

    Science.gov (United States)

    Amini, Kamran; Akhbarizadeh, Amin; Javadpour, Sirus

    2016-02-01

    Deep cryogenic heat treatment is a supplementary process performed on steels specifically tool steels before tempering to improve the wear resistance and hardness of these materials. The carbide distribution changes via the electric current flow or the application of a magnetic field during the deep cryogenic heat treatment. Hence, the electric current and the magnetic field were applied to the samples to investigate the corrosion behavior of the deep cryogenically treated samples by electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results showed that increasing the carbide percentage and achieving a more homogenous carbide distribution during the deep cryogenic heat treatment will remarkably decrease the corrosion resistance due to a decrease in the solutionized chromium atoms in the structure as well as the increase in the martensite-carbide grain boundaries (the galvanic cell areas). Moreover, it was clarified that the electric current flow and magnetic fields reduce the carbide percentage, which leads to an increase in the corrosion resistance of these samples in comparison with the deep cryogenically treated samples.

  11. Effects of Mo Composites on the Corrosion Behaviors of Low Alloy Steel

    Institute of Scientific and Technical Information of China (English)

    LIANG Chenghao; GUO Jianwei; HU Xianqi

    2007-01-01

    By using electrochemical and weight loss methods, the effect of MoO42-on the corrosion behaviors of low alloy steel was investigated in the 55%LiBr+0.07 mol/L LiOH solution at high temperature.The results show that MoO42-, being an anodic inhibitor, would form a passive film rapidly and impede both anodic and cathodic reactions. Moreover, Na2MoO4 effectively prevents corrosion in 55%LiBr+0.07 mol/L LiOH solution when its concentration is higher than 200 mg/L. Some elements of alloy, such as chromium and nickel, may cause the widening of passive potential region and the decrease of passive density, which indicates that the corrosion resistance increases. AES analysis shows that molybdenum participates in forming a protection film. The synergistic effect between chromium and molybdenum induces Cr-steel to be in passive state in lower Na2MoO4 concentration.

  12. Study on Surface Adsorption and Inhibition Behavior of Corrosion Inhibitors Contained in Copper Foil Rolling Oil

    Institute of Scientific and Technical Information of China (English)

    Xiong Sang; Sun Jianlin; Jiang Wei; Xu Yang; Zeng Yingfeng; Xia Lei

    2015-01-01

    Adsorption and inhibition behavior of 2,5-bis(ethyldisulfanyl)-1,3,4-thiadiazole (DMTDA) andN-((6-methyl-1H -benzo[d][1,2,3]triazol-1-yl)methyl)-N-octyloctan-1-amine (EAMBA) as corrosion inhibitors contained in copper foil roll-ing oil have been investigated using gravimetric and electrochemical techniques. Meanwhile, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) have been employed to observe the surface topography and analyze the components on copper foil. The results show that the rolling oil containing DMTDA and EAMBA can signiifcantly decrease the dissolution rate and increase the inhibition efifciency of samples, especially in the case of best compounded rolling oil system. The SEM and EDS investigations also conifrmed that the protection of the copper foil surface is achieved by strong adsorption of the molecules which can prevent copper from being corroded easily. Reactivity descriptors of the corrosion inhibitors have been calculated by the density functional theory (DFT) and the reactivity has been analyzed through the molecular orbital and Fukui indices. Active sites of inhibitor are mainly concentrated on the ring and the polar functional groups, and in the meanwhile, the distribution is helpful to form coordination and backbonding among molecules and then to form stable adsorption on the metal surface. And this work provides theoretical evidence for the selection of corrosion inhibitors contained in copper foil rolling oil.

  13. Influence of Ga and Hg on microstructure and electrochemical corrosion behavior of Mg alloy anode materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effects of Hg and Ga on the electrochemical corrosion behavior of Mg-5%Hg (molar fraction) alloys were investigated by the measurement of polarization curves and galvanostatic test. The microstructure of the alloys and the corroded surface of the specimens were investigated by scanning electron microscopy, X-ray diffractometry and emission spectrum analysis. It can be concluded that the addition of 1%Ga (molar fraction) reduces corrosion current density from 26.98 mA/cm2 to 2.34 mA/cm2;while the addition of 1%Hg (molar fraction) increases corrosion current density. The addition of Ga and Hg both promotes the electrochemical activity of the alloys and the influence of Ga is more effective than Hg. Mg-5%Hg-1%Ga alloy has the best electrochemical activity, showing mean potential of-1.992 V. The activation mechanism of the magnesium alloy produced by Hg and Ga was put forward. Magnesium atoms are dissolved in liquid Hg and Ga to form amalgam and undergo severe oxidation at the amalgam/electrolyte interface.

  14. Corrosion behaviors of NdFeB magnets prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Tao Li; Ming Yue; Aizhi Sun; Baoqin Qiu; Yaofu Xiao; Jiuxing Zhang

    2004-01-01

    The spark plasma sintering (SPS) technique was introduced into the field of NdFeB preparation due to its own advantages.High property NdFeB magnets with fine grains were prepared by SPS method. The corrosion behaviors of SPS NdFeB were studied by electrochemical measurements and 92% RH hyther tests at 353 K. The results were compared with those of the traditional sintered NdFeB magnets. It shows that both the SPS NdFeB and the traditional sintered NdFeB have good corrosion resistance in alkaline environment due to surface passivation; while, the fine grain microstructure of SPS NdFeB results in a more homogeneous phase composition distribution and thus reduces the electrochemical inhomogenity between the ferromagnetic phase and the Nd-rich intergranular phase in the magnet. Therefore, the SPS NdFeB exhibits better corrosion resistance than the traditional sintered NdFeB in neutral and weak acidic environment.

  15. Microstructure and Corrosion Behavior of Electrodeposited Ni-Co-ZrC Coatings

    Science.gov (United States)

    Zhang, Zhongquan; Jiang, Chuanhai; Ma, Naiheng

    2014-11-01

    In this present work, ZrC particles incorporated Ni-Co composite coatings were electrodeposited. The objective of this article is to study the influence of Co content on the microstructure and properties of Ni-Co-ZrC coatings. Pure Ni and Ni-ZrC coatings have also been electrodeposited for comparison. Surface morphology, chemical composition, microstructure, and microhardness of Ni-Co-ZrC coatings were characterized by scanning electron microscopy, energy dispersive spectrometer, x-ray diffractometer, and Vicker microhardness tester. The potentiodynamic polarization technique was applied to measure the corrosion behavior of the coatings. By increasing Co concentration in electrolyte, Co content of the coatings was modified from 0 to 80 wt.% and ZrC particles content of the coatings was reduced. As the Co content increased, the dominant phase structure was changed from face centered cubic to hexagonal close packed crystal structure. Surface morphology of the Ni-Co-ZrC coatings was changed from nodular to sharp corner structure, and finally branched morphology with increasing Co content of the coating. Among the electrodeposited coatings, Ni-Co-ZrC coating with 42 wt.% Co content exhibited the highest microhardness. The corrosion potential of the coating was shifted to more positive with increasing the Co content from 0 to 64 wt.%. The lowest corrosion rate of 4.507 × 10-7 g·h-1·cm-2 was found for Ni-Co-ZrC coating at the Co content of 75 wt.%.

  16. Corrosion behavior of dental alloys used for retention elements in prosthodontics.

    Science.gov (United States)

    Nierlich, Judith; Papageorgiou, Spyridon N; Bourauel, Christoph; Hültenschmidt, Robert; Bayer, Stefan; Stark, Helmut; Keilig, Ludger

    2016-06-01

    The purpose of this study was to investigate the corrosion behavior of 10 different high noble gold-based dental alloys, used for prosthodontic retention elements, according to ISO 10271. Samples of 10 high-noble and noble gold-based dental alloys were subjected to: (i) static immersion tests with subsequent analysis of ion release for eight different elements using mass spectrometry; (ii) electrochemical tests, including open-circuit potential and potentiodynamic scans; and (iii) scanning electron microscopy, followed by energy-dispersive X-ray microscopy. The results were analyzed using one-way ANOVA and Sidak multiple-comparisons post-hoc test at a level of significance of α = 0.05. Significant differences were found among the 10 alloys studied for all ions (P potential and from 566.7 to 1367.5 mV for the breakdown potential. Both the open-circuit and the breakdown potential varied considerably among these alloys. Scanning electron microscopy analysis confirmed the existence of typically small-diameter corrosion defects, whilst the energy-dispersive X-ray analysis found no significant alteration in the elemental composition of the alloys. The results of this study reveal the variability in the corrosive resistance among the materials used for retention elements in prosthodontics.

  17. Corrosion behavior of EUROFER steel in flowing eutectic Pb-17Li alloy

    Energy Technology Data Exchange (ETDEWEB)

    Konys, J. E-mail: juergen.konys@imf.fzk.de; Krauss, W.; Voss, Z.; Wedemeyer, O

    2004-08-01

    Reduced-activation-ferritic-martensitic (RAFM) steels are considered for application in fusion technology as structural materials. The alloy EUROFER 97 was developed on the basis of the experience gained with steels of the OPTIFER, MANET and F82H-mod. type. These alloys will be in contact with the liquid breeder Pb-17Li and their corrosion behavior is of significance for their successful application. Corrosion tests of EUROFER 97 in flowing Pb-17Li at 480 deg. C were performed up to about 12 000 h to evaluate the kinetics of the dissolution attack. The exposed samples were analysed by metallography and scanning electron microscopy (SEM) with EDX. The results show that EUROFER 97 is attacked by flowing liquid Pb-17Li with a flow velocity of about 0.3 m/s similar to the earlier examined steels and that the typical steel elements are dissolved. The observed attack is of uniform type with values of about 90 {mu}m/year. The corrosion rate is a somewhat smaller for EUROFER compared to the other RAFM steels but with equal activation energy.

  18. Corrosion and Nano-mechanical Behaviors of Magnetron Sputtered Al-Mo Gradient Coated Steel

    Science.gov (United States)

    Venugopal, A.; Srinath, J.; Ramesh Narayanan, P.; Sharma, S. C.; Venkitakrishnan, P. V.

    2016-11-01

    A gradient three-layer Al-Mo coating was deposited on steel using magnetron sputtering method. The corrosion and nano-mechanical properties of the coating were examined by electrochemical impedance spectroscopy and nano-indentation tests and compared with the conventional electroplated cadmium and IVD aluminum coatings. Electrochemical impedance spectroscopy was performed by immersing the coated specimens in 3.5% NaCl solution, and the impedance behavior was recorded as a function of immersion time. The mechanical properties (hardness and elastic modulus) were obtained from each indentation as a function of the penetration depth across the coating cross section. The adhesion resistance of the coatings was evaluated by scratch tests on the coated surface using nano-indentation method. The results show that the gradient Al-Mo coating exhibits better corrosion resistance than the other coatings in view of the better microstructure. The impedance results were modeled using appropriate electrical equivalent circuits for all the coated systems. The uniform, smooth and dense Al-Mo coating obtained by magnetron sputtering exhibits good adhesion with the steel substrate as per scratch test method. The poor corrosion resistance of the later coatings was shown to be due to the defects/cracks as well as the lesser adhesion of the coatings with steel. The hardness and elastic modulus of the Al-Mo coating are found to be high when compared to the other coatings.

  19. Effect of temperature on corrosion behavior of 3003 aluminum alloy in ethylene glycol-water solution

    Institute of Scientific and Technical Information of China (English)

    Chen Xin; Tian Wenming; Li Songmei; Yu Mei; Liu Jianhua

    2016-01-01

    The effect of temperature on the corrosion behavior of 3003 aluminum alloy in ethylene glycol–water solution was investigated by potentiodynamic polarization and electrochemical impe-dance spectroscopy (EIS) techniques. The surface characterization was observed and determined by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive spec-trometer (EDS). The results demonstrate that the anodic aluminum dissolution and the cathodic oxygen reduction were accelerated by the increased temperature. However, as temperature was over 60 °C, the solubility and concentration of oxygen decreased, resulting in the inhibition of cathodic reaction. The cathodic reaction rate of 3003 aluminum alloy rose to the maximum at 60 °C. The Warburg impedance in Nyquist diagram diminished and then was replaced by a negative capaci-tance caused by the absorption of intermediate corrosion product on electrode. On the other hand, after potentiodynamic measurements, 3003 aluminum alloy suffered pitting corrosion. The dissolu-tion of aluminum alloy around secondary phase particles expanded both horizontally and vertically. © 2016 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.

  20. In vitro corrosion behavior and cytotoxicity property of magnesium matrix composite with chitosan coating

    Institute of Scientific and Technical Information of China (English)

    戴翌龙; 余琨; 陈良建; 陈畅; 乔雪岩; 颜阳

    2015-01-01

    Mg-6%Zn-10%β-Ca3(PO4)2 composite was prepared through powder metallurgy methods with different chitosan coatings on its surface. The properties of the chitosan coatings on the surface of Mg-6%Zn-10%β-Ca3(PO4)2 composite, such as the adhesion ability, the corrosion behavior and the cytotoxicity properties, were investigated, and the microstructure of the chitosan coating was observed by scanning electron microscope (SEM). The results show that chitosan coating improves the corrosion resistance of the magnesium composite specimens significantly. Mg-6%Zn-10%β-Ca3(PO4)2 composite specimens exhibit good corrosion resistance and low pH values in simulated body fluid (SBF) at 37 °C in the immersion test with 7-layer chitosan coating whose relative molecular mass is 30×104 Da. The cytotoxicity tests indicate that Mg-6%Zn-10%β-Ca3(PO4)2 with chitosan coating is nontoxic with a cytotoxicity grade of zero against L-929 cells, which is better than that of uncoated composites.

  1. Behavior of tritium permeation induced by water corrosion of alpha iron around room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Otsuka, T.; Hashizume, K. [Kyushu University, Kasuga, Fukuoka (Japan)

    2015-03-15

    Tritium (T) permeation leakage to surroundings is a great safety concern in fission and fusion reactor systems. T permeation potentially occurs from T contaminated water through cooling tubes or storage tank made of metals which dissolve some T evolved by water corrosion. In order to understand behaviors of hydrogen uptake and permeation in pure α-iron (αFe) during water corrosion around room temperature, hydrogen permeation experiments for an αFe membrane have been conducted by means of tritium tracer techniques. The present study suggests that hydrogen produced by water corrosion of αFe is trapped in product oxide layers to delay hydrogen uptake in αFe for a moment. However, the oxide layers do not work as a sufficient barrier for hydrogen uptake. Some of hydrogen dissolved in αFe normally diffuses and permeates through the bulk in the early stage of permeation. In a later stage, hydrogen permeation could be apparently stopped by the disappearance of concentration difference of tritium. Hydrogen partial pressure at the water/αFe interface could be ranged from 0.7 to 9.5 kPa around room temperature.

  2. The relation between severe plastic deformation microstructure and corrosion behavior of AZ31 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ben Hamu, G. [Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Eliezer, D. [Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Institute of Materials Science and Engineering, TU Clausthal (Germany)], E-mail: deliezer@bgu.ac.il; Wagner, L. [Institute of Materials Science and Engineering, TU Clausthal (Germany)

    2009-01-22

    The quest for ever, higher performance in structural applications has resulted in the outgoing development of new or improved materials with novel crystallographic textures, microstructures, and compositions. However, commercial applicability of such materials depends heavily on the development of economical and robust manufacturing methods. Due to the promise of excellent properties, such as superplasticity, high strength, good ductility, enhanced high cycle fatigue life, and good corrosion resistance, interest has grown in nanostructure bulk materials. Those materials are defined most often as materials exhibiting nanocrystalline grain structures and particle sizes below 100 nm in at least one dimension. In recent years, bulk nanostructure materials processed by methods of severe plastic deformation (SPD) such as equal channel angular extrusion (ECAE) have attracted the growing interest of specialists in materials science. The main object of this research is to compare the microstructural changing and corrosion behavior of magnesium alloy AZ31 after extrusion and severe plastic deformation by ECAE process. The ECAE process can produce intense and uniform deformation by simple shear and provides a convenient procedure for introducing an ultra fine grain size into a material. The samples were prepared by using hot extrusion methods. Hardness and AC and DC polarization tests were carried out on the extruded rods, and the microstructure was examined using optical, electron microscopy (SEM, TEM) and EDS. The results showed that the severe plastic deformation process affected both the microstructure and the corrosion behavior of AZ31 Mg alloy. These results can be explained by the effects of the process on microstructure of AZ31 Mg alloy such as grain size and dislocation density caused by the change in recrystallization behavior.

  3. Electrochemical Corrosion Behavior ofthe Laser Continuous Heat Treatment Welded Joints of 2205 Duplex Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    LIU Heping; JIN Xuejun

    2011-01-01

    The electrochemical corrosion behaviors of the welded joints of 2205 duplex stainless steel with the laser continuous heat treatment were investigated.The secondary austenite formation is the outcome of thermodynamic equilibrium breach of the alloy during heat treatment and the result of the continuous heat treatment which has the most important effect on the weld material.The partitioning behaviors of chromium and molybdenum as well as the volume fraction of ferrite and austenite have a remarkable influence on the composition of the individual phase.Mechanical examination of the laser trated weld demonstrates that the tensile strength and yield strength increase with increasing the amount of the secondary austenite.It is shown that the ultimate tensile strength of the 6 kW laser-treated weld is higher about 20 MPa than no heat treatment weld and the ductility can be further improved without compromising strength.The results indicate that the welding alters the corrosion behavior because of different post heat treatment power and the broad active peak is not identified which is attributed to the dissolution of the secondary austenitic in the ferrite phase.It is indicated that pitting resistance equivalent (PRE) values of base metal and 6 kW weld are higher than that of other welds; base metal is 33.7,6 kW weld 33.3,no treatment 32.4,4 kW weld 32.8,8 kW weld 32.5.The extent of corrosion resistance improvement after reheating treatment is mainly caused by the removal of nitrogen from ferritic regions,which occurred as a consequence of secondary austenite growth.

  4. Corrosion behavior of pyroclore-rich titanate ceramics for plutonium disposition ; impurity effects.

    Energy Technology Data Exchange (ETDEWEB)

    Bakel, A. J.

    1999-01-13

    The baseline ceramic contains Ti, U, Ca, Hf, Gd, and Ce, and is made up of only four phases, pyrochlore, zirconolite, rutile, and brannerite. The impurities present in the three other ceramics represent impurities expected in the feed, and result in different phase distributions. The results from 3 day, 90 C MCC-1 tests with impurity ceramics were significantly different than the results from tests with the baseline ceramic. Overall, the addition of impurities to these titanate ceramics alters the phase distributions, which in turn, affects the corrosion behavior.

  5. Crystallization and Corrosion Resistance in Different Aqueous Solutions of Zr50.7Ni28Cu9Al12.3 Amorphous Alloy and Its Crystallization Counterparts

    Science.gov (United States)

    Ge, Wenjuan; Li, Boyu; Axinte, Eugen; Zhang, Zitang; Shang, Caiyun; Wang, Yan

    2017-02-01

    The Zr50.7Ni28Cu9Al12.3 amorphous alloy and its crystallization counterparts have been prepared using a melt spinning technique and proper annealing treatment. The as-annealed products at 768 K are amorphous composites consisting of a main amorphous phase and a few ZrO2 nanocrystals. The corrosion behaviors have been investigated in 0.5-M NaCl, 1-M HCl, and 0.5-M H2SO4 solutions. The results show that amorphous composites present the enhanced corrosion resistance in Cl- containing solutions due to the formation of compact passive films, which are promoted by an appropriate quantity of ZrO2 nanocrystals. Nevertheless, the relaxed samples possess good corrosion resistance in H2SO4 solution, which is attributed to the existence of Zr(Al, Ni)-rich protective film induced by the depletion of Cu. In addition, corrosion resistance of the tested alloys is relatively superior in H2SO4 solution, especially for pitting corrosion resistance, and inferior in HCl solution.

  6. Magnetically induced electrodeposition of Zn–Ni alloy coatings and their corrosion behaviors

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Vaishaka R. [Electrochemistry Research Laboratory, Department of Chemistry, National Institute of Technology Karnataka, NITK, Surathkal, Srinivasnagar 575025, Mangalore, Karnataka (India); Bangera, Kasturi V. [Electrochemistry Research Laboratory, Department of Chemistry, National Institute of Technology Karnataka, NITK, Surathkal, Srinivasnagar 575025, Mangalore, Karnataka (India); Electrochemistry Research Laboratory, Department of Physics, National Institute of Technology Karnataka, NITK, Surathkal, Srinivasnagar, 575025, Mangalore, Karnataka (India); Hegde, A. Chitharanjan, E-mail: hegdeac@rediffmail.com [Electrochemistry Research Laboratory, Department of Chemistry, National Institute of Technology Karnataka, NITK, Surathkal, Srinivasnagar 575025, Mangalore, Karnataka (India)

    2013-11-15

    The less magnetic features of Zn–Ni alloy compared to Fe–Ni and Fe–Co alloys made it interesting to develop them under the influence of applied magnetic field. In this regard, the effects of a magnetic field (B) applied in a direction parallel and perpendicular to the nominal current, during electrodeposition process of Zn–Ni alloy have been investigated by means of X-ray diffraction and EDX analysis. The modification of crystal orientation by superimposition of a varying magnetic field is studied for alloys of constant nickel content (8 a %.), deposited at optimal current density (j) of 3.0 A dm{sup −2}. The effect of magnetic field on crystallographic orientation and hence the corrosion behaviors of the coatings were studied. The preferential orientations (101) and (002) of the zinc phase and (330) γ-Ni{sub 5}Zn{sub 21} phase are always favored to exist with parallel and perpendicular magnetic field. The preferential (321) γ-Ni{sub 5}Zn{sub 21} orientation is found to be the characteristic of perpendicular magnetic field. Further, Zn (100) orientation is found to be non-responsive to the effect of parallel magnetic field. The coatings developed using perpendicular magnetic field is more corrosion resistant compare to that for parallel magnetic field. This is attributed to the additional (321) γ-Ni{sub 5}Zn{sub 21} orientations. The changes in the phase structure of the coatings deposited at different magnetic field are attributed to the effect caused by the magnetic convection induced in the electrolytic solution, called MHD effect (magneto-hydrodynamic effect). The chemical composition of the alloy was found to be same in both natural and magnetically induced deposition due to constant Ni content in the bath. The variation in the surface morphology of the coatings was studied by scanning electron microscopy (SEM). The Zn–Ni alloy coating deposited at 0.8 T perpendicular B showed the highest corrosion resistance (with corrosion rate=0.26×10{sup

  7. Behavior of suspending and wetting agents in aqueous environment

    Directory of Open Access Journals (Sweden)

    Dhawale Shashikant

    2009-01-01

    Full Text Available This work describes the changes in viscosity, conductivity, pH, electrical conductivity, dielectric constant, zeta potential, UV, and IR spectra of aqueous solutions/dispersions of sodium carboxy methyl cellulose (CMC, Tween 80, and sodium lauryl sulphate (SLS during aging at different temperatures. Significant reduction in viscosity ofh sodium CMC occurred during aging studies, while relatively small decrease in viscosity was seen with Tween 80 and SLS. Increment in specific conductivity was seen with aging of excipients. Significant increase of zeta potential was also seen with aging of samples. Concomitant shift in IR spectra of samples was observed with aging at 40°C.

  8. The Impact of Corrosion on the Mechanical Behavior of Welded Splices of Reinforcing Steel S400 and B500c

    Science.gov (United States)

    Apostolopoulos, Ch. Alk.; Michalopoulos, D.; Dimitrov, L.

    2008-02-01

    The reinforcing steel, used in concrete structures, when corroded causes reduction of the strength properties and especially drastic reduction of ductility. Steel corrosion constitutes an important factor of progressive devaluation of its mechanical properties and serious reduction of the integrity of structures. The problem becomes more evident specifically for structures near coastal areas where salt corrosion is predominant. Reinforced concrete columns and beams are quite often extended by welding new steel reinforcement to the already corroded existing steel. In the present article the impact of corrosion on the mechanical properties of welded splices of reinforcing Steel S400 and B500c is examined. An experimental investigation was conducted and tensile and compressive results are presented for welded precorroded S400 and noncorroded B500c steel splices. The mechanical behavior of welded splices in tension are different in compression and depend strongly on the level of corrosion of the S400 bars.

  9. Effect of Multipass Friction Stir Processing on Mechanical and Corrosion Behavior of 2507 Super Duplex Stainless Steel

    Science.gov (United States)

    Mishra, M. K.; Gunasekaran, G.; Rao, A. G.; Kashyap, B. P.; Prabhu, N.

    2016-12-01

    The microstructure, mechanical properties, and corrosion behavior of 2507 super duplex stainless steel after multipass friction stir processing (FSP) were examined. A significant refinement in grain size of both ferrite and austenite was observed in stir zone resulting in improved yield and tensile strength. Electrochemical impedance spectroscopy and anodic polarization studies in 3.5 wt.% NaCl solution showed nobler corrosion characteristics with increasing number of FSP passes. This was evident from the decrease in corrosion current density, decrease in passive current density, and increase in polarization resistance. Also, the decrease in density of defects, based on Mott-Schottky analysis, further confirms the improvement in corrosion resistance of 2507 super duplex stainless steel after multipass FSP.

  10. Corrosion behavior of NiCr alloys in HCl-containing oxidation atmosphere at 700-800 ℃

    Institute of Scientific and Technical Information of China (English)

    张轲; 牛焱; 潘太军; 吴维(山文)

    2004-01-01

    Corrosion behaviors of pure Ni and three NiCr alloys were investigated in an HCl-containing oxidizing atmosphere at 700 ℃ and 800 ℃. All materials suffer from accelerated corrosion at both temperatures. NiCr alloys show an initial mass loss due to the formation of volatile CrCl3 and CrO2Cl2. Some chlorides are detected at the scale/substrate interface and many voids are also found there. NiCr alloys with higher chromium content have better corrosion resistance. However, Ni50Cr is inferior to Ni25Cr due to its two-phase structure, which makes it easy for chlorine to diffuse along grain boundary and to occur inner oxidation. The relevant corrosion mechanism was also discussed.

  11. Adsorption behavior of caffeine as a green corrosion inhibitor for copper

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Fernando Silvio de [Grupo de Estudos de Processos Eletroquimicos e Eletroanaliticos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Giacomelli, Cristiano [Departamento de Quimica, Universidade Federal de Santa Maria, Av. Roraima 1000, 97119-900, Santa Maria, RS (Brazil); Goncalves, Reinaldo Simoes [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970, Porto Alegre, RS (Brazil); Spinelli, Almir, E-mail: almir.spinelli@ufsc.br [Grupo de Estudos de Processos Eletroquimicos e Eletroanaliticos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil)

    2012-12-01

    Electrochemical and impedance experiments were carried out to evaluate the corrosion behavior of copper in aerated 0.1 mol L{sup -1} H{sub 2}SO{sub 4} solutions in the presence of three xanthine derivatives with similar chemical structures. The corrosion rate of copper was found to increase in the presence of theophylline and theobromine and decrease in the presence of caffeine. The adsorption and inhibitory effect of caffeine on copper surfaces in aerated 0.1 mol L{sup -1} H{sub 2}SO{sub 4} solutions were then investigated in detail by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), contact angle measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and fluorescence experiments. The data obtained indicate that caffeine behaves as a cathodic-type inhibitor adsorbing onto the copper surface according to the Temkin isotherm, with the negative Increment G Degree-Sign {sub ads} value of - 31.1 kJ mol{sup -1} signifying a spontaneous adsorption process. The corrosion inhibition efficiency increased with caffeine concentration in the range of 1.0-10.0 mmol L{sup -1}. Furthermore, the EIS results obtained at the open-circuit potential and surface analysis (SEM, EDS and fluorescence) clearly demonstrated the adsorption of the organic compound onto the copper electrode. The contact angle measurements revealed the formation of a hydrophobic protective film. This film covers up to 72% of the total active surface, acts as a protective barrier and prevents interaction between the metal, water and oxygen molecules. - Highlights: Black-Right-Pointing-Pointer We have investigated the adsorption and corrosion inhibition of caffeine on copper surfaces. Black-Right-Pointing-Pointer Caffeine behaves as a cathodic-type inhibitor. Black-Right-Pointing-Pointer Caffeine adsorbs onto copper surface according to Temkin isotherm. Black-Right-Pointing-Pointer There exists the formation of a hydrophobic film that acts as a

  12. Effects of Sodium Thiosulfate and Sodium Sulfide on the Corrosion Behavior of Carbon Steel in an MDEA-Based CO2 Capture Process

    Science.gov (United States)

    Emori, W.; Jiang, S. L.; Duan, D. L.; Zheng, Y. G.

    2016-12-01

    The corrosion behavior of carbon steel has been tested in the presence of sodium thiosulfate and sodium sulfide in an MDEA-based CO2 capture system using electrochemical methods, weight loss measurements and surface analysis. The results of electrochemical measurements revealed that both thiosulfate and sulfide showed corrosion resistance properties to carbon steel corrosion. The corrosion resistance for the system with thiosulfate increased with concentration, while the system with sulfide yielded better corrosion resistance to carbon steel at lower concentrations as increase in sulfide concentration decreased the corrosion resistance. The corrosion inhibition behaviors for both systems at 0.05 M salt concentrations were confirmed by weight loss measurement, and the solution with sodium sulfide exhibited a better inhibition with time.

  13. Effects of Sodium Thiosulfate and Sodium Sulfide on the Corrosion Behavior of Carbon Steel in an MDEA-Based CO2 Capture Process

    Science.gov (United States)

    Emori, W.; Jiang, S. L.; Duan, D. L.; Zheng, Y. G.

    2017-01-01

    The corrosion behavior of carbon steel has been tested in the presence of sodium thiosulfate and sodium sulfide in an MDEA-based CO2 capture system using electrochemical methods, weight loss measurements and surface analysis. The results of electrochemical measurements revealed that both thiosulfate and sulfide showed corrosion resistance properties to carbon steel corrosion. The corrosion resistance for the system with thiosulfate increased with concentration, while the system with sulfide yielded better corrosion resistance to carbon steel at lower concentrations as increase in sulfide concentration decreased the corrosion resistance. The corrosion inhibition behaviors for both systems at 0.05 M salt concentrations were confirmed by weight loss measurement, and the solution with sodium sulfide exhibited a better inhibition with time.

  14. Thermodynamic Modelling of Dolomite Behavior in Aqueous Media

    Directory of Open Access Journals (Sweden)

    Tadeusz Michałowski

    2012-01-01

    Full Text Available The compact thermodynamic approach to the systems containing calcium, magnesium, and carbonate species is referred to dissolution of dolomite, as an example of nonequilibrium ternary salt when introduced into aqueous media. The study of dolomite is based on all attainable physicochemical knowledge, involved in expressions for equilibrium constants, where the species of the system are interrelated. The species are also involved in charge and concentration balances, considered as constraints put on a closed system, separated from the environment by diathermal walls. The inferences are gained from calculations performed with use of an iterative computer program. The simulated quasistatic processes occurred under isothermal conditions, started at a preassumed pH0 value of the solution where dolomite was introduced, and are usually involved with formation of other solid phases. None simplifying assumptions in the calculations were made.

  15. VISCOSITY BEHAVIOR OF LACQUER POLYSACCHARIDE IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    QIU Xingping; ZHANG Lina; DU Yumin; QIAN Baogong

    1991-01-01

    The dependence of measured viscosity on NaCl concentration (0.1 to 3.0M), pH (range of 2-13) and cadoxen composition Wcad (from 2% to 100% ) for the lacquer polysaccharide in NaCl/cadoxen/H2O mixture containing HCl or without were obtained. All the viscosity exponents γ in the Mark-Houwink equations under three different solvent condition are close to 0.5. The wcad dependence of reduced viscosity ηsp/c confirms the single strand chain of the polysaccharide. As the γ values close to 0.5 and values of unperturbed dimension θ/M and [η] much smaller than those for usual linear polymers, these facts suggest that the polysaccharide chains in the aqueous solutions should be dense random coil owing to the highly branched structure.

  16. Influence of chromium on the initial corrosion behavior of low alloy steels in the CO2-O2-H2S-SO2 wet-dry corrosion environment of cargo oil tankers

    Institute of Scientific and Technical Information of China (English)

    Qing-he Zhao; Wei Liu; Jie Zhao; Dong Zhang; Peng-cheng Liu; Min-xu Lu

    2015-01-01

    The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2wet–dry corrosion envi-ronment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance (Rct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.

  17. Corrosion Behavior of Anodic Oxidized TiO2 Film in Seawater

    Institute of Scientific and Technical Information of China (English)

    WANG Min; WANG Wei; HE Benlin; SUN Mingliang; YIN Yansheng; LIU Lan; ZOU Wuyuan; XU Xuefei

    2010-01-01

    TiO2 films were formed on metallic titanium substrates by the anodic oxidation method in H2SO4 solution under the 80V D.C..Phase component and microstructure were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions.Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum(EIS)and polarization curves.The result showed that the TiO2 film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface.The average water contact angle of the film was 116.4 ° in dark,in contrast to an angle of 42.7 ° under the UV illumination for 2 hours,which demonstrates good hydrophobic property.The anti-corrosion behavior of the TiO2 film was declining with the extended immersion time.Under dark conditions,however,the hydrophobic TiO2 film retarded the water infiltrating into the substrate.The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight.All of those mentioned above indicate that the TiO2 film possesses much better performance under dark condition,and it can be applied as an engineering material under dark seawater environment.

  18. Suppression of aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} by reducing dissolved oxygen concentration for high-performance magnetic refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Fujieda, S., E-mail: fujieda@tagen.tohoku.ac.jp; Fukamichi, K.; Suzuki, S.

    2014-07-05

    Highlights: • The aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} and its suppression were investigated. • The lattice expansion after immersion was caused by the hydrogen absorption. • The itinerant-electron metamagnetic transition became indistinct after immersion. • The aqueous corrosion was suppressed by reducing the dissolved oxygen concentration. - Abstract: The itinerant-electron metamagnetic transition of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} becomes indistinct after immersion in distilled-water containing about 8 ppm of the dissolved oxygen (DO) concentration because of aqueous corrosion. However, the aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} is significantly suppressed by reducing the DO concentration. Thus, isothermal magnetic entropy change after immersion for 30 days in deaerated distilled-water with a DO concentration less than 0.1 ppm is larger than that after immersion for 5 days in distilled-water containing about 8 ppm of the DO concentration. Consequently, the reduction of the DO concentration is effective for preservation of the excellent magnetocaloric effects of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} in an aqueous solution, which is a promising heat transfer fluid of room-temperature magnetic refrigeration.

  19. Corrosion Behavior of Mg65Cu25-xZnxGd10 (x=0, 5) Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    LI Guoqiang; HUANG Wei; LI Huanxi; ZHENG Lijing; Hashmi M F

    2008-01-01

    The effect of substitutional element Zn on corrosion behavior of Mg65Cu25Gd10 glass was investigated. The amorphous structure of Mg65Cu25-xZnxGd10(x=0, 5) alloys were examined by X-ray diffractometry and differential scanning calorimetry (DSC). The dissolution rates of Mg65Cu25-xZnxGd10(x=0,5) metallic glasses in a 5 wt% NaCl solution with pH value of 7 were determined by a hydrogen evolution testing method. The corrosion behavior of these alloys was characterized using dipping tests with 5 wt% NaCl, in combination with electrochemical measurements and scanning electron microscopy (SEM). Results show that the anti-corrosion ability of Mg65Cu25Gd10 alloy is significantly improved due to the addition of Zn. Possible mechanism responsible for the improvement is discussed.

  20. Corrosion behaviour of austenitic stainless steel, nickel-base alloy and its weldments in aqueous LiBr solutions

    Energy Technology Data Exchange (ETDEWEB)

    Blasco-Tamarit, E.; Igual-Munoz, A.; Garcia Anton, J.; Garcia-Garcia, D. [Departamento de Ingenieria Quimica y Nuclear. E.T.S.I.Industriales, Universidad Politecnica de Valencia, P.O. Box 22012 E-46071 Valencia (Spain)

    2004-07-01

    With the advances in materials production new alloys have been developed, such as High- Alloy Austenitic Stainless Steels and Nickel-base alloys, with high corrosion resistance. These new alloys are finding applications in Lithium Bromide absorption refrigeration systems, because LiBr is a corrosive medium which can cause serious corrosion problems, in spite of its favourable properties as absorbent. The objective of the present work was to study the corrosion resistance of a highly alloyed austenitic stainless steel (UNS N08031) used as base metal, a Nickel-base alloy (UNS N06059) used as its corresponding filler metal, and the weld metal obtained by the Gas Tungsten Arc Welding (GTAW) procedure. The materials have been tested in different LiBr solutions (400 g/l, 700 g/l, 850 g/l and a commercial 850 g/l LiBr heavy brine containing Lithium Chromate as corrosion inhibitor), at 25 deg. C. Open Circuit Potential tests and potentiodynamic anodic polarization curves have been carried out to obtain information about the general electrochemical behaviour of the materials. The polarization curves of all the alloys tested were typical of passivable materials. Pitting corrosion susceptibility has been evaluated by means of cyclic potentiodynamic curves, which provide parameters to analyse re-passivation properties. The galvanic corrosion generated by the electrical contact between the welded and the base material has been estimated from the polarization diagrams according to the Mixed Potential Method. Samples have been etched to study the microstructure by Scanning Electron Microscopy (SEM). The results demonstrate that the pitting resistance of all these materials increases as the LiBr concentration decreases. In general, the presence of chromate tended to shift the pitting potential to more positive values than those obtained in the 850 g/l LiBr solution. (authors)

  1. Effect of Chloride ion and Zirconium hydride on thr corrosion and SCC behaviors of functionally graded Zirconium alloy p.683

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Y. [Department of Metallurgical and Materials Engineering, Sunmoon University, Asam (Korea, Republic of); Kim, B. G.; Lee, J. W.; Kang, Y. H. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2000-07-01

    Effect of chloride ion and zirconium hydride on the corrosion and stress corrosion cracking behaviors of functionally graded zirconium alloy was studied to develop an advanced nuclear cladding tubing. The functionally graded zirconium alloy had composition gradient of niobium, which was prepared with a hot pressing followed by cold deformation. The corrosion rates and potentials decreased with increasing FeCl{sub 3} and hydride content. The corrosion potentials before and after hydriding are -4.3 V{sub SHE}, 8.8x10{sup -5} A{sub cm}{sup -2} and -12.5 V{sub SHE}, 3.9x10{sup -4} A{sub cm}{sup -2}, respectively. The stress corrosion cracking susceptibility decreased with elongation rate, indicating the saturation value at 5x10{sup -7} sec{sup -1}. SEM observation showed that brittle fracture with corrosion products and pits were observed on the failed surface of hydrided zirconium alloy, suggesting anodic dissolution occurred during exposure after cracking growth along zirconium hydrides. (author)

  2. Influence of the solution temperature on the corrosion behavior of an austenitic stainless steel in phosphoric acid medium

    Energy Technology Data Exchange (ETDEWEB)

    Ibanez-Ferrandiz, M.V.; Blasco-Tamarit, E.; Garcia-Garcia, D.M.; Garcia-Anton, J. [Valencia Univ. Politecnica, Dept. de Ingenieria Quimica y Nuclear. ETSI Industriales, Valencia (Spain); Guenbour, A.; Bakour, S.; Benckokroun, A. [University Mohammed V-Agdal, Lab. Corrosion-Electrochimie, Faculty of Sciences, Rabat (Morocco)

    2009-07-01

    The objective of the present work is to study the effect of the solution temperature on the corrosion resistance of a highly alloyed austenitic stainless steel (UNS N08031) used as base metal, the welded metal obtained by TIG (Tungsten Inert Gas) welding using a Nickel-base alloy (UNS N06059) as filler metal, and the Heat Affected Zone (HAZ) of the base metal. The materials were tested in 5.5 M phosphoric acid solution at 25 C, 40 C, 60 C and 80 C. Open Circuit Potential tests and potentiodynamic anodic polarization curves have been carried out to obtain information about the electrochemical behavior of the materials. Corrosion potentials and corrosion current densities were obtained from Tafel analysis. The critic potentials and passivation current densities of the studied materials were also analyzed. The galvanic corrosion generated by the electrical contact between the welded metal, the base metal and the HAZ, was estimated from the polarisation diagrams according to the Mixed Potential Theory. The samples were etched to study their microstructure by Optical Microscopy. Results demonstrated that the corrosion potential values shift to more anodic potentials as temperature increases. The corrosion current densities and the passive current densities increased with temperature. Open circuit potential values were located in the passive zone of the potentiodynamic curves, which means that the materials passivated spontaneously. (authors)

  3. Corrosion Behavior and Strength of Dissimilar Bonding Material between Ti and Mg Alloys Fabricated by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Patchara Pripanapong

    2016-08-01

    Full Text Available Ti and solution treated Mg alloys such as AZ31B (ST, AZ61 (ST, AZ80 (ST and AZ91 (ST were successfully bonded at 475 °C by spark plasma sintering, which is a promising new method in welding field. The formation of Ti3Al intermetallic compound was found to be an important factor in controlling the bonding strength and galvanic corrosion resistance of dissimilar materials. The maximum bonding strength and bonding efficiency at 193 MPa and 96% were obtained from Ti/AZ91 (ST, in which a thick and uniform nano-level Ti3Al layer was observed. This sample also shows the highest galvanic corrosion resistance with a measured galvanic width and depth of 281 and 19 µm, respectively. The corrosion resistance of the matrix on Mg alloy side was controlled by its Al content. AZ91 (ST exhibited the highest corrosion resistance considered from its corrode surface after corrosion test in Kroll’s etchant. The effect of Al content in Mg alloy on bonding strength and corrosion behavior of Ti/Mg alloy (ST dissimilar materials is discussed in this work.

  4. Corrosion Behavior of Ceramic Cup of Blast Furnace Hearth by Liquid Iron and Slag

    Science.gov (United States)

    Li, Yanglong; Cheng, Shusen; Wang, Zhifeng

    2016-10-01

    Three kinds of sample bricks of ceramic cups for blast furnace hearth were studied by dynamic corrosion tests based on different corrosion systems, i.e., liquid iron system, liquid slag system and liquid iron-slag system. Considering the influence of temperature and sample rotational speed, the corrosion profiles and mass loss of the samples were analyzed. In addition, the microstructure of the corroded samples was observed by optical microscope (OM) and scanning electron microscope (SEM). It was found that the corrosion profiles could be divided into iron corrosion region, slag corrosion region and iron-slag corrosion region via corrosion degree after iron-slag corrosion experiment. The most serious corrosion occurred in iron-slag corrosion region. This is due to Marangoni effect, which promotes a slag film formed between liquid iron and ceramic cup and results in local corrosion. The corrosion of the samples deepened with increasing temperature of liquid iron and slag from 1,623 K to 1,823 K. The variation of slag composition had greater influence on the erosion degree than that of rotational speed in this experiment. Taking these results into account the ceramic cup composition should be close to slag composition to decrease the chemical reaction. A microporous and strong material should be applied for ceramic cup.

  5. Corrosion and Discharge Behaviors of Al-Mg-Sn-Ga-In in Different Solutions

    Science.gov (United States)

    Xiong, Hanqing; Yin, Xiang; Yan, Yang; Dai, Yilong; Fan, Sufeng; Qiao, Xueyan; Yu, Kun

    2016-08-01

    Al-0.5 wt.%Mg-0.08 wt.%Sn-0.05 wt.%Ga-0.05 wt.%In and Al-0.5 wt.%Mg-0.08 wt.%Sn-0.05 wt.%Ga alloys were prepared by melting, casting and cold rolling. Corrosion and discharge behaviors of the two experimental alloys were investigated by electrochemical measurement, self-corrosion rate measurement, air battery testing, and scanning electron microscopy. The results showed that Al-Mg-Sn-Ga-In alloy exhibited higher electrochemical activity than Al-Mg-Sn-Ga alloy in 2 M NaCl solution, while it showed lower electrochemical activity than Al-Mg-Sn-Ga alloy in 4 M NaOH solution. By comparison with the air battery based on Al-Mg-Sn-Ga alloy, the battery with Al-Mg-Sn-Ga-In alloy cannot exhibit better discharge performance in 4 M NaOH electrolyte. However, the performance of the air battery based on Al-Mg-Sn-Ga-In alloy was greatly improved due to the In-rich inclusions and the uniform corroded morphology in 2 M NaCl electrolyte. Thus, Al-Mg-Sn-Ga-In alloy was a good anode material for Al-air battery in 2 M NaCl electrolyte.

  6. Slurry Erosion and Corrosion Behavior of Some Engineering Polymers Applied by Low-Pressure Flame Spray

    Science.gov (United States)

    Lima, Carlos Roberto Camello; Mojena, Miguel Angel Reyes; Rovere, Carlos Alberto Della; de Souza, Natalia Ferraresso Cardoso; Fals, Hipolito Domingo Carvajal

    2016-11-01

    The erosive wear and corrosion resistance of three types of flame spray-deposited polymer coatings was analyzed. The erosive wear test was performed in slurry pot tester with rotational movement using distilled water and mix quartz particles (300 g/l). Two impact angles of the particles were used, reaching 4.15 m/s average impact velocity. Corrosion resistance of the polymer coatings and degradation behavior were investigated by electrochemical impedance spectroscopy in a solution of 0.5 M sodium chloride at room temperature for a total immersion time of 1 year. The interpretation of the results was made according to the Bode plot. It is proven a better slurry erosion wear performance for PEEK and PA12 coatings when the particles impact at 90° angle. For impact angle of 30°, there is no significant difference in the erosion performance of PEEK, PEI, and PA12 coatings. No major changes occurred in the impedance module for PA12 and PEEK samples, indicating that these coatings can protect the steel substrate for extended periods of time. The lower PEI performance is believed to be related to the improper choice of spraying parameters, as the spray conditions were kept constant for the three feedstock materials.

  7. Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst

    Directory of Open Access Journals (Sweden)

    Hebé Gurdián

    2014-04-01

    Full Text Available The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes.

  8. CREVICE CORROSION BEHAVIOR OF X70 STEEL IN HCO3- SOLUTION UNDER CATHODIC POLARIZATION

    Institute of Scientific and Technical Information of China (English)

    C.W.Du; X.G.Li; X.Chen; P.Liang; H.Guo

    2008-01-01

    The crevice corrosion behavior of X70 steel was investigated with a wedge-shaped crevice assembly under-1000 mV (SCE) cathodic polarization in the solutions with various HCO3- concentrations.The potential,current,pH and the oxygen content within the crevice were measured with or without outside coupled specimen.The re-sults indicated that the polarization potential of X70 steel in the crevice dropped with the increase of time under the cathodic polarization.There was a remarkable in-fluence of HCO3- concentration on the potential of X70 steel in the crevice.When HCO3- concentration was up to 0.125%,the surface of the metal was covered with the corrosion products that resulted in the polarization extent of X70 steel decreased.The pH value in the crevice rose and it dropped gradually from the crevice mouth to the bottom under the cathodic polarization.With the increasing of HCO3- concentration, the hydrolyzation reaction of metal in the crevice bottom aggravated.Most of the dis-solved oxygen in the crevice was consumed by the cathodic current.The maximum cathodic current on the metal surface was at the crevice mouth and it was much more than that at the crevice bottom.

  9. Inhibitory Effect of Kopsia Singapurensis Extract on the Corrosion Behavior of Mild Steel in Acid Media

    Institute of Scientific and Technical Information of China (English)

    RAJA Pandian Bothi; RAHIM Afidah Abdul; OSMAN Hasnah; AWANG Khalijah

    2010-01-01

    The influence of the alkaloid extract of Kopsia singapurensis on the corrosion behavior of mild steel (MS) in 1 mol·L-1 HC1 and 1 mol·L-1 H2SO4 was studied using electrochemical techniques,viz.,potentiodynamic polarization and AC impedance.The experimental results clearly show that the plant extract effectively inhibits corrosion in both acid media and the inhibition efficiency obtained from the electrochemical techniques is in good agreement.Furthermore,the polarization technique indicates that the extract acts as an anodic type inhibitor in HC1 and as a mixed type in H2SO4 Scanning election microscopy (SEM) was carried out to examine the surface morphological changes of metal specimens in both the inhibited and uninhibited solutions.SEM images show the formation of an adsorbed layer over the metal surface by the inhibitor molecule.The presence of alkaloidal constituents in the plant extract was confirmed by Fourier transform infrared (FTIR) spectroscopy and chemical analysis.

  10. Study of mechanical, physical, and corrosion behavior of 0.5% cobalt alloyed austempered ductile iron

    Science.gov (United States)

    Abdullah, Bulan; Jaffar, Ahmed; Alias, Siti Khadijah; Ramli, Abdullah; Izham, Mohd Faizul

    2010-03-01

    Objectives: The purpose of this research was to determine the mechanical properties and corrosion behavior of 0.5% Co-DI before and after heat treatment and compare with commercial ductile iron. Methods: Molten metal of newly developed ductile iron which alloyed with 0.5% Cobalt produced through CO2 sand casting method. The specimens then performed preheat to 500°C in an hour then oil quenched. Specimens then performed annealing to 900°C in half an hour before oil quenched again. 500°C, 600°C and 700°C austempering temperature had been selected subjected to the specimens in half an hour before cooled to room temperature. The tests involved are microstructure analysis which included nodule count and phase analysis, polarization test, spectrometer test, density test, tensile test (ASTM E 8M), hardness test and impact test (ASTM A327) on as cast and austempered specimen. Results: 0.5% Cobalt alloyed austempered ductile iron with 500°C austempered temperature is the optimum temperature for 0.5% Co-ADI. It's not only increase the nodule count in the content, but also improve the mechanical properties such as impact toughness and tensile strength. Corrosion rate of 0.5% Co-DI also improved compare to unalloyed DI.

  11. Tribological Behavior of Electroless Ni-P Coatings in Various Corrosive Environments

    Science.gov (United States)

    Panja, Bikash; Das, Suman Kalyan; Sahoo, Prasanta

    2016-04-01

    The present paper deals with the study of tribological characteristics, viz. friction and wear, of electroless Ni-P coating in corrosive environments (brine, acidic and alkaline) by varying different coating process parameters as well as varying the tribological testing parameters, viz. applied load and speed. The optimized results of coating process parameters for minimum friction and wear performance of the coating are presented. Moreover, a detailed study of the tribological behavior of the coating is undertaken individually for the three corrosive environments. The results obtained are compared among each other and also with the dry condition test of the coating. It is found that the friction coefficient of Ni-P coating decreases with increase in load for all environments. In case of wear, the wear rate of Ni-P coating gradually increases with increase in load for all mediums but the same decreases after 40N in brine and alkaline mediums. However, for acidic solution, the wear rate shows a continuous increasing trend. It is observed that alkaline and brine environments are favorable from friction and wear point of view of the coating, respectively. Microstructure study of the coatings is also performed and the coating is found to be of cauliflower-like morphology. The coating also exhibits amorphous structure in as-deposited condition, which gradually turns crystalline with heat treatment.

  12. Nanostructure and corrosion behaviors of nanotube formed Ti-Zr alloy

    Institute of Scientific and Technical Information of China (English)

    Won-Gi KIM; Han-Cheol CHOE

    2009-01-01

    In order to investigate the nanostructures and corrosion behaviors of Ti-Zr alloys, nanotube formed Ti-Zr(10%, 20%, 30% and 40% in mass fraction) alloys were prepared by arc melting and the condition of controlling nanostructure was at 1 000 ℃ for 24 h in argon atmosphere; formation of nanotubes was conducted by anodizing a Ti-Zr alloy in H3PO4 electrolyte with a small amount of fluoride ions at room temperature. The corrosion properties of specimens were examined through potentiodynamic test (potential range of -1 500-2 000 mV) in 0.9% NaCl solution by using potentiostat. Microstructures of the alloys were observed by optical microscope(OM), field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). Diameter of nanotube does not depend on Zr content, but interspace of nanotube predominantly depends on Zr content, which confirms that ZrO2 oxides play a role to increase the interspace of nanotube formed on the surface.

  13. Structure and phase behavior of aqueous methylcellulose solutions

    Science.gov (United States)

    McAllister, John; Schmidt, Peter; Lodge, Timothy; Bates, Frank

    2015-03-01

    Cellulose ethers (CE) constitute a multi-billion dollar industry, and have found end uses in a broad array of applications from construction materials, food products, personal care products, and pharmaceuticals for more than 80 years. Methylcellulose (MC, with the trade name METHOCEL™) is a CE in which there is a partial substitution of -OH groups with -OCH3 groups. This results in a polymer that is water-soluble at low temperatures, and aqueous solutions of MC display gelation and phase separation at higher temperatures. The nature of MC gelation has been debated for many years, and this project has made significant advances in the understanding of the solution properties of CEs. We have characterized a fibrillar structure of MC gels by cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS). Using light scattering, turbidity measurements, and dynamic mechanical spectroscopy (DMS) we report that MC microphase separates by nucleation and growth of fibril aggregates, and is a different process from LCST phase separation.

  14. EFFECT OF SULPHATE-REDUCING BACTERIA ON ELECTRO-CHEMICAL CORROSION BEHAVIOR OF 16Mn STEEL IN SEA MUD

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of sulfate-reducing bacteria (SRB) on electrochemical corrosion behavior of 16Mn steel, and galvanic corrosion behavior of the steels in the juncture area between bacterial and bacteria-free sea mud was studied in laboratory under simulated conditions. Sea mud dense with SRB was taken from the Qingdao beach. Part of the sea mud was sterilized and the rest was kept in the original condition. The sterilized and original sea mud was put respectively into two plastic testing troughs electrically-connected by an agar potassium chloride salt bridge. Galvanic and non-galvanic 16Mn steel samples were put into the trough at the same intervals. The SRB number measured by the MPN tri-tube method was about 2.4×105 per 100 g mud and was kept basically the same during the experimental period. The ρ, pH, eH, T, S (salinity) were measured simultaneously. The galvanic current was measured with zero-resistance galvanometer and the corrosion rate was measured with the weight loss method.The results showed that (1) the corrosion rate of 16Mn steel in bacterial sea mud was 4.0 times that in bacteria-free sea mud; (2) galvanic corrosion occurs between steel samples buried in different (bacterial and bacteria-free) sea mud. The steel sample in the bacterial sea mud was the anode of a galvanic couple and had higher corrosion rate than that of the non-galvanic sample. The existence of the galvanic couple increased the corrosion rate of the sample in bacterial sea mud by 4.1%.

  15. Wear and Corrosion Behavior of Functionally Graded Nano-SiC/2014Al Composites Produced by Powder Metallurgy

    Science.gov (United States)

    Wang, Zhi-Guo; Li, Chuan-Peng; Wang, Hui-Yuan; Zhu, Jia-Ning; Wang, Cheng; Jiang, Qi-Chuan

    2017-02-01

    Functionally graded 2014Al/SiC composites (FGMs) with varying volume fractions (1-7%) of nano-SiC particulates (n-SiCp) were fabricated by powder metallurgy. The effect of n-SiCp content on corrosion and wear behaviors was studied. The microstructures of composites were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. The corrosion behavior of the composites was evaluated by potentiodynamic polarization scans in 3.5 wt.% NaCl solution. Corrosion results show that corrosion current of composite layer with 3 vol.% n-SiC was much lower than that of 2014Al matrix. Mechanical properties of the composites were assessed by microhardness tests and ball-on-disk wear tests. As the applied load changed from 15 to 30 N, wear rates of the composites increased significantly and the wear mechanism transformed from mild to severe wear regime. It also shows that 3 vol.% n-SiCp/2014Al composite layer observed the lowest wear rate where adhesive and abrasive wear mechanisms played a major role. These results suggest that the n-SiCp are effective candidates for fabricating FGMs for the applications demanding a tough core and a hard, wear or corrosion resisting surface.

  16. Effects of hydrogen water chemistry on corrosion fatigue behavior of cold-worked 304L stainless steel in simulated BWR coolant environments

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, M.F., E-mail: mfchiang@iner.gov.tw [Institute of Nuclear Energy Research, Division of Nuclear Fuels and Materials, Lungtan, Taoyuan 325, Taiwan (China); Young, M.C.; Huang, J.Y. [Institute of Nuclear Energy Research, Division of Nuclear Fuels and Materials, Lungtan, Taoyuan 325, Taiwan (China)

    2011-04-15

    Corrosion fatigue behavior of stainless steel 304L (SS304L) in a simulated BWR coolant with hydrogen injection was investigated. Hydrogen water chemistry slightly mitigated the corrosion fatigue degradation of the as-received SS304L specimens, but, on the contrary, it slightly increased the corrosion fatigue crack growth rates (CFCGRs) of the cold-worked specimens. All the CFCGR-tested specimens showed similar fracture features, except for the amounts of deposited corrosion debris. The results indicated that decreasing the oxygen concentration of water environment is not an effective measure to suppress the fatigue crack growth rate of cold-worked SS304L. The CFCGRs of the SS304L were determined by an interaction between corrosion, oxide-induced crack closure and cold work in corrosive environments. At a specific level of reduction, cold work could enhance the corrosion fatigue resistance of SS304 both in the air-saturated and HWC coolant environments.

  17. Effects of hydrogen water chemistry on corrosion fatigue behavior of cold-worked 304L stainless steel in simulated BWR coolant environments

    Science.gov (United States)

    Chiang, M. F.; Young, M. C.; Huang, J. Y.

    2011-04-01

    Corrosion fatigue behavior of stainless steel 304L (SS304L) in a simulated BWR coolant with hydrogen injection was investigated. Hydrogen water chemistry slightly mitigated the corrosion fatigue degradation of the as-received SS304L specimens, but, on the contrary, it slightly increased the corrosion fatigue crack growth rates (CFCGRs) of the cold-worked specimens. All the CFCGR-tested specimens showed similar fracture features, except for the amounts of deposited corrosion debris. The results indicated that decreasing the oxygen concentration of water environment is not an effective measure to suppress the fatigue crack growth rate of cold-worked SS304L. The CFCGRs of the SS304L were determined by an interaction between corrosion, oxide-induced crack closure and cold work in corrosive environments. At a specific level of reduction, cold work could enhance the corrosion fatigue resistance of SS304 both in the air-saturated and HWC coolant environments.

  18. Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

    Science.gov (United States)

    Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

    2016-08-01

    Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.

  19. Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

    Science.gov (United States)

    Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

    2016-01-01

    Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces. PMID:27503635

  20. Inhibiting properties and adsorption of an amine based fatty acid corrosion inhibitor on carbon steel in aqueous carbon dioxide solutions

    Energy Technology Data Exchange (ETDEWEB)

    Buchweishaija, Joseph

    1997-12-31

    Carbon dioxide corrosion is a major corrosion problem in oil and gas production systems and many organic inhibitors have been tested and used to protect the substrate from corrosion. This thesis studies the mechanism of interaction of the inhibitor molecule with the metallic substrate and how this affects the dissolution rate of the metal. The performance of a commercial amine based fatty acid corrosion inhibitor has been investigated using rotating cylinder electrodes and carbon steel electrodes in CO{sub 2} saturated formation water in the temperature range between 35 to 80{sup o}C. The corrosion process was monitored by electrochemical impedance measurements, and at the end of each experiment full polarization curves were recorded. When the inhibitor was applied on noncorroded electrodes, high inhibitor performance, over 99.7%, was observed independent of temperature. On precorroded electrodes inhibitor performance was found to depend on temperature and time of precorrosion. Above 60{sup o}C, the inhibitor performance decreased with increasing time of precorrosion, presumably because of the formation of a corrosion film of either iron carbonate or a combination of iron carbonate and iron carbide which prevent the inhibitor from reaching the surface. The inhibitor protection efficiency was assumed to be associated with the degree of inhibitor coverage at the material surface, and adsorption isotherms have been calculated in the concentration range between 0.1 ppm and 100 ppm. A Langmuir isotherm was found to give the best fit. The inhibitor performance on a 2 days precorroded rotating electrode was investigated at different solution pH ranging between 4.5 and 6.5 at 35{sup o}C. 130 refs., 80 figs., 22 tabs.

  1. The Corrosion Behavior of Stainless Steels and Copper Alloys Exposed to Natural Seawater

    Science.gov (United States)

    1991-01-01

    significant changes of the corrosion potential (Ecw) or surface properties. Rotating cylinder experiments indicated that both E., and corrosion rates for...and inorganic chloride corrosion layer that contained alloying elements; a biof ilm; and crystalline, spherical phosphate-rich deposits. All copper...nichtrostendem Stahl und bacteria and diatoms that did not cause significant changes of the Titan entstehenden dfinnen Biofilme bestanden aus

  2. Corrosion inhibition of low phosphonic multipolymer water treatment agent of industry circulating on brass in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In response to environmental guidelines, a low phosphonic multipolymer was synthesized and its corrosion inhibition efficiency to brass in synthetic water was investigated through weight loss measurements and electrochemical tests.It showed that the synthesized inhibitor decreased corrosion under the conditions tested.Potentiodynamic polarization curves indicated that the new inhibitor acted as an anodic inhibitor, reducing metal dissolution.The composition of protective films formed on the brass was studied by energy-dispersive X-ray analysis (EDX).The inhibition effects were due to the formation of a protective film of the multipolymer inhibitor on the metal surface.

  3. Nanophase formation and its behavior of corrosion resistance in C+Ti dual implanted steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    [1]Zhang Huixing,Zhang Xiaoji,Zhou Fengsheng et al.,High current metal-ion source for ion implantation,Rev.Sci.Instrum.,1990,61(1): 574.[2]Zhang Tonghe,Ji Chengzhou,Shen Jinghua et al.,Surface modification of steel by high-dose pulse-ion implantation of titanium,tungsten,molybdenum and carbon,Nucl.Instrum.Methods,1991,B59/60: 828.[3]Zhang Tonghe,Ji Chengzhou,Shen Jinghua et al.,The influence of Ti,N and Ti+N implantation on phase change,microstructure,growth of metallic compounds and correlated effects in hardness and wear resistance in H13 steel,Nucl.Instrum.Methods,1993,B72: 409-420.[4]Zhang Tonghe,Huang Huapeng,Ji Chengzhou et al.,The formation of metallic silicides of Ti,Y,Fe,Mo and W using metal vapor vacuum arc implantation,Surf.Coat.Technol.,1994,66: 355-360.[5]Zhang Tonghe,Ji Chengzhou,Shen Jinghua et al.,Formation of intermetallic compounds with a high flux pulse molybdenum ion beam in steel and aluminum,Surf.Coat.Technol.,1992,51:455-460.[6]Zhang Tonghe,Wang Xiaoyan,Liang Hong et al.,Behavior of MEVVA metal ion implantation for surface modification of materials,Surf.Coat.Technol.,1996,83: 280-283.[7]Zhang Tonghe,Wang Xiaoyan,Liang Hong et al.,Behavior of MEVVA metal ion implantation for surface modification of materials,Surf.Coat.Technol.,1996,83: 280-283.[8]Takakashi,K.,Waki,M.I.,Chemical and electrochemical properties of ion implanted metals,Surf.Coat.Technol.,1994,65:57-63.[9]Wolf,G K.,An historical perspective of ion bombardment research for corrosion studies,Surf.Coat.Technol.,1996,83: 1-9.[10]Zhang Tonghe,Wu Yuguang,Deng Zhiwei et al.,The corrosion behavior of nanometer embedded phase in Ti implanted H13 steel,Science in China,Ser.E,1999,42(6): 623-630.[11]Zhang Tonghe,Wu Yuguang,Yi Zhongzhen et al.,Nanophase formation and its behavior of corrosion resistance in C+Mo dual implanted steel,Science in China,Ser.E,2001,4(4): 383-388.[12]Zhang Tonghe,Wu Yuguang,Deng Zhiwei et al.Properties of corrosion

  4. Corrosion of low Si-alloyed steels in aqueous solution at 90 deg. C. Inhibitive action of silicates; Corrosion d'aciers faiblement allies au silicium en solution aqueuse a 90 deg. C. Action inhibitrice des silicates

    Energy Technology Data Exchange (ETDEWEB)

    Giordana, S

    2002-02-01

    Low-Si alloyed steels, with Si content ranging from 0.25 to 3.2 wt%, as potential candidate materials for high-level nuclear waste disposal containers, have been studied four the point of view of their corrosion behaviour at 90 deg C in an aqueous solution simulating groundwater (0.1 M NaCl borate-buffered solution with a pH of 8.5) both in reducing and in aerated conditions. The influence of silicate addition to the solution is examined so as to represent the silicon of groundwater, coming from the clay dissolution. When no silicate was added to the solution, silicon as an alloying element was proved to degrade in the first moments the steel ability to passivate. For longer immersion times, protective effects developed most efficiently on the steel containing 3.2 wt% silicon both in reducing an in aerating conditions, Infrared spectroscopy, EDSX, XRD and Raman microprobe were applied to characterise the oxide layer composition, which was found to be a mixture of magnetite and maghemite. In the presence of silicate in the solution, clay-like iron silicates appeared in the corrosion layer. Electrochemical tests results show that adding silicate into solution resulted in increasing the steel ability to passivate. In the short term, the inhibiting effect of silicate was confirmed by mass loss tests, but the tendency was inverse in the long term. Silicate iron layers were eventually less protective than the magnetite layers formed in the absence of silicate. (author)

  5. Electrochemical investigation on the hydrogen permeation behavior of 7075-T6 Al alloy and its influence on stress corrosion cracking

    Science.gov (United States)

    Zheng, Chuan-bo; Yan, Bing-hao; Zhang, Ke; Yi, Guo

    2015-07-01

    The hydrogen permeation behavior and stress corrosion cracking (SCC) susceptibility of precharged 7075-T6 Al alloy were investigated in this paper. Devanthan-Stachurski (D-S) cell tests were used to measure the apparent hydrogen diffusivity and hydrogen permeation current density of specimens immersed in 3.5wt% NaCl solution. Electrochemical experiment results show that the SCC susceptibility is low during anodic polarization. Both corrosion pits and hydrogen-induced cracking are evident in scanning electron microscope images after the specimens have been charging for 24 h.

  6. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-06-01

    Iron aluminides containing greater than about 20-25 @ % Al have oxidation/sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. In addition to alloying modifications for improved creep resistance of wrought material, this strength limitation is being addressed by development of oxide-dispersion- strengthened (ODS) iron aluminides and by evaluation of Fe{sub 3}Al alloy compositions as coatings or claddings on higher-strength, less corrosion-resistant materials. As part of these efforts, the high-temperature corrosion behavior of iron-aluminide weld overlays and ODS alloys is being characterized and compared to previous results for ingot-processed material.

  7. Cooling and Freezing Behaviors of Aqueous Sodium Chloride Solution in a Closed Rectangular Container

    Science.gov (United States)

    Narumi, Akira; Kashiwagi, Takao; Nakane, Ichirou

    This paper investigates cooling and freezing behaviors of NaCl aqueous solution in a rectangular container equipped with horizontal partitions of micro porous film in order to determine the mechanisms of heat and mass transfer through cell wall for the purpose of freezing food. For comparison, experiments were performed using partitions of copper plate, no partition, and water. These processes were visualized and measured using real-time laser holographic interferometry. It was found that there was very little difference in the cooling process due to partitions, but that there were significant differences in freezing process when NaCl aqueous solution is used.

  8. Phase Behavior of Light Gases in Hydrocarbon and Aqueous Solvents

    Energy Technology Data Exchange (ETDEWEB)

    Gasem, K.A.M.; Robinson, R.L., Jr.; Trvedi, N.J., Gao, W.

    1997-09-01

    Under previous support from the Department of Energy, an experimental facility has been established and operated to measure valuable vapor-liquid equilibrium data for systems of interest in the production and processing of coal fluids. To facilitate the development and testing of models for prediction of the phase behavior for such systems, we have acquired substantial amounts of data on the equilibrium phase compositions for binary mixtures of heavy hydrocarbon solvents with a variety of supercritical solutes, including hydrogen, methane, ethane, carbon monoxide, and carbon dioxide. The present project focuses on measuring the phase behavior of light gases and water in Fischer-Tropsch (F-T) type solvents at conditions encountered in indirect liquefaction processes and evaluating and developing theoretically-based correlating frameworks to predict the phase behavior of such systems. Specific goals of the proposed work include (a) developing a state-of-the-art experimental facility to permit highly accurate measurements of equilibrium phase compositions (solubilities) of challenging F-T systems, (b) measuring these properties for systematically-selected binary, ternary and molten F-T wax mixtures to provide critically needed input data for correlation development, (c) developing and testing models suitable for describing the phase behavior of such mixtures, and (d) presenting the modeling results in generalized, practical formats suitable for use in process engineering calculations. During the present reporting period, our solubility apparatus was refurbished and restored to full service. To test the experimental apparatus and procedures used, measurements were obtained for the solubility Of C0{sub 2} in benzene at 160{degrees}F. Having confirmed the accuracy of the newly acquired data in comparison with our previous measurements and data reported in the literature for this test system, we have begun to measure the solubility of hydrogen in hexane. The measurements

  9. Corrosion behavior of Pd-Cu and Pd-Co alloys in synthetic saliva.

    Science.gov (United States)

    Goehlich, V; Marek, M

    1990-04-01

    Pd-based alloys are major alternatives to gold-based alloys for PFM applications. In electrolytes simulating oral fluids, these alloys exhibit electrode behavior similar to passivity of active metals, i.e., a potential region of almost constant current density up to a critical potential, above which the current increases. The objective of this study was to correlate the electrode behavior with the results of solution analyses and changes in the surface composition of the alloys. Binary alloys Pd-15 wt% Cu and Pd-19 wt% Co, as well as the pure components, were examined. Corrosion potentials vs. time, potentiodynamic anodic polarization curves, polarization resistances vs. time, and potentiostatic anodic charges were measured with synthetic saliva used as the electrolyte. The concentrations of Pd, Cu, and Co in the solution after various exposures were determined by atomic absorption. The surfaces of the alloys were examined by x-ray photoelectron spectroscopy before and after the exposures. The results show that selective dissolution of the less-noble components occurred on the surfaces of both alloys for all the exposures, leaving the surfaces highly enriched in Pd. This enrichment contributed to the potential changes and the passive-type behavior. Copper dissolved more than cobalt at longer exposures and higher potentials, in spite of its higher nobility. Dissolution of cobalt seemed to be limited by the formation of a surface film, which may be related to the transition character of this element.

  10. Corrosion behavior of friction stir welded AZ31B Mg alloy - Al6063 alloy joint

    Directory of Open Access Journals (Sweden)

    B. Ratna Sunil

    2016-12-01

    Full Text Available In the present work, AZ31B Mg alloy and Al6063 alloy-rolled sheets were successfully joined by friction stir welding. Microstructural studies revealed a sound joint with good mechanical mixing of both the alloys at the nugget zone. Corrosion performance of the joint was assessed by immersing in 3.5% NaCl solution for different intervals of time and the corrosion rate was calculated. The joint has undergone severe corrosion attack compared with both the base materials (AZ31B and Al6063 alloys. The predominant corrosion mechanism behind the high corrosion rate of the joint was found to be high galvanic corrosion. From the results, it can be suggested that the severe corrosion of dissimilar Mg–Al joints must be considered as a valid input while designing structures intended to work in corroding environment.

  11. Corrosion Behavior and Durability of Low-Alloy Steel Rebars in Marine Environment

    Science.gov (United States)

    Liu, Ming; Cheng, Xuequn; Li, Xiaogang; Yue, Pan; Li, Jun

    2016-10-01

    The corrosion resistance of Cr-modified low-alloy steels and HRB400 carbon steel was estimated using the open-circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopic, and weight loss methods in simulated concrete pore solution. Results show that Cr-modified steels exhibit a higher corrosion resistance with a higher critical chloride level (CTL), lower corrosion current density, and higher impedance than carbon steel. The CTL of the steels significantly reduces with increasing temperature. Weight loss measurement shows that the Cr-modified steels exhibit low corrosion rates and small corrosion pitting. The primary constituents of the corrosion scales are Fe2O3, Fe3O4, β-FeOOH, γ-FeOOH, and α-FeOOH. A large amount of α-FeOOH could be detected in the Cr-modified steel corrosion products. Moreover, the Cr-modified steels demonstrate a higher durability than HRB400 carbon steel.

  12. Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys

    Directory of Open Access Journals (Sweden)

    Mi-Kyung Han

    2015-09-01

    Full Text Available In this paper, the effects of Nb addition (5–20 wt % on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed using X-ray diffraction (XRD, SEM, and TEM. The results indicated that the Ti-xNb alloys (x = 10, 15, and 20 wt % were mainly composed of α + β phases with precipitation of the isothermal ω phase. The volume percentage of the ω phase increased with increasing Nb content. We also investigated the effects of the alloying element Nb on the mechanical properties (including Vickers hardness and elastic modulus, oxidation protection ability, and corrosion behavior of Ti-xNb binary alloys. The mechanical properties and corrosion behavior of Ti-xNb alloys were found to be sensitive to Nb content. These experimental results indicated that the addition of Nb contributed to the hardening of cp-Ti and to the improvement of its oxidation resistance. Electrochemical experiments showed that the Ti-xNb alloys exhibited superior corrosion resistance to that of cp-Ti. The cytotoxicities of the Ti-xNb alloys were similar to that of pure titanium.

  13. Microstructure characterization and electrochemical corrosion behavior of Zn and Zn/Mg alloys in H2SO4 solution

    Institute of Scientific and Technical Information of China (English)

    S H Ettefagh Far; A Rahimi; M Chaghazardi; A Davoodi

    2015-01-01

    The three systems of pure Zn, Zn−0.10% Mg (mass fraction), and Zn−0.15% Mg (mass fraction) were cast under controlled atmosphere and their microstructures were characterized by SEM/EDS analysis. The electrochemical corrosion behavior of these three samples was examined in the very aggressive solution of 50% H2SO4 (mass fraction) using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that magnesium improves in some extent the corrosion resistance of pure Zn in 50% H2SO4 (mass fraction) confirmed by EIS test. Results of polarization measurment also demonstrate that small amount of Mg significantly improves the passivation of Zn in the test solution. Results of surface morphology of the samples and EDS analysis reveal that Mg reduced the corrosion attacks to pure Zn.

  14. Electrochemical Corrosion Behavior of TiN-Coated Biomedical Ti-Cu Alloy Foam in Fluoride Containing Artificial Saliva

    Science.gov (United States)

    Mutlu, Ilven

    2014-07-01

    Highly porous Ti-Cu alloy foams were produced by powder metallurgy method for implant applications. Ti-Cu alloys were prepared with 3, 5, 7, and 10 wt pct Cu contents in order to determine optimum Cu addition. Cu addition enhances sinterability, and the Ti-Cu compacts were sintered at lower temperatures and times than pure Ti. Specimens were coated with a TiN film to enhance wear and corrosion resistance. Sintered specimens were precipitation hardened (aged) in order to increase mechanical properties. Corrosion properties of foams were examined by electrochemical techniques, such as potentiodynamic polarization, cyclic polarization, Tafel extrapolation, linear polarization resistance, and open-circuit potential measurement. Effect of Cu content, TiN coating, pH, and fluoride content of artificial saliva on electrochemical corrosion behavior of specimens was investigated.

  15. Hot Corrosion Behavior of High-Chromium, High-Carbon Cast Irons in NaCl-KCl Molten Salts

    Directory of Open Access Journals (Sweden)

    S. Vuelvas-Rayo

    2012-01-01

    Full Text Available A study on the corrosion behavior of a series of experimental high-chromium (18.53–30.48 wt.%, high-carbon (3.82–5.17% cast irons in NaCl-KCl (1 : 1 M at 670°C has been evaluated by using weight loss technique and compared with a 304-type stainless steel. It was found that all castings had a higher corrosion rate than conventional 304SS and that the addition of Cr increased the degradation rate of the cast irons. Additionally, corrosion rate increased by increasing the C contents up to 4.29%, but it decreased with a further increase in its contents. Results are discussed in terms of consumption of the Cr2O3 layer by the melt.

  16. Effect of Sn on Corrosion Behavior of Ultra-pure 17 mass% Cr Ferritic Stainless Steels in Sulphuric Acid

    Institute of Scientific and Technical Information of China (English)

    Xiang-jun ZHANG; Fei GAO; Zhen-yu LIU

    2016-01-01

    The effect of Sn on corrosion behavior of ferritic stainless steels in 20 mass% H2 SO4 was investigated by alternating current and direct current electrochemical methods and gravimetric tests at 25 ℃.The results show that Sn can effectively improve general corrosion resistance of ferritic stainless steels in H2 SO4 ,mainly due to highly raised hydrogen evolution overpotential which is in favour of strong suppression of hydrogen evolution reaction,and inhibitive effect of dissolved Sn2+ on elementary anodic reactions.With increasing Sn content,the better corrosion re-sistance can be reached.The Electrochemical Impedance Spectroscopy (EIS)includes four time constants and can be perfectly fitted by equivalent circuit:Rs(CdlRct)(QadsRads(RL1(L1(RL2L2)))).

  17. Comparison Between Corrosion Behavior of Copper and Stainless Steel 90° Elbow and Failure Investigation of 90° Copper Elbow

    Science.gov (United States)

    Fouad, Mohamed Ahmed; Zewail, Taghreed Mohamed; Amine, Nieven Abbas; El-Tawail, Yehia Ahmed

    2016-06-01

    Frequently found in elbow, erosion failures may lead to the leakage of pipes and even damage the whole system. Erosion is a form of material degradation that involves electrochemical corrosion and mechanical wear processes encountered on the surface of metal pipes. Research on the erosion-corrosion mechanism indicates that the erosion mainly results from the interactions between the elbow surface and the fluid traveling along the surface. Corrosion behavior of 90° copper and stainless steel elbow was studied. Scanning electron microscopy was processed on the 90° copper elbow to show the surface morphology of the failed copper elbow. Failure investigation was carried out on 90° copper elbow to determine failure location and failure causes.

  18. CORROSION BEHAVIORS OF THE EXPOSED SIDE AND UNDERSIDE OF LOW ALLOY WEATHERING STEEL IN QINGDAO AND WANNING FOR 18 MONTHS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    For 18 months, a newly developed low alloy weathering steel has been exposed in two coastal sites (Qingdao in the north China, Wanning in the south China). The different corrosion behaviors of the exposed side and the underside of the samples were characterized by X-ray diffraction (XRD), polarization curve, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and N2 adsorp-tion approach. It was found that the samples exhibited higher corrosion rate in Wan-ning than that in Qingdao. The underside of the samples corrodes more seriously than the exposed side in Qingdao, whereas the result in Wanning is just the reverse.The protection performance of rust layers mainly depends on its compactness and the enrichment of Cu and Cr is a secondary causation. The different compactness of rust layers in the exposed side and the underside originates from different corrosion conditions of the two sides.

  19. Investigation of the Corrosion Behaviors of HVOF-Sprayed Carbide Cernet Coatings in Molten Al-Zn-Si Alloy Bath

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhen-hua; TAN Xing-hai; ZHANG Yue-gang; SUN Jia-shu

    2004-01-01

    In continuous hot-dip galvanization process the corrosion and chemical stability of the sink roll in the galvanizing bath are important problem which effects on the quality and productivity. In order to protect the sink roll the carbide cermet and/or ceramic coatings were deposited on the surface of the sink roll. The WC-, Cr3 C2-cermet coatings were deposited by high velocity oxygen fuel (HVOF) spray, respectively. The coating samples were immersed in molten Zn-alloy containing 50 wt % aluminum at 833 K for 24 hr and 144 hr, respectively. The inter-diffusion and inter-reaction of Zn, Al and elements in coating and corrosion behaviors of these coatings were investigated by XRD, SEM and EPMA etc. The corrosion mechanisms of the carbide cermet coatings and ceramic coatings in molten High Al-Zn-alloy were approached.

  20. The synergistic effect of Na{sub 3}PO{sub 4} and benzotriazole on the inhibition of copper corrosion in tetra-n-butylammonium bromide aerated aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S.; Dong, J.; Guan, W.W.; Duan, J.M.; Jiang, R.Y. [Department of Applied Chemistry, South China University of Technology, Guangzhou 510640 (China); Feng, Z.P.; Song, W.J. [Guangzhou Institute of Energy Conversion, CAS, Guangzhou 510640 (China)

    2012-11-15

    The effect of Na{sub 3}PO{sub 4} and the mixture of benzotriazole (BTA) and Na{sub 3}PO{sub 4} (SP) on the corrosion of copper in 17 wt% (0.534 mol/L) tetra-n-butylammonium bromide (TBAB) aerated aqueous solution has been investigated by means of weight-loss test, potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy/energy dispersive X-ray techniques. The experimental results showed that a dosage of Na{sub 3}PO{sub 4} stimulated the copper corrosion, and the corrosion rate increased with increasing Na{sub 3}PO{sub 4} concentration, whereas the mixture of BTA and Na{sub 3}PO{sub 4} could protect copper in aqueous TBAB solution. The inhibition action of the mixture of BTA and Na{sub 3}PO{sub 4} on the corrosion of copper is mainly due to the inhibition of the anodic process of corrosion. The inhibition efficiency of a mixture consisting of 2 g/L BTA and 1 g/L Na{sub 3}PO{sub 4} was about 96%. The mixture of BTA and Na{sub 3}PO{sub 4} inhibits the corrosion of copper better than BTA by itself, indicating that Na{sub 3}PO{sub 4} has a synergistic role with BTA on the corrosion inhibition of copper in TBAB aqueous solution. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Corrosion protection of galvanized steel and electroplating steel by decanoic acid in aqueous solution: Electrochemical impedance spectroscopy, XPS and ATR-FTIR

    Energy Technology Data Exchange (ETDEWEB)

    Lebrini, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France)], E-mail: mounim.lebrini@pop.ensc-lille.fr; Fontaine, G. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Gengembre, L. [Unite de Catalyse et Chimie du solide UMR 8181 Bat C3, USTL, F-59655 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Lerasle, O.; Genet, N. [TOTAL France, Centre de Recherche de Solaize, Chemin du canal, BP 22, F-69360 Solaize (France)

    2009-06-15

    The inhibiting action of decanoic acid towards the corrosion behaviour of galvanized steel and electroplating steel in aqueous solution has been studied using electrochemical impedance spectroscopy (EIS) techniques. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. Results obtained revealed that decanoic acid is an effective inhibitor. The better performance was obtained in the case of electroplating steel. X-ray photoelectron spectroscopy surface analysis shows that, decanoic acid is chemisorbed on surface of galvanized steel and electroplating steel. These studies have shown that the active site for binding the film on metal surface is the anionic carboxylate head. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to identify the nature of the deposits on the metal surface.

  2. Electrochemical corrosion behavior of Cu-40Ni-20Cr alloys with different grain sizes in solutions containing chloride ions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The electrochemical corrosion behavior of the two Cu-40Ni-20Cr alloys prepared by conventional casting(CA) and mechanical alloying(MA) with the different grain sizes was studied by using open-circuit potential(OCP), potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) methods in solutions containing chloride ions. The results show that the free corrosion potentials of the two alloys move towards negative values, corrosion currents increase and therefore corrosion rates become faster with the increase of chloride ion concentrations. EIS plots of CACu-40Ni-20Cr alloy are composed of single capacitive loop, while EIS plots of MACu-40Ni-20Cr alloy are composed of double capacitive loops in solution containing lower chloride ion concentrations. EIS plots of the two alloys have Warburg impedance with the increase of chloride ion concentrations.Corrosion rates of MACu-40Ni-20Cr alloy become faster than those of CACu-40Ni-20Cr alloy obviously in solutions containing the same chloride ion concentrations because MACu-40Ni-20Cr alloy is able to produce large concentrations of grain boundaries in the course of reduction in grain size by mechanical alloying.

  3. Electrochemical and Sulfide Stress Corrosion Cracking Behaviors of Tubing Steels in a H2S/CO2 Annular Environment

    Science.gov (United States)

    Liu, Z. Y.; Wang, X. Z.; Liu, R. K.; Du, C. W.; Li, X. G.

    2014-04-01

    The electrochemical and sulfide stress corrosion cracking (SSCC) behaviors of 13Cr stainless steel and P110 steel were investigated in a simulated acidic annular environment with low-temperature and high-pressure H2S/CO2 using electrochemical methods, U-bend immersion tests, and scanning electron microscopy. In the solution containing high pressure CO2, 13Cr, and P110 steels exhibited general corrosion and severe pitting, respectively. Compared with sweet corrosion, additional H2S in the solution enhanced the corrosion of 13Cr steel but inhibited the corrosion of P110 steel. By contrast, in a solution containing 4 MPa CO2 and different (0-0.3 MPa), the susceptibility of both 13Cr stainless steel and P110 steel toward SSCC was significantly promoted by increases in H2S partial pressure. The 13Cr stainless steel exhibited higher susceptibility toward SSCC than P110 steel under a H2S/CO2 environment but lower susceptibility under a pure CO2 environment.

  4. Comparative study on CO2 corrosion behavior of N80,P110,X52 and 13Cr pipe lines in simulated stratum water

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    To better understand the carbon dioxide (CO2) corrosion behavior of carbon steel and its influence on petroleum development (including drilling,production and transportation) in the Daqing Oilfield,CO2 corrosion behaviors of N80,P110,X52 and 13Cr pipe lines in simulated solution at high temperature and high pressure condition are investigated by dynamic corrosion experiments,scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses.Results show that the corrosion rate of all pipe lines increases quickly when CO2 partial pressure increases from 0.5 to 1.5 MPa,but it slows down when CO2 partial pressure further increases from 1.5 to 4.5 MPa,during which localized corrosion is prevailing.When the experimental temperature ranges from 60 to 120°C,localized corrosion prevails.The corrosion rate of all pipe lines decreases sharply when the temperature changes from 60 to 100°C,and it becomes stable after the temperature is higher than 100°C.When the flow rate is in the range of 0–1.5 m/s,the corrosion rate of sample X52 remains unchanged,but localized corrosion gradually becomes very serious when the flow rate further increases.By analyzing the corrosion product scales of sample 13Cr,some remarkable phenomena are observed.At the temperature range of 60–100°C,the corrosion product scales are loose and thick,but become very compact when the temperature increases above 100°C.In the later case,localized corrosion is prevailing.The main components of the corrosion product scales are FeCO3 and Cr2O3.

  5. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

    2015-09-25

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

  6. A Facile Method to Modify the Characteristics and Corrosion Behavior of 304 Stainless Steel by Surface Nanostructuring toward Biomedical Applications.

    Science.gov (United States)

    Thangaraj, Balusamy; Nellaiappan, Sankara Narayanan T S; Kulandaivelu, Ravichandran; Lee, Min Ho; Nishimura, Toshiyasu

    2015-08-19

    The study addresses how surface nanostructuring of AISI 304 stainless steel (SS) by surface mechanical attrition treatment (SMAT) influences its characteristic properties and corrosion behavior in Ringer's solution. SMAT of 304 SS induced plastic deformation, enabled surface nanocrystallization, refined the grain size, transformed the austenite phase to strain induced α'-martensite phase, increased the surface roughness, induced defects/dislocations, imparted compressive residual stresses at the surface, decreased the contact angle, and increased surface energy. The change in properties of 304 SS following treatment using 5 and 8 mm ⌀ balls for 15, 30, 45, and 60 min has caused a deleterious influence on its corrosion resistance in Ringer's solution, while an improvement in corrosion behavior is observed for those treated using 2 mm ⌀ balls. The increase in surface roughness, transformation of the austenite to α'-martensite phase, a higher extent of deformation, and the presence of larger number of defects/dislocations are main factors responsible for the lower corrosion resistance observed for 304 SS treated using 5 and 8 mm ⌀ balls in Ringer's solution. In spite of having these attributes with a relatively lower extent, 304 SS treated using 2 mm ⌀ balls offered a better corrosion resistance and exhibits a better passivity. For those treated using 2 mm ⌀ balls, the ability of the nanocrystalline surface to promote passivation outweighs the deleterious influences caused by the limited amount of deformation and defects/dislocations. Based on the findings of this study, it is recommend that SMAT of 304 SS using 2 mm ⌀ balls for 15-30 min is the optimum condition to achieve the suitable surface profile, surface characteristics with better corrosion resistance.

  7. The effect of various deformation processes on the corrosion behavior of casing and tubing carbon steels in sweet environment

    Science.gov (United States)

    Elramady, Alyaa Gamal

    The aim of this research project is to correlate the plastic deformation and mechanical instability of casing steel materials with corrosion behavior and surface change, in order to identify a tolerable degree of deformation for casing steel materials. While the corrosion of pipeline and casing steels has been investigated extensively, corrosion of these steels in sweet environments with respect to plastic deformation due to bending, rolling, autofrettage, or handling needs more investigation. Downhole tubular expansion of pipes (casings) is becoming standard practice in the petroleum industry to repair damaged casings, shutdown perforations, and ultimately achieve mono-diameter wells. Tubular expansion is a cold-drawing metal forming process, which consists of running conical mandrels through casings either mechanically using a piston or hydraulically by applying a back pressure. This mechanism subjects the pipes to large radial plastic deformations of up to 30 pct. of the inner diameter. It is known that cold-working is a way of strengthening materials such as low carbon steel, but given that this material will be subjected to corrosive environments, susceptibility to stress corrosion cracking (SCC) should be investigated. This research studies the effect of cold-work, in the form of cold-rolling and cold-expansion, on the surface behavior of API 5CT steels when it is exposed to a CO2-containing environment. Cold-work has a pronounced influence on the corrosion behavior of both API 5CT K55 and P110 grade steels. The lowest strength grade steel, API 5CT K55, performed poorly in a corrosive environment in the slow strain rate test. The ductile material exhibited the highest loss in strength and highest susceptibility to stress corrosion cracking in a CO 2-containing environment. The loss in strength declined with cold-rolling, which can be ascribed to the surface compressive stresses induced by cold-work. On the other hand, API 5CT P110 grade steels showed higher

  8. Initial corrosion behaviors of AZ91 magnesium alloy in the presence of SO2

    Institute of Scientific and Technical Information of China (English)

    Cui Lin; Xiaogang Li

    2004-01-01

    The effects of SO2 on the initial atmospheric corrosion of AZ91D magnesium alloy were investigated in laboratory. Metallographic observation, SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Proton Spectrograph) were used to analyze and discuss the initial surface morphology of corrosion layers and corrosion products. The corrosion rate of the alloy increases with increasing the content of SO2. The initial attack has the characteristics of localized corrosion and preferentially concentrates on α phase. MgO and Mg(OH)2 form at first, which provide a protective layer, then the existence of SO2 decreases the pH of the thin solution on the alloy, accelerates dissolution process, and promotes the formation of MgSO3·6H20 and MgSO4·6H20,meanwhile cracks were found on the corrosion products with corrosion continuation. These soluble corrosion products and the cracks provide the paths for filtering oxygen and corrosion pollutants into the matrix, which results in severe localized corrosion and the loss of protective function of film.

  9. Corrosion performance of reinforced mortar in the presence of polymeric nano-aggregates: electrochemical behavior, surface analysis, and properties of the steel/cement paste interface

    NARCIS (Netherlands)

    Hu, J.; Koleva, D.A.; Van Breugel, K.

    2012-01-01

    This study reports on the effect of admixed polyethylene oxide-b-polystyrene (PEO113-b-PS70)micelles on corrosion behavior of reinforced mortar. The electrochemical measurement shows that the corrosion performance of the reinforcing steel was not significantly improved. However, surface analysis and

  10. Comparative study on the corrosion behavior of the cold rolled and hot rolled low-alloy steels containing copper and antimony in flue gas desulfurization environment

    Science.gov (United States)

    Park, S. A.; Kim, J. G.; He, Y. S.; Shin, K. S.; Yoon, J. B.

    2014-12-01

    The correlation between the corrosion and microstructual characteristics of cold rolled and hot rolled low-alloy steels containing copper and antimony was established. The corrosion behavior of the specimens used in flue gas desulfurization systems was examined by electrochemical and weight loss measurements in an aggressive solution of 16.9 vol % H2SO4 + 0.35 vol % HCl at 60°C, pH 0.3. It has been shown that the corrosion rate of hot rolled steel is lower than that of cold rolled steel. The corrosion rate of cold rolled steel was increased by grain refinement, inclusion formation, and preferred grain orientation.

  11. Corrosion Inhibitors for Aluminum.

    Science.gov (United States)

    Muller, Bodo

    1995-01-01

    Describes a simple and reliable test method used to investigate the corrosion-inhibiting effects of various chelating agents on aluminum pigments in aqueous alkaline media. The experiments that are presented require no complicated or expensive electronic equipment. (DDR)

  12. Investigation of the Effects of Solution Temperature on the Corrosion Behavior of Austenitic Low-Nickel Stainless Steels in Citric Acid using Impedance and Polarization Measurements

    Directory of Open Access Journals (Sweden)

    Mulimbayan Francis M.

    2015-01-01

    Full Text Available Stainless steels may be classified according to alloy microstructure – ferritic, austenitic, martensitic, duplex, and precipitation hardening grades. Among these, austenitic grade has the largest contribution to market due to the alloy’s numerous industrial and domestic applications. In this study, the corrosion behavior of low-Nickel stainless steel in citric acid was investigated using potentiodynamic polarization techniques and Electrochemical Impedance Spectroscopy (EIS. The corrosion current density which is directly related to corrosion rate was extracted from the generated anodic polarization curve. Increasing the temperature of the citric acid resulted to increased corrosion current densities indicating higher corrosion rates at initial corrosion condition. EIS was performed to generate Nyquist plots whose shape and size depicts the corrosion mechanism and corrosion resistance of the alloy in citric acid, respectively. All the generated Nyquist plots have depressed semi-circle shapes implying that corrosion process takes place with charge-transfer as the rate-determining step. Based from the extracted values of polarization resistance (Rp, the temperature of the solution has negative correlation with the corrosion resistance of the studied alloy.

  13. Corrosion behavior of 2195 and 1420 Al-Li alloys in neutral 3.5% NaCl solution under tensile stress

    Institute of Scientific and Technical Information of China (English)

    LI Jin-feng; CHEN Wen-jing; ZHAO Xu-shan; REN Wen-da; ZHENG Zi-qiao

    2006-01-01

    The corrosion behaviors of 1420 and 2195 Al-Li alloys under 308 and 490 MPa tensile stress respectively in neutral 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy(EIS) and scanning electron microscope(SEM). It is found that the unstressed 1420 alloy is featured with large and discrete pits, while general corrosion and localized corrosion including intergranular corrosion and pitting corrosion occur on the unstressed 2195 alloy. As stress is applied to 1420 alloy, the pit becomes denser and its size is decreased. While, for the stressed 2195 alloy, intergranular corrosion is greatly aggravated and severe general corrosion is developed from connected pits. The EIS analysis shows that more severe general corrosion and localized corrosion occur on the stressed 2195 Al-Li alloy than on 1420 Al-Li alloy. It is suggested that tensile stress has greater effect on the corrosion of 2195 Al-Li alloy than on 1420 Al-Li alloy.

  14. Corrosion behavior of extrusion, under-aged, peaked-aged and over-aged WE93 alloys in NaHSO3 solutions

    Institute of Scientific and Technical Information of China (English)

    蒋全通; 马鸣龙; 张奎; 李兴刚; 李永军; 石国梁; 袁家伟

    2014-01-01

    The corrosion behaviors of extrusion, under-aged, peaked-aged and over-aged WE93 alloys in NaHSO3 solutions were in-vestigated by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The weight loss rates, corrosion morphologies and polarization curves were analyzed. The peak-aged specimen in NaHSO3 salt spray had the highest corro-sion rate of 0.9787 mg/cm2/d, while extrusion specimen led to the lowest of 0.2184 mg/cm2/d. The specimens could be arranged in decreasing order of corrosion rates:extrusioncorrosion rates in agreement. The NaHSO3 played a great role in the corrosion behaviors of WE93 alloys. The main reasons were that HSO3–developed a reaction:O2+2HSO3–+2e→2HSO42–→2H++2SO42–to generate H+, accelerating the process of corrosion re-action. SO42–stimulated corrosion and led to an autocatalytic type of reaction:Mg2++SO42–+7H2O→MgSO4–7H2O. XRD character-ized that Mg(OH)2 and MgSO4·7H2O were the main corrosion products.

  15. Corrosion behavior of CRA`s in high density packer fluids at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Scoppio, L.; Barteri, M. [Centro Sviluppo Materiali Spa Via di Castel Romano, Roma (Italy); Cheldi, T. [AGIP Spa, Milanese (Italy); Ke, M. [OSC, Lafayette, LA (United States); Massi, S. [Univ. degli Studi di Roma (Italy)

    1999-11-01

    Results from an experimental investigation carried out in high density brine packer fluids are presented. Different variables were examined, namely temperature, time of exposure, chemical inhibition and brine composition and density. Tests to compare the performance of different classes of stainless steels were carried out by autoclave exposure under different deaerated brines solutions: NaCl/NaBr, CaCl{sub 2}/CaBr{sub 2} and CaBr{sub 3}/ZnBr{sub 2}, CaCl{sub 2}, CaCl{sub 2}/CaBr{sub 2}/ZnBr{sub 2}. General corrosion, localized corrosion (pitting and crevice), galvanic corrosion and resistance to environmental cracking were evaluated both in absence of corrosion inhibitor and with the addition of two different commercial inhibitors. Duplex steels were very resistant to the localized corrosion, although pitting and crevice were present in some combination of brine and temperature. The martensitic steel was very sensitive to the general and the localized corrosion. Brine CaCl{sub 2}/CaBr{sub 2} {rho} = 1.75 g/cm{sup 3}, showed at 200 C, a pitting on 13%Cr lower than expected. This is probably due to the general corrosion which show a mechanism competitive with localized corrosion. As a result, pitting corrosion is a matter of big concern when applications in heavy brine are considered. In fact only the most alloyed materials at temperature below 200 C can be considered as immune. As a consequence, the effect of commercially available corrosion inhibitors is sometime lower than expected and there is a need of further improvements of corrosion inhibitors for the application to the CRA`S (Corrosion Resistant Alloys) in brine environments at 200 C.

  16. Localized Electrochemical Impedance Spectroscopy Study on the Corrosion Behavior of Fe-Cr Alloy in the Solution with Cl- and SO42-

    Institute of Scientific and Technical Information of China (English)

    XIAO Kui; ZHANG Xin; DONG Chaofang; WEI Dan; WANG Chen; LI Xiaogang

    2012-01-01

    The corrosion behaviors of Fe-Cr alloy under three different pH values solutions with Cl-and SO42- were investigated by localized electrochemical impedance spectroscopy (LEIS) measurements and the corrosion products were analyzed by laser Raman spectrometry.The results show that the high corrosion resistance of Fe-Cr Alloy is attributed to a passive film which is formed more easily when the alloy contains a large quantity of Cr element.However,its corrosion resistance varies in the solutions with different pH values,especially in the initial corrosion.The average impedance values in neutral and alkaline solution are much higher than that in acidic solution because the passive film is more likely to dissolve in the acidic condition.Moreover,the destructive effect of Cl- and SO42+ ions on the passive film is also demonstrated in corrosion process through the change of the impedance value with the steeping time.

  17. Effect of Incorporation of Inhibitor Loaded Mesoporous Silica on the Corrosion Behavior of Epoxy Coatings

    Directory of Open Access Journals (Sweden)

    Mahdi Yeganeh

    2013-12-01

    Full Text Available In this research, mesoporous silica was applied as the host of corrosion inhibitor (molybdate. The loaded mesoporous silica was dispersed in an epoxy matrix. The composite was then coated on the mild steel plate. Results showed that the corrosion resistance of the scratched epoxy/mesoporous silica loaded by molybdate was better than the one without molybdate or neat epoxy. On the other hand, EDX and FTIR studies showed the release of corrosion inhibitor in the scratched zone. It was due to pH-sensitive release of corrosion inhibitor in the aggressive media. Also, XRD data showed the presence of Mo compounds on the surface of steel.

  18. Irradiation-assisted stress corrosion cracking behavior of austenitic stainless steels applicable to LWR core internals.

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. M.; Shack, W. J.; Energy Technology

    2006-01-31

    This report summarizes work performed at Argonne National Laboratory on irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels that were irradiated in the Halden reactor in simulation of irradiation-induced degradation of boiling water reactor (BWR) core internal components. Slow-strain-rate tensile tests in BWR-like oxidizing water were conducted on 27 austenitic stainless steel alloys that were irradiated at 288 C in helium to 0.4, 1.3, and 3.0 dpa. Fractographic analysis was conducted to determine the fracture surface morphology. Microchemical analysis by Auger electron spectroscopy was performed on BWR neutron absorber tubes to characterize grain-boundary segregation of important elements under BWR conditions. At 0.4 and 1.4 dpa, transgranular fracture was mixed with intergranular fracture. At 3 dpa, transgranular cracking was negligible, and fracture surface was either dominantly intergranular, as in field-cracked core internals, or dominantly ductile or mixed. This behavior indicates that percent intergranular stress corrosion cracking determined at {approx}3 dpa is a good measure of IASCC susceptibility. At {approx}1.4 dpa, a beneficial effect of a high concentration of Si (0.8-1.5 wt.%) was observed. At {approx}3 dpa, however, such effect was obscured by a deleterious effect of S. Excellent resistance to IASCC was observed up to {approx}3 dpa for eight heats of Types 304, 316, and 348 steel that contain very low concentrations of S. Susceptibility of Types 304 and 316 steels that contain >0.003 wt.% S increased drastically. This indicates that a sulfur related critical phenomenon plays an important role in IASCC. A sulfur content of <0.002 wt.% is the primary material factor necessary to ensure good resistance to IASCC. However, for Types 304L and 316L steel and their high-purity counterparts, a sulfur content of <0.002 wt.% alone is not a sufficient condition to ensure good resistance to IASCC. This is in distinct contrast to

  19. Anomalous dissolution of metals and chemical corrosion

    Directory of Open Access Journals (Sweden)

    DRAGUTIN M. DRAZIC

    2005-03-01

    Full Text Available An overview is given of the anomalous behavior of some metals, in particular Fe and Cr, in acidic aqueous solutions during anodic dissolution. The anomaly is recognizable by the fact that during anodic dissolutionmore material dissolves than would be expected from the Faraday law with the use of the expected valence of the formed ions. Mechanical disintegration, gas bubble blocking, hydrogen embrittlement, passive layer cracking and other possible reasons for such behavior have been discussed. It was shown, as suggested by Kolotyrkin and coworkers, that the reason can be, also, the chemical reaction in which H2O molecules with the metal form metal ions and gaseous H2 in a potential independent process. It occurs simultaneously with the electrochemical corrosion process, but the electrochemical process controls the corrosion potential. On the example of Cr in acid solution itwas shown that the reason for the anomalous behavior is dominantly chemical dissolution, which is considerably faster than the electrochemical corrosion, and that the increasing temperature favors chemical reaction, while the other possible reasons for the anomalous behavior are of negligible effect. This effect is much smaller in the case of Fe, but exists. The possible role of the chemical dissolution reacton and hydrogen evolution during pitting of steels and Al and stress corrosion cracking or corrosion fatigue are discussed.

  20. Effect of Chromium on Corrosion Behavior of P110 Steels in CO2-H2S Environment with High Pressure and High Temperature

    Directory of Open Access Journals (Sweden)

    Jianbo Sun

    2016-03-01

    Full Text Available The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO2 environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO2 and H2S coexistence conditions, the corrosion behavior of low-chromium steels in CO2-H2S environment with high pressure and high temperature was investigated using weight loss measurement and surface characterization. The results showed that P110 steel suffered localized corrosion and both 3Cr-P110 and 5Cr-P110 steels exhibited general corrosion. However, the corrosion rate of 5Cr-P110 was the highest among them. The corrosion process of the steels was simultaneously governed by CO2 and H2S. The outer scales on the three steels mainly consisted of FeS1−x crystals, whereas the inner scales on Cr-containing steels comprised of amorphous FeS1−x, Cr(OH3 and FeCO3, in contrast with the amorphous FeS1−x and FeCO3 mixture film of P110 steel. The more chromium the steel contains, the more chromium compounds the corrosion products contain. The addition of chromium in steels increases the uniformity of the Cr-enriched corrosion scales, eliminates the localized corrosion, but cannot decrease the general corrosion rates. The formation of FeS1−x may interfere with Cr-enriched corrosion scales and lowering the corrosion performance of 3Cr-P110 and 5Cr-P110 steels.

  1. Comparison of corrosion behaviors of AZ31, AZ91,AM60 and ZK60 magnesium alloys

    Institute of Scientific and Technical Information of China (English)

    CHENG Ying-liang; QIN Ting-wei; WANG Hui-min; ZHANG Zhao

    2009-01-01

    The corrosion behaviours of four kinds of rolled magnesium alloys of AZ31, AZ91, AM60 and ZK60 were studied in 1 mol/L sodium chloride solution. The results of EIS and potentiodynamic polarization show that the corrosion resistance of the four materials is ranked as ZK60>AM60>AZ31>AZ91. The corrosion processes of the four magnesium alloys were also analyzed by SEM and energy dispersive spectroscopy(EDS). The results show that the corrosion patterns of the four alloys are localized corrosion and the galvanic couples formed by the second phase particles and the matrix are the main source of the localized corrosion of magnesium alloys. The corrosion resistance of the different magnesium alloys has direct relationship with the concentration of alloying elements and microstructure of magnesium alloys. The ratio of the β phase in AZ91 is higher than that in AZ31 and the β phase can form micro-galvanic cell with the alloy matrix, as a result, the corrosion resistance of AZ31 will be higher than AZ91. The manganese element in AM60 magnesium alloy can form the second phase particle of AlMnFe, which can reduce the Fe content in magnesium alloy matrix, purifying the microstructure of alloy, as a result, the corrosion resistance of AM60 is improved. However, due to the more noble galvanic couples of AlMnFe and matrix, the microscopic corrosion morphology of AM60 is more localized. The zirconium element in ZK60 magnesium alloy can refine grain, form stable compounds with Fe and Si, and purify the composition of alloy, which results in the good corrosion resistance of ZK60 magnesium alloy.

  2. Effects of environmental factors on corrosion behaviors of metal-fiber porous components in a simulated direct methanol fuel cell environment

    Institute of Scientific and Technical Information of China (English)

    Wei Yuan; Bo Zhou; Yong Tang; Zhao-chun Zhang; Jun Deng

    2014-01-01

    To enable the use of metallic components in direct methanol fuel cells (DMFCs), issues related to corrosion resistance must be considered because of an acid environment induced by the solid electrolyte. In this study, we report the electrochemical behaviors of metal-fiber-based porous sintered components in a simulated corrosive environment of DMFCs. Three materials were evaluated:pure copper, AISI304, and AISI316L. The environmental factors and related mechanisms affecting the corrosion behaviors were analyzed. The results demonstrated that AISI316L exhibits the best performance. A higher SO42-concentration increases the risk of material corrosion, whereas an increase in methanol concentration inhibits corrosion. The morphological features of the corroded samples were also characterized in this study.

  3. Microstructure and corrosion behavior of micro-arc oxidation coating on 6061 aluminum alloy pre-treated by high-temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Dejiu, E-mail: sdj217@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Li, Guolong, E-mail: lglysu@163.com [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Guo, Changhong [College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Zou, Jie [China Aviation Industry Chengdu Engine (Group) Co. Ltd., Chengdu 610503 (China); Cai, Jingrui; He, Donglei; Ma, Haojie; Liu, Fangfei [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2013-12-15

    In this paper, we investigate the microstructure and corrosion behavior of the micro-arc oxidation (MAO) coating on 6061 aluminum alloy that pre-treated by high-temperature oxidation (HTO). Microstructure, chemical and corrosion behaviors of the fabricated MAO ceramic coatings were studied by using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and electrochemical corrosion tests. The results reveal that the pre-fabricated HTO film remarkably affects the formation of the MAO coating, leads to an enriched content of Mg, and decreases the compactness of the coating. The corrosion resistance of the 6061 aluminum alloy has been significantly improved by treatments of HTO, normal MAO (NMAO) and HTO pre-treated MAO (HTO-MAO), and the NMAO coating exhibits the best corrosion performance. The content of Mg in HTO pre-fabricated film is remarkedly higher than that in the substrate, which greatly influences the formation of the MAO coating.

  4. Stress Corrosion Crack Growth Behavior of Titanium Alloy/Bioactive Glasses Sandwiches in Simulated Human Physiological Environment

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on a series of newly developed bioactive glasses having suitable thermo-mechanical properties to allow application as fixation agents between bone and titanium alloy biomedical implants, the stress corrosion crack growth(SCCG) behavior of their interfaces with Ti6Al4V was investigated in simulated body fluid (SBF) with the objectiveof discerning the salient mechanisms of crack advance and to assess the reliability of the bonds. Results indicatedthat crack growth rates in Ti6Al4V/glass/Ti6Al4V sandwich specimens were nearly the same as or slightly lowerthan those in the bulk glasses at comparable stress intensities; indeed, cracks would prefer to propagate off theinterface, suggesting that the Ti6Al4V/glass interface has relatively good crack-growth resistance. Mechanistically,interfacial crack growth appears to be controlled by the classic stress corrosion mechanisms for silicate glasses, withno discernible effect of bioactivity on the SCCG behavior being observed.

  5. In vivo oxide-induced stress corrosion cracking of Ti-6Al-4V in a neck-stem modular taper: Emergent behavior in a new mechanism of in vivo corrosion.

    Science.gov (United States)

    Gilbert, Jeremy L; Mali, Sachin; Urban, Robert M; Silverton, Craig D; Jacobs, Joshua J

    2012-02-01

    In vivo modular taper corrosion in orthopedic total joint replacements has been documented to occur for head-neck tapers, modular-body tapers, and neck-stem tapers. While the fretting corrosion mechanism by which this corrosion occurs has been described in the literature, this report shows new and as yet unreported mechanisms at play. A retrieved Ti-6Al-4V/Ti-6Al-4V neck-stem taper interface, implanted for 6 years is subjected to failure analysis to document taper corrosion processes that lead to oxide driven crack formation on the medial side of the taper. Metallurgical sectioning techniques and scanning electron microscopy analysis are used to document the taper corrosion processes. The results show large penetrating pitting attack of both sides of the taper interface where corrosion selectively attacks the beta phase of the microstructure and eventually consumes the alpha phase. The pitting attack evolves into plunging pits that ultimately develop into cracks where the crack propagation process is one of corrosion resulting in oxide formation and subsequent reorganization. This process drives open the crack and advances the front by a combination of oxide-driven crack opening stresses and corrosion attack at the tip. The oxide that forms has a complex evolving structure including a network of transport channels that provide access of fluid to the crack tip. This emergent behavior does not appear to require continued fretting corrosion to propagate the pitting and cracking. This new mechanism is similar to stress corrosion cracking where the crack tip stresses arise from the oxide formation in the crack and not externally applied tensile stresses.

  6. Effect of cold working on the aging and corrosion behavior of Fe-Mn-Al stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ghayad, I.M.; Girgis, N.N.; Ghanem, W. [Central Metallurgical Research and Development Institute, CMRDI, P.O. Box 87, Helwan, Cairo (Egypt); Hamada, A.S. [Dept. of Metallurgy and Materials Eng., Faculty of Petrol. and Min. Eng., Suez Canal University, el-Shikg Zayed, 41522 Ismailia (Egypt)

    2004-07-01

    The cold working; aging process; and corrosion behavior of the Fe-Mn-Al stainless steel having a composition of Fe-29wt%Mn-3.5wt%Al-0.5wt%C were investigated. Three different groups of specimens of the alloy were subjected to different procedures of cold working and aging. The first group were cold worked then solution treated at 1100 deg. C for 24 hr, coded as CW+ST. The second group were cold worked, solution treated at 1100 deg. C for 24 hr then cold worked again, coded as CW+ST+CW. The third group were solution treated at 1100 deg. C for 24 hr then cold worked, coded as ST+CW. Subsequent aging treatments of the controlled-worked alloy showed age hardening similar to that reported for the solution-treated alloys. The strengthening of the experimental alloy due to the controlled-working and aging is discussed on the basis of microstructural observations and X-ray diffraction analysis. The corrosion behavior of the different groups of the alloy, CW+ST; CW+ST+CW; ST+CW, with their peak aged and over aged conditions has been examined in 3.5% NaCl solution. The electrochemical techniques, potentiodynamic polarization and Tafel plots were employed. All the alloy groups did not passivate in 3.5% NaCl solution and the major corrosion type observed was general corrosion. The peak aged and over aged of the CW+ST+CW exhibited higher corrosion rates due to the formation of ferrite phase that formed a galvanic couple with the austenitic matrix. (authors)

  7. Microstructural evolution and corrosion behavior of directionally solidified FeCoNiCrAl high entropy alloy

    OpenAIRE

    2011-01-01

    The FeCoNiCrAl alloys have many potential applications in the fields of structural materials, but few attempts were made to characterize the directional solidification of high entropy alloys. In the present research, the microstructure and corrosion behavior of FeCoNiCrAl high entropy alloy have been investigated under directional solidification. The results show that with increasing solidification rate, the interface morphology of the alloy evolves from planar to cellular and dendritic. The ...

  8. Effect of Saturated CO2 on Corrosion Behavior of 13Cr Pipe Steel in High Chloride Environment%高氯环境中饱和CO2对13Cr油管钢腐蚀行为的影响

    Institute of Scientific and Technical Information of China (English)

    雷冰; 马元泰; 李瑛; 王福会; 常泽亮; 谢俊峰; 宋文文; 周理志

    2013-01-01

    The effect of saturated CO2 on corrosion behavior of 13Cr pipe steel in high concentration chloride environment was studied by EIS, polarization test, EN test and SEM. The results indicated that the corrosion rate and corrosion probability of 13Cr pipe steel were accelerated in high chloride environment with the presence of saturated CO2. The 13Cr pipe steel suffered from pitting corrosion in high chloride concentration environment, whilst, from uniform corrosion by the synergistic effect of Cl and CO2. The stability of the passive film of 13Cr pipe steel decreased in high concentration chloride environment with saturated CO2, which can be explained by the dehydroxylation of the outer part of the passive film by carbonic acid and the increase of ionic conductivity of the passive film in aqueous electrolytes.%采用电化学阻抗(EIS)、极化曲线、电化学噪声(EN)和扫描电子显微镜(SEM)研究了高氯环境中饱和CO2对13Cr油管钢腐蚀行为的影响.结果表明:饱和CO2加速材料的腐蚀,增大了腐蚀的发生频率,使材料的腐蚀由点蚀转变为均匀腐蚀.碳酸对钝化膜的去羟基化作用和增大钝化膜的导通率,是材料腐蚀行为变化的原因.

  9. Numerical investigation on stress corrosion cracking behavior of dissimilar weld joints in pressurized water reactor plants

    Directory of Open Access Journals (Sweden)

    Lingyan Zhao

    2014-07-01

    Full Text Available There have been incidents recently where stress corrosion cracking (SCC observed in the dissimilar metal weld (DMW joints connecting the reactor pressure vessel (RPV nozzle with the hot leg pipe. Due to the complex microstructure and mechanical heterogeneity in the weld region, dissimilar metal weld joints are more susceptible to SCC than the bulk steels in the simulated high temperature water environment of pressurized water reactor (PWR. Tensile residual stress (RS, in addition to operating loads, has a great contribution to SCC crack growth. Limited experimental conditions, varied influence factors and diverging experimental data make it difficult to accurately predict the SCC behavior of DMW joints with complex geometry, material configuration, operating loads and crack shape. Based on the film slip/dissolution oxidation model and elastic-plastic finite element method (EPFEM, an approach is developed to quantitatively predict the SCC growth rate of a RPV outlet nozzle DMW joint. Moreover, this approach is expected to be a pre-analytical tool for SCC experiment of DMW joints in PWR primary water environment.

  10. Corrosion behavior of Cu-Ni-Ag-Al alloy anodes in aluminium electrolysis

    Institute of Scientific and Technical Information of China (English)

    徐君莉; 石忠宁; 邱竹贤

    2004-01-01

    The behavior of Cu-Ni-Ag-Al alloy used as anode for aluminum electrolysis was directly visualized in a two-compartment see-through cell during electrolysis, and its performances were tested at 850℃ in acidic electrolyte molten salts consisting of 39.3 % NaF-43.7 % AlF3-8 % NaCl-5 % CAF2-4 % Al2 O3 for 40 h in a laboratory cell. The results show that nascent oxygen oxidizes the anodic surface to form oxide film at the beginning of electrolysis. X-ray diffraction analysis of alloy surface show that the oxide film on the anodic surface consists of CuO, NiO, Al2O3,CuAl2 O4 and NiAl2 O4. However, SEM image shows the oxide film is porous, loose and easy to fall into electrolyte and to contaminate aluminum. The corrosion mechanism of metal anodes was analyzed.

  11. Utilizing various test methods to study the stress corrosion behavior of Al-Li-Cu alloys

    Science.gov (United States)

    Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

    1984-01-01

    Recently, much attention has been given to aluminum-lithium alloys because of rather substantial specific-strength and specific-stiffness advantages offered over commercial 2000and 7000-series aluminum alloys. An obstacle to Al-Li alloy development has been inherent limited ductility. In order to obtain a more refined microstructure, powder metallurgy (P/M) has been employed in alloy development programs. As stress corrosion (SC) of high-strength aluminum alloys has been a major problem in the aircraft industry, the possibility of an employment of Al-Li alloys has been considered, taking into account a use of Al-Li-Cu alloys. Attention is given to a research program concerned with the evaluation of the relative SC resistance of two P/M processed Al-Li-Cu alloys. The behavior of the alloys, with and without an addition of magnesium, was studied with the aid of three test methods. The susceptibility to SC was found to depend on the microstructure of the alloys.

  12. Effect of friction stir welding on microstructure and corrosion behavior of LF6 aluminum alloy

    Science.gov (United States)

    Ghauri, Faizan Ali; Farooq, A.; Ahmad, A.; Deen, K. M.

    2017-03-01

    The LF6 aluminum alloy plates were joined by friction stir welding method. The tool rotational (1180 rpm) and transverse speed (0.56 mm s‑1) were kept constant during welding of 4 mm thick plates. The microstructural features, hardness and tensile properties of the welded samples were determined to evaluate the structural integrity in comparison with the base metal. The electrochemical behavior of base metal (BM), thermo-mechanically affected zone (TMAZ) and weld nugget zone (WNZ) was also investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5% NaCl solution. The microstructural study revealed significant grain refinement and agglomeration of β (Mg2Al3) intermetallic precipitates in the WNZ. The relatively higher hardness and a decrease in the ductility (3%) also assured the formation of precipitates β precipitates in the WNZ welded samples. The fracture surface of welded sample also revealed the existence of β precipitates within the elongated dimples which may be considered as the crack initiation sites. The relatively lower corrosion rate (23.68 mpy) and higher charge transfer resistance (403 Ω cm2) of BM compared to WNZ could be associated with the galvanic dissolution of Al-matrix through competitive charge transfer and relaxation (adsorption/desorption of intermediate species) processes specifically at the vicinity of the β precipitates.

  13. Corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film deposited by double glow plasmas technique

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In order to improve the corrosion resistance of AZ31 magnesium alloy,the amorphous/nanocrystal Al-Cr-Fe film has been successfully prepared on AZ31 magnesium alloy by double glow plasma tech-nology.The amorphous/nanocrystalline consists of two different regions,i.e.,an amorphous layer on outmost surface and an underlying lamellar nanocrystalline layer with a grain size of less than 10 nm.The corrosion behavior of amorphous/nanocrystalline Al-Cr-Fe film in 3.5% NaCl solution is investi-gated using an electrochemical polarization measurement.Compared with the AZ31 magnesium alloy,the amorphous/nanocrystalline Al-Cr-Fe film exhibits more positive corrosion potentials and lower corrosion current densities than that of AZ31 magnesium alloy.XPS measurement reveals that the passive film formed on the Al-Cr-Fe film after the anodic polarization tests is strongly enriched in Cr2O3,Fe2O3 and Al2O3 at outer surface of the film and in the inner layer consists of Cr2O3,FeO and Al2O3.

  14. Long-term in vivo corrosion behavior, biocompatibility and bioresorption mechanism of a bioresorbable nitrided iron scaffold.

    Science.gov (United States)

    Lin, Wenjiao; Qin, Li; Qi, Haiping; Zhang, Deyuan; Zhang, Gui; Gao, Runlin; Qiu, Hong; Xia, Ying; Cao, Ping; Wang, Xiang; Zheng, Wei

    2017-03-15

    Pure iron as a potential bioresorbable material for bioresorbable coronary scaffold has major disadvantages of slow corrosion and bioresorption. However, so far, there are neither quantitative data of long-term in vivo corrosion nor direct experimental evidence for bioresorption of pure iron and its alloys, which are fundamental and vital for developing novel Fe-based alloys overcoming the intrinsic drawbacks of pure iron. This work systemically investigated scaffold performance, long-term in vivo corrosion behavior and biocompatibility of a nitrided iron coronary scaffold and explored its bioresorption mechanism. It was found that the 70μm Fe-based scaffold was superior to a state of the art Co-Cr alloy stent (Xience Prime™) in terms of crossing profile, recoil and radial strength. Mass loss was 76.0±8.5wt% for the nitrided iron scaffold and 44.2±11.4wt% for the pure iron scaffold after 36months implantation in rabbit abdominal aorta (pscaffold showed good long-term biocompatibility in both rabbit and porcine model. Its insoluble corrosion products were demonstrated biosafe and could be cleared away by macrophages from in situ to adventitia to be indiscernible by Micro Computed Tomography and probably finally enter the lymphatics and travel to lymph nodes after 53months implantion in porcine coronary artery. The results indicate that the nitrided iron scaffold with further improvements shall be promising for coronary application.

  15. Study on hemocompatibility and corrosion behavior of ion implanted TiNi shape memory alloy and Co-based alloys.

    Science.gov (United States)

    Liang, Chenghao; Huang, Naibao

    2007-10-01

    Biomedical TiNi shape memory alloy and Co-based alloys were ion implanted, and corrosion resistance and hemocompatibility of these had been investigated with electrochemical method, dynamic clotting time, and hemolysis rate tests. The results indicated that the electrochemical stability and anodic polarization behavior of the materials were improved significantly after ion implantation. When TiNi, Co-based alloys were implanted Mo + C and Ti + C, respectively, the corrosion potentials were enhanced more than 200 mV, passive current densities decreased, and passive ranges were broadened. Dynamic clotting time of the ion implanted substances was prolonged and hemolysis rate decreased. All the results pointed out that corrosion resistance and hemocompatibility of the alloys were improved by ion implantation, and effects of dual implantation was better than that of C single implantation. X-ray diffraction analysis of the alloys after dual implantation revealed that TiC, Mo(2)C, Mo(9)Ti(4), and Mo appeared on the surface of TiNi alloy, and CoC(x), Co(3)Ti, TiC, and TiO on the surface of Co-based alloys. These phases dispersing on the alloy surface formed amorphous film, prevented dissolving of alloy elements and improved the corrosion resistance and hemocompatibility of the alloys.

  16. Hot Corrosion Behavior of Double-ceramic-layer LaTi2Al9O19/YSZ Thermal Barrier Coatings

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoyun; GUO Hongbo; GONG Shengkai; XU Huibin

    2012-01-01

    LaTi2Al9O19 (LTA) exhibits promising potential as a new kind of thermal barrier coating (TBC) material,due to its excellent high-temperature capability and low thermal conductivity.In this paper,LTA/yttria stabilized zirconia (YSZ) TBCs are produccd by atmospheric plasma spraying.Hot corrosion behavior and the related failure mechanism of the coating are investigated.Decomposition of LTA does not occur even after 1 458 hot corrosion cycles at 1 373 K,revealing good chemical stability in molten salt of Na2SO4 and NaCl.However,the molten salt infiltrates to the bond coat,causing dissolving of the thermally grown oxide (TGO) in the molten salt and hot corrosion of the bond coat.As a result,cracking of the TBC occurs within the oxide layer.In conclusion,the ceranic materials LTA and YSZ reveal good chemical stability in molten salts of Na2SO4 and NaCl,and the bond coat plays a significant role in providing protection for the component against hot corrosion in the LTA/YSZ TBCs.LTA exhibits very promising potential as a novel TBC material.

  17. MRI-compatible Nb-60Ta-2Zr alloy for vascular stents: Electrochemical corrosion behavior in simulated plasma solution.

    Science.gov (United States)

    Li, Hui-Zhe; Zhao, Xu; Xu, Jian

    2015-11-01

    Using revised simulated body fluid (r-SBF), the electrochemical corrosion behavior of an Nb-60Ta-2Zr alloy for MRI compatible vascular stents was characterized in vitro. As indicated by XPS analysis, the surface passive oxide film of approximately 1.3nm thickness was identified as a mixture of Nb2O5, Ta2O5 and ZrO2 after immersion in the r-SBF. The Nb-60Ta-2Zr alloy manifests a low corrosion rate and high polarization resistance similar to pure Nb and Ta, as shown by the potentiodynamic polarization curves and EIS. Unlike 316L stainless steel and the L605 Co-Cr alloy, no localized corrosion has been detected. Semiconducting property of passive film on the Nb-60Ta-2Zr alloy was identified as the n-type, with growth mechanism of high-field controlled growth. The excellent corrosion resistance in simulated human blood enviroment renders the Nb-60Ta-2Zr alloy promising as stent candidate material.

  18. Influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of biodegradable Mg-Zn-Ca alloy

    Science.gov (United States)

    Ly, Xuan Nam; Yang, S.; Qin, Y.

    2017-03-01

    The influence of solid-solution treatment on microstructure, mechanical property and corrosion behavior of Mg-Zn-Ca alloy was studied in the present investigation by SEM, tensile test, electrochemical and immersion test. The results show that the microstructure of Mg alloys after solid solution treatment significantly changed, a large number of the second phase (Ca2Mg6Zn3, Mg2Ca) dissolved into the α-Mg matrix reaching a supersaturated state, and the grains size was bigger than before solid solution treatment; the mechanical properties were obviously improved. In particular the tensile strength of 0.5wt.% Ca of Mg alloy reached 220MPa and the ductility reached 16.6%. Compared with the as-cast Mg alloys, the corrosion potential after solid-solution treatment slightly shifted negative, but the corrosion current density significantly decreased. After solid solution treatment, the surface corrosion was not serious and the result of weight gain was lower compared with those of the as-cast Mg alloys.

  19. Effects of dissolved hydrogen on general corrosion behavior and oxide films of alloy 690TT in PWR primary water

    Science.gov (United States)

    Jeon, Soon-Hyeok; Lee, Eun-Hee; Hur, Do Haeng

    2017-03-01

    The effect of dissolved hydrogen (DH) on the general corrosion behavior and oxide films of Alloy 690TT is investigated in simulated primary water at 330 °C. With increasing DH, the structure of oxide film significantly changed and the corrosion rate decreased. At DH = 5 cm3/kg H2O, the oxide layer was thick, and consisted of outer Ni oxide layer and inner Cr2O3 layer. Under the conditions of DH = 35 and 100 cm3/kg H2O, the oxide films grew thinner and composed of outer polyhedral spinel oxide particles such as NiCr2O4 or NiCrFeO4 and an intermediate metallic Ni-rich layer, with inner Cr2O3 layer. The general corrosion rate significantly decreased by about 72% as DH concentration increased from 5 to 35 cm3/kg H2O. In the range of 35-65 cm3/kg H2O, the corrosion rate slightly decreased with increasing DH concentration. However, no further changes were observed in the range of 65-100 cm3/kg H2O.

  20. Structure, mechanical property and corrosion behaviors of (HA+β-TCP)/Mg-5Sn composite with interpenetrating networks.

    Science.gov (United States)

    Wang, X; Li, J T; Xie, M Y; Qu, L J; Zhang, P; Li, X L

    2015-11-01

    In this paper, a novel (Hydroxyapatite+β-tricalcium phosphate)/Mg-5Sn ((HA+β-TCP)/Mg-5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg-5Sn alloy into porous HA+β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg-5Sn alloy has infiltrated not only into the pores but also into the struts of the HA+β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA+β-TCP closely, and no reaction layer can be found between Mg-5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176MPa, which is about four fifths of the strength of the Mg-5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg-5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH)2, Ca3(PO4)2 and HA. Appropriate mechanical and corrosion properties of the (HA+β-TCP)/Mg-5Sn composite indicate its possibility for new bone tissue implant materials.

  1. Electrochemical Corrosion Behavior of Are Sprayed Zn and Zn(1)5Al Coatings in Simulated Salina Soil and Neutral Meadow Soil Solutions

    Institute of Scientific and Technical Information of China (English)

    LIN Bilan; LU Xinying; LI Long

    2011-01-01

    Arc sprayed Zn and Zn(1)5Al coatings were chosen to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against corrosion of salina soil in northern china and neutral meadow soil in northeast China.The corrosion behavior of the coated Q235 steel samples in two simulated soil solutions were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods.The experimental results show that the corrosion of the matrix Q235 steel in both simulated solutions is remarkably inhibited by Zn and Znl5A1 coatings.The corrosion products on Zn and Zn(1)5Al are thick,compact,firm and protective.The corrosion current density icorr of both Zn and Zn(1)5Al-coated samples is decreased evidently with corrosion time,and the charge transfer resistance Rct is increased greatly.The corrosion resistance indexes of Zn and Zn(1)5Al in simulated neutral meadow soil solution are more outstanding than those in salina soil.The corrosion resistance of Zn(1)5Al in salina soil is slightly superior to that of Zn.When the sprayed coatings are sealed with epoxy resin,the corrosion resistance of the coatings is further enhanced markedly.

  2. Understanding corrosion behavior of Mg-Zn-Ca alloys from subcutaneous mouse model: effect of Zn element concentration and plasma electrolytic oxidation.

    Science.gov (United States)

    Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Xu, Zhigang; Dong, Zhongyun; Collins, Boyce; Yun, Yeoheung; Sankar, Jagannathan

    2015-03-01

    Mg-Zn-Ca alloys are considered as suitable biodegradable metallic implants because of their biocompatibility and proper physical properties. In this study, we investigated the effect of Zn concentration of Mg-xZn-0.3Ca (x=1, 3 and 5wt.%) alloys and surface modification by plasma electrolytic oxidation (PEO) on corrosion behavior in in vivo environment in terms of microstructure, corrosion rate, types of corrosion, and corrosion product formation. Microstructure analysis of alloys and morphological characterization of corrosion products were conducted using x-ray computed tomography (micro-CT) and scanning electron microscopy (SEM). Elemental composition and crystal structure of corrosion products were determined using x-ray diffraction (XRD) and electron dispersive x-ray spectroscopy (EDX). The results show that 1) as-cast Mg-xZn-0.3Ca alloys are composed of Mg matrix and a secondary phase of Ca2Mg6Zn3 formed along grain boundaries, 2) the corrosion rate of Mg-xZn-0.3Ca alloys increases with increasing concentration of Zn in the alloy, 3) corrosion rates of alloys treated by PEO sample are decreased in in vivo environment, and 4) the corrosion products of these alloys after in vivo tests are identified as brucite (Mg(OH)2), hydroxyapatite (Ca10(PO4)6(OH)2), and magnesite (MgCO3·3H2O).

  3. An electrochemical investigation of the corrosion behavior of aluminum alloys in chloride containing solutions; Investigacao eletroquimica da corrosao de ligas de aluminio em solucoes contendo cloretos

    Energy Technology Data Exchange (ETDEWEB)

    Campos Filho, Jorge Eustaquio de [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Escola de Engenharia. Dept. de Engenharia Quimica]. E-mail: jorgecamposfilho@yahoo.com.br; Neves, Celia de Figueiredo Cordeiro; Campos, Wagner Reis da Costa; Moreira, Marcilio Soares [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil)]. E-mail: caf@cdtn.br; wrcc@cdtn.br; msm@cdtn.br

    2005-07-01

    Aluminum alloys have been used as cladding materials for nuclear fuel in research reactors due to its corrosion resistance. Aluminum owes its good corrosion resistance to a protective barrier oxide film formed and strongly bonded to its surface. In pool type TRIGA IPR-R1 reactor, located at Centro de Desenvolvimento da Tecnologia Nuclear in Belo Horizonte, previous immersion coupon tests revealed that aluminum alloys suffer from pitting corrosion, in spite of high quality of water control. Corrosion attack is initiated by breaking the protective oxide film on aluminum alloy surface. Chloride ions can break this oxide film and stimulate metal dissolution. In this study the aluminum alloys 1050, 5052 and 6061 were used to evaluate their corrosion behavior in chloride containing solutions. The electrochemical techniques used were potentiodynamic anodic polarization and cyclic polarization. Results showed that aluminum alloys 5052 and 6061 present similar corrosion resistance in low chloride solutions (0,1 ppm NaCl) and in reactor water but both alloys are less resistant in high chloride solution (1 ppm NaCl). Aluminum alloy 1050 presented similar behavior in the three electrolytes used, regarding to pitting corrosion, indicating that the concentration of the chloride ions was not the only variable to influence its corrosion susceptibility. (author)

  4. ELECTROCHEMICAL CORROSION BEHAVIORS OF ARC-SPRAYED ALUMINUM COATING%电弧喷涂铝涂层的腐蚀电化学行为

    Institute of Scientific and Technical Information of China (English)

    刘存; 赵卫民; 艾华; 王勇; 董立先

    2011-01-01

    用电弧喷涂方法在钢表面制备铝涂层,研究其在3.5%NaCl溶液中的电化学腐蚀行为.采用电子探针技术(EPMA)分析研究浸泡30 d后涂层横截面的成分分布特征,发现腐蚀介质可沿孔隙或夹杂物向涂层内部渗入,且已有部分Cl-渗达涂层深处.动电位极化实验结果显示,原始铝涂层具有明显的钝化现象,这与胶冻状腐蚀产物Al(OH)3的附着力较强以及Al2O3膜的形成有关.电化学阻抗谱(EIS)测试结果表明,铝涂层在测试期内的EIS图谱变化可分成4个阶段:孔蚀萌生阶段、孔内酸化析氢阶段、介质渗达钢基体后涂层作为牺牲阳极的阶段和孔蚀群急剧发展阶段.提出电极在腐蚀过程中的不同阻抗模型.%Aluminum was deposited on steel using arc spraying, and the corrosion electrochemical behavior of the coatings in 3.5% NaCl aqueous solution was investigated.The electron probe micro-analysis (EPMA)was used to examine composition profiles of the coating cross section after 30 day immersion.The results showed that the corrosion medium could penetrate into the coatings along the pores or inclusions, and chloride ions have penetrated into the depth of the coatings.The potentiodynamic polarization curves showed the passivation phenomenon of the original aluminum coating, which was related to the strong adhesion of jelly corrosion product Al(OH)3 and the existence of Al2O3 films.The corrosion failure process of aluminum coating was investigated by means of electrochemical impedance spectroscopy (EIS) measurements.On the basis of the impedance diagram changes during the testing, the process can be separated into four stages: initiation of cavitations, acidification and hydrogen evolution in the hole, coating as the sacrificial anode when the corrosion medium penetrates into steel substrate and rapid development of cavitation groups.Finally various models for the electrode in the corrosion process were proposed.

  5. Corrosion behaviors of zinc and Zn-Ni alloy compositionally modulated multilayer coatings

    Institute of Scientific and Technical Information of China (English)

    Jingyin Fei; Guozheng Liang; Wenli Xin; Weikang Wang; Jianghong Liu

    2005-01-01

    Zinc and Zn-Ni alloy compositionally modulated multilayer (CMM) coatings were electrodeposited from dual baths. The coated samples were evaluated in terms of surface appearance, surface and cross-sectional morphologies, as well as corrosion resistance. The results obtained from the salt spray test show that the zinc and Zn-Ni alloy CMM coatings are more corrosion-resistant than the monolithic coatings of zinc or Zn-Ni alloy alone with a similar thickness. The corrosion potential measurement and anodic polarisation tests were undertaken to examine the probable corrosion mechanisms of zinc and Zn-Ni alloy CMM coatings. Analysis on the micrographic features of zinc and Zn-Ni alloy CMM coatings after the corrosion test explains the probable reasons why the Zn-Ni/Zn CMM coatings have a better protective performance. Surface morphologies and compositional analysis of the remaining coating material of Zn-Ni alloy deposit after the corrosion test confirms the dezincification mechanism of the Zn-Ni alloy deposit during the corrosion process.

  6. Corrosion behavior of Cr/Ni alloy coated ferritic stainless steel in simulated cathodic PEMFC environments

    Energy Technology Data Exchange (ETDEWEB)

    Rendon, M.; Rivas, S.V.; Arriga, L.G.; Orozco, G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Queretaro (Mexico); Perez-Quiroz, J.T. [Inst. Mexicano del Transporte, Queretaro (Mexico); Porcayo, J. [Inst. de Investigaciones Electricas, Morelos (Mexico)

    2008-07-01

    The bipolar plate in a proton exchange membrane fuel cell (PEMFC) must be corrosion resistant and the interfacial contact resistance (ICR) with the gas diffusion layer must be low. For these reasons, stainless steel with high Cr content is considered to be a viable material for use in bipolar plate construction. This study evaluated the corrosion resistance of ferritic stainless steels 441 and 439, with and without a Cr/Ni coating, under simulated cathodic PEMFC conditions. Steel 441 without coating has a low corrosion current density and can be considered as a candidate material to be used as bipolar plate. The study showed that after the Cr/Ni coating was applied by Thermal Spray Metal method, the corrosion current density increased due to selective dissolution of an alloy element. The corrosion current density of the coatings was higher than the DOE target value, rendering them an unfeasible option to be used in bipolar plates for fuel cell applications. However, previous studies have shown that after the coating was applied, a passivation process improved the corrosion resistance. Although steel 441 appears to be a better candidate than steel 316 because of its lower cost, the behaviour of the Ni-Cr alloys was not satisfactory in corrosive acidic medium. 5 refs.

  7. Relationship between solution structure and phase behavior: a neutron scattering study of concentrated aqueous hexamethylenetetramine solutions.

    Science.gov (United States)

    Burton, R C; Ferrari, E S; Davey, R J; Finney, J L; Bowron, D T

    2009-04-30

    The water-hexamethylenetetramine system displays features of significant interest in the context of phase equilibria in molecular materials. First, it is possible to crystallize two solid phases depending on temperature, both hexahydrate and anhydrous forms. Second, saturated aqueous solutions in equilibrium with these forms exhibit a negative dependence of solubility (retrograde) on temperature. In this contribution, neutron scattering experiments (with isotopic substitution) of concentrated aqueous hexamethylenetetramine solutions combined with empirical potential structure refinement (EPSR) were used to investigate the time-averaged atomistic details of this system. Through the derivation of radial distribution functions, quantitative details emerge of the solution coordination, its relationship to the nature of the solid phases, and of the underlying cause of the solubility behavior of this molecule.

  8. Corrosion behavior of Haynes {sup registered} 230 {sup registered} nickel-based super-alloys for integrated coal gasification combined cycle syngas plants. A plant exposure study

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sungkyu; Lee, Jieun; Kang, Suk-Hwan; Lee, Seung-Jong; Yun, Yongseung [Institute for Advanced Engineering (IAE), Gyeonggi-do (Korea, Republic of). Plant Engineering Center; Kim, Min Jung [Sungkyunkwan Univ, Gyeonggi-do (Korea, Republic of). Advanced Materials Technology Research Center

    2015-07-01

    The corrosion behavior of commercially available Haynes {sup registered} 230 {sup registered} nickel-based alloy samples was investigated by exposure to coal-gasifying integrated coal gasification combined cycle pilot plant facilities affiliated with the Institute for Advanced Engineering (2.005 MPa and 160-300 C). The morphological and microstructural analyses of the exposed samples were conducted using scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis on the external surface of the recovered corrosion test samples to obtain information of the corrosion scale. These analyses based on the pre- and post-exposure corrosion test samples combined with thermodynamic Ellingham-Pourbaix stability diagrams provided preliminary insight into the mechanism of the observed corrosion behavior prevailing in the piping materials that connected the particulate removal unit and water scrubber of the integrated coal gasification combined cycle pilot plant. Uniform material wastage was observed after 46 hours of operation, and a preliminary corrosion mechanism was suggested: the observed material waste and corrosion behavior of the Haynes {sup registered} 230 {sup registered} nickel-based alloy samples cut off from the coal syngas integrated coal gasification combined cycle plant were explained by the formation of discontinuous (complex) oxide phases and subsequent chlorine-induced active oxidation under the predominantly reducing environment encountered. This contribution continues the already published studies of the Fe-Ni-Cr-Co alloy Haynes {sup registered} 556 {sup registered}.

  9. Structure, mechanical property and corrosion behaviors of (HA + β-TCP)/Mg–5Sn composite with interpenetrating networks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X., E-mail: wangxiang@hrbeu.edu.cn [Center for Biomedical Materials and Engineering, Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, 150001 (China); Li, J.T.; Xie, M.Y. [Center for Biomedical Materials and Engineering, Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, 150001 (China); Qu, L.J. [Key Lab of Biomedical Materials of University in Heilongjiang Province, Jiamusi University, Jiamusi 154007 (China); Zhang, P.; Li, X.L. [Center for Biomedical Materials and Engineering, Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, 150001 (China)

    2015-11-01

    In this paper, a novel (Hydroxyapatite + β-tricalcium phosphate)/Mg–5Sn ((HA + β-TCP)/Mg–5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg–5Sn alloy into porous HA + β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg–5Sn alloy has infiltrated not only into the pores but also into the struts of the HA + β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA + β-TCP closely, and no reaction layer can be found between Mg–5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176 MPa, which is about four fifths of the strength of the Mg–5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg–5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH){sub 2}, Ca{sub 3}(PO{sub 4}){sub 2} and HA. Appropriate mechanical and corrosion properties of the (HA + β-TCP)/Mg–5Sn composite indicate its possibility for new bone tissue implant materials. - Highlights: • The novel (HA + β-TCP)/Mg–5Sn composite with interpenetrating networks was fabricated using suction casting technique. • The ultimate compressive strength of the composite was near with the natural bone. • And the corrosion resistance of the composite was better than that of the Mg–5Sn bulk alloy.

  10. Issues of Corrosion Mechanism for Zircaloy-4 in Aqueous Lithium Hydroxide Solution%Zr-4合金在 LiOH水溶液中腐蚀机理的概述

    Institute of Scientific and Technical Information of China (English)

    刘文庆; 周邦新

    2001-01-01

    综述了近十几年国内外对 Zr-4合金在 LiOH水溶液中腐蚀的研究,着重讨论了在 LiOH水溶液中加速腐蚀的规律和机理,并分析了目前解释这种腐蚀机理的各种假说中存在的问题。%The studies on corrosion of Zircaloy-4 in aqueous lithium hydroxide solution have been reviewed with the emphasis on the kinetics and mechanism of the accelerated corrosion.The problems of hypotheses for the explanation of the accelerated corrosion mechanical are analyzed.

  11. Microstructural evolution and corrosion behavior of directionally solidified FeCoNiCrAl high entropy alloy

    Directory of Open Access Journals (Sweden)

    Cui Hongbao

    2011-08-01

    Full Text Available The FeCoNiCrAl alloys have many potential applications in the fields of structural materials, but few attempts were made to characterize the directional solidification of high entropy alloys. In the present research, the microstructure and corrosion behavior of FeCoNiCrAl high entropy alloy have been investigated under directional solidification. The results show that with increasing solidification rate, the interface morphology of the alloy evolves from planar to cellular and dendritic. The electrochemical experiment results demonstrate that the corrosion products of both non-directionally and directionally solidified FeCoNiCrAl alloys appear as rectangular blocks in phases which Cr and Fe are enriched, while Al and Ni are depleted, suggesting that Al and Ni are dissolved into the NaCl solution. Comparison of the potentiodynamic polarization behaviors between the two differently solidified FeCoNiCrAl high entropy alloys in a 3.5%NaCl solution shows that the corrosion resistance of directionally solidified FeCoNiCrAl alloy is superior to that of the non-directionally solidified FeCoNiCrAl alloy.

  12. Effect of Inclusion Size and Distribution on the Corrosion Behavior of Medical-Device Grade Nitinol Tubing

    Science.gov (United States)

    Wohlschlögel, Markus; Steegmüller, Rainer; Schüßler, Andreas

    2014-07-01

    Nonmetallic inclusions in Nitinol, such as carbides (TiC) and intermetallic oxides (Ti4Ni2O x ), are known to be triggers for fatigue failure of Nitinol medical devices. These mechanically brittle inclusions are introduced during the melting process. As a result of hot and cold working in the production of Nitinol tubing inclusions are fractionalized due to the mechanical deformation imposed. While the role of inclusions regarding Nitinol fatigue performance has been studied extensively in the past, their effect on Nitinol corrosion behavior was investigated in only a limited number of studies. The focus of the present work was to understand the effect of inclusion size and distribution on the corrosion behavior of medical-device grade Nitinol tubing made from three different ingot sources during different manufacturing stages: (i) for the initial stage (hollow: round bar with centric hole), (ii) after hot drawing, and (iii) after the final drawing step (final tubing dimensions: outer diameter 0.3 mm, wall thickness 0.1 mm). For one ingot source, two different material qualities were investigated. Potentiodynamic polarization tests were performed for electropolished samples of the above-mentioned stages. Results indicate that inclusion size rather than inclusion quantity affects the susceptibility of electropolished Nitinol to pitting corrosion.

  13. Effects of duty cycle on microstructure and corrosion behavior of TiC coatings prepared by DC pulsed plasma CVD

    Energy Technology Data Exchange (ETDEWEB)

    Shanaghi, Ali, E-mail: alishanaghi@gmail.com [Surface Engineering Laboratory, Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Rouhaghdam, Ali Reza Sabour, E-mail: sabour01@modares.ac.ir [Surface Engineering Laboratory, Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Ahangarani, Shahrokh, E-mail: sh.ahangarani@gmail.com [Advanced Materials and Renewable Energies Department, Iranian Research organization for science and technology, P.O. Box 15815-3538, Tehran (Iran, Islamic Republic of); Chu, Paul K., E-mail: paul.chu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Farahani, Taghi Shahrabi, E-mail: tshahrabi34@modares.ac.ir [Surface Engineering Laboratory, Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2012-01-15

    Titanium carbide coatings are deposited on hot-work steel (H{sub 11}) by plasma-assisted chemical vapor deposition (PACVD) and the dependence of the corrosion behavior on fabrication parameters is investigated. Grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), Raman and electrochemical tests are used to study the structure as well as corrosion behaviors. Grazing incidence X-ray diffraction reveals the (2 0 0) plane implying that the TiC coatings are deposited via the kinetics-limited crystal growth mechanism and under thermodynamically stable conditions. The SEM results indicate that the formation of a homogeneous and uniform titanium carbide nanostructure coatings. Potentiodynamic and electrochemical impedance tests performed in 0.5 M H{sub 2}SO{sub 4} and 0.05 M NaCl show that the TiC coating produced using a 40% duty cycle possesses high corrosion resistance in both media. The R{sub p} values of the TiC coating (50% duty cycle) in 0.05 M NaCl and the other TiC coating (40% duty cycle) in 0.5 M H{sub 2}SO{sub 4} are approximately four and sixteen orders of magnitude higher than that of the bare steel, respectively. Our results reveal that the duty cycles not only affect the structure and morphology of the coatings but also influence the electrochemical properties.

  14. Study of the corrosion behaviors of 304 austenite stainless steel specimens exposed to static liquid lithium at 600 K

    Science.gov (United States)

    Meng, Xiancai; Zuo, Guizhong; Ren, Jun; Xu, Wei; Sun, Zhen; Huang, Ming; Hu, Wangyu; Hu, Jiansheng; Deng, Huiqiu

    2016-11-01

    Investigation of corrosion behavior of stainless steel served as one kind of structure materials exposed to liquid lithium (Li) is one of the keys to apply liquid Li as potential plasma facing materials (PFM) or blanket coolant in the fusion device. Corrosion experiments of 304 austenite stainless steel (304 SS) were carried out in static liquid Li at 600 K and up to1584 h at high vacuum with pressure less than 4 × 10-4 Pa. After exposure to liquid Li, it was found that the weight of 304 SS slightly decreased with weight loss rate of 5.7 × 10-4 g/m2/h and surface hardness increased by about 50 HV. Lots of spinel-like grains and holes were observed on the surface of specimens measured by SEM. By further EDS, XRD and metallographic analyzing, it was confirmed that the main compositions of spinel-like grains were M23C6 carbides, and 304 SS produced a non-uniform corrosion behavior by preferential grain boundary attack, possibly due to the easy formation of M23C6 carbides and/or formation of Li compound at grain boundaries.

  15. Corrosion protection of low-carbon steel using exopolysaccharide coatings from Leuconostoc mesenteroides.

    Science.gov (United States)

    Finkenstadt, Victoria L; Côté, Gregory L; Willett, J L

    2011-06-01

    Corrosion of metals is a serious and challenging problem faced worldwide by industry. Purified Leuconostoc mesenteroides exopolysaccharide (EPS) coatings, cast from aqueous solution, inhibited the corrosion of low-carbon steel as determined by electrochemical impedance spectroscopy (EIS). There were two different corrosion behaviors exhibited when EPS films from different strains were cast onto the steel. One EPS coating reacted immediately with the steel substrate to form an iron (III) oxide layer ("rust") during the drying process while another did not. The samples that did not flash corrode had higher corrosion inhibition and formed an iron (II) passivation layer during EIS testing that persisted after the cells were disassembled. Corrosion inhibition was strain-specific as polysaccharides with similar structure did not have the same corrosion potential.

  16. Stress-Corrosion Interactions in Zr-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Petre Flaviu Gostin

    2015-07-01

    Full Text Available Stress-corrosion interactions in materials may lead to early unpredictable catastrophic failure of structural parts, which can have dramatic effects. In Zr-based bulk metallic glasses, such interactions are particularly important as these have very high yield strength, limited ductility, and are relatively susceptible to localized corrosion in halide-containing aqueous environments. Relevant features of the mechanical and corrosion behavior of Zr-based bulk metallic glasses are described, and an account of knowledge regarding corrosion-deformation interactions gathered from ex situ experimental procedures is provided. Subsequently the literature on key phenomena including hydrogen damage, stress corrosion cracking, and corrosion fatigue is reviewed. Critical factors for such phenomena will be highlighted. The review also presents an outlook for the topic.

  17. Influence of coating defects on the corrosion behavior of cold sprayed refractory metals

    Science.gov (United States)

    Kumar, S.; Rao, A. Arjuna

    2017-02-01

    The defects in the cold sprayed coatings are critical in the case of corrosion performances of the coatings in aggressive conditions. To understand the influence of coating defects on corrosion, immersion tests have been carried out in HF solution for the cold sprayed and heat treated Titanium, Tantalum and Niobium coatings. Long duration immersion tests reveal inhomogeneous weight losses of the samples prepared at different heat treatment conditions. The weight loss for different coatings has been well corroborated with the coating defects and microstructures. Chemical and micro structural analysis elucidates the reason behind the inhomogeneous performance of different type of cold sprayed coatings in corrosion medium. In the case of cold sprayed titanium, formation of stable oxide along the inter-splat boundary hinders the aggressive attack of the corrosion medium which is not so in other cases.

  18. Analysis of corrosion resistance behavior of inhibitors in concrete using electrochemical techniques

    Science.gov (United States)

    Song, Ha-Won; Saraswathy, Velu

    2006-08-01

    Reinforced concrete is one of the most durable and cost effective construction materials. However, in high chloride environments, it can suffer from corrosion due to chloride induced breakdown of the normal passive layer protecting the reinforcing steel bars inside concrete. One means of protecting embedded steel reinforcement from chloride induced corrosion is the addition of corrosion inhibiting admixtures. In the present investigation, various inhibitors such as sodium nitrite, zinc oxide, mono ethanol amine, diethanolamine, and triethanol amine have been used in concrete in different percentages. Their effectiveness was then studied using various electrochemical techniques such as rapid chloride ion penetration test, open circuit potential measurement, electrochemical impedance measurement, potentiodynamic polarization measurement, and gravimetric weight loss measurement. The results thus obtained indicate that the addition of inhibitors enhances the corrosion resistance properties.

  19. The Study Programm Report of the Corrosion Behavior of New Zirconium-based Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The corrosion of fuel cladding in PWR limits the extension of burnup. To compare the corrosion resistance of Zr-4 and new zirconium-based alloys, the out-of-pile water-side corrosion test has been conducted for these materials.To study the effects of heat flux on the corrosion of cladding, and keep the surface of cladding as an original ’as-received’ statement, the heat elements are introduced into the inside of the cladding tubes.The materials have been exposed for 205 d till now. The oxide film performed on the surface of cladding is black and glossy. The thickness of oxide is measured by the method of eddy current.

  20. Evaluation of anti-corrosive lubricating behavior of dicationic ionic liquid coatings for biomedical alloys

    Science.gov (United States)

    Siddiqui, Danyal Alam

    Since their inception, orthopedic implants composed of biomedical alloys have been plagued with failures associated with corrosion and wear processes. Despite current surface treatments and techniques being employed to mitigate corrosion and wear, these failure mechanisms continue to occur as prevalent failure modes. Recently, a novel class of compounds known as ionic liquids has been proposed as a multi-functional coating to protect the surfaces of commercially pure titanium surfaces comprising dental implants. In this study, the goal was to evaluate select formulations of these ionic liquids to serve as anti-corrosive lubricants for titanium and cobalt chromium molybdenum alloys widely used in orthopedic implants. Electrochemical and tribological testing of dicationic imidazolium-based ionic liquids revealed these compounds to be superior candidates as corrosion inhibitors and lubricants of biomedical alloy surfaces.

  1. Corrosion Behavior of MIG Brazed and MIG Welded Joints of Automotive DP600-GI Steel Sheet

    Science.gov (United States)

    Basak, Sushovan; Das, Hrishikesh; Pal, Tapan Kumar; Shome, Mahadev

    2016-12-01

    Galvanized dual-phase steel sheets are extensively used by the auto industry for their corrosion resistance property. Welding by the metal inert gas (MIG) process causes degradation of the steel in the vicinity of the joint due to excessive zinc evaporation. In order to minimize Zn loss, the MIG brazing process has been tried out in lap joint configuration over a heat input range of 136-204 J mm-1. The amount of zinc loss, intermetallic formation and corrosion properties in the joint area has been evaluated for both MIG brazing and MIG welding. Corrosion rate of 21 mm year-1 has been reduced to 2 mm year-1 by adopting MIGB in place MIGW. Impedance study has shown that the corrosion mechanism in base metal, MIG brazed and MIG welded joints is dominated by charge transfer, diffusion and mixed mode control processes, respectively.

  2. Fretting corrosion behavior of nitinol spinal rods in conjunction with titanium pedicle screws.

    Science.gov (United States)

    Lukina, Elena; Kollerov, Mikhail; Meswania, Jay; Khon, Alla; Panin, Pavel; Blunn, Gordon W

    2017-03-01

    Untypical corrosion damage including erosions combined with the build-up of titanium oxide as a corrosion product on the surface of explanted Nitinol spinal rods in the areas where it was in contact with titanium pedicle screw head is reported. It was suggested that Nitinol rods might have inferior fretting corrosion resistance compared with that made of titanium or CoCr. Fretting corrosion of Nitinol spinal rods with titanium (Ti6Al4V) pedicle screws were tested in-vitro by conducting a series of potentiostatic measurements of the peak-to-peak values of fretting corrosion current under bending in a 10% solution of calf serum in PBS. The test included Nitinol rods locked in titanium pedicle screws of different designs. Performance of commercially available titanium (Ti6Al4V) and CoCr spinal rods was also investigated for a comparison. Corrosion damage observed after the in-vitro tests was studied using SEM and EDAX analysis and was compared with patterns on Nitinol rods retrieved 12months after initial surgery. Metal ions level was measured in the test media after in-vitro experiments and in the blood and tissues of the patients who had the rods explanted. The results of this study revealed that Nitinol spinal rods locked in Ti pedicle screws are susceptible to fretting corrosion demonstrating higher fretting corrosion current compared with commercially used Ti6Al4V and CoCr rods. On the surface of Nitinol rods after in-vitro tests and on those retrieved from the patients similar corrosion patterns were observed. Improved resistance to fretting corrosion was observed with Nitinol rods in the in-vitro tests where pedicle screws were used with a stiffer locking mechanism. Since the development of the localized corrosion damage might increase the risk of premature fatigue failure of the rods and result in leaching of Ni ions, it is concluded that Nitinol rods should not be used in conjunction with Ti pedicle screws without special protection especially where the

  3. Hot corrosion behavior of neodymium magnesium hexaaluminate by vanadium pentoxide in air

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhan-Guo, E-mail: zgliu@hit.edu.cn; Ouyang, Jia-Hu, E-mail: ouyangjh@hit.edu.cn; Zhou, Yu; Zhu, Ren-Xian

    2013-11-25

    Highlights: •Hot corrosion products are different at temperatures ranging from 650 to 950 °C. •At 650 °C, the main corrosion products are AlVO{sub 4} and NdVO{sub 4}. •At 750 °C, V{sub 2}O{sub 5} reacts with NdMgAl{sub 11}O{sub 19} to form NdVO{sub 4}, MgV{sub 2}O{sub 6}, AlVO{sub 4} and alumina. •At 850 °C, the corrosion products consist of θ-Al{sub 2}O{sub 3}, NdVO{sub 4} and MgAl{sub 2}O{sub 4}. •At 950 °C, the corrosion products are composed of α-Al{sub 2}O{sub 3}, NdVO{sub 4} and MgAl{sub 2}O{sub 4}. -- Abstract: Hot corrosion due to molten salt attack is one of the main failure mechanisms of lanthanide magnesium hexaaluminate thermal barrier coating materials. Thermochemical attack of the NdMgAl{sub 11}O{sub 19} ceramic by V{sub 2}O{sub 5} was studied at different temperatures ranging from 650 to 950 °C using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The corrosion products of the NdMgAl{sub 11}O{sub 19} ceramic by V{sub 2}O{sub 5} depend mainly upon corrosion temperatures. At 650 °C, the corrosion products are mainly composed of AlVO{sub 4} and NdVO{sub 4}. However, molten V{sub 2}O{sub 5} reacts with NdMgAl{sub 11}O{sub 19} to form NdVO{sub 4}, MgV{sub 2}O{sub 6}, a small amount of AlVO{sub 4} and alumina at 750 °C. At 850 °C, the corrosion products consist of θ-Al{sub 2}O{sub 3}, NdVO{sub 4} and a small amount of MgAl{sub 2}O{sub 4}. After hot corrosion at 950 °C, the corrosion products are composed of α-Al{sub 2}O{sub 3}, NdVO{sub 4} and MgAl{sub 2}O{sub 4}.

  4. Experimental Investigation of the Corrosion Behavior of Friction Stir Welded AZ61A Magnesium Alloy Welds under Salt Spray Corrosion Test and Galvanic Corrosion Test Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    A. Dhanapal

    2013-01-01

    Full Text Available Extruded Mg alloy plates of 6 mm thick of AZ61A grade were butt welded using advanced welding process and friction stir welding (FSW processes. The specimens were exposed to salt spray conditions and immersion conditions to characterize their corrosion rates on the effect of pH value, chloride ion concentration, and corrosion time. In addition, an attempt was made to develop an empirical relationship to predict the corrosion rate of FSW welds in salt spray corrosion test and galvanic corrosion test using design of experiments. The corrosion morphology and the pit morphology were analyzed by optical microscopy, and the corrosion products were examined using scanning electron microscope and X-ray diffraction analysis. From this research work, it is found that, in both corrosion tests, the corrosion rate decreases with the increase in pH value, the decrease in chloride ion concentration, and a higher corrosion time. The results show the usage of the magnesium alloy for best environments and suitable applications from the aforementioned conditions. Also, it is found that AZ61A magnesium alloy welds possess low-corrosion rate and higher-corrosion resistance in the galvanic corrosion test than in the salt spray corrosion test.

  5. Microstructure and corrosion behavior of electrodeposited nano-crystalline nickel coating on AZ91 Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zarebidaki, Arman, E-mail: arman.zare@iauyazd.ac.ir; Mahmoudikohani, Hassan, E-mail: hassanmahmoudi.k@gmail.com; Aboutalebi, Mohammad-Reza

    2014-12-05

    Highlights: • Activation, zincating, and Cu electrodeposition were used as pretreatment processes for electrodeposition of nickel coatings. • Nano-crystalline nickel coatings were successfully electrodeposited onto the AZ91 Mg alloys. • Effect of nickel electrodeposited coating on the corrosion resistance of AZ91 Mg alloy has been studied. - Abstract: In order to enhance the corrosion resistance, nickel coating was electrodeposited onto AZ91 Mg alloy. Activation, zincating, and Cu electrodeposition used as pretreatment processes for better adhesion and corrosion performance of the nickel over layer. The corrosion properties of the AZ91 Mg alloy, nickel electroplated AZ91 Mg alloy, and pure nickel was assessed via polarization and electrochemical impedance spectroscopy (EIS) methods in 3.5 wt% NaCl solution. Moreover, the structure of the coating was investigated by means of X-ray diffraction, whereas specimen’s morphology and elemental composition were analyzed using scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). Measurements revealed that the coating has a nano-crystalline structure with the grain size of 95 nm. Corrosion results showed superior corrosion resistance for the coated AZ91 Mg alloy as the corrosion current density decreased from 2.5 × 10{sup −4} A cm{sup −2}, for the uncoated sample, to 1.5 × 10{sup −5} A cm{sup −2}, for coated specimen and the corrosion potential increased from −1.55 V to −0.98 V (vs. Ag/AgCl) at the same condition.

  6. Study of mechanical properties, microstructures and corrosion behavior of al 7075 t651 alloy with varying strain rate

    Science.gov (United States)

    Mukherjee, A.; Ghosh, M.; Mondal, K.; Venkitanarayanan, P.; Moon, A. P.; Varshney, A.

    2015-02-01

    Compression test of Al 7075 T651 was carried out at high strain rates (1138 - 2534 s-1) using Split Hopkinson Pressure Bar and at slow strain rate (10-4s-1) in 100KN Universal Testing machine to understand the improvement in mechanical properties and associated changes in microstructures. Cylindrical specimens of 6 mm height and 6 mm diameter were compressed dynamically. The influence of strain rates on mechanical properties, microstructure evolution and corrosion behavior after immersion test in 3.5% NaCl solution was also investigated. Strain rate, withdrawal stress and yield stress were observed to increase with impact velocity in high strain rate tests, while in slow strain rate tests, n value was observed to increase with increasing total strain. Microstructural observations revealed that after high strain rate test, grains of Al matrix were elongated. It was observed that corrosion resistance decreased with increase in impact velocity.

  7. Corrosivity and leaching behavior of controlled low-strength material (CLSM) made using bottom ash and quarry dust.

    Science.gov (United States)

    Naganathan, Sivakumar; Razak, Hashim Abdul; Hamid, Siti Nadzriah Abdul

    2013-10-15

    This paper reports the corrosivity and leaching behavior of CLSM made using two different industrial wastes i.e. bottom ash from an incineration facility and quarry dust. The leachate samples were derived from fresh and hardened CLSM mixtures, and studied for leaching and electrical resistivity. The release of various contaminants and the consequent environmental impact caused by the contaminants were studied by the measurement of contaminants in the bleed, in the leachate at 28 days, and on the leachate derived from crushed block and whole block leaching done over a period of 126 days. Results indicated that the CLSM mixtures are non corrosive; diffusion was the leaching mechanism; and the contaminants were found to be moderate to low mobility.

  8. Effect of Phosphate-Buffered Solution Corrosion on the Ratcheting Fatigue Behavior of a Duplex Mg-Li-Al Alloy

    Science.gov (United States)

    Yuan, Xin; Yu, Dunji; Gao, Li-Lan; Gao, Hong

    2016-05-01

    This work reports the uniaxial ratcheting and fatigue behavior of a duplex Mg-Li-Al alloy under the influence of phosphate-buffered solution corrosion. Microstructural observations reveal pitting and filament corrosion defects, which impair the load-bearing capacity of the alloy and cause stress concentration, thus leading to an accelerated accumulation of ratcheting strain and shortened fatigue life under the same nominal loading conditions. Comparing Smith model, Smith-Watson-Topper model, and Paul-Sivaprasad-Dhar model, a ratcheting fatigue life prediction model based on the Broberg damage rule and the Paul-Sivaprasad-Dhar model was proposed, and the model yielded a superior prediction for the studied magnesium alloy.

  9. Surface characteristics and electrochemical corrosion behavior of a pre-anodized microarc oxidation coating on titanium alloy.

    Science.gov (United States)

    Cui, W F; Jin, L; Zhou, L

    2013-10-01

    A porous bioactive titania coating on biomedical β titanium alloy was prepared by pre-anodization followed by micro arc oxidation technology. The effects of pre-anodization on the phase constituent, morphology and electrochemical corrosion behavior of the microarc oxidation coating were investigated. The results show that pre-anodization has less influence on the phase constituent and the surface morphology of the microarc oxidation coating, but improves the inner layer density of the microarc oxidation coating. The decrease of plasma discharge strength due to the presence of the pre-anodized oxide film contributes to the formation of the compact inner layer. The pre-anodized microarc oxidation coating effectively inhibits the penetration of the electrolyte in 0.9% NaCl solution and thus increases the corrosion resistance of the coated titanium alloy in physiological solution.

  10. Improve the corrosion and cytotoxic behavior of NiTi implants with use of the ion beam technologies

    Energy Technology Data Exchange (ETDEWEB)

    Meisner, L. L., E-mail: llm@isps.tsc.ru; Meisner, S. N. [Institute of Strength Physics and Materials Science SB RAS, 2/4 Akademichesky Ave., Tomsk, 634021 (Russian Federation); National Research Tomsk State University, 36, Lenina Avenue, Tomsk, 634050 (Russian Federation); Matveeva, V. A.; Matveev, A. L. [Institute of Chemical Biology and Fundamental Medicine, Siberian Branch,Russian Academy of Sciences, Novosibirsk, 630090 (Russian Federation)

    2015-11-17

    The corrosion resistance behavior and cytotoxicity of binary NiTi-base alloy specimens subjected to surface modification by silicon ion beams and the proliferative ability of mesenchymal stem cells (MSC) of rat marrow on an ion-implanted surface of the alloy have been studied. The silicon ion beam processing of specimen surfaces is shown to bring about a nearly two-fold improvement in the corrosion resistance of the material to attack by acqueous solutions of NaCl and human plasma and a drastic decrease in the nickel concentration after immersion of the specimens into the solutions for ∼3400 and ∼6000 h, respectively. It is found that MSC proliferation strongly depends on the surface structure, roughness and chemical condition of NiTi implants.

  11. Microstructure and Corrosion Behavior of Hf-40 Wt Pct Ti Alloy in Nitric Acid Medium for Reprocessing Applications

    Science.gov (United States)

    Jayaraj, J.; Ravi, K. R.; Mallika, C.; Kamachi Mudali, U.

    2016-09-01

    The Hf-40 wt pct Ti (Hf-Ti) alloy was developed for neutron poison application in the spent nuclear fuel reprocessing plant. The furnace-cooled Hf-Ti sample exhibited the microstructure comprising equiaxed-α, lamellar-α, and feathery-α. The water-quenched Hf-Ti sample confirmed the presence of lath and internally twinned martensite. In comparison to the furnace-cooled sample, low corrosion current density and passivation current density values obtained for the water-quenched Hf-Ti in 6 M HNO3 at 298 K (25 °C) indicated better passivation ability. The martensitic structure exhibited high hardness (660 HV) and negligible corrosion rate in 6 M nitric acid at 298 K (25 °C). X-ray photoelectron spectroscopic (XPS) analysis confirmed that passivation behavior of this alloy was due to the protective passive film composed of TiO2 and HfO2.

  12. Mechanical Properties and Corrosion Behavior of CeO2 and SiC Incorporated Al5083 Alloy Surface Composites

    Science.gov (United States)

    Amra, M.; Ranjbar, Khalil; Dehmolaei, R.

    2015-08-01

    In this investigation, nano-sized cerium oxide (CeO2) and silicon carbide (SiC) particles were stirred and mixed into the surface of an Al5083 alloy rolled plate using friction stir processing (FSP) to form a surface nano-composite layer. For this purpose, various volume ratios of the reinforcements either separately or in the combined form were packed into a pre-machined groove on the surface of the plate. Microstructural features, mechanical properties, and corrosion behavior of the resultant surface composites were determined. Microstructural analysis, optical microscopy and scanning electron microscopy, showed that reinforcement particles were fairly dispersed inside the stir zone and grain refinement was gained. Compared with the base alloy, all of the FSP composites showed higher hardness and tensile strength values with the maximum being obtained for the composite containing 100% SiC particles, i.e., Al5083/SiC. The corrosion behavior of the samples was studied by conducting potentiodynamic polarization tests and assessed in terms of corrosion potential, pitting potential, and passivation range. The result shows a significant increase in corrosion resistance of the base alloy; i.e., the longest passivation range when CeO2 alone was incorporated into the surface by acting as cathodic inhibitors. Composites reinforced with SiC particles exhibited lower pitting resistance due to the formation of microgalvanic couples between cathodic SiC particles and anodic aluminum matrix. The study was aimed to fabricate metal matrix surface composites with improved hardness, tensile strength, and corrosion resistance by the incorporation of CeO2 and SiC reinforcement particles into the surface of Al5083 base alloy. Optimum mechanical properties and corrosion resistance were obtained for the FSP composite Al5083/(75%CeO2 + 25%SiC). In this particular FSP composite, hardness and tensile strength were increased by 30, and 14%, respectively, and passivation range was increased

  13. Hot Corrosion Behavior of HVOF Sprayed Coatings on ASTM SA213-T11 Steel

    Science.gov (United States)

    Sidhu, H. S.; Sidhu, B. S.; Prakash, S.

    2007-09-01

    Cr3C2-NiCr, NiCr, WC-Co and Stellite-6 alloy coatings were sprayed on ASTM SA213-T11 steel using the HVOF process. Liquid petroleum gas was used as the fuel gas. Hot corrosion studies were conducted on the uncoated as well as HVOF sprayed specimens after exposure to molten salt at 900 °C under cyclic conditions. The thermo-gravimetric technique was used to establish the kinetics of corrosion. XRD, SEM/EDAX and EPMA techniques were used to analyze the corrosion products. All these overlay coatings showed a better resistance to hot corrosion as compared to that of uncoated steel. NiCr Coating was found to be most protective followed by the Cr3C2-NiCr coating. WC-Co coating was least effective to protect the substrate steel. It is concluded that the formation of Cr2O3, NiO, NiCr2O4, and CoO in the coatings may contribute to the development of a better hot-corrosion resistance. The uncoated steel suffered corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of unprotective Fe2O3 oxide scale.

  14. Surface characteristics and electrochemical corrosion behavior of NiTi alloy coated with IrO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Wang, Y.B.; Zhang, X.; Li, Q.H.; Liu, Q. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Cheng, Y., E-mail: chengyan@pku.edu.cn [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Biomedical engineering research center, Shenzhen institution of Peking University, Shenzhen 518057 (China); Zheng, Y.F. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Biomedical engineering research center, Shenzhen institution of Peking University, Shenzhen 518057 (China); Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871 (China); Xi, T.F. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Biomedical engineering research center, Shenzhen institution of Peking University, Shenzhen 518057 (China); Wei, S.C. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Biomedical engineering research center, Shenzhen institution of Peking University, Shenzhen 518057 (China); Department of Oral and Maxillofacial Surgery, School and Hospital of Stomatology, Peking University, Beijing 100871 (China)

    2013-01-01

    The aim of this work is to investigate the surface characteristics and corrosion behavior of NiTi (50.6 at.% Ni) shape memory alloy coated by a ceramic-like and highly biocompatible material, iridium oxide (IrO{sub 2}). IrO{sub 2} coatings were prepared by thermal decomposition of H{sub 2}IrCl{sub 6} {center_dot} 6H{sub 2}O precursor solution at the temperature of 300 Degree-Sign C, 400 Degree-Sign C and 500 Degree-Sign C, respectively. The surface morphology and microstructure of the coatings were investigated by scanning electron microscope (SEM) and glancing angle X-ray diffraction (GAXRD). X-ray photoelectron spectroscopy (XPS) was employed to determine the surface elemental composition. Corrosion resistance property of the coated samples was studied in a simulated body fluid at 37 {+-} 1 Degree-Sign C by electrochemical method. It was found that the morphology and microstructure of the coatings were closely related to the oxidizing temperatures. A relatively smooth, intact and amorphous coating was obtained when the H{sub 2}IrCl{sub 6}{center_dot}6H{sub 2}O precursor solution (0.03 mol/L) was thermally decomposed at 300 Degree-Sign C for 0.5 h. Compared with the bare NiTi alloy, IrO{sub 2} coated samples exhibited better corrosion resistance behavior to some extent. - Highlights: Black-Right-Pointing-Pointer First report on the surface coating of NiTi alloy by iridium oxide (IrO{sub 2}). Black-Right-Pointing-Pointer The coatings' microstructure was closely related to the oxidizing temperatures. Black-Right-Pointing-Pointer The corrosion resistance of NiTi alloy was improved by IrO{sub 2} coatings.

  15. Photodegradation of 2-mercaptobenzothiazole and 1,2,3-benzotriazole corrosion inhibitors in aqueous solutions and organic solvents.

    Science.gov (United States)

    Serdechnova, Maria; Ivanov, Vladimir L; Domingues, M Rosario M; Evtuguin, Dmitry V; Ferreira, Mario G S; Zheludkevich, Mikhail L

    2014-12-07

    The photochemical degradation of 2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) inhibitors was studied in the present work in aqueous and in organic solutions. The extent of photodegradation was assessed by UV-Vis spectroscopy and the main reaction products were identified by tandem electrospray ionization mass spectrometry (ESI-MS/MS). The analysis of degradation products upon UV irradiation revealed the predominant formation of dimeric compounds from MBT and oligomeric structures from BTA, which were further converted into aniline. The increase of the quantum yield of MBT and BTA photodegradation reactions under aerobic conditions both in aqueous and organic solvents was explained by an increase of the spin-orbit conversion of the singlet radical pairs into the triplet radical pairs in the presence of oxygen. These triplet pairs further dissociate into free radicals, or convert to the parent compounds. At the early stage of UV irradiation, free radical coupling leads essentially to dimer formation in the case of MBT and to the formation of oligomers in the case of BTA irradiation.

  16. Electrochemical behavior of LiCoO2 as aqueous lithium-ion battery electrodes

    KAUST Repository

    Ruffo, Riccardo

    2009-02-01

    Despite the large number of studies on the behavior of LiCoO2 in organic electrolytes and its recent application as a positive electrode in rechargeable water battery prototypes, a little information is available about the lithium intercalation reaction in this layered compound in aqueous electrolytes. This work shows that LiCoO2 electrodes can be reversibly cycled in LiNO3 aqueous electrolytes for tens of cycles at remarkably high rates with impressive values specific capacity higher than 100 mAh/g, and with a coulomb efficiency greater than 99.7%. Stable and reproducible cycling measurements have been made using a simple cell design that can be easily applied to the study of other intercalation materials, assuming that they are stable in water and that their intercalation potential range matches the electrochemical stability window of the aqueous electrolyte. The experimental arrangement uses a three-electrode flooded cell in which another insertion compound acts as a reversible source and sink of lithium ions, i.e., as the counter electrode. A commercial reference electrode is also present. Both the working and the counter electrodes have been prepared as thin layers on a metallic substrate using the procedures typical for the study of electrodes for lithium-ion batteries in organic solvent electrolytes. © 2008 Elsevier B.V. All rights reserved.

  17. Corrosion behavior of heat-treated low grade duplex stainless steel (type Fe-15Cr-5Ni-1.9Cu) in sweet environments

    Energy Technology Data Exchange (ETDEWEB)

    Ezuber, H. M. [Faculty of Engineering University of Bahrain P.O. Box 32038 Bahrain (Bahrain)

    2004-07-01

    Sweet and/or sour service environments require the use of corrosion resistant materials since conventional steels usually exhibit general corrosion, pitting attack and Stress Corrosion Cracking (SCC) under these conditions. Long term performance and cost effectiveness must be considered when evaluating material selection. Low grade duplex stainless steel may be considered as a useful material under corrosive conditions. These materials are immune to general corrosion and low nickel content is an advantage from a SCC stand point. In this study, the pitting corrosion behavior of low grade duplex stainless steel (type Fe-15Cr-5Ni-1.9Cu) alloys were evaluated in 01 M NaCl solutions saturated with CO{sub 2} (sweet environment) and containing no or little thiosulfate species at 50 deg. C. The effect of inappropriate heat treatment is also studied under such conditions. The results revealed that this alloy is susceptible to chloride pitting corrosion. The intensity of the chloride attack is remarkably increased with the application of inappropriate heat treatment, addition of CO{sub 2} and presence of thiosulfate species. Although chloride solutions containing saturated dissolved CO{sub 2} are more corrosive than those containing thiosulfate species, the presence of both species (CO{sub 2} and S{sub 2}O{sub 3}{sup 2}) has a more negative effect on the chloride pitting resistance than would occur for either component by it self. (authors)

  18. Relationship between the specific surface area of rust and the electrochemical behavior of rusted steel in a wet-dry acid corrosion environment

    Science.gov (United States)

    Liu, Wei; Zhao, Qing-he; Li, Shuan-zhu

    2017-01-01

    The relationship between the specific surface area (SSA) of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.

  19. Corrosion Behavior of Top and Bottom Surfaces for Single-Side and Double-Side Friction Stir Welded 7085-T7651 Aluminum Alloy Thick Plate Joints

    Science.gov (United States)

    Xu, Weifeng; Zhang, Wei; Wu, Xiaoli

    2017-01-01

    Thick plate joints of 7085-T7451 aluminum alloy were obtained through both single-side and double-side friction stir welding (SS or DS-FSW). The chloride ions effects on the corrosion behavior of the top and bottom surfaces of the joints were examined by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Results show that the corrosion susceptibility was suppressed significantly in the weld nugget zone, while the base material and heat-affected zone were prone to be corrosion attacked. For the SS-FSWed joint, the top surface showed a higher corrosion resistance than that of the bottom surface, but the larger corrosive heterogeneity was observed between the top and bottom surfaces compared with the two welds of DS-FSWed joint, which was confirmed by the morphology of corrosion attack. A deep insight on the microstructure of the joints indicates that the intermetallic particles played a key role in the corrosion behavior of the FSWed AA7085 aluminum alloy joints in chloride solution.

  20. Corrosion Behavior of Top and Bottom Surfaces for Single-Side and Double-Side Friction Stir Welded 7085-T7651 Aluminum Alloy Thick Plate Joints

    Science.gov (United States)

    Xu, Weifeng; Zhang, Wei; Wu, Xiaoli

    2017-03-01

    Thick plate joints of 7085-T7451 aluminum alloy were obtained through both single-side and double-side friction stir welding (SS or DS-FSW). The chloride ions effects on the corrosion behavior of the top and bottom surfaces of the joints were examined by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Results show that the corrosion susceptibility was suppressed significantly in the weld nugget zone, while the base material and heat-affected zone were prone to be corrosion attacked. For the SS-FSWed joint, the top surface showed a higher corrosion resistance than that of the bottom surface, but the larger corrosive heterogeneity was observed between the top and bottom surfaces compared with the two welds of DS-FSWed joint, which was confirmed by the morphology of corrosion attack. A deep insight on the microstructure of the joints indicates that the intermetallic particles played a key role in the corrosion behavior of the FSWed AA7085 aluminum alloy joints in chloride solution.

  1. Effect of replacement of V by Nb and Fe on the electrochemical and corrosion behavior of Ti-6Al-4V in simulated physiological environment

    Energy Technology Data Exchange (ETDEWEB)

    Choubey, A.; Balasubramaniam, R.; Basu, B

    2004-11-03

    The electrochemical and corrosion behavior of Ti-6Al-4V, Ti-6Al-4Nb, Ti-6Al-4Fe and Ti-5Al-2.5Fe alloys has been evaluated in Hank's solution at 37 deg. C. The effect of substituting vanadium in Ti-6Al-4V alloy has been specifically addressed. The corrosion rates were estimated by the Tafel extrapolation method. All the alloys were found to be passivated immediately on immersion. The passivation properties were comparable for the alloys. The estimated corrosion rates of the alloys were also comparable. The microstructures of the alloy have been discussed. The electrochemical and corrosion behavior of Ti-6Al-4V is not affected significantly on substituting vanadium with niobium and iron.

  2. Effect of heat treatment on corrosion behavior of low pressure sand cast Mg-10Gd-3Y-0.5Zr alloys

    OpenAIRE

    2016-01-01

    The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr (wt.%) alloys in as-cast, solution treated (T4) and aged (T6) conditions were studied by means of immersion test and electrochemical measurements in 5wt.% NaCl solution saturated with Mg(OH)2. It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4; while the corrosion resistance of the ...

  3. Effect of equal channel angular extrusion on wear and corrosion behavior of the orthopedic Ti-13Nb-13Zr alloy in simulated body fluid

    Energy Technology Data Exchange (ETDEWEB)

    Suresh, K.S. [Department of Materials. Engineering, Indian Institute of Science, Bangalore 560012 (India); Geetha, M., E-mail: geethamanivasagam@vit.ac.in [School of Mechanical and Building Sciences, VIT University, Vellore (India); Richard, C. [Laboratoire de Mecanique et de Rheologie EA 2640, Polytech' Tours, 37000 Tours (France); Landoulsi, J. [Laboratoire de Reactivite de Surface, UMR 7197 CNRS, Universite Pierre and Marie Curie - Paris VI, 4 Place Jussieu, Case 178, F-75252 Paris (France); Ramasawmy, H. [University of Mauritius, Faculty of Engineering, Reduit (Mauritius); Suwas, S. [Department of Materials. Engineering, Indian Institute of Science, Bangalore 560012 (India); Asokamani, R. [School of Mechanical and Building Sciences, VIT University, Vellore (India)

    2012-05-01

    We report investigations on the texture, corrosion and wear behavior of ultra-fine grained (UFG) Ti-13Nb-Zr alloy, processed by equal channel angular extrusion (ECAE) technique, for biomedical applications. The microstructure obtained was characterized by X-ray line profile analysis, scanning electron microscope (SEM) and electron back scattered diffraction (EBSD). We focus on the corrosion resistance and the fretting behavior, the main considerations for such biomaterials, in simulated body fluid. To this end, potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the UFG alloy in Hanks solution at 37 Degree-Sign C. The fretting wear behavior was carried out against bearing steel in the same conditions. The roughness of the samples was also measured to examine the effect of topography on the wear behavior of the samples. Our results showed that the ECAE process increases noticeably the performance of the alloy as orthopedic implant. Although no significant difference was observed in the fretting wear behavior, the corrosion resistance of the UFG alloy was found to be higher than the non-treated material. Highlights: Black-Right-Pointing-Pointer Relevancy of ECAE process applied to titanium alloy for biomedical applications. Black-Right-Pointing-Pointer Significant improvement of mechanical properties of the surface. Black-Right-Pointing-Pointer Noticeable increase of the corrosion resistance in simulated body fluid.

  4. Corrosion performance of reinforced mortar in the presence of polymeric nano-aggregates: electrochemical behavior, surface analysis, and properties of the steel/cement paste interface

    OpenAIRE

    Hu, J; Koleva, D. A.; Breugel, K. van

    2012-01-01

    This study reports on the effect of admixed polyethylene oxide-b-polystyrene (PEO113-b-PS70)micelles on corrosion behavior of reinforced mortar. The electrochemical measurement shows that the corrosion performance of the reinforcing steel was not significantly improved. However, surface analysis and microstructural investigation at the steel/cement paste interface reveal that the admixed micelles lead to a steel surface layer with enhanced barrier properties in terms of morphology and composi...

  5. Corrosion behavior of metals and alloys in marine-industrial environment

    Directory of Open Access Journals (Sweden)

    Mariappan Natesan, Subbiah Selvaraj, Tharmakkannu Manickam and Gopalachari Venkatachari

    2008-01-01

    Full Text Available This work deals with atmospheric corrosion to assess the degrading effects of air pollutants on ferrous and non-ferrous metals and alloys, which are mostly used as engineering materials. An exposure study was conducted in the Tuticorin port area located on the east coast of South India, in the Gulf of Mannar with Sri Lanka to the southeast. Common engineering materials, namely mild steel, galvanized iron, Zn, Al, Cu and Cu–Zn alloys (Cu–27Zn, Cu–30Zn and Cu–37Zn, were used in the investigation. The site was chosen where the metals are exposed to marine and industrial atmospheres. Seasonal 1 to 12 month corrosion losses of these metals and alloys were determined by a weight loss method. The weight losses showed strong corrosion of mild steel, galvanized iron, Cu and Zn and minor effect on Al and Cu–Zn alloys. Linear regression analysis was conducted to study the mechanism of corrosion. The composition of corrosion products formed on the metal surfaces was identified by x-ray diffraction and Fourier transform infrared spectroscopy.

  6. Effects of Linear Alkylbenzene Sulfonate on Aggregation Behaviors of Titanium Dioxide Nanoparticles in Aqueous Environment

    Institute of Scientific and Technical Information of China (English)

    Xiuheng Wang

    2015-01-01

    In aqueous environment, organic matters may exert impacts on the aggregation behaviors of titanium dioxide nanoparticles ( TiO2⁃NPs). Owing to the deficiency of studies on the aggregation of TiO2⁃NPs in the presence of synthetic organic compound, this study used linear alkylbenzene sulfonate ( LAS) as a representative to evaluate the effects of TiO2⁃NPs concentration (1⁃10 mg/L), LAS concentration (0-1 mg/L), pH (4-8) and ionic strength ( NaCl, CaCl2; 5-20 mM ) during aggregation of TiO2⁃NPs suspensions based on the detection of hydrodynamic diameters and electrophoretic mobilities and the calculation of interaction energies. The results showed that the TiO2⁃NPs in the presence of LAS are more stable than that in the absence of LAS. With the increase of ionic strength, the hydrodynamic diameter of NPs decreases, and the existence of LAS changes the point of zero charge from 5�4 to a lower value and thus alteres the aggregation behaviors of TiO2⁃NPs. The present study suggests that the LAS has a significant impact to the transportation and transformation of nanoparticles in aqueous environment.

  7. Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Yanjun Guo

    2014-09-01

    Full Text Available The effect of annealing temperature (1000–1150 °C on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM, scanning electron microscopy (SEM, magnetic force microscopy (MFM, scanning Kelvin probe force microscopy (SKPFM, energy dispersive X-ray spectroscopy (EDS, uniaxial tensile tests (UTT, and potentiostatic critical pitting temperature (CPT. The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP. The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN.

  8. Effect of coupling asynchronous acoustoelectric effects on the corrosion behavior, microhardness and biocompatibility of biomedical titanium alloy strips.

    Science.gov (United States)

    Ye, Xiaoxin; Tang, Guoyi

    2015-01-01

    The coupling asynchronous acoustoelectric effects (CAAE) of the high-energy electropulsing treatment (EPT) technique and ultrasonic surface strengthening modification (USSM) are innovatively combined in improving the surface microhardness, corrosion behavior and biocompatibility of the pre-deformed titanium alloy strips. Experimental results show that EPT and USSM processes facilitate the surface grain refining and USSM brings in the micro-dimples on the materials surface, which is attributed to the atoms diffusion acceleration under EPT and severe surface plastic deformation under USSM. These microstructure changes can not only enhance the corrosion resistance in the acidic simulated body fluids and fluoridated acidic artificial saliva but also improve the biocompatibility of the titanium alloy strip materials. Moreover, the surface microhardness of the titanium alloy strips is enhanced to improve the wear resistance. Therefore, CAAE processing is a high-efficiency and energy-saving method for obtaining biomedical titanium alloys with superior anti-corrosion performance, microhardness and biocompatibility, which can be widely applied in dental implants and artificial joint.

  9. Weld Bead Size, Microstructure and Corrosion Behavior of Zirconium Alloys Joints Welded by Pulsed Laser Spot Welding

    Science.gov (United States)

    Cai, Chuang; Li, Liqun; Tao, Wang; Peng, Genchen; Wang, Xian

    2016-09-01

    Pulsed laser spot welding of intersection points of zirconium alloys straps was performed. Weld bead size, microstructure and the corrosion behavior of weld bead were investigated. With the increasing laser peak power or number of shots, the weld width of the beads increased, the protrusion decreased and the dimple increased with further increase in heat input. The fusion zone consisted of a mixture of αZr and residual βZr phases. After annealing treatment, βNb and Zr(Fe, Nb)2 second phase particles were precipitated inter- and intragranular of αZr grains adequately. The oxide thickness of annealed weld bead was about 3.90 μm, decreased by about 18.1% relative to the 4.76 μm of as-welded specimen corroded at 400 °C and 10.3 MPa for 20 days. The corrosion resistance of annealed specimen was better than that of as-welded specimen, since the second phase particles exerted better corrosion resistance, and the content of Nb in βZr and the fraction of βZr decreased after the annealing treatment.

  10. Microstructure, texture evolution, mechanical properties and corrosion behavior of ECAP processed ZK60 magnesium alloy for biodegradable applications.

    Science.gov (United States)

    Mostaed, Ehsan; Hashempour, Mazdak; Fabrizi, Alberto; Dellasega, David; Bestetti, Massimiliano; Bonollo, Franco; Vedani, Maurizio

    2014-09-01

    Ultra-fine grained ZK60 Mg alloy was obtained by multi-pass equal-channel angular pressing at different temperatures of 250°C, 200°C and 150°C. Microstructural observations showed a significant grain refinement after ECAP, leading to an equiaxed and ultrafine grain (UFG) structure with average size of 600nm. The original extrusion fiber texture with planes oriented parallel to extrusion direction was gradually undermined during ECAP process and eventually it was substituted by a newly stronger texture component with considerably higher intensity, coinciding with ECAP shear plane. A combination of texture modification and grain refinement in UFG samples led to a marked reduction in mechanical asymmetric behavior compared to the as-received alloy, as well as adequate mechanical properties with about 100% improvement in elongation to failure while keeping relatively high tensile strength. Open circuit potential, potentiodynamic and weight loss measurements in a phosphate buffer solution electrolyte revealed an improved corrosion resistance of UFG alloy compared to the extruded one, stemming from a shift of corrosion regime from localized pitting in the as-received sample to a more uniform corrosion mode with reduced localized attack in ECAP processed alloy. Compression tests on immersed samples showed that the rate of loss of mechanical integrity in the UFG sample was lower than that in the as-received sample.

  11. A study of early corrosion behaviors of FeCrAl alloys in liquid lead-bismuth eutectic environments

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jun [Nuclear Transmutation Energy Research Center of Korea (NUTRECK), Seoul National University, San 56-1 Shinlim-dong, Gwanak-ku, Seoul 151-742 (Korea, Republic of); Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Nam, Hyo On; Hwang, Il Soon [Nuclear Transmutation Energy Research Center of Korea (NUTRECK), Seoul National University, San 56-1 Shinlim-dong, Gwanak-ku, Seoul 151-742 (Korea, Republic of); Kim, Ji Hyun, E-mail: kimjh@unist.ac.k [Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2010-12-31

    Lead and lead-bismuth eutectic (LBE) alloy have been increasingly receiving attention as heavy liquid metal coolants (HLMC) for future nuclear energy systems. The compatibility of structural materials and components with lead-bismuth eutectic liquid at high temperature is one of key issues for the commercialization of lead fast reactors. In the present study, the corrosion behaviors of iron-based alumina-forming alloys (Kanthal-AF (registered) , PM2000, MA956) were investigated by exposing to stagnant LBE environments at 500 {sup o}C and 550 {sup o}C for up to 500 h. After exposures, the thickness and chemistry of the oxide layer on the specimens were analyzed by scanning electron microscopy, scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. As a result, the oxide characteristics and the corrosion resistance were compared. In this study, it was shown that the corrosion resistance of FeCrAl ODS steels (PM2000, MA956) are superior to that of FeCrAl ferritic steel (Kanthal-AF (registered)) in higher temperature LBE.

  12. Effect of cobalt content on wear and corrosion behaviors of electrodeposited Ni-Co/WC nano-composite coatings.

    Science.gov (United States)

    Amadeh, A; Ebadpour, R

    2013-02-01

    Metal-ceramic composite coatings are widely used in automotive and aerospace industries as well as micro-electronic systems. Electrodeposition is an economic method for application of these coatings. In this research, nickel-cobalt coatings reinforced by nano WC particles were applied on carbon steel substrate by pulse electrodeposition from modified Watts bath containing different amounts of cobalt sulphate as an additive. Saccharin and sodium dodecyl sulphate (SDS) were also added to electroplating bath as grain refiner and surfactant, respectively. The effect of cobalt content on wear and corrosion behavior of the coatings was investigated. Wear and corrosion properties were assessed by pin-on-disk and potentiodynamic polarization methods, respectively. Phase analysis was performed by X-ray diffraction (XRD) using CuK(alpha) radiation and the worn surfaces were studied by means of Scanning Electron Microscopy (SEM). The results showed that the addition of cobalt improved the wear resistance of the coatings. In the presence of 18 g/L cobalt in electrodeposition bath, the wear rate of the coating decreased to 0.002 mg/m and the coefficient of friction reduced to 0.695 while they were 0.004 mg/m and 0.77 in the absence of cobalt, respectively. This improvement in wear properties can be attributed to the formation of hcp phase in metallic matrix. Meanwhile, the corrosion resistance of the coatings slightly reduced because cobalt is more active metal with respect to nickel.

  13. Influence of gelatin on corrosion behavior of copper in acid media

    Directory of Open Access Journals (Sweden)

    Todorović Dragiša A.

    2012-01-01

    Full Text Available This paper presents the results of gelatin and benzotriazole (BTA inhibitory action on copper in the acid medium by the method of weight loss. The investigation was carried out in the citric acid solution (1, 5 and 20% at the temperature of 293 K. Under such conditions, the gelatin showed higher efficiency of corrosion protection in comparison to BTA. The results, obtained through the Gibbs and Langmuir adsorption isotherm, show that gelatin adsorption on copper surface obey the Langmuir adsorption isotherm model, as well as that the adsorption is a spontaneous process. The polarization measurements show the potential of full passivation shift towards more negative values, and the increase of corrosion current in both cases but being more pronounced with the BTA. The results obtained in this paper indicate that the inhibition gelatin can be used as the BTA substitute for the copper corrosion protection.

  14. Electrochemical corrosion behavior of X52 and X60 steels in carbon dioxide containing saltwater solution

    Directory of Open Access Journals (Sweden)

    Rihan Omar Rihan

    2012-01-01

    Full Text Available X52 and X60 high strength low alloy (HSLA steels are widely used in the construction of petroleum pipelines. This paper discusses the corrosion resistance of X52 and X60 steels in CO2 containing saltwater at pH 4.4 and 50 ºC. A circulating flow loop system inside an autoclave was used for conducting the experimental work. The rotating impeller speed was 2000 rpm. The corrosion rate was monitored using in situ electrochemical methods such as potentiodynamic sweep, linear polarization resistance, and electrochemical impedance spectroscopy (EIS methods. Results indicated that the corrosion rate of X60 steel is relatively higher than that of X52 steel.

  15. Electrochemical corrosion behavior of X52 and X60 steels in carbon dioxide containing saltwater solution

    Directory of Open Access Journals (Sweden)

    Rihan Omar Rihan

    2013-02-01

    Full Text Available X52 and X60 high strength low alloy (HSLA steels are widely used in the construction of petroleum pipelines. This paper discusses the corrosion resistance of X52 and X60 steels in CO2 containing saltwater at pH 4.4 and 50 ºC. A circulating flow loop system inside an autoclave was used for conducting the experimental work. The rotating impeller speed was 2000 rpm. The corrosion rate was monitored using in situ electrochemical methods such as potentiodynamic sweep, linear polarization resistance, and electrochemical impedance spectroscopy (EIS methods. Results indicated that the corrosion rate of X60 steel is relatively higher than that of X52 steel.

  16. Effect of Ca addition on the corrosion behavior of Mg-Al-Mn alloy

    Science.gov (United States)

    Yang, Jiang; Peng, Jian; Nyberg, Eric A.; Pan, Fu-sheng

    2016-04-01

    The microstructures and corrosion resistance of magnesium-5 wt% aluminum-0.3 wt% manganese alloys (Mg-Al-Mn) with different Ca additions (0.2-4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.

  17. Microstructure, In Vitro Corrosion Behavior and Cytotoxicity of Biodegradable Mg-Ca-Zn and Mg-Ca-Zn-Bi Alloys

    Science.gov (United States)

    Bakhsheshi-Rad, H. R.; Hamzah, E.; Tok, H. Y.; Kasiri-Asgarani, M.; Jabbarzare, S.; Medraj, M.

    2017-02-01

    The effects of bismuth (Bi) addition on the microstructure and corrosion behavior of the Mg-Ca-Zn-Bi alloys were evaluated using electron microscopy, electrochemical test and electrochemical impedance spectroscopy. Microstructural observations showed that Mg-1.2Ca-1Zn- xBi ( x = 0.5, 1.5, 3 wt.%) are composed of Mg2Ca, Ca2Mg6Zn3 and Mg3Bi2 phases while a new phase Mg2Bi2Ca appeared after the addition of 5 and 12 wt.% Bi to the Mg-1.2Ca-1Zn alloy. Furthermore, the additions of 0.5 wt.% Bi to the Mg-1.2Ca-1Zn alloy slightly improved the corrosion behavior of the alloy, while further increase in Bi amount from 1.5 to 12 wt.% has a deleterious effect on the corrosion behavior of the ternary Mg-1.2Ca-1Zn alloy which is driven by galvanic coupling effect. Cytotoxicity tests indicate that the Mg-1.2Ca-1Zn presents higher cell viability compared to Mg-1.2Ca-1Zn-0.5Bi alloy. In addition, the cell viability of both alloys increased with increasing incubation time while diluting the extracts to 50% and 10% improved the cell viabilities. The present results suggest that the Mg-1.2Ca-1Zn-0.5Bi can be interesting candidate for the development of degradable biomaterials and it is worthwhile for further investigation in an in vivo environment.

  18. Understanding corrosion behavior of Mg–Zn–Ca alloys from subcutaneous mouse model: Effect of Zn element concentration and plasma electrolytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Yongseok [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC 27411 (United States); Tan, Zongqing [Department of Internal Medicine, College of Medicine, University of Cincinnati, Cincinnati, OH 45221 (United States); Jurey, Chris [Luke Engineering, Wadsworth, OH 44282 (United States); Xu, Zhigang [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC 27411 (United States); Dong, Zhongyun [Department of Internal Medicine, College of Medicine, University of Cincinnati, Cincinnati, OH 45221 (United States); Collins, Boyce [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC 27411 (United States); Yun, Yeoheung, E-mail: yyun@ncat.edu [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC 27411 (United States); Sankar, Jagannathan [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC 27411 (United States)

    2015-03-01

    Mg–Zn–Ca alloys are considered as suitable biodegradable metallic implants because of their biocompatibility and proper physical properties. In this study, we investigated the effect of Zn concentration of Mg–xZn–0.3Ca (x = 1, 3 and 5 wt.%) alloys and surface modification by plasma electrolytic oxidation (PEO) on corrosion behavior in in vivo environment in terms of microstructure, corrosion rate, types of corrosion, and corrosion product formation. Microstructure analysis of alloys and morphological characterization of corrosion products were conducted using x-ray computed tomography (micro-CT) and scanning electron microscopy (SEM). Elemental composition and crystal structure of corrosion products were determined using x-ray diffraction (XRD) and electron dispersive x-ray spectroscopy (EDX). The results show that 1) as-cast Mg–xZn–0.3Ca alloys are composed of Mg matrix and a secondary phase of Ca{sub 2}Mg{sub 6}Zn{sub 3} formed along grain boundaries, 2) the corrosion rate of Mg–xZn–0.3Ca alloys increases with increasing concentration of Zn in the alloy, 3) corrosion rates of alloys treated by PEO sample are decreased in in vivo environment, and 4) the corrosion products of these alloys after in vivo tests are identified as brucite (Mg(OH){sub 2}), hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}), and magnesite (MgCO{sub 3}·3H{sub 2}O). - Highlights: • Effects of PEO and Zn concentration in Mg–xZn–0.3Ca alloys on biodegradation • Corrosion rate of Mg–xZn–0.3Ca alloys increases with increasing Zn concentration. • Plasma electrolytic oxidation retards the biodegradation of Mg–xZn–0.3Ca alloys.

  19. Corrosion Behavior of Mg-6Al-1Zn+XRE Magnesium Alloy with Minor Addition of Yttrium

    Science.gov (United States)

    Manivannan, S.; Babu, S. P. Kumaresh; Sundarrajan, Srinivasan

    2015-04-01

    The effect of yttrium addition on the microstructure of Mg-6Al-1Zn alloy was investigated by optical microscopy, x-ray diffraction analysis, and scanning electron microscopy. The experimental alloys were prepared by melting high-purity Mg, Al, Zn, and Y, respectively. Melting was carried out in a Inconel 718 crucible under SF6 and ultra pure Ar (99.999%) gas mixture environment using electric arc furnace. The corrosion behavior of Mg-6Al-1Zn+ xYttrium ( x = 0.5, 1.0 and 1.5 wt.% Y) magnesium alloy with different levels of yttrium additions was studied in 3.5 wt.% NaCl solution. Microstructure of yttrium-added alloy shows that higher grainrefinement is obtained in Mg-6Al-1Zn+0.5wt.%Y. Increasing yttrium content reduces the size of α-grain and alters the distribution of the β-phase (Mg17Al12) from continuous network morphology to small and dispersive distribution. It forms secondary intermetallic phase Al2Y which has high melting point along the grain boundary. The corrosion resistance of Mg-6Al-1Zn magnesium alloy improved with addition of Yttrium. It was confirmed by the results of electrochemical polarization test. Based on the polarization curves, it is seen that fine precipitates of Al-Y intermetallic phase in Mg-6Al-1Zn alloy decrease the corrosion current density, thereby improving the corrosion resistance of the Mg-6Al-1Zn magnesium alloy.

  20. Structure, mechanical properties, corrosion behavior and cytotoxicity of biodegradable Mg–X (X = Sn, Ga, In) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kubásek, J., E-mail: Jiri.Kubasek@vscht.cz [Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6 (Czech Republic); Vojtěch, D. [Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6 (Czech Republic); Lipov, J.; Ruml, T. [Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6 (Czech Republic)

    2013-05-01

    As-cast Mg–Sn, Mg–Ga and Mg–In alloys containing 1–7 wt.% of alloying elements were studied in this work. Structural and chemical analysis of the alloys was performed by using light and scanning electron microscopy, energy dispersive spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy and glow discharge spectrometry. Mechanical properties were determined by Vickers hardness measurements and tensile testing. Corrosion behavior in a simulated physiological solution (9 g/l NaCl) was studied by immersion tests and potentiodynamic measurements. The cytotoxicity effect of the alloys on human osteosarcoma cells (U-2 OS) was determined by an indirect contact assay. Structural investigation revealed the dendritic morphology of the as-cast alloys with the presence of secondary eutectic phases in the Mg–Sn and Mg–Ga alloys. All the alloying elements showed hardening and strengthening effects on magnesium. This effect was the most pronounced in the case of Ga. All the alloying elements at low concentrations of approximately 1 wt.% were also shown to positively affect the corrosion resistance of Mg. But at higher concentrations of Ga and Sn the corrosion resistance worsened due to galvanic effects of secondary phases. Cytotoxicity tests indicated that Ga had the lowest toxicity, followed by Sn. The most severe toxicity was observed in the case of In. - Highlights: ► Gallium addition (up to 7 wt.%) improves the strength and toughness of as-cast Mg. ► The effect of indium addition (up to 7 wt.%) on mechanical properties is small. ► Gallium, Tin and Indium addition improves the corrosion resistance of as-cast Mg. ► Gallium shows no toxic effect on osteosarcoma cells. ► Tin and indium show serious toxic effect on osteosarcoma cells.

  1. Corrosion behavior of plasma electrolytically oxidized gamma titanium aluminide alloy in simulated body fluid.

    Science.gov (United States)

    Lara Rodriguez, L; Sundaram, P A

    2016-09-15

    Plasma electrolytic oxidized (PEO) γTiAl alloy samples were electrochemically characterized by open circuit potential (OCP), cyclic polarization and electrochemical impedance spectroscopy (EIS) to evaluate their corrosion resistance in simulated body fluid (SBF) in order to gauge their potential for biomedical applications. Experimental results through OCP and cyclic polarization studies demonstrated the protective nature and the beneficial effect of the PEO coatings on γTiAl. The PEO surface increased corrosion resistance of these surface modified alloys. EIS data indicated the presence of an underlying compact oxide layer with surface pores represented by two domes in the Nyquist plots. Electrical equivalent circuits to describe the EIS results are proposed.

  2. Electrochemical corrosion behavior of X52 and X60 steels in carbon dioxide containing saltwater solution

    OpenAIRE

    Rihan Omar Rihan

    2013-01-01

    X52 and X60 high strength low alloy (HSLA) steels are widely used in the construction of petroleum pipelines. This paper discusses the corrosion resistance of X52 and X60 steels in CO2 containing saltwater at pH 4.4 and 50 ºC. A circulating flow loop system inside an autoclave was used for conducting the experimental work. The rotating impeller speed was 2000 rpm. The corrosion rate was monitored using in situ electrochemical methods such as potentiodynamic sweep, linear polarization resistan...

  3. Distribution of Microelements and Their Influence on the Corrosion Behavior of Aluminum Foil

    Institute of Scientific and Technical Information of China (English)

    Weimin MAO; Heng JIANG; Ping YANG; Huiping FENG; Yongning YU

    2005-01-01

    The distribution of microelement Fe, Si, Cu and Mg in the surface layer of aluminum foil annealed at 300℃ and 500℃ were determined by secondary ion mass spectrometer. The corrosion structure produced by electrochemical etching was also observed. It was found that the Mg concentration at external surface was increased exponentially over the fourth degree and promoted by higher annealing temperature, which will increase the number of corrosion pits inside the large grains, and therefore the specific capacity of the foils for electrolytic capacitors. The similar effects of microelement Fe, Si and Cu were not so strong.

  4. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    Science.gov (United States)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  5. The effect of post-treatment of a high-velocity oxy-fuel Ni-Cr-Mo-Si-B coating part 2: Erosion-corrosion behavior

    Science.gov (United States)

    Shrestha, S.; Hodgkiess, T.; Neville, A.

    2001-12-01

    In this paper, a study of the erosion-corrosion characteristics of a Ni-Cr-Mo-Si-B coating applied by the high-velocity oxy-fuel (HVOF) process on to an austenitic stainless steel (UNS S31603) substrate are reported. The coatings were studied in the as-sprayed condition, after vacuum sealing with polymer impregnation and after vacuum furnace fusion. The erosion-corrosion characteristics were assessed in an impinging liquid jet of 3.5% NaCl solution at 18 °C at a velocity of 17 m/s at normal incidence in two conditions: (1) free from added solids and (2) containing 800 ppm silica sand. The methodology employed electrochemical control and monitoring to facilitate the identification of the separate and interrelated erosion and corrosion contributions to the erosion-corrosion process. The rates of erosion-corrosion damage were drastically accelerated in the presence of the suspended solids. The application of cathodic protection significantly reduced the deterioration process. The study showed the effect of sealing with polymer impregnation did not significantly alter the erosion-corrosion behavior of the sprayed coating. However, there was a significant improvement in erosion-corrosion durability afforded by the postfusion process. The mechanisms by which the improved performance of vacuum-fused coatings is achieved are discussed.

  6. The corrosion behavior of CVI SiC matrix in SiCf/SiC composites under molten fluoride salt environment

    Science.gov (United States)

    Wang, Hongda; Feng, Qian; Wang, Zhen; Zhou, Haijun; Kan, Yanmei; Hu, Jianbao; Dong, Shaoming

    2017-04-01

    High temperature corrosion behavior and microstructural evolution of designed chemical-vapor-infiltrated SiC matrix in SiC fiber reinforced SiC ceramic matrix composites in 46.5LiF-11.5NaF-42.0KF (mol. %) eutectic salt at 800 °C for various corrosion time was studied. Worse damage was observed as extending the exposure time, with the mass loss ratio increasing from 0.716 wt. % for 50 h to 5.914 wt. % for 500 h. The mass loss rate showed a trend of first decrease and then increase with the extended corrosion exposure. Compared with the near-stoichiometric SiC matrix layers, the O-contained boundaries between deposited matrix layers and the designed Si-rich SiC matrix layers were much less corrosion resistant and preferentially corroded. Liner relationship between the mass loss ratio and the corrosion time obtained from 50 h to 300 h indicated that the corrosion action was reaction-control process. Further corrosion would lead to matrix layer exfoliation and higher mass loss ratio.

  7. Electrochemical Corrosion Behavior of Spray-Formed Boron-Modified Supermartensitic Stainless Steel

    Science.gov (United States)

    Zepon, Guilherme; Nogueira, Ricardo P.; Kiminami, Claudio S.; Botta, Walter J.; Bolfarini, Claudemiro

    2017-04-01

    Spray-formed boron-modified supermartensitic stainless steel (SMSS) grades are alloys developed to withstand severe wear conditions. The addition of boron to the conventional chemical composition of SMSS, combined with the solidification features promoted by the spray forming process, leads to a microstructure composed of low carbon martensitic matrix reinforced by an eutectic network of M2B-type borides, which considerably increases the wear resistance of the stainless steel. Although the presence of borides in the microstructure has a very beneficial effect on the wear properties of the alloy, their effect on the corrosion resistance of the stainless steel was not comprehensively evaluated. The present work presents a study of the effect of boron addition on the corrosion resistance of the spray-formed boron-modified SMSS grades by means of electrochemical techniques. The borides fraction seems to have some influence on the repassivation kinetics of the spray-formed boron-modified SMSS. It was shown that the Cr content of the martensitic matrix is the microstructural feature deciding the corrosion resistance of this sort of alloys. Therefore, if the Cr content in the alloy is increased to around 14 wt pct to compensate for the boron consumed by the borides formation, the corrosion resistance of the alloy is kept at the same level of the alloy without boron addition.

  8. Evaluation of the Hot-Corrosion Behavior of Thermal Barrier Coatings

    Science.gov (United States)

    1974-11-01

    coat the components with an insulating material. Ceramic thermal barriers intended for this application must be resistant to thermal shock, spalling...corrosive environment found in a gas turbine. 4428 APPROACH The purpose of using thermal barriers is to allow t-he utilization of high gas

  9. Effect of surface stress states on the corrosion behavior of alloy 690

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Myung Mo; Shim, Hee Sang; Seo, Myung Ji; Hur, Do Haeng [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The test environment simulated the primary water chemistry in PWRs. Dissolved oxygen (DO), dissolved hydrogen (DH), pH and conductivity were monitored at room temperature using sensors manufactured by Orbisphere and Mettler Toledo. The temperature and pressure were maintained at 330 .deg. C and 150 bars during the corrosion test. The condition of the test solution was lithium (LiOH) 2 ppm and boron (H3BO4) 1,200 ppm, DH 35 cc/kg (STP) and less than 5 ppb DO. The flow rate of the loop system was 3.8 L/hour. Corrosion tests were conducted for 500 hours. The corrosion release rate was evaluated by a gravimetric analysis method using a two-step alkaline permanganate-ammonium citrate (AP/AC) descaling process. Compressive residual stress is induced by shot peening treatment but its value reveals some different trend between the shot peening intensity on the surface of Alloy 690 TT. A higher shot peening intensity causes a reduction in the corrosion rate and it is considered that the compressive residual stress beneath the surface layer suppresses the metal ion transfer in an alloy matrix.

  10. Electrochemical Corrosion Behavior of Spray-Formed Boron-Modified Supermartensitic Stainless Steel

    Science.gov (United States)

    Zepon, Guilherme; Nogueira, Ricardo P.; Kiminami, Claudio S.; Botta, Walter J.; Bolfarini, Claudemiro

    2017-01-01

    Spray-formed boron-modified supermartensitic stainless steel (SMSS) grades are alloys developed to withstand severe wear conditions. The addition of boron to the conventional chemical composition of SMSS, combined with the solidification features promoted by the spray forming process, leads to a microstructure composed of low carbon martensitic matrix reinforced by an eutectic network of M2B-type borides, which considerably increases the wear resistance of the stainless steel. Although the presence of borides in the microstructure has a very beneficial effect on the wear properties of the alloy, their effect on the corrosion resistance of the stainless steel was not comprehensively evaluated. The present work presents a study of the effect of boron addition on the corrosion resistance of the spray-formed boron-modified SMSS grades by means of electrochemical techniques. The borides fraction seems to have some influence on the repassivation kinetics of the spray-formed boron-modified SMSS. It was shown that the Cr content of the martensitic matrix is the microstructural feature deciding the corrosion resistance of this sort of alloys. Therefore, if the Cr content in the alloy is increased to around 14 wt pct to compensate for the boron consumed by the borides formation, the corrosion resistance of the alloy is kept at the same level of the alloy without boron addition.

  11. Oxidation and corrosion behavior of titanium aluminum nitride coatings by arc ion plating

    Institute of Scientific and Technical Information of China (English)

    LI Ming-sheng; FENG Chang-jie; ZHANG Zhi-feng; WANG Fu-hui

    2006-01-01

    Composite metastable TiN and Ti1-xAlxN coatings with different Al content were deposited on 1Cr11Ni2W2MoV stainless steel for aero-engine compressor blades by arc ion plating. The results show that all coatings have a B1NaCl structure and the preferred orientation changes from (111) to (220) with increasing Al content; the lattice parameter of Ti1-xAlxN decreases with the increase of Al content. The oxidation-resistance of (Ti,Al)N coatings is significantly improved owing to the formation of Al-riched oxide on the surface of the coatings. The nitride coatings can significantly improve the corrosion-resistance of 1Cr11Ni2W2MoV stainless steel under the synergistic of water vapor and NaCl, and the corrosion-resistance becomes better when the Al content increases, because not only the quick formation of thin alumina layer prevents the further corrosion but also the formation of alumina seals the pinholes or defects in the coatings, which prevents the occurrence of localized nodules-like corrosion.

  12. Effect of Acidified Feronia elephantum Leaf Extract on the Corrosion Behavior of Mild Steel

    Science.gov (United States)

    Muthukrishnan, Pitchaipillai; Prakash, Periakaruppan; Ilayaraja, Murugan; Jeyaprabha, Balasubramanian; Shankar, Karikalan

    2015-03-01

    Mild steel is used as a structural material for pipes, tank, reaction vessels, etc. which are known to corrode invariably in contact with various solvents. From the view point of a nation's economy and financial implications of corrosion hazard, it is necessary to adopt appropriate means and ways to reduce the losses due to corrosion. The use of eco-friendly corrosion inhibitors are increasing day by day. Feronia elephantum leaf extract (FELE) has been tested as eco-friendly corrosion inhibitor for A262 mild steel in 1 M H2SO4 and 1 M HCl solutions using non-electrochemical (Gravimetric, X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy) and electrochemical techniques (open circuit potential, potentiostatic polarization, and electrochemical impedance measurements). The protection efficiency is found to increase with increase in FELE concentration but decrease with temperature, which is suggestive of physical adsorption mechanism. The adsorption of FELE on mild steel surface obeys the Langmuir adsorption isotherm. SEM results confirm the formation of a protective layer by FELE over mild steel surface.

  13. Method of Monitoring the Corrosion Behavior the Surface Treated FMS and CVD Coated Specimen in Liquid Sodium Environment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Hyeon; Shin, Sang Hun; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

    2014-10-15

    Gr.92 and HT9 (Ferritic/martensitic steels) are considered as candidates of cladding materials of Sodium-cooled Fast Reactors (SFRs). HT9 and Gr.92 are known as compatible in sodium environment because the usual refueling time of SFRs is designed about 54 months. In the Ultra-long Cycle Fast Reactor (UCFR) which is developed in UNIST, however, cladding is exposed long-term in high temperature liquid sodium environment. So, it is very important to investigate the corrosion-related behavior such as surface corrosion rate, carburization, decarburization and mechanical properties for its operation time. The decarburization process where dissolved carbon near the specimen surface diffused in to the liquid sodium. This process can originate from the difference between dissolved carbon activity in the material and liquid sodium. A compatibility test the cladding tube revealed that a decrease of the mechanical property instigated by the aging proves governed the whole mechanical property. SiC and Si3N4 Chemical Vapor Deposition (CVD) coating for decarburization barrier on the surface of FMS is considered in this study. The CVD coated specimens are experiment for compatibility of high temperature liquid sodium. To monitor the corrosion behavior of these candidate materials in sodium environment, Electrochemical Impedance Spectroscopy (EIS) method is first introduced and investigated in this study. The use of the technique of impedance spectroscopy to measure the electrical impedance response of any oxide layers, SiC and Si{sub 3}N{sub 4} that may be present may be a solution to this monitoring problem.

  14. Effect of Process Parameters on Microstructural Evolution, Mechanical Properties and Corrosion Behavior of Friction Stir Processed Al 7075 Alloy

    Science.gov (United States)

    Kumar, Atul; Sharma, Sandan Kumar; Pal, Kaushik; Mula, Suhrit

    2017-02-01

    Aim of the present study is to investigate the effect of process parameters on microstructural evolution, mechanical properties and corrosion behavior of an age-hardenable Al 7075 alloy. The alloy plates (6 mm thickness) were friction stir processed (FSPed) at various traverse speed, namely 25, 45, 65, 85, 100 and 150 mm/min at 2 different rpm of 508 and 720. The optimized result in terms of defect-free processed zone with refined microstructure was obtained only at a rotational speed of 720 rpm for a traverse speed of 25, 45, 65 and 85 mm/min. The microstructural evolution was investigated using optical, scanning and transmission electron microscopy. The grain size of the nugget zone was found to decrease with increase in the traverse speed from 25 to 85 mm/min at a constant rpm of 720. The mechanical properties were evaluated by Vickers hardness measurements, tensile and wear testing. Yield strength was found to be the maximum ( 366 MPa) for the FSPed sample processed at 85 mm/min. The hardness values also followed the similar increasing trend with increase in the traverse speed. The wear volume loss decreased by 38% for the sample processed at a traverse speed of 85 mm/min as compared to that of the sample processed at 25 mm/min. The friction coefficient was found to substantiate well with the wear track morphology. The improvement in mechanical properties is ascertained to the refinement of grain size at higher traverse speed (due to less heat input). The FSPed samples showed inferior corrosion resistance in contrast to that of the base metal. This is possibly due to the coarsening of precipitates and depletion of solutes in the matrix. The morphology of the corroded samples corroborated well with the corrosion behavior of the corresponding specimen.

  15. Effect of Process Parameters on Microstructural Evolution, Mechanical Properties and Corrosion Behavior of Friction Stir Processed Al 7075 Alloy

    Science.gov (United States)

    Kumar, Atul; Sharma, Sandan Kumar; Pal, Kaushik; Mula, Suhrit

    2017-03-01

    Aim of the present study is to investigate the effect of process parameters on microstructural evolution, mechanical properties and corrosion behavior of an age-hardenable Al 7075 alloy. The alloy plates (6 mm thickness) were friction stir processed (FSPed) at various traverse speed, namely 25, 45, 65, 85, 100 and 150 mm/min at 2 different rpm of 508 and 720. The optimized result in terms of defect-free processed zone with refined microstructure was obtained only at a rotational speed of 720 rpm for a traverse speed of 25, 45, 65 and 85 mm/min. The microstructural evolution was investigated using optical, scanning and transmission electron microscopy. The grain size of the nugget zone was found to decrease with increase in the traverse speed from 25 to 85 mm/min at a constant rpm of 720. The mechanical properties were evaluated by Vickers hardness measurements, tensile and wear testing. Yield strength was found to be the maximum ( 366 MPa) for the FSPed sample processed at 85 mm/min. The hardness values also followed the similar increasing trend with increase in the traverse speed. The wear volume loss decreased by 38% for the sample processed at a traverse speed of 85 mm/min as compared to that of the sample processed at 25 mm/min. The friction coefficient was found to substantiate well with the wear track morphology. The improvement in mechanical properties is ascertained to the refinement of grain size at higher traverse speed (due to less heat input). The FSPed samples showed inferior corrosion resistance in contrast to that of the base metal. This is possibly due to the coarsening of precipitates and depletion of solutes in the matrix. The morphology of the corroded samples corroborated well with the corrosion behavior of the corresponding specimen.

  16. Development of modeling tools to describe the corrosion behavior of uncoated EUROFER in flowing Pb-17Li and their validation by performing of corrosion tests at T up to 550 C

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, W.; Konys, J.; Steiner, H.; Novotny, J.; Voss, Z.; Wedemeyer, O.

    2007-03-15

    Reduced activation ferritic-martensitic steels (e.g. EUROFER) are considered for application in future fusion technology as structural material, which is in contact with the breeding material Pb-17Li. Various corrosion experiments have been made in the past, however, evaluation of these tests, which were mostly conducted up to moderate temperatures of up to 480 C, was performed with respect to determine corrosion rates and mechanisms e.g. dissolution of some elements out of the steels and comparison of the results with earlier tested RAFM-steels of type F82H-mod. OPTIFER, and MANET. In the mean time the envisaged operation limits e.g. in temperature increased to roughly 550 C and flow regimes may change. Thus extrapolations of the RAFM steel corrosion behavior determined in the past to the new working conditions may be problematic due to large uncertainties or reliability and, additionally, only low knowledge on transport of dissolved components in the Pb-17Li flow is present. In contrast to earlier investigations, these changes in requirements need the going over from (only) mechanism based corrosion tests to model supported tests. Furthermore, the whole loop has to be considered in the evaluation of the corrosion tests together with other occurring phenomena and mechanisms as transport effects and precipitations. Therefore, under this task the development of modeling tools for describing Pb 17Li corrosion (dissolution, material transport and precipitations) was started. The modular structured tools are based on physical, chemical and thermo-hydraulic parameters and, in the first stage, the development was focused on the dissolution of EUROFER and validation with older test results obtained at 480 C in our PICOLO loop earlier. In the second stage the new 550 C test results - obtained in the part corrosion testing of this task - were used for validation at a second temperature level and transport phenomena were considered. (orig.)

  17. Case reviews on the effect of microstructure on the corrosion behavior of austenitic alloys for processing and storage of nuclear waste

    Science.gov (United States)

    Kain, V.; Sengupta, P.; de, P. K.; Banerjee, S.

    2005-05-01

    This article describes the corrosion behavior of special austenitic alloys for waste management applications. The special stainless steels have controlled levels of alloying and impurity elements and inclusion levels. It is shown that “active” inclusions and segregation of chromium along flow lines accelerated IGC of nonsensitized stainless steels. Concentration of Cr+6 ions in the grooves of dissolved inclusions increased the potential to the transpassive region of the material, leading to accelerated attack. It is shown that a combination of cold working and controlled solution annealing resulted in a microstructure that resisted corrosion even after a sensitization heat treatment. This imparted extra resistance to corrosion by increasing the fraction of “random” grain boundaries above a threshold value. Randomization of grain boundaries made the stainless steels resistant to sensitization, IGC, and intergranular stress corrosion cracking (IGSCC) in even hot chloride environments. The increased corrosion resistance has been attributed to connectivity of random grain boundaries. The reaction mechanism between the molten glass and the material for process pot, alloy 690, during the vitrification process has been shown to result in depletion of chromium from the reacting surfaces. A comparison is drawn between the electrochemical behavior of alloys 33 and 22 in 1 M HCl at 65 °C. It is shown that a secondary phase formed during welding of alloy 33 impaired corrosion properties in the HCl environment.

  18. Corrosion behavior of 6061/Al-15 vol. pct. SiC(p composite and the base alloy in sodium hydroxide solution

    Directory of Open Access Journals (Sweden)

    P.D. Reena Kumari

    2016-11-01

    Full Text Available The corrosion behavior of 6061/Al-15 vol. pct. SiC(p composite and 6061 Al base alloy was investigated in a sodium hydroxide solution. The electrochemical parameters were derived from potentiodynamic polarization and electrochemical impedance spectroscopic (EIS techniques. The results showed that the corrosion resistance of the composite was lower than that of the base alloy in selected corrosion media. The corrosion rates of both the composite and the base alloy increased with the increase in the concentration of sodium hydroxide and also with the increase in temperature. The surface morphology of the metal surface was investigated using scanning electron microscope (SEM. Activation energy was evaluated using Arrhenius equation, and enthalpy of activation and entropy of activation values were calculated using transition state equation.

  19. The Influence of Current Density and Frequency on the Microstructure and Corrosion Behavior of Plasma Electrolytic Oxidation Coatings on Ti6Al4V

    Science.gov (United States)

    Khanmohammadi, H.; Allahkaram, S. R.; Igual Munoz, A.; Towhidi, N.

    2017-02-01

    The effect of processing current density and frequency on the microstructure and corrosion behavior of the PEO coatings was studied. Coatings were characterized using FESEM, EDS, potentiodynamic polarization and EIS. The results indicated that the surface roughness, porosity and Al/Ti chemical value on the surface of the coatings increase with an increase in the current density and a decrease in the frequency of the PEO process. Corrosion investigations showed a relation between a mixed structural parameter (that contains thickness, porosity percentage and average pore diameter of the coatings) and the corrosion resistance of the PEO coatings. EIS data showed that higher coating thickness, lower surface porosity percentage and smaller pore diameter lead to the higher corrosion resistance.

  20. Effect of heat treatment on corrosion behavior of low pressure sand cast Mg-10Gd-3Y-0.5Zr alloys

    Institute of Scientific and Technical Information of China (English)

    Qian-qian Wu; Guang-ling Wei; Guo-hua Wu; Wen-cai Liu; Tian-peng Xuan; Wen-jiang Ding

    2016-01-01

    The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr (wt.%) aloys in as-cast, solution treated (T4) and aged (T6) conditions were studied by means of immersion test and electrochemical measurements in 5wt.% NaCl solution saturated with Mg(OH)2. It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4; while the corrosion resistance of the permanent mold casting is superior to the sand casting. The morphologies of the corrosion products are similar porous structures consisting of tiny erect lfakes perpendicular to the corroded surface of the aloy, irrespective of the heat treatment conditions. Especialy, the corrosion iflm in T4 condition is more compact than that in the other two conditions. In addition, the severer corrosion happening to the as-cast condition is correlated with the galvanic corrosion between the matrix and the eutectic compounds; while improved corrosion resistance for the T4 and T6 conditions is ascribed to the dissolution of the secondary eutectic compounds. The measured corrosion current densities of Mg-10Gd-3Y-0.5Zr aloys in as-cast, T4, and T6 conditions are 36 μA·cm-2, 10 μA·cm-2, and 33 μA·cm-2, respectively. The proposed equivalent circuit [Rs(CPE1(Rt(RfCPE2))] by Zview software matches wel with the tested electrochemical impedance spectra (EIS) data.

  1. Effect of heat treatment on corrosion behavior of low pressure sand cast Mg-10Gd-3Y-0.5Zr alloys

    Directory of Open Access Journals (Sweden)

    Qian-qian Wu

    2016-07-01

    Full Text Available The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr (wt.% alloys in as-cast, solution treated (T4 and aged (T6 conditions were studied by means of immersion test and electrochemical measurements in 5wt.% NaCl solution saturated with Mg(OH2. It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4; while the corrosion resistance of the permanent mold casting is superior to the sand casting. The morphologies of the corrosion products are similar porous structures consisting of tiny erect flakes perpendicular to the corroded surface of the alloy, irrespective of the heat treatment conditions. Especially, the corrosion film in T4 condition is more compact than that in the other two conditions. In addition, the severer corrosion happening to the as-cast condition is correlated with the galvanic corrosion between the matrix and the eutectic compounds; while improved corrosion resistance for the T4 and T6 conditions is ascribed to the dissolution of the secondary eutectic compounds. The measured corrosion current densities of Mg-10Gd-3Y-0.5Zr alloys in as-cast, T4, and T6 conditions are 36 μA·cm-2, 10 μA·cm-2, and 33 μA·cm-2, respectively. The proposed equivalent circuit [Rs(CPE1(Rt(RfCPE2] by Zview software matches well with the tested electrochemical impedance spectra (EIS data.

  2. Influence of pH and Chloride Concentration on the Corrosion Behavior of Unalloyed Copper in NaCl Solution: A Comparative Study Between the Micro and Macro Scales

    Directory of Open Access Journals (Sweden)

    Annemie Adriaens

    2012-11-01

    Full Text Available The effects of pH and chloride concentration on the electrochemical corrosion of copper in aqueous sodium chloride (NaCl media were studied at the micro scale using a microcapillary droplet cell and at the macro scale using a conventional large scale cell. Using an experimental design strategy, electrochemical response surface models of copper versus pH and NaCl concentration were constructed with the minimum number of experiments required. Results show that the electrochemical behavior of copper under corrosive media shows significant differences between the micro and macro scale experiments. At the micro scale, the pit initiation of copper occurs at more negative potentials for high NaCl concentrations and alkaline pH values. Also, the micro scale potentiostatic measurements indicate higher stabilised passive currents at high NaCl concentrations and low (acidic pH values. At the macro scale, the pH is shown to have a greater influence on the corrosion potential. The chloride concentration is the most significant factor in the passive current case while at the micro scale the effect of these two factors on the passive current was found to be the same. The surface morphology of the formed patina on the corroded copper in both micro and macro systems reveal a more significant role of the chloride concentration on the structure and the grain size of the patinas. Finally, micro and macro electrochemical impedance spectroscopy of copper at various NaCl concentrations and pH values demonstrates a different behavior of copper after several potentiodynamic polarization cycles.

  3. The effect of mucine, IgA, urea, and lysozyme on the corrosion behavior of various non-precious dental alloys and pure titanium in artificial saliva.

    Science.gov (United States)

    Bilhan, H; Bilgin, T; Cakir, A F; Yuksel, B; Von Fraunhofer, J A

    2007-11-01

    The corrosion of dental alloys has biological, functional, and aesthetic consequences. Various studies have shown that protein solutions can inhibit the corrosion of alloys. This study is planned to determine the relationship of organic constituents of saliva and the corrosion of dental alloys. The organic constituents are IgA, mucine, urea, and lysozyme which are encountered in the highest amounts in saliva and the dental materials are titanium (Ti), Co-Cr-Mo and Ni-Cr-Mo alloys, and dental amalgam, the most often used metallic components in dentistry. In particular, the interactions between the commonest salivary proteins, IgA, mucine, urea and lysozyme, and Ti, Co-Cr-Mo, Ni-Cr-Mo and dental amalgam were investigated. Each alloy was evaluated by cyclic polarization in each medium. The general anodic and cathodic behavior during forward and reverse cycles, the corrosion and passivation current densities (muA/cm2 ), and the corrosion and the pitting potentials (mV) were determined. The results have shown that Ni-Cr-Mo and dental amalgam alloys are highly susceptible to corrosion in all the investigated media. The Co-Cr-Mo alloy has shown high passive current densities in the solution of mucine and lysozyme in artificial saliva. Titanium instead, has shown a high resistance to corrosion and a stable passive behavior in all media, especially in a solution of mucine and IgA in synthetic saliva. Mucine and IgA, as well as urea and lysozyme, appeared to enhance the formation of a passive film layer on the Ti metal surface, thus inhibiting the corrosion. Based on the study findings, and especially considering the problem of nickel allergy and toxicity of mercury released from dental amalgam, the use of Co-Cr-Mo alloys and Ti to Ni-Cr-Mo alloys is recommended and alternatives to dental amalgam should be sought for patients with impaired salivary flow.

  4. The decisive role of free water in determining homogenous ice nucleation behavior of aqueous solutions.

    Science.gov (United States)

    Wang, Qiang; Zhao, Lishan; Li, Chenxi; Cao, Zexian

    2016-05-26

    It is a challenging issue to quantitatively characterize how the solute and pressure affect the homogeneous ice nucleation in a supercooled solution. By measuring the glass transition behavior of solutions, a universal feature of water-content dependence of glass transition temperature is recognized, which can be used to quantify hydration water in solutions. The amount of free water can then be determined for water-rich solutions, whose mass fraction, Xf, is found to serve as a universal relevant parameter for characterizing the homogeneous ice nucleation temperature, the meting temperature of primary ice, and even the water activity of solutions of electrolytes and smaller organic molecules. Moreover, the effects of hydrated solute and pressure on ice nucleation is comparable, and the pressure, when properly scaled, can be incorporated into the universal parameter Xf. These results help establish the decisive role of free water in determining ice nucleation and other relevant properties of aqueous solutions.

  5. Crossover Leung-Griffiths model and the phase behavior of dilute aqueous ionic solutions

    Science.gov (United States)

    Belyakov, M. Yu.; Kiselev, S. B.; Rainwater, J. C.

    1997-08-01

    A new parametric crossover model for the phase behavior of a binary mixture is presented that corresponds to the Leung-Griffiths model in the critical region and is transformed into the regular classical expansion far away from the critical point. The model is optimized to, and leads to excellent agreement with, isothermal vapor-liquid equilibrium data for dilute aqueous solutions of sodium chloride by Bischoff and co-workers. It then accurately predicts constant-composition phase equilibrium loci as measured by independent workers. This crossover model is therefore capable of representing the thermodynamic surface of ionic solutions in a large range of temperatures and densities around the critical points of vapor-liquid equilibrium.

  6. Mechanical Behavior of Yttria-Stabilized Zirconia Aqueous Cast Tapes and Laminates

    Directory of Open Access Journals (Sweden)

    V. Moreno

    2014-01-01

    Full Text Available Aqueous tape casting was used to produce yttria-stabilized zirconia films for electrolyte-supported solid oxide fuel cell (SOFC. Tape casting slurries were prepared varying the binder content between 20 and 25 wt%. A commercial acrylic emulsion served as binder. Rheological measurements of the two slurries were performed. Both slurries showed a shear-thinning behavior. Tapes with 25 wt% binder exhibited adequate flexibility and a smooth and homogeneous surface, free of cracks and other defects. Suitable conditions of lamination were found and a theoretical density of 54% in the laminates was achieved. Laminated tapes showed higher tensile strength compared to single sheets. Tape orientation has a significant influence on the mechanical properties. Tensile strength, elongation to strain, and Young’s modulus measured in samples produced in the direction of casting showed higher property values.

  7. VOLTAMMETRIC BEHAVIOR OF SOME STEELS IN AQUEOUS SOLUTIONS OF HNO3

    Directory of Open Access Journals (Sweden)

    Gheorghe Nemtoi

    2011-06-01

    Full Text Available The corrosion process of some steels immersed in HNO3 solutions of different concentrations by means of voltammetric measurements was investigated. For different values of the corrosion potential, or of the contact time: solid steel-aggressive medium, several equations of the type: I = f (E were proposed, only for linear domains of the voltammograms.

  8. In vitro plasma protein binding and aqueous aggregation behavior of astaxanthin dilysinate tetrahydrochloride.

    Science.gov (United States)

    Zsila, Ferenc; Fitos, Ilona; Bikádi, Zsolt; Simonyi, Miklós; Jackson, Henry L; Lockwood, Samuel F

    2004-11-01

    The tetrahydrochloride salt of astaxanthin di-L-lysinate (lys(2)AST) is a highly water-dispersible astaxanthin-amino acid conjugate, with an aqueous dispersibility of > or = 181.6 mg/mL. The statistical mixture of stereoisomers has been well characterized as an aqueous-phase superoxide anion scavenger, effective at micromolar (microM) concentrations. In the current study, the aqueous aggregation behavior and in vitro plasma protein binding [with fatty-acid-free human serum albumin (HSA) and alpha(1)-acid glycoprotein (AGP)] were investigated with a suite of techniques, including circular dichroism (CD) and UV-vis spectroscopy, ultrafiltration, competitive ligand displacement, and fluorescence quenching. Induced CD bands obtained in Ringer buffer solution of HSA demonstrated high affinity monomeric binding of the compound at low ligand per protein (L/P) ratios (in aqueous solution alone the carotenoid molecules formed card-pack aggregates). The binding constant ( approximately 10(6)M(-1)) and the binding stoichiometry (approximately 0.2 per albumin molecule) were calculated from CD titration data. CD displacement and ultrafiltration experiments performed with marker ligands of HSA indicated that the ligand binding occurred at a site distinct from the main drug binding sites of HSA (i.e., Sites I and II). At intermediate L/P ratios, both monomeric and aggregated ("chirally complexed") binding occurred simultaneously at distinct sites of the protein. At high L/P ratios, chiral complexation predominantly occurred on the asymmetric protein template. The tentative location of the chirally-complexed aggregation on the HSA template was identified as the large interdomain cleft of HSA, where carotenoid derivatives have been found to bind previously. Only weak binding to AGP was observed. These results suggest that parenteral use of this highly potent, water-dispersible astaxanthin-amino acid conjugate will result in plasma protein association, and plasma protein binding at

  9. Aggregation behavior modulation of 1-dodecyl-3-methylimidazolium bromide by organic solvents in aqueous solution.

    Science.gov (United States)

    Wang, Jianji; Zhang, Lamei; Wang, Huiyong; Wu, Changzeng

    2011-05-05

    Material preparation in ionic liquids and environmental pollution control by ionic liquids are often closely dependent on the aggregation behavior of ionic liquids in solution. In the present work, conductivity, fluorescence probe, and dynamic light scattering techniques have been used to study the effect of organic solvents on the aggregation behavior of 1-dodecyl-3-methylimidazolium bromide in water. It was shown that the critical aggregation concentration (CAC), the ionization degree of the aggregates (α), and the standard Gibbs energy of aggregation (ΔG(m)°) of the ionic liquid increase, while its aggregation number (N(agg)) and aggregates' size decrease with increasing concentration of organic additives in water. These results have been discussed from the favorable interactions of alkyl chain of the ionic liquid with the mixed solvents. It is suggested that the solvophobic parameter, characterized quantitatively by Gibbs energy of transfer of hydrocarbon from gas into a given solvent, can be used to account for the effect of organic additives on the formation and growth of the ionic liquid aggregates in water. Aggregation behavior of ionic liquids in aqueous organic solutions can be modulated simply by the solvophobic parameters of hydrocarbon in the mixed solvents.

  10. Influence of thermo-mechanical processing on microstructure, mechanical properties and corrosion behavior of a new metastable -titanium biomedical alloy

    Indian Academy of Sciences (India)

    Mohsin Talib Mohammed; Zahid A Khan; M Geetha; Arshad N Siddiquee; Prabhash Mishra

    2015-02-01

    This paper presents the results on the influence of different thermo-mechanical processing (TMP) on themechanical properties and electrochemical behavior of newmetastable -alloy Ti–20.6Nb–13.6Zr–0.5V (TNZV). TMP included hot working in below -transus, solution heat treatments at same temperature in different cooling rates in addition to aging. Depending upon the TMP conditions, a wide range of microstructures with varying spatial distributions and morphologies of equiaxed/elongated , phases were attained, allowing for a wide range of mechanical and electrochemical properties to be achieved. The corrosion behavior of studied alloy was evaluated in Ringer’s solution at 37°C using open-circuit potential-time and potentiodynamic polarization measurements.

  11. Influence of albumin and inorganic ions on electrochemical corrosion behavior of plasma electrolytic oxidation coated magnesium for surgical implants

    Science.gov (United States)

    Wan, Peng; Lin, Xiao; Tan, LiLi; Li, Lugee; Li, WeiRong; Yang, Ke

    2013-10-01

    Magnesium and its alloys are of great interest for biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium treated with coating in physiological environment in the presence of organic compound such as albumin have not been elucidated. In this study, the plasma electrolytic oxidation coated magnesium immersed in four different simulated body fluids: NaCl, PBS and with the addition of albumin to investigate the influence of protein and inorganic ions on degradation behavior by electrochemical methods. The results of electrochemical tests showed that aggressive corrosion took place in 0.9 wt.% NaCl solution; whereas albumin can act as an inhibitor, its adsorption impeded further dissolution of the coating. The mechanism was attributed to the synergistic effect of protein adsorption and precipitation of insoluble salts.

  12. Influence of chain length and double bond on the aqueous behavior of choline carboxylate soaps.

    Science.gov (United States)

    Rengstl, Doris; Diat, Olivier; Klein, Regina; Kunz, Werner

    2013-02-26

    In preceding studies, we demonstrated that choline carboxylates ChC(m) with alkyl chain lengths of m = 12 - 18 are highly water-soluble (for m = 12, soluble up to 93 wt % soap and 0 °C). In addition, choline soaps are featured by an extraordinary lyotropic phase behavior. With decreasing water concentration, the following phases were found: micellar phase (L(1)), discontinuous cubic phase (I(1)' and I(1)"), hexagonal phase (H(1)), bicontinuous cubic phase (V(1)), and lamellar phase (L(α)). The present work is also focused on the lyotropic phase behavior of choline soaps but with shorter alkyl chains or different alkyl chain properties. We have investigated the aqueous phase behavior of choline soaps with C(8) and C(10) chain-lengths (choline octanoate and choline decanoate) and with a C(18) chain-length with a cis-double bond (choline oleate). We found that choline decanoate follows the lyotropic phase behavior of the longer-chain homologues mentioned above. Choline octanoate in water shows no discontinuous cubic phases, but an extended, isotropic micellar solution phase. In addition, choline octanoate is at the limit between a surfactant and a hydrotrope. The double bond in choline oleate leads also to a better solubility in water and a decrease of the solubilization temperature. It also influences the Gaussian curvature of the aggregates which results in a loss of discontinuous cubic phases in the binary phase diagram. The different lyotropic mesophases were identified by the penetration scan technique with polarizing light microscope and visual observations. To clarify the structural behavior small (SAXS) and wide (WAXS) angle X-ray scattering were performed. To further characterize the extended, isotropic micellar solution phase in the binary phase diagram of choline octanoate viscosity and conductivity measurements were also carried out.

  13. Corrosion behavior of low energy, high temperature nitrogen ion-implanted AISI 304 stainless steel

    Indian Academy of Sciences (India)

    M Ghorannevis; A Shokouhy; M M Larijani; S H Haji Hosseini; M Yari; A Anvari; M Gholipur Shahraki; A H Sari; M R Hantehzadeh

    2007-01-01

    This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate temperature of about 500° C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion current density of 100 A cm-2. Nitrogen ion concentration of 6 × 1017, 8 × 1017 and 1018 ions cm-2, were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry (SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing nitrogen ion concentration.

  14. Effect of Tryptophan on the corrosion behavior of low alloy steel in sulfamic acid

    Directory of Open Access Journals (Sweden)

    Hesham T.M. Abdel-Fatah

    2016-11-01

    Full Text Available Sulfamic acid is widely used in various industrial acid cleaning applications. In the present work, the inhibition effect of Tryptophan (Tryp on the corrosion of low alloy steel in sulfamic acid solutions at four different temperatures was studied. The investigations involved electrochemical methods (electrochemical impedance spectroscopy; EIS and the new technique electrochemical frequency modulation; EFM as well as gravimetric measurements. The inhibition efficiency and the apparent activation energy have been calculated in the presence and in the absence of Tryp. It is most probable that the inhibition property of Tryp was due to the electrostatic adsorption of the protonated form of Tryp on the steel surface. Adsorption of the inhibitor molecule, onto the steel surface followed the Temkin adsorption isotherm. The thermodynamic parameters of adsorption were determined and discussed. All of the obtained data from the three techniques were in close agreement, which confirmed that EFM technique can be used efficiently for monitoring the corrosion inhibition under the studied conditions.

  15. Analysis of corrosion behavior of LY12 in sodium chloride solution with wavelet transform technique

    Institute of Scientific and Technical Information of China (English)

    张昭; 曹发和; 程英亮; 张鉴清; 王建明; 曹楚南

    2002-01-01

    Wavelet transforms(WT) are proposed as an alternative tool to overcome the limitations of fast Fourier transforms(FFT) in the analysis of electrochemical noise(EN) data. The most relevant feature of this method of analysis is its capability of decomposing electrochemical noise records into different sets of wavelet coefficients(distinct type of events), which contains information about the time scale characteristic of the associated corrosion event. In this context, the potential noise fluctuations during the free corrosion of commercial aluminum alloy LY12 in sodium chloride solution was recorded and analyzed with wavelet transform technique. The typical results show that the EN signal is composed of distinct type of events, which can be classified according to their scales, i.e. their time constants. Meanwhile, the energy distribution plot(EDP) can be used as "fingerprints" of EN signals and can be very useful for analyzing EN data in the future.

  16. Anodic Oxidation of Carbon Steel at High Current Densities and Investigation of Its Corrosion Behavior

    Science.gov (United States)

    Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

    2017-02-01

    This work aims at studying the influence of high current densities on the anodization of carbon steel. Anodic protective coatings were prepared on carbon steel at current densities of 100, 125, and 150 A/dm2 followed by a final heat treatment. Coatings microstructures and morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the uncoated carbon steel substrate and the anodic coatings were evaluated in 3.5 wt pct NaCl solution through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the anodic oxide coatings which were prepared at higher current densities had thicker coatings as a result of a higher anodic forming voltage. Therefore, the anodized coatings showed better anti-corrosion properties compared to those obtained at lower current densities and the base metal.

  17. Corrosion behavior of Ti-Ag alloys used in dentistry in lactic acid solution

    Science.gov (United States)

    Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo

    2011-02-01

    The purpose of this study was to evaluate the corrosion resistance of experimental Ti-Ag alloys used as dental materials. An elution test and a rest-potential measurement of alloys with 5-30 mass.% Ag were performed in a 1 % lactic acid solution. The amount of Ti ions released from the α phase of the Ti-Ag alloys decreased as the Ag concentration increased. TiAg present in the alloys dissolved preferentially, but Ti2Ag did not. The rest potentials of the Ti-Ag alloys were significantly higher than that of pure titanium. The elution test and the rest-potential measurement revealed that the Ti-Ag alloys, which formed a single α-titanium structure or contained a titanium and Ti2Ag, had excellent corrosion resistance that was comparable or superior to that of pure titanium.

  18. Influence of gelatine on corrosion behavior of copper in acidic media

    OpenAIRE

    Todorović Dragiša A.; Milenković Dragan D.; Milosavljević Milutin M.; Marković Dragan A.

    2012-01-01

    This paper presents the results of gelatin and benzotriazole (BTA) inhibitory action on copper in the acid medium by the method of weight loss. The investigation was carried out in the citric acid solution (1, 5 and 20%) at the temperature of 293 K. Under such conditions, the gelatin showed higher efficiency of corrosion protection in comparison to BTA. The results, obtained through the Gibbs and Langmuir adsorption isotherm, show that gelatin adsorption on copper surface obey the Langm...

  19. Electrochemical Corrosion Behavior of the DLC Coated and Uncoated NiTi Alloys

    Institute of Scientific and Technical Information of China (English)

    Jiehe SUI; Wei CAI; Liancheng ZHAO

    2006-01-01

    A dense and well-adhered diamond