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Sample records for hot corrosion pits

  1. Pitting corrosion resistant austenite stainless steel

    Science.gov (United States)

    van Rooyen, D.; Bandy, R.

    A pitting corrosion resistant austenite stainless steel comprises 17 to 28 wt. % chromium, 15 to 26 wt. % nickel, 5 to 8 wt. % molybdenum, and 0.3 to 0.5 wt. % nitrogen, the balance being iron, unavoidable impurities, minor additions made in the normal course of melting and casting alloys of this type, and may optionally include up to 10 wt. % of manganese, up to 5 wt. % of silicon, and up to 0.08 wt. % of carbon.

  2. 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.

  3. Pitting corrosion of copper. An equilibrium - mass transport study

    Energy Technology Data Exchange (ETDEWEB)

    Taxen, C. [Swedish Corrosion Inst., Stockholm (Sweden)

    2002-08-01

    A mathematical model for the propagation of corrosion pits is described and used to calculate the potentials below which copper is immune to pitting. The model uses equilibrium data and diffusion coefficients and calculates the stationary concentration profiles of 26 aqueous species from the bulk water outside a corrosion pit to the site of the metal dissolution. Precipitation of oxides and salts of copper is considered. Studied conditions include water compositions from tap waters to seawater at the temperatures 25 deg C and 75 deg C. Carbonate and sulphate are aggressive towards copper because of complex formation with divalent copper. Carbonate is less aggressive in a corrosion pit than outside at the pH of the bulk. Carbonate carries acidity out from the pit, favours oxide formation and may prevent the initiation of acidic corrosion pits. The concentration profiles are used to estimate the maximum propagation rates for a corrosion pit. A high potential is found to be the most important factor for the rate of propagation. The levels of potential copper can sustain, as corrosion potentials are discussed in terms of the stability of cuprous oxide as a cathode material for oxygen reduction relative to non-conducting cupric phases.

  4. Corrosion Resistance and Pitting Behaviour of Low-Carbon High-Mn Steels in Chloride Solution

    Directory of Open Access Journals (Sweden)

    Grajcar A.

    2016-06-01

    Full Text Available Corrosion resistance of the X4MnSiAlNbTi27-4-2 and X6MnSiAlNbTi26-3-3 type austenitic steels, after hot deformation as well as after cold rolling, were evaluated in 3.5% NaCl solution using potentiodynamic polarization tests. A type of nonmetallic inclusions and their pitting corrosion behaviour were investigated. Additionally, the effect of cold deformation on the corrosion resistance of high-Mn steels was studied. The SEM micrographs revealed that corrosion damage formed in both investigated steels is characterized by various shapes and an irregular distribution at the metallic matrix, independently on the steel state (thermomechanically treated or cold worked. Corrosion pits are generated both in grain interiors, grain boundaries and along the deformation bands. Moreover, corrosion damage is stronger in cold deformed steels in comparison to the thermomechanically treated specimens. EDS analysis revealed that corrosion pits preferentially nucleated on MnS and AlN inclusions or complex oxysulphides. The morphology of corrosion damage in 3.5% NaCl supports the data registered in potentiodynamic tests.

  5. Mechanism of Pitting Corrosion Protection of Metals and Alloys

    OpenAIRE

    Vladimir Alexandrovich Grachev; Andrei Evgenievich Rozen; Gennadii Vasilievich Kozlov; Andrei Andreievich Rozen

    2016-01-01

    In this article authors set out a principle of pitting corrosion protection, suggested a new class of multilayer materials with high corrosion resistance. They substantiated the choice of the layers for the multilayer material designed for exploitation in oxidizing and non-oxidizing environment. The sphere of application of the multilayer materials was defined.

  6. Influence of remanent magnetization on pitting corrosion in pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J. H. [ESIME Zacatenco, SEPI Electronica Instituto Politecnico Nacional Mexico, D. F. (Mexico); Caleyo, F.; Hallen, J. M. [DIM-ESIQIE, Instituto Politecnico Nacional Mexico D. F. (Mexico); Lopez-Montenegro, A.; Perez-Baruch, E. [Pemex Exploracion y Produccion, Region Sur Villahermosa, Tabasco (Mexico)

    2010-07-01

    Statistical studies performed in Mexico indicate that leakage due to external pitting corrosion is the most likely cause of failure of buried pipelines. When pipelines are inspected with the magnetic flux leakage (MFL) technology, which is routinely used, the magnetization level of every part of the pipeline changes as the MFL tool travels through it. Remanent magnetization stays in the pipeline wall after inspection, at levels that may differ from a point to the next. This paper studies the influence of the magnetic field on pitting corrosion. Experiments were carried out on grade 52 steel under a level of remanent magnetization and other laboratory conditions that imitated the conditions of a pipeline after an MLF inspection. Non-magnetized control samples and magnetized samples were subjected to pitting by immersion in a solution containing chlorine and sulfide ions for seven days, and then inspected with optical microscopy. Results show that the magnetic field in the pipeline wall significantly increases pitting corrosion.

  7. Inhibition of Copper Pitting Corrosion in Aggressive Potable Waters

    Directory of Open Access Journals (Sweden)

    Emily Sarver

    2012-01-01

    Full Text Available Copper pitting corrosion can lead to premature plumbing failures, and can be caused by aggressive potable waters characterized by high pH, free chlorine residual and low alkalinity. In such waters and under continuous flow, certain inhibitors including phosphate, silica or natural organic matter may greatly reduce pitting occurrence. In the current work, 1 mg/L phosphate (as P completely prevented initiation of pits, and 5 mg/L silica (as Si significantly decelerated pitting. However, much lower doses of these inhibitors had little benefit and actually accelerated the rate of attack in some cases. Effects of organic matter were dependent on both the type (e.g., natural versus ozonated humic substances and dosage. Dose-response effects of free chlorine and alkalinity were also investigated. Based on electrochemical data, pits initiated more rapidly with increased free chlorine, but even moderate levels of chlorine (~0.4 mg/L eventually caused severe pitting. High alkalinity decreased pit propagation rates but did not prevent pit formation.

  8. Pitting Corrosion of Cu-Zn-Al Shape Memory Alloy in Simulated Uterine Fluid

    Institute of Scientific and Technical Information of China (English)

    Bangyi CHEN; Chenghao LIANG; Daojun FU

    2005-01-01

    Electrochemical test technology and surface analysis method were employed to investigate the pitting corrosion of Cu-Zn-Al shape memory alloy in simulated uterine fluid. The results showed that the breakage of the breakingrenovating equilibrium of surface layers resulted in the pitting corrosion of Cu-Zn-Al shape memory alloy in simulated uterine fluid. The development of pitting corrosion was controlled by dissolution of surface layers. The critical pitting corrosion potential was 1.70 VsCE. The kinetics equation for the development of pitting corrosion for Cu-Zn-Al shape memory alloy in simulated uterine fluid was i0=465.68 t-0.5+1.5. Pitting appearances of pits could be two types: tortoise-shell, and anomaly abscess. Cl- ion facilitated the pitting corrosion of Cu-Zn-Al shape memory alloy by competing adsorption and concentrating on alloy surface at high positive potential.

  9. Markov chain model helps predict pitting corrosion depth and rate in underground pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Caleyo, F.; Velazquez, J.C.; Hallen, J. M. [ESIQIE, Instituto Politecnico Nacional, Mexico D. F. (Mexico); Esquivel-Amezcua, A. [PEMEX PEP Region Sur, Villahermosa, Tabasco (Mexico); Valor, A. [Universidad de la Habana, Vedado, La Habana (Cuba)

    2010-07-01

    Recent reports place pipeline corrosion costs in North America at seven billion dollars per year. Pitting corrosion causes the higher percentage of failures among other corrosion mechanisms. This has motivated multiple modelling studies to be focused on corrosion pitting of underground pipelines. In this study, a continuous-time, non-homogenous pure birth Markov chain serves to model external pitting corrosion in buried pipelines. The analytical solution of Kolmogorov's forward equations for this type of Markov process gives the transition probability function in a discrete space of pit depths. The transition probability function can be completely identified by making a correlation between the stochastic pit depth mean and the deterministic mean obtained experimentally. The model proposed in this study can be applied to pitting corrosion data from repeated in-line pipeline inspections. Case studies presented in this work show how pipeline inspection and maintenance planning can be improved by using the proposed Markovian model for pitting corrosion.

  10. Oxidation And Hot Corrosion Of ODS Alloy

    Science.gov (United States)

    Lowell, Carl E.; Barrett, Charles A.

    1993-01-01

    Report reviews oxidation and hot corrosion of oxide-dispersion-strengthened (ODS) alloys, intended for use at high temperatures. Classifies environmental resistances of such alloys by rates of growth of oxides, volatilities of oxides, spalling of oxides, and limitations imposed by hot corrosion. Also discusses environmentally resistant coatings for ODS materials. Concludes ODS NICrAl and FeCrAl alloys highly resistant to oxidation and corrosion and can be used uncoated.

  11. 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.

  12. Fundamental Investigation of Pitting Corrosion in Structural Metals

    Science.gov (United States)

    1981-07-01

    to .1. Electrochem. Soc.; abbreviated version submitted to H. H. Uhlig 75th Birthday Symposium Volume, The Electrochemical Society , Fall Meeting...Films During the Initial Stages of Corrosion, Ext. Abs. No. 93, The Electrochemical Society , Fall Meeting, Las Vegas, NV, October 17-22, 1976. 2. T. R...Beck, Pitting of Titanium, III Electrical Properties of Salt Film, Ext. Abs. No. 64, The Electrochemical Society , Spring Meeting, Seattle, WA, May 21

  13. Review and Study of Physics Driven Pitting Corrosion Modeling in 2024-T3 Aluminum Alloys (Postprint)

    Science.gov (United States)

    2015-05-01

    measuring the maximum pit size and its effect on the fatigue life. Microstructure and corrosion currents were neglected. In this paper we present the...Figure 2 Appearance of the pits on the surface of 7075 -T6 (Wang et al., 2003) Proc. of SPIE Vol. 9437 94372E-2 2 Distribution Statement A. Approved... density (Harlow and Wei, 1994). It can be seen that the definition of pitting current Ip is the key element in the pitting corrosion modeling, which

  14. Intermetallic particles-induced pitting corrosion in 6061-T651 aluminium alloy

    CSIR Research Space (South Africa)

    Mutombo, K

    2011-07-01

    Full Text Available -Induced Pitting Corrosion in 6061-T651 Aluminium Alloy Kalenda Mutombo Council for Scientific and Industrial Research (CSIR), South Africa kmutombo@csir.co.za Keywords: pitting corrosion, 6061-T651 aluminium alloy, intermetallic particles, 3.5% Na... extrudability, reasonable weldability and good corrosion resistance. This alloy finds widespread application in ship building and in the fabrication of tank containers for transporting various liquids. 6061-T651 aluminium alloy is, however, prone to pitting...

  15. Pitting Corrosion of 13Cr Steel in Oxygen-free Completion Fluids of Organic Salt

    Institute of Scientific and Technical Information of China (English)

    Lining XU; Yao MENG; Yunguang SHI; Yan LIU

    2013-01-01

    Corrosion behavior of 13Cr steel in oxygen-free completion fluids of the organic salt at 180 ℃ was studied.Cross-sectional morphologies of the corrosion products were observed by scanning electron microscopy.Energy dispersive spectrum (EDS) was used to study the element distribution of the corrosion product inside and outside the pits.The results show that the organic salt causes severe pitting corrosion of 13Cr steel.The width and depth of the pits increase simultaneously when the test duration prolongs,and potassium enriches inside the pits.

  16. Copper Tube Pitting in Santa Fe Municipal Water Caused by Microbial Induced Corrosion

    Directory of Open Access Journals (Sweden)

    Thomas D. Burleigh

    2014-06-01

    Full Text Available Many copper water lines for municipal drinking water in Santa Fe, New Mexico USA, have developed pinhole leaks. The pitting matches the description of Type I pitting of copper, which has historically been attributed to water chemistry and to contaminants on the copper tubing surface. However, more recent studies attribute copper pitting to microbial induced corrosion (MIC. In order to test for microbes, the copper tubing was fixed in hexamethyldisilazane (HMDS, then the tops of the corrosion mounds were broken open, and the interior of the corrosion pits were examined with scanning electron microscopy (SEM. The analysis found that microbes resembling actinobacteria were deep inside the pits and wedged between the crystallographic planes of the corroded copper grains. The presence of actinobacteria confirms the possibility that the cause of this pitting corrosion was MIC. This observation provides better understanding and new methods for preventing the pitting of copper tubing in municipal water.

  17. A Comprehensive Investigation of Copper Pitting Corrosion in a Drinking Water Distribution System

    Science.gov (United States)

    Copper pipe pitting is a complicated corrosion process for which exact causes and solutions are uncertain. This paper presents the findings of a comprehensive investigation of a cold water copper pitting corrosion problem in a drinking water distribution system, including a refi...

  18. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    WANG Qingyuan (王清远); N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials,loading,and environmental conditions.A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e.the pit nucleation and growth,pit-crack transition,short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size,corrosion pitting current,and material properties due to the scatter found in the experimental data.Monte Carlo simulations were performed to define the failure probability distribution.Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.

  19. 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.

  20. Electrochemical and pitting corrosion resistance of AISI 4145 steel subjected to massive laser shock peening treatment with different coverage layers

    Science.gov (United States)

    Lu, J. Z.; Han, B.; Cui, C. Y.; Li, C. J.; Luo, K. Y.

    2017-02-01

    The effects of massive laser shock peening (LSP) treatment with different coverage layers on residual stress, pitting morphologies in a standard corrosive solution and electrochemical corrosion resistance of AISI 4145 steel were investigated by pitting corrosion test, potentiodynamic polarisation test, and SEM observations. Results showed massive LSP treatment can effectively cause an obvious improvement of pitting corrosion resistance of AISI 4145 steel, and increased coverage layer can also gradually improve its corrosion resistance. Massive LSP treatment with multiple layers was shown to influence pitting corrosion behaviour in a standard corrosive solution.

  1. Pitting corrosion of Al2024-T3 in sodium chloride solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Pitting corrosion behavior of Al2024-T3 in sodium chloride solution was investigated by using potentiodynamic scanning (PDS) measurements and electrochemical impedance spectroscopy (EIS) technique. When pitting corrosion of the alloy occurs, there exists a passive region in the anodic branch of PDS polarization curve, which is enlarged with the increasing of immersion time due to the competition of the halide ions with OH- ions to adsorb on the oxide film to form the corrosion products film and the increase of pitting corrosion area. Two capacitive semicircles were observed in complex plane plot. For more extensive pitting and general corrosion of Al2024-T3, the passive region in PDS disappeared, while another depressed semicircle was observed in Nyquist plot because of the formation of corrosion products film. On the other hand, the low frequency inductive loop, which had often been regarded as a manifestation of pitting or formation and precipitation of a salt film, was not observed, which indicates that the low frequency inductive loop can not be the characteristic of pitting corrosion or the formation of salt film. The results also show that higher reactant CPE exponent values will correspond to more extensive transformation of a metal surface by very localized corrosion, while general corrosion can result in a smaller CPE exponent value.

  2. Study of pitting corrosion in line-pipe steel under the influence of remanent magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J.H.; Caleyo, F.; Hallen, J.M. [Instituto Politecnico Nacional (IPN), Zacatenco (Mexico)

    2009-07-01

    The influence of remanent magnetization on pitting corrosion in line-pipe steels is studied. Pitting corrosion experiments have been carried out on samples of an API 5L grade 52 steel under a magnetization level of the same order of magnitude of the remanent magnetization in the pipeline wall after in-line inspection based on magnetic flux leakage. The samples were magnetized using rings of the same grade as the investigated steel. Immediately after magnetization, the investigated samples were subjected to pitting by immersing them in a solution containing dissolved Cl{sup -} and SO{sup 2-}{sub 4} and ions. The pitting experiments were conducted during a seven days period. The pit depth distribution and the maximum pit depth in each sample were recorded and used to conduct extreme value analyses of the pitting process in magnetized and non-magnetized control samples. The statistical assessment of the pitting corrosion data collected during this study shows that the magnetic field reduces the average depth of the pit population and also the extreme pit depth values that can be predicted from the maximum values observed in the magnetized samples in comparison with to the non-magnetized control samples. Scanning electron microscopy observations show that the magnetic field alters the pit morphology by increasing the pit mouth opening. (author)

  3. Study of pitting corrosion in line-pipe steel under the influence of remanent magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J.H.; Caleyo, F.; Hallen, J.M. [Instituto Politecnico Nacional (IPN), Zacatenco (Mexico)

    2009-07-01

    The influence of remanent magnetization on pitting corrosion in line-pipe steels is studied. Pitting corrosion experiments have been carried out on samples of an API 5L grade 52 steel under a magnetization level of the same order of magnitude of the remanent magnetization in the pipeline wall after in-line inspection based on magnetic flux leakage. The samples were magnetized using rings of the same grade as the investigated steel. Immediately after magnetization, the investigated samples were subjected to pitting by immersing them in a solution containing dissolved Cl{sup -} and SO{sup 2-}{sub 4} and ions. The pitting experiments were conducted during a seven days period. The pit depth distribution and the maximum pit depth in each sample were recorded and used to conduct extreme value analyses of the pitting process in magnetized and non-magnetized control samples. The statistical assessment of the pitting corrosion data collected during this study shows that the magnetic field reduces the average depth of the pit population and also the extreme pit depth values that can be predicted from the maximum values observed in the magnetized samples in comparison with to the non-magnetized control samples. Scanning electron microscopy observations show that the magnetic field alters the pit morphology by increasing the pit mouth opening. (author)

  4. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS

    Institute of Scientific and Technical Information of China (English)

    王清远; N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI

    2003-01-01

    Corrosion and fatigue properties of aircraft materials axe known to have a considerablescatter due to the random nature of materials, loading, and environmental conditions. A probabilisticapproach for predicting the pitting corrosion fatigue life has been investigated which captures the effectof the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigueprocess (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pittingcurrent, and material properties due to the scatter found in the experimental data. Monte Carlo simu-lations were performed to define the failure probability distribution. Predicted cumulative distributionfunctions of fatigue life agreed reasonably well with the existing experimental data.

  5. Coatings for Oxidation and Hot Corrosion Protection of Disk Alloys

    Science.gov (United States)

    Nesbitt, Jim; Gabb, Tim; Draper, Sue; Miller, Bob; Locci, Ivan; Sudbrack, Chantal

    2017-01-01

    Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can potentially seriously degrade the life of the disk. Application of metallic coatings are one means of protecting disk alloys from this environmental attack. However, simply the presence of a metallic coating, even without environmental exposure, can degrade the LCF life of a disk alloy. Therefore, coatings must be designed which are not only resistant to oxidation and corrosion attack, but must not significantly degrade the LCF life of the alloy. Three different Ni-Cr coating compositions (29, 35.5, 45wt. Cr) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One coating also received a thin ZrO2 overcoat. The coated samples were also given a short oxidation exposure in a low PO2 environment to encourage chromia scale formation. Without further environmental exposure, the LCF life of the coated samples, evaluated at 760C, was less than that of uncoated samples. Hence, application of the coating alone degraded the LCF life of the disk alloy. Since shot peening is commonly employed to improve LCF life, the effect of shot peening the coated and uncoated surface was also evaluated. For all cases, shot peening improved the LCF life of the coated samples. Coated and uncoated samples were shot peened and given environmental exposures consisting of 500 hrs of oxidation followed by 50 hrs of hot corrosion, both at 760C). The high-Cr coating showed the best LCF life after the environmental exposures. Results of the LCF testing and post-test characterization of the various coatings will be presented and future research directions discussed.

  6. Microstructural Modeling of Pitting Corrosion in Steels Using an Arbitrary Lagrangian-Eulerian Method

    Science.gov (United States)

    Yu, Qifeng; Pan, Tongyan

    2017-05-01

    Two microscale numerical models are developed in this work using a moving-mesh approach to investigate the growth process of pitting in different iron phases and the corrosion prevention capability of polyaniline (PANi) on steels. The distributions of corrosion potential and current in the electrolyte-coating-steel system are computed to evaluate the anti-corrosion ability of PANi. The arbitrary Lagrangian-Eulerian approach was used to accomplish the continuous remesh process as was needed to simulate the dynamic growing forefront of the modeled pitting domain. Experimental validation of the numerical models was conducted using the technique of scanning kelvin probe force microscopy (SKPFM). The SKPFM-scanned surface topography and Volta potential difference exhibit comparable results to and thereby prove the numerical results. The potential distribution in the electrolyte phase of the validated models shows that the corrosion pit grows faster in the epoxy-only-coated steel than that in the PANi-primer-coated steel over the simulation time; also, the corrosion pit grows faster in the ferrite phase than in the cementite phase. The simulation results indicate that the epoxy-only coating lost its anti-corrosion capability as the coating was penetrated by electrolyte, while the PANi-based coating can still protect the steel from corrosion after the electrolyte penetration. The models developed in this work can be used to study the mechanisms of pitting corrosion as well as develop more effective corrosion prevention strategies for general metallic materials.

  7. Microstructural Modeling of Pitting Corrosion in Steels Using an Arbitrary Lagrangian-Eulerian Method

    Science.gov (United States)

    Yu, Qifeng; Pan, Tongyan

    2017-03-01

    Abstracts Two microscale numerical models are developed in this work using a moving-mesh approach to investigate the growth process of pitting in different iron phases and the corrosion prevention capability of polyaniline (PANi) on steels. The distributions of corrosion potential and current in the electrolyte-coating-steel system are computed to evaluate the anti-corrosion ability of PANi. The arbitrary Lagrangian-Eulerian approach was used to accomplish the continuous remesh process as was needed to simulate the dynamic growing forefront of the modeled pitting domain. Experimental validation of the numerical models was conducted using the technique of scanning kelvin probe force microscopy (SKPFM). The SKPFM-scanned surface topography and Volta potential difference exhibit comparable results to and thereby prove the numerical results. The potential distribution in the electrolyte phase of the validated models shows that the corrosion pit grows faster in the epoxy-only-coated steel than that in the PANi-primer-coated steel over the simulation time; also, the corrosion pit grows faster in the ferrite phase than in the cementite phase. The simulation results indicate that the epoxy-only coating lost its anti-corrosion capability as the coating was penetrated by electrolyte, while the PANi-based coating can still protect the steel from corrosion after the electrolyte penetration. The models developed in this work can be used to study the mechanisms of pitting corrosion as well as develop more effective corrosion prevention strategies for general metallic materials.

  8. 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.

  9. Pitting Corrosion Behaviour of New Corrosion-Resistant Reinforcement Bars in Chloride-Containing Concrete Pore Solution

    Science.gov (United States)

    Liu, Yao; Chu, Hong-yan; Wang, Danqian; Ma, Han; Sun, Wei

    2017-01-01

    In this study, the pitting behaviour of a new corrosion-resistant alloy steel (CR) is compared to that of low-carbon steel (LC) in a simulated concrete pore solution with a chloride concentration of 5 mol/L. The electrochemical behaviour of the bars was characterised using linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS). The pitting profiles were detected by reflective digital holographic microscopy (DHM), scanning electron microscopy (SEM), and the chemical components produced in the pitting process were analysed by X-ray energy dispersive spectroscopy (EDS). The results show that the CR bars have a higher resistance to pitting corrosion than the LC bars. This is primarily because of the periodic occurrence of metastable pitting during pitting development. Compared to the pitting process in the LC bars, the pitting depth grows slowly in the CR bars, which greatly reduces the risk of pitting. The possible reason for this result is that the capability of the CR bars to heal the passivation film helps to restore the metastable pits to the passivation state. PMID:28777327

  10. 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.

  11. Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

    18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical duc-tile-brittle transition behavior and excellent pitting corrosion resistance properties.

  12. Hot Corrosion of Cobalt-Base Alloys

    Science.gov (United States)

    1975-06-01

    scale is similar to that which has already been proposed for cobalt . The oxide ions would react with the Al203 to form aluminate ions in the Na2S04...resistance of cobalt -base and nickel-base alloys. The contract was accomplished under the technical direction of Dr. H. C. Graham of the Aerospace Research...Oxidized Specimens RESULTS AND DISCUSSION 1. INTRODUCfiON 2. SODIUM SULFATE INDUCED HOT CORROSION OF COBALT a. Introduction b. Experimental c

  13. A single precursor pit for pitting corrosion on defect of tinplate alloy layer visualized by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cui Guofeng [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)]. E-mail: cuiguofeng@hit.edu.cn; Wang Jinghe [Research of Precise Engineering, Harbin Institute of Technology, Harbin 150001 (China); Li Ning [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Huang Xingqiao [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

    2006-06-10

    The gray points highly disperse on the alloy layer surface after free tin coating removed on poorly corrosion-resistant tinplate. The morphology and composition of normal area and the gray point were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersion spectroscopy (EDS) on the same tinplate sheet. Additional, the cyclic voltammetry results indicate that corrosion resistance of alloy layer containing gray points is less than that of normal area. Those indicate that gray points are defects of Sn-Fe alloy layer. AFM was applied to obtain detail information on topography change of the gray point in electrolyte. Furthermore, profile lines of the sample at varied time were determined and delivered additional arguments for corrosion rate of the gray point. The results of a single pit corrosion measurement show that corrosion rate is determined by a mass-transport controlled mechanism in acid electrolyte.

  14. Microstructure and pitting corrosion of 13CrNiMo weld metals

    Energy Technology Data Exchange (ETDEWEB)

    Bilmes, P.D. [Laboratorio de Investigaciones de Metalurgia Fisica ' Ing. Gregorio Cusminsky' (LIMF), Departamento Mecanica, Facultad de Ingenieria, Universidad Nacional de la Plata, calle 1 y 47, 1900 La Plata (Argentina); Llorente, C.L. [Laboratorio de Investigaciones de Metalurgia Fisica ' Ing. Gregorio Cusminsky' (LIMF), Departamento Mecanica, Facultad de Ingenieria, Universidad Nacional de la Plata, calle 1 y 47, 1900 La Plata (Argentina); Saire Huaman, L. [Instituto de Investigaciones, Fisicoquimicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de la Plata, Sucursal 4-C.C. 16, 1900 La Plata (Argentina); Laboratorio de Ingenieria de Corrosion y Tecnologia Electroquimica (LICTE), Departamento Ingenieria Quimica, Facultad de Ingenieria, Universidad Nacional de la Plata, 1 y 47, 1900 La Plata (Argentina); Gassa, L.M. [Instituto de Investigaciones, Fisicoquimicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de la Plata, Sucursal 4-C.C. 16, 1900 La Plata (Argentina); Laboratorio de Ingenieria de Corrosion y Tecnologia Electroquimica (LICTE), Departamento Ingenieria Quimica, Facultad de Ingenieria, Universidad Nacional de la Plata, 1 y 47, 1900 La Plata (Argentina); Gervasi, C.A. [Instituto de Investigaciones, Fisicoquimicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de la Plata, Sucursal 4-C.C. 16, 1900 La Plata (Argentina) and Laboratorio de Ingenieria de Corrosion y Tecnologia Electroquimica (LICTE), Departamento Ingenieria Quimica, Facultad de Ingenieria, Universidad Nacional de la Plata, 1 y 47, 1900 La Plata (Argentina)]. E-mail: gervasi@inifta.unlp.edu.ar

    2006-10-15

    Cyclic potentiodynamic measurements and scanning electron microscopy were used to analyze susceptibility to pitting corrosion of 13CrNiMo weld metals. In order to carry out a critical assessment of the influence of microstructural factors on localized corrosion, different heat treatments were applied to the alloys under investigation. Volume fractions of austenite in tempered conditions as well as the amount and size of precipitated carbides strongly affect pitting resistance. Characteristic potentials (pitting potential and repassivation potential) increase according to the retained austenite content. Results can be discussed in terms of a model that describes the structural refinement resulting from a double-tempering procedure.

  15. Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloys

    Science.gov (United States)

    Gabb, Timothy P.; Miller, Robert A.; Sudbrack, Chantal K.; Draper, Susan L.; Nesbitt, James A.; Rogers, Richard B.; Telesman, Ignacy; Ngo, Vanda; Healy, Jonathan

    2016-01-01

    Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 degrees Centigrade and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 degrees Centigrade. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. This cyclic oxidation did not impair the coating's resistance to subsequent hot corrosion pitting attack.

  16. Pitting corrosion transformation of SUS304 stainless steel in lithium bromide solution at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H.X.; Ma, X.H.; Chen, J.B.; Bo, S.S. [Institute of Chemical Engineering, Dalian University of Technology, Dalian (China)

    2009-05-15

    The foundational data and rules of SUS304 corrosion in aqueous lithium bromide solution at 150-200 C have been investigated by means of weight loss in this paper. The Taguchi method was chosen to investigate the effects of variables on corrosion at higher temperature. Concentration of dissolved oxygen was controlled by keeping the vessel pressure at 1.3 kPa (absolute) before the experiment. The results showed that there was a transformation tendency from pitting corrosion to general corrosion and transition concentration of pitting and film corrosion decreased with increase in solution temperature. The adsorption, activity, and diffusivity of bromine ion led to different corrosion modalities. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  17. Effects of Inclusions in HSLA Carbon Steel on Pitting Corrosion in CaCl2

    Energy Technology Data Exchange (ETDEWEB)

    M. Ziomek-Moroz; S. Bullard; K. Rozman; J.J. Kruzic

    2011-12-05

    Susceptibility of high strength low alloy steel to localized corrosion was studied in 6.7 M CaCl{sub 2} for oil and natural gas drilling applications. Results of the immersion and electrochemical experiments showed that the steel is susceptible to pitting corrosion. Optical microscopy investigations of the polished samples revealed that 10% of the surface area was occupied by defects in the form of pits. The energy dispersive X-ray (EDX) and wavelength dispersive X-ray (WDX) chemical analyses revealed higher concentrations of Mn and S compared to the metal matrix in defected areas. These areas served as the sites for development of corrosion pits during both immersion and electrochemical experiments. The fatigue results of the corroded samples indicate that if the pit was the most significant defect, the fatigue crack initiated and propagated at this site.

  18. Passivation and pitting corrosion of. alpha. -brass (Cu/Zn: 63/37) in neutral buffer solutions containing chloride ions

    Energy Technology Data Exchange (ETDEWEB)

    Abd El-Rahman, H.A. (Cairo Univ., Gizeh (Egypt). Chemistry Dept.)

    1990-11-01

    The passivation behaviour and pitting corrosion of a commercial grade {alpha}-brass (Cu/Zn: 63/37) in neutral buffer solutions (borate and phosphate) in the presence and absence of chloride ions were investigated by electrochemical techniques. The results indicated the dezincification in absence of chloride ions at highly enough anodic potentials and both dezincification and pitting corrosion in the presence of chloride ions. The pitting susceptibility was found to depend on the composition of the buffer solution, chloride ion concentration and nature of the passive layer on the metal surface before pitting. Current transients corresponding to passivity, dezincification and pitting corrosion were identified and analyzed. (orig.).

  19. Prediction of Pitting Corrosion Mass Loss for 304 Stainless Steel by Image Processing and BP Neural Network

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei; LIANG Cheng-hao

    2005-01-01

    Image processing technique was employed to analyze pitting corrosion morphologies of 304 stainless steel exposed to FeCl3 environments. BP neural network models were developed for the prediction of pitting corrosion mass loss using the obtained data of the total and the average pit areas which were extracted from pitting binary image. The results showed that the predicted results obtained by the 2-5-1 type BP neural network model are in good agreement with the experimental data of pitting corrosion mass loss. The maximum relative error of prediction is 6.78%.

  20. Prediction of microsegregation and pitting corrosion resistance of austenitic stainless steel welds by modelling

    Energy Technology Data Exchange (ETDEWEB)

    Vilpas, M. [VTT Manufacturing Technology, Espoo (Finland). Materials and Structural Integrity

    1999-07-01

    The present study focuses on the ability of several computer models to accurately predict the solidification, microsegregation and pitting corrosion resistance of austenitic stainless steel weld metals. Emphasis was given to modelling the effect of welding speed on solute redistribution and ultimately to the prediction of weld pitting corrosion resistance. Calculations were experimentally verified by applying autogenous GTA- and laser processes over the welding speed range of 0.1 to 5 m/min for several austenitic stainless steel grades. Analytical and computer aided models were applied and linked together for modelling the solidification behaviour of welds. The combined use of macroscopic and microscopic modelling is a unique feature of this work. This procedure made it possible to demonstrate the effect of weld pool shape and the resulting solidification parameters on microsegregation and pitting corrosion resistance. Microscopic models were also used separately to study the role of welding speed and solidification mode in the development of microsegregation and pitting corrosion resistance. These investigations demonstrate that the macroscopic model can be implemented to predict solidification parameters that agree well with experimentally measured values. The linked macro-micro modelling was also able to accurately predict segregation profiles and CPT-temperatures obtained from experiments. The macro-micro simulations clearly showed the major roles of weld composition and welding speed in determining segregation and pitting corrosion resistance while the effect of weld shape variations remained negligible. The microscopic dendrite tip and interdendritic models were applied to welds with good agreement with measured segregation profiles. Simulations predicted that weld inhomogeneity can be substantially decreased with increasing welding speed resulting in a corresponding improvement in the weld pitting corrosion resistance. In the case of primary austenitic

  1. DARWIN-HC:? A Tool to Predict Hot Corrosion of Nickel-Based Turbine Disks Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Hot Corrosion of turbine engine components has been studied for many years. The underlying mechan-isms of Type I Hot Corrosion and Type II Hot Corrosion are...

  2. DARWIN-HC: A Tool to Predict Hot Corrosion of Nickel-Based Turbine Disks Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Hot Corrosion of turbine engine components has been studied for many years. The underlying mechan-isms of Type I Hot Corrosion and Type II Hot Corrosion are...

  3. Influence of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel welding joints

    Science.gov (United States)

    Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei; Zhang, Jianli

    2017-02-01

    The influences of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel joints welded by gas tungsten arc welding (GTAW) and flux-cored arc welding (FCAW) with different shielding gas compositions were studied by optical microscopy, electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, electron probe microanalysis, and potentiostatic and potentiodynamic polarization methods The adding 2% N2 in shielding gas facilitated primary austenite formation in GTAW weld metal (WM) and suppressed Cr2N precipitation in GTAW weld root. In the HAZ, the banded microstructure disappeared while the coarse ferrite grains maintained same orientation as the banded ferrite in the BM. In the WM, the ferrite had one single orientation throughout a grain, whereas several families of austenite appeared. The austenite both in BM and WM enriched in Ni and nitro`gen, while Cr and Mo were concentrated in the ferrite and thus no element showed clear dendritic distribution in the WM (ER2209 and E2209T1). In addition, the secondary austenite had higher Ni content but lower Cr and Mo content than the primary austenite. The N2-supplemented shielding gas promoted nitrogen solid-solution in the primary and secondary austenite. Furthermore, the secondary austenite had relatively lower pitting resistance equivalent number (PREN) than the ferrite and primary austenite, thereby resulting in its preferential corrosion. The Cr2N precipitation led to relatively poor resistance to pitting corrosion in three HAZs and pure Ar shielding GTAW weld root. The N2-supplemented shielding gas improved pitting corrosion resistance of GTAW joint by increasing PREN of secondary austenite and suppressing Cr2N precipitation. In addition, the FCAW WM had much poorer resistance to pitting corrosion than the GTAW WM due to many O-Ti-Si-Mn inclusions. In the BM, since the austenite with lower PREN compared

  4. Corrosion pathways in liquid sulfur run-down pits and other liquid sulfur handling facilities

    Energy Technology Data Exchange (ETDEWEB)

    Clark, P.D.; Dowling, N.I.; Huang, M.

    2010-01-15

    This poster presentation explained why sulfur pits deteriorate over time and provided the detailed chemistry of the mechanisms for the deterioration of concrete in sulfur pits. Liquid and solid sulfur may build up in the pore structure of the concrete, which is followed by chemical reactions. The sulfur formation inside the concrete pore structure is catalyzed by concrete constituents. The sulfate formation in sulfur pit concrete was described. The chemical process that produces the corrosion of re-enforcing steel rods used in the construction of sulfur pits was also described. The consequence of such corrosion is the loss of structural integrity. The secondary corrosion processes at concrete pit reinforcing steel were also presented. To limit the deterioration of sulfur pit concrete, high-density silica facing should be used on the concrete to prevent the ingress of gases into the concrete. Silica does not catalyze the conversion of hydrogen disulfide and sulfur dioxide to sulfur, so there is no formation of stable sulfates and acidic intermediates. 8 figs.

  5. PITTING CORROSION OF AISI 316Ti STAINLESS STEEL WITH POLISHED SURFACE

    Directory of Open Access Journals (Sweden)

    Viera Zatkalíková

    2010-05-01

    Full Text Available AISI 316Ti is Cr–Ni–Mo austenitic stainless steel with the high Pitting Resistance Equivalent Number (PREN. The effect of the surface finishing by polishing on the pitting corrosion resistance was tested in aggressive 5% FeCl3 solution. The immersion tests were curried out at the temperature 30, 50, 80 °C. The electrochemical cyclic potentiodynamic tests were carried out in the same solution at temperature 30 and 50 °C. The evaluation of the corrosion resistance arose from the comparison of the results of the immersion and the cyclic potentiodynamic tests.

  6. Effect of Equal-Channel Angular Pressing on Pitting Corrosion of Pure Aluminum

    Directory of Open Access Journals (Sweden)

    Injoon Son

    2012-01-01

    Full Text Available The effect of equal-channel angular pressing (ECAP on the pitting corrosion of pure Al was investigated using electrochemical techniques in solutions containing 0.1 m mol·dm−3 of Na2SO4 and 8.46 mol·dm−3 of NaCl (300 ppm Cl− and followed by surface analysis. The potential for pitting corrosion of pure Al was clearly shifted in the noble direction by the ECAP process indicating that this process improves resistance to pitting corrosion. The time dependence of corrosion potential and the anodic potential at 1 A·m−2 revealed that the rate of formation of Al oxide films increased due to a decrease in the grain size of the Al after ECAP. Since there exists a negligible amount of impurity precipitates in pure Al, the improvement in pitting corrosion resistance of pure Al by ECAP appears to be attributable to an increase in the rate of formation of Al oxide films.

  7. The intrinsically high pitting corrosion resistance of mechanically polished nitinol in simulated physiological solutions.

    Science.gov (United States)

    Bai, Zhijun; Rotermund, Harm H

    2011-10-01

    Nitinol wires have been widely used in many biomedical applications, such as cardiovascular stent due to their superelasticity and shape memory effect. However, their corrosion properties and the related biocompatibility are not well understood, and the reported results are controversial. In this study, we evaluate the pitting corrosion property of nitinol, titanium, nickel, and 316L stainless steel (316LSS) wires with different surface roughnesses in a saline solution at 37 °C. The cyclic potentiodynamic polarization results show that mechanically polished nitinol and Ti wires are highly resistant to pitting corrosion, while Ni and 316LSS wires are susceptible to pitting corrosion. Electrochemical impedance spectroscopy is used to study the interface of oxide film/solution and all mechanically polished nitinol wires are covered by 2-3 nm thick films formed under open circuit potential. Furthermore, the electronic structures and semiconducting properties of passive films on nitinol, Ti and Ni wires are studied by Mott-Schottky analysis. Passive films formed on nitinol and Ti exhibit n-type semiconducting characteristics, whereas films on Ni show p-type semiconducting characteristics. Scanning Kelvin Microscopy is used to measure the surface potential difference between common inclusions from the nitinol matrix and the results indicate that the inclusions are more electrochemically noble than the nitinol matrix. Band energy theory is used to model the electrochemical interface between the passive films of nitinol and the solution under different applied potential conditions. A mechanism for the strong pitting corrosion resistance of nitinol in saline solution is proposed.

  8. Modeling pitting corrosion of iron exposed to alkaline solutions containing nitrate and nitrite

    Science.gov (United States)

    Chen, Lifeng

    2001-07-01

    Pitting corrosion could be extremely serious for dilute high-level radioactive waste stored or processed in carbon steel tanks at the Savannah River Site. In these solutions, nitrate is an aggressive ion with respect to pitting of carbon steel while nitrite can be used as an inhibitor. Excessive additions of nitrite increase the risk of generating unstable nitrogen compounds during waste processing, and insufficient additions of nitrite could increase the risk of corrosion-induced failure. Thus there are strong incentives to obtain a fundamental understanding of the role of nitrite in pitting corrosion prevention with these solution chemistries. In this dissertation, both a 1-D and a 2-D model are used to study the pitting mechanism as a function of nitrite/nitrate ratios. The 1-D model used BAND(J) to test a reaction mechanism for the passivation behavior by comparing the predicted Open Circuit Potential (OCP) with OCP data from experiments at different NO2-/NO3- ratio. The model predictions are compared with Cyclic Potentiodynamic Polarization (CPP) experiments. A 2-D model was developed for the propagation of a pit in iron by writing subroutines for finite element software of GAMBIT and FIDAP. Geometrically distributed anodic and cathodic reactions are assumed. The results show three partial explanations describing the inhibition influence of nitrite to iron corrosion: the competing reduction reaction of nitrate to nitrite, the formation of Fe(OH)+, and the function of the porous film. The current distributions and the effect of porosity of the film on pH are also explained. The calculation results also show that rate of pit growth decreases as the pit diameter increases until it reaches a constant value. The profile of the local current density on the pit wall is parabolic for small pits and it changes to a linear distribution for large pits. The model predicts that addition of nitrite will decrease the production of ferrous ions and those can prevent iron from

  9. Pitting corrosion detection in stainless steels using ultrasounds; Deteccion de la corrosion por picadura en aceros inoxidables empleando ultrasonidos

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, C.; Biezma, M. V.

    2014-04-01

    Passive metallic systems are able to develop in a spontaneous way a protective layer on the metallic surface that offers excellent corrosion resistance since really in a physical barrier for the reaction with the environment. However, some factors can break locally this layer, promoting one of the most insidious attack, pitting corrosion, which produces local chemical conditions that favouring the corrosive process causing defects in the material, as externals and internals ones, with a random distribution on the metal surface. In this work, ultrasounds non destructive technique has been employed using as variable the maximum amplitude of the back wall echo in order to detect this type of attack. The material employed is an austenitic stainless steel AISI 304, wherein appear several defectology distributions as superficial such as depths simulating pits. (Author)

  10. Corrosion behaviour of hot dip zinc and zinc-aluminium coatings on steel in seawater

    Indian Academy of Sciences (India)

    Yan Li

    2001-08-01

    A comparative investigation of hot dip Zn–25Al alloy, Zn–55Al–Si and Zn coatings on steel was performed with attention to their corrosion performance in seawater. The results of 2-year exposure testing of these at Zhoushan test site are reported here. In tidal and immersion environments, Zn–25Al alloy coating is several times more durable than zinc coating of double thickness. At long exposure times, corrosion rate for the Zn–25Al alloy coating remains indistinguishable from that for the Zn–55Al–Si coating of similar thickness in tidal zone, and is two to three times lower than the latter in immersion zone. The decrease in tensile strength suggested that galvanized and Zn–55Al–Si coated steel suffer intense pitting corrosion in immersion zone. The electrochemical tests showed that all these coatings provide cathodic protection to the substrate metal; the galvanic potentials are equal to – 1,050, – 1,025 and – 880 mV (SCE) for zinc, Zn–25Al alloy and Zn–55Al–Si coating, respectively, which are adequate to keep the steel inside the immunity region. It is believed that the superior performance of the Zn–25Al alloy coating is due to its optimal combination of the uniform corrosion resistance and pitting corrosion resistance. The inferior corrosion performance by comparison of the Zn coating mainly results from its larger dissolution rate, while the failure of the Zn–55Al–Si coating is probably related to its higher susceptibility to pitting corrosion in seawater.

  11. Exfoliation Corrosion and Pitting Corrosion and Their Role in Fatigue Predictive Modeling: State-of-the-Art Review

    Directory of Open Access Journals (Sweden)

    David W. Hoeppner

    2012-01-01

    Full Text Available Intergranular attack (IG and exfoliation corrosion (EC have a detrimental impact on the structural integrity of aircraft structures of all types. Understanding the mechanisms and methods for dealing with these processes and with corrosion in general has been and is critical to the safety of critical components of aircraft. Discussion of cases where IG attack and exfoliation caused issues in structural integrity in aircraft in operational fleets is presented herein along with a much more detailed presentation of the issues involved in dealing with corrosion of aircraft. Issues of corrosion and fatigue related to the structural integrity of aging aircraft are introduced herein. Mechanisms of pitting nucleation are discussed which include adsorption-induced, ion migration-penetration, and chemicomechanical film breakdown theories. In addition, pitting corrosion (PC fatigue models are presented as well as a critical assessment of their application to aircraft structures and materials. Finally environmental effects on short crack behavior of materials are discussed, and a compilation of definitions related to corrosion and fatigue are presented.

  12. Pitting corrosion of A357 aluminium alloy obtained by semisolid processing

    Energy Technology Data Exchange (ETDEWEB)

    Bastidas, J.M.; Polo, J.L.; Torres, C.L. [National Centre for Metallurgical Research (CSIC), Madrid (Spain); Forn, A.; Baile, M.T. [Polytechnic Univ. of Catalonia, Vilanova i la Geltru (Spain)

    2001-09-01

    This paper studies the pitting corrosion of a structural component of A357 aluminium alloy obtained by a semisolid metal forming process. The mechanical properties of the A357 alloy were improved by applying standard heat treatments T5 and T6. Impedance measurements were conducted at the rest potential and polarisation curves were plotted using a 3% NaCl test solution. After polarisation experiments the specimens were analysed by scanning electron microscopy. The corrosion process is favoured through the eutectic regions. The results show that T6 heat treatment improved the corrosion resistance of the A357 aluminium alloy. (orig.)

  13. Pitting Corrosion of 316L Stainless Steel under Low Stress below Yield Strength

    Institute of Scientific and Technical Information of China (English)

    L(U) Shengjie; CHENG Xuequn; LI Xiaogang

    2012-01-01

    Pitting corrosion of 316L stainless steel (316L SS) under various stress was studied by potentiodynamic polarization,electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis in 3.5% NaCl solution.The results of polarization curves show that,with the increase of the stress,the pitting potentials and the passive current density markedly decrease firstly (180 MPa),and then increase greatly (200 MPa).The corresponding surface morphologies of the samples after the polarization test well correspond to the results.Mott-Schottky analysis proved the least Cl- adsorbed to the surface of passive film with more positive flat potential,indicating that a moderate stress could increase the pitting corrosion resistance of 316L SS in 3.5% NaCl solution.

  14. ANALYSIS OF PITTING CORROSION ON AN INCONEL 718 ALLOY SUBMITTED TO AGING HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    Felipe Rocha Caliari

    2014-10-01

    Full Text Available Inconel 718 is one of the most important superalloys, and it is mainly used in the aerospace field on account of its high mechanical strength, good resistance to fatigue and creep, good corrosion resistance and ability to operate continuously at elevated temperatures. In this work the resistance to pitting corrosion of a superalloy, Inconel 718, is analyzed before and after double aging heat treatment. The used heat treatment increases the creep resistance of the alloy, which usually is used up to 0.6 Tm. Samples were subjected to pitting corrosion tests in chloride-containing aqueous solution, according to ASTM-F746-04 and the procedure described by Yashiro et al. The results of these trials show that after heat treatment the superalloy presents higher corrosion resistance, i.e., the pitting corrosion currents of the as received surfaces are about 6 (six times bigger (~0.15 mA than those of double aged surfaces (~0.025 mA.

  15. ELECTROCHEMICAL FEATURES DURING PITTING CORROSION OF LY12 ALUMINUM ALLOY IN DIFFERENT NEUTRAL SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    F.H. Cao; Z. Zhang; Y.L. Cheng; J.F. Li; J.Q. Zhang; C.N. Cao

    2003-01-01

    The electrochemical features of commercial airframe material, Al alloy LY12, in 0. 349mol/L neutral sodium chloride (NaCl) and sodium sulfate (Na2SO4) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The microstructure of the as-tested samples was studied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different fe atures, indicating that the Cl- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO2-4 solution isn't easy to dissolve, and it will cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.

  16. Hot Corrosion of Coated Single Crystal Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Simms, N. J.; Encinas-Oropesa, A.; Nicholls, J.R. [Cranfield University, Power Generation Technology Centre, Cranfield, Beds, MK43 0AL (United Kingdom)

    2004-07-01

    Gas turbines are at the heart of many modern power systems, with combined cycle power generation utilising natural gas being an effective way of reducing environmental emissions compared to conventional pulverized coal fired plants. The development of gas turbine technology has been focused on increasing its efficiency. However, the lives of the hot gas path components within these gas turbines are also critical to the viability of the power systems. Single crystal superalloys have been developed for use with clean fuel/air but are now being used in industrial gas turbines that may need to run with dirtier fuel/air. Indeed, gas turbine based power systems are being evaluated in which solid fuels (e.g. coal and/or biomass) are gasified to produce fuel gases, which introduces the potential for significant corrosive and erosive damage to gas turbine blades and vanes. The performance of these materials, with coatings, has to be determined before they can be used with confidence in dirtier fuel environments. This paper reports results from a series of laboratory tests carried out using the 'deposit replenishment' technique to investigate the sensitivity of candidate materials to exposure conditions anticipated in such gas turbines. The materials investigated have included CMSX-4 and SC{sup 2}-B (both bare and with Pt-Al and Amdry 997 coatings) as well as conventional nickel based superalloys such as IN738LC for comparison. The exposure conditions within the laboratory tests have covered ranges of SO{sub x} (50 and 500 vpm) and HCl (0 and 500 vpm) in air, as well as 4/1 (Na/K){sub 2}SO{sub 4} deposits, with deposition fluxes of 1.5, 5 and 15 {mu}g/cm{sup 2}/h, for periods of up to 500 hours at 700 and 900 deg. C. Data on the performance of materials has been obtained using dimensional metrology: pre-exposure contact measurements and post-exposure measurements of features on polished cross-sections. These measurement methods allow distributions of damage data to

  17. Impact of chlorinated disinfection on copper corrosion in hot water systems

    Energy Technology Data Exchange (ETDEWEB)

    Montes, J. Castillo [Centre Scientifique et Technique du Bâtiment Nantes, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 03 (France); Laboratoire des Sciences de l’Ingénieur pour l’Environnement, UMR-CNRS 7356, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1 (France); Hamdani, F. [Laboratoire des Sciences de l’Ingénieur pour l’Environnement, UMR-CNRS 7356, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1 (France); Creus, J., E-mail: jcreus@univ-lr.fr [Laboratoire des Sciences de l’Ingénieur pour l’Environnement, UMR-CNRS 7356, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1 (France); Touzain, S. [Laboratoire des Sciences de l’Ingénieur pour l’Environnement, UMR-CNRS 7356, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1 (France); Correc, O. [Centre Scientifique et Technique du Bâtiment Nantes, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 03 (France)

    2014-09-30

    Highlights: • Impact of disinfectant treatment on the durability of copper pipes. • Synergy between disinfectant concentration and temperature. • Pitting corrosion of copper associated to the corrosion products formation on copper. - Abstract: In France, hot water quality control inside buildings is occasionally ensured by disinfection treatments using temperature increases or addition of sodium hypochlorite (between 0.5 ppm and 1 ppm residual free chlorine). This disinfectant is a strong oxidiser and it could interact with metallic pipes usually used in hot water systems. This work deals with the study of the impact of these treatments on the durability of copper pipes. The objective of this work was to investigate the influence of sodium hypochlorite concentration and temperature on the copper corrosion mechanism. Copper samples were tested under dynamic and static conditions of ageing with sodium hypochlorite solutions ranging from 0 to 100 ppm with temperature at 50 °C and 70 °C. The efficiency of a corrosion inhibitor was investigated in dynamic conditions. Visual observations and analytical analyses of the internal surface of samples was studied at different ageing duration. Corrosion products were characterised by X-ray diffraction and Raman spectroscopy. Temperature and disinfectant were found to considerably affect the copper corrosion mechanism. Surprisingly, the corrosiveness of the solution was higher at lower temperatures. The temperature influences the nature of corrosion products. The protection efficiency is then strongly depend on the nature of the corrosion products formed at the surface of copper samples exposed to the aggressive solutions containing different concentration of disinfectant.

  18. Effect of halide ions on passivation and pitting corrosion of copper in alkaline solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gad Allah, A.G.; Abou-Romia, M.M.; Badawy, W.A.; Rehan, H.H. (Cairo Univ., Gizeh (Egypt). Dept. of Chemistry)

    1991-11-01

    The passivity of copper in NaOH and borate buffer solutions containing chloride, bromide and fluoride ions was studied by using cyclic voltammetry and potentiostatic current transient measurements. At scan rates >> 20 mVs{sup -1}, the addition of halide ions does not nearly affect the cyclic voltammograms in the absence of pitting. But they differ considerably in presence of pitting. The pitting potential was found to depend on the solution pH and decreased linearly with increase of logarithm of halide ion concentration. The current transients in the passivity as well as in the pitting potential regions were analyzed. Before the pitting, i-time curves were rather similar to those obtained in the plain solutions. At times > 20 seconds, the current varies linearly with the reciprocal of the square root of time indicating diffusional characteristics of the metal corrosion through the passive layer. In presence of pitting, the pitting current versus time relations fit the Engell-Stolica equation. (orig.).

  19. Contribution to the Study of Effects of Surface State of Welded Joints in Stainless Steel Upon Resistance Towards Pitting Corrosion

    Directory of Open Access Journals (Sweden)

    Juraga, I.

    2007-01-01

    Full Text Available Successful corrosion resistance of stainless steels is based on their natural ability of passivation, i.e. formation of film of chromium oxides that prevents corrosion in many environments. Any nonuniformity of surface layers may be initial spot for corrosion processes and damages. In this contribution, beside real corrosion damages occurred in practice, results of testing of pitting corrosion resistance of weld beads made applying TIG process on AISI 316L steel grade are presented. SEM and EDX testing, as well as electrochemical corrosion testing confirmed adverse effects of heat tints zones upon corrosion resistance of stainless steels.

  20. Controlling internal corrosion of oil and gas pipelines : the systematic treatment of pitting sequence (SToPS) program

    Energy Technology Data Exchange (ETDEWEB)

    Doiron, A.; Chu, F.Y.; Papavinasam, S. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Materials Technology Laboratory

    2009-07-01

    The oil and gas pipeline industry relies on the use of carbon and low-alloy steels. As such, there is a need to predict the corrosivity of brines containing carbon dioxide (CO{sub 2}) when designing production equipment and transportation facilities. A true industry-standard approach to predicting CO{sub 2} and hydrogen sulphide (H{sub 2}S) corrosion does not exist, but there are similarities in existing approaches and models. This paper reviewed the Systematic Treatment of Pitting Sequence (SToPS) software program developed by the materials assessment team at Natural Resources Canada to predict the internal pitting corrosion rate of multiphase, oil producing, gas producing, oil transmission, and gas transmission pipelines. The main output of SToPS is the prediction of how long the pipe is safe. SToPS considers the pipeline to be safe until the depth of the deepest pit is 50 percent of the pipe wall thickness. In addition, SToPS predicts pH, wall shear stress, flow regime, as well as the probability of pitting corrosion. SToPS requires details about pipeline properties, production conditions of the pipeline and gas composition in order to accurately predict the pitting corrosion. SToPS calculates the pitting corrosion rate by combining the effect of 11 different operational parameters. This paper explained how each of these components affects the pitting corrosion rate and how to calculate their individual corrosion rates. The paper showed that each operational parameter can alter the pitting corrosion rate. There are currently 2 versions of SToPS, notably SToPS v1.1, and SToPS v2.0 which produces 7 different graphs to help the user understand the corrosion occurring in their pipeline over the production periods. 16 refs., 1 tab., 6 figs.

  1. Microscopic investigation of pitting corrosion in plasma nitrided austenitic stainless steel; Mikroskopische Untersuchung von Lochkorrosion an plasmanitriertem austenitischem rostfreiem Stahl

    Energy Technology Data Exchange (ETDEWEB)

    Escalada, Lisandro; Simison, Silvia N. [Univ. of Mar del Plata (Argentina). Faculty of Engineering; Bruehl, Sonia P. [National Univ. of Technology, Concepcion del Uruguay (Argentina). Surface Engineering Group

    2014-10-01

    UNS 31603 austenitic stainless steel was nitrided using different techniques, and pitting corrosion resistance was analysed in a chloride solution. All nitriding techniques, LEII, PI. and convectional DC nitriding produced a nitrided layer called S phase which is corrosion resistant. Pits morphology and layer structure was investigated using optical and electronic microscopy, SEM-FIB, EDS, and a 3D reconstruction of a pit was assessed using FIB tomography. It was concluded that pits are initiated in MnS inclusions and a channel was generated passing through the nitrided layer, connecting the steel with the electrolyte. Base alloy dissolution was observed beneath the nitrided layer.

  2. EVOLUTION OF THE ELECTROCHEMICAL CHARACTERISTICS DURING PITTING CORROSION OF PURE ALUMINUM IN SODIUM CHLORIDE SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Z. Zhang; C. Cai; F.H. Cao; Z.N. Gao; J.Q. Zhang; C.N. Cao

    2005-01-01

    The corrosion behavior of pure aluminum in neutral 3.0% (mass fraction) sodium chloride (NaCl) solution has been studied using electrochemical impedance spectroscopy (ELS) measurement in conjunction with the scanning electron microscopy (SEM) technique. EIS information on the evolution of pitting corrosion over a period of 15 days has been obtained and analyzed with equivalent circuit technique. The results shown that, during the ensemble constant immersion time, two time constants involved, the high frequency one originated from the protective layer on the corroding surface while the low frequency one from the diffusion process or the corrosion reaction and so on. And there existed a period for oxide film to growth and thickening prior to the commencement of the attacking of chloride ions to the substrate. Meanwhile, good relationship between EIS and the material corrosion type/severity has been obtained, which has been interpreted according to the characteristics of corrosion process such as auto acceleration of pitting corrosion and the protection of local anodic reaction to the area around them.

  3. A point defect model for the general and pitting corrosion on iron-oxide-electrolyte interface deduced from current oscillations

    CERN Document Server

    Pagitsas, M; Sazou, D

    2003-01-01

    Analysis of the passive-active oscillatory region of the Fe-0.75 M H sub 2 SO sub 4 system, perturbed by adding small amounts of halide species, allow the distinction between pitting and general corrosion. Complex periodic and aperiodic current oscillations characterize pitting corrosion whereas monoperiodic oscillations of a relaxation type indicate general corrosion. A point defect model (PDM) is considered for the microscopic description of the growth and breakdown of the iron oxide film. The physicochemical processes leading to different types of corrosion can be clarified in terms of the PDM. Occupation of an anion vacancy by a halide ion results in the localized attack of the passive oxide and pitting corrosion. On the other hand, the formation of surface soluble iron complexes is related to the uniform dissolution of the passive oxide and general corrosion.

  4. Internal corrosion of carbon steel piping in hot aquifers service

    Directory of Open Access Journals (Sweden)

    Simičić Miloš V.

    2011-01-01

    Full Text Available Internal corrosion of carbon steel pipelines is a major problem encountered in water service. In terms of prediction of the remaining lifetime for water pipelines based on the corrosion allowance, the three main approaches are corrosion modelling, corrosion inhibitor availability, and corrosion monitoring. In this study we used two theoretical corrosion models, CASSANDRA and NORSOK M-506 of quite different origin in order to predict uniform corrosivity of hot aquifers in eight different pipelines. Because of the varying calculation criteria for the different models, these can give very different corrosion rate predictions for the same data input. This is especially true under conditions where the formation of protective films may occur, such as at elevated temperatures. The evaluation of models was conducted by comparison using weight-loss coupons and three corrosion inhibitors were obtained from commercial suppliers. The tests were performed during the 60-day period. Even though inhibitors’ efficiencies of 98% had been achieved in laboratory testing, inhibitors’ availabilities of 85% have been used due to logistics problems and other issues. The results, given in mmpy, i.e. millimeter per year, are very consistent with NORSOK M-506 prediction. This is presumably because the model considers the effect of the formation of a passive iron carbonate film at temperatures above 80 °C and significant reduction in corrosion rate. Corrosion inhibitor A showed a better performance than inhibitors B and C in all cases but the target corrosion rates of less than 0.1 mmpy were achieved for all inhibitors. The chemical type of corrosion inhibitor A is based on quaternary amines mixed with methanol, isopropyl alcohol, xylene and ethylbenzene. Based on the obtained results the carbon steel lifetime of 30 years, provided proper inhibitors are present and 3mm corrosion allowance, can be achieved for hot aquifers service with presented water compositions.

  5. Effect of boron addition on pitting corrosion resistance of modified 9Cr-1Mo steel: Application of electrochemical noise

    Energy Technology Data Exchange (ETDEWEB)

    Pujar, M.G., E-mail: pujar55@gmail.com [Metallurgy and Materials Group (MMG), Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Das, C.R.; Thirunavukkarasu, S.; Kamachi Mudali, U.; Bhaduri, A.K. [Metallurgy and Materials Group (MMG), Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Brijitta, J.; Tata, B.V.R. [Materials Science Group (MSG), Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India)

    2011-10-17

    Highlights: {yields} Weibull probability plots separate pitting and passive corrosion events. {yields} Gumbel distribution analysis gives maximum metastable pit depths. {yields} Addition of boron results in superior pitting corrosion resistance in 0.1 M NaCl. {yields} Incorporation of B into M{sub 23}C{sub 6} carbides refines them and improves pitting resistance. {yields} Coarse M{sub 23}C{sub 6} carbides and delta-ferrite result in inferior pitting resistance. - Abstract: 9Cr-1Mo steels indigenously melted with the addition of boron (Alloy B) and without it (Alloy D) along with Alloy C (without boron addition with minor changes in the trace element concentrations) were studied for their pitting corrosion resistance in 0.001 M, 0.01 M, 0.05 M and 0.1 M sodium chloride solutions using electrochemical noise (EN) technique. Weibull probability plots were used to determine the pit embryo generation rates. Gumbel extreme value analysis was conducted to determine the maximum metastable as well as stable pit radii. The analysis of the data showed superior pitting corrosion resistance of the Alloy B compared to Alloy C as well as Alloy D.

  6. 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.

  7. ELECTROCHEMICAL NOISE FEATURES OF PURE ALUMINUM DURING PITTING CORROSION IN NEUTRAL NaCl SOLUTION

    Institute of Scientific and Technical Information of China (English)

    F.H. Cao; Z. Zhang; Y.L. Cheng; J.F. Li; J.Q. Zhang; J.M. Wang; C.N. Cao

    2003-01-01

    Spontaneous electrochemical noise (EN) can be a rich source of information concern-ing the processes simultaneously occurring at a corroding interface. Potential noisefluctuations during the free corrosion of pure aluminum in different concentration ofneutral sodium chloride solution are investigated, and the breakdown and restorationof passive metal's film are studied using potentiodynamic scanning (PDS) measure-ments and electrochemical impedance spectroscopy (EIS) technique. Two capacitanceloops are observed in the Nyquist plots in two kinds of concentration, and the corro-sion process is under activation control at first, then become diffusion control withinthe oxide film and corrosion products of (Al(OH)p-m Cl-m) accumulated on the surfaceof the corroding electrode. It is suggested that the pitting corrosion is much easierto occur for pure aluminum in 7.0wt% than in 2.0wt% NaCl solution, and the highconcentration of chloride ion in solution inhibits the repassivation of a metastable pit.The corrosion rate deterministic step does not involve Cl-.

  8. ELECTROCHEMICAL NOISE FEATURES OF PURE ALUMINUM DURING PITTING CORROSION IN NEUTRAL NaCl SOLUTION

    Institute of Scientific and Technical Information of China (English)

    F.H.Cao; J.Q.Zhang; 等

    2003-01-01

    Spontaneous electrochemical noise(EN)can be a rich source of information concern-ing the processes simultaneously occurring at a corroding interface.Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride solution are investigated,and the breakdowm and restoration of passive metal's film are studied using potentiodynamic scanning(PDS)measure-ments and electrochemical impedance spectroscopy(EIS)technique.Two capacitance loops are observed in the Nyquist plots in two kinds of concentration,and the corro-sion process is under activation control at first,then become diffusion control within the oxide film and corrosion products of (Al(OH)p-mClm-)accumulated on the surface of the corroding electrode.It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wt% than in 2.0wt% NaCl solution,and the high concentration of chloride ion in solution inhibits the repassivation of a metastable pit.The corrosion rate deterministic step does not involve Cl-.

  9. CREVICE CORROSION & PITTING OF HIGH-LEVEL WASTE CONTAINERS: INTEGRATION OF DETERMINISTIC & PROBABILISTIC MODELS

    Energy Technology Data Exchange (ETDEWEB)

    JOSEPH C. FARMER AND R. DANIEL MCCRIGHT

    1997-10-01

    A key component of the Engineered Barrier System (EBS) being designed for containment of spent-fuel and high-level waste at the proposed geological repository at Yucca Mountain, Nevada is a two-layer canister. In this particular design, the inner barrier is made of a corrosion resistant material (CRM) such as Alloy 625 or C-22, while the outer barrier is made of a corrosion-allowance material (CAM) such as carbon steel or Monel 400. An integrated predictive model is being developed to account for the effects of localized environmental conditions in the CRM-CAM crevice on the initiation and propagation of pits through the CRM.

  10. Hot Corrosion Studies in Coal Fired Boiler Environment

    Directory of Open Access Journals (Sweden)

    Kamal Subhash

    2014-07-01

    Full Text Available Hot corrosion behaviour of the bare and D-gun coated superfer 800H exposed to low temperature super-heater zone of the coal fired boiler of Guru Nanak Dev Thermal Power Plant, Bathinda, Punjab, India. The specimens were hanged in the platen super-heater of coal fired boiler where the gas temperature was around 900 °C ±10 °C. Hot corrosion experiments were performed for 10 cycles, each cycle consisting of 100 hours exposure followed by 1 hour cooling at ambient temperature. Weight change measurements were done at the end of each cycle. The weight change data used for predicting hot corrosion behaviour of the coated alloys after the total exposure of 1000 hours. The different phases and their distribution in the hot corroded specimens were analysed with the help of FE-SEM/EDS and X-ray mapping.

  11. Evaluation of pitting corrosion with electrochemical impedance spectroscopy (EIS) for alumina/aluminium alloys composites

    Energy Technology Data Exchange (ETDEWEB)

    Odegard, C.; Bronson, A. [Univ. of Texas, El Paso, TX (United States)

    1998-12-31

    The pitting susceptibility of monolithic aluminum 6061 alloy and alumina/aluminum alloy composites has been analyzed by using electrochemical impedance spectroscopy and subsequent comparison with their polarization scans. The composites consisting of 0.10 and 0.15 volume fraction of alumina particles (VFAP) and the monolith as cylindrical electrodes were rotated at 1500 rpm while immersed in NaCl solution. The passive currents of the composites were greater than that of the monolith as per the polarization scans. The impedance spectra were acquired at constant potential increments along the passive region up to the pitting potential. The impedance spectra represented by semicircles on a Nyquist plot acquired above the pitting potential collapsed underneath the spectra obtained in the passive region near the corrosion potential for the monolithic alloy and composites. The impedance spectra modeled with a simplified equivalent circuit indicate that the effective capacitance for the composites is greater than that of the monolithic alloy.

  12. Mechanism of Pitting Corrosion Prevention by Nitrite in Carbon Steel Exposed to Dilute Salt Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Philip E. Zapp; John W. Van Zee

    2002-02-01

    The research has developed a broad fundamental understanding of the inhibition action of nitrite ions in preventing nitrate pitting corrosion of carbon steel tanks containing high-level radioactive waste. This fundamental understanding can be applied to specific situations during waste removal for permanent disposition and waste tank closure to ensure that the tanks are maintained safely. The results of the research provide the insight necessary to develop solutions that prevent further degradation.

  13. Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 High Strength Aluminum Alloy

    Science.gov (United States)

    2013-06-01

    was not used to measure the transition from corrosion pit to long crack [25]. . . . . . . . . . . 22 3.1 Composition of a typical sample of 7075 -T6...lives. 24 III. Methodology 3.1 Material Research was conducted using 7075 -T6 aluminum. This alloy is commonly used in aerospace applications and as a... material properties of this alloy. It is important to note that these properties were also used in all finite element models. Table 3.1: Composition of

  14. Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

    OpenAIRE

    Raffi Mohammed; G. Madhusudhan Reddy; K. Srinivasa Rao

    2015-01-01

    The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy (OM) and field emission scanning electron microscopy (FESEM). Energy back scattered diffraction (EBSD) method was used to determine t...

  15. Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 Under Biaxial and Uniaxial Fatigue

    Science.gov (United States)

    2014-06-19

    general conical , hemispherical, and roughly saucer-shaped for steel and many alloys [41], as shown in Figure 2.2. Pits usually nucleate at chemical or...performed in a piezoelectric resonance system. Their results indicated that the presence of corrosion pits notably reduces the fatigue life of the

  16. Atomic-scale decoration for improving the pitting corrosion resistance of austenitic stainless steels

    Science.gov (United States)

    Zhou, Y. T.; Zhang, B.; Zheng, S. J.; Wang, J.; San, X. Y.; Ma, X. L.

    2014-01-01

    Stainless steels are susceptible to the localized pitting corrosion that leads to a huge loss to our society. Studies in the past decades confirmed that the pitting events generally originate from the local dissolution in MnS inclusions which are more or less ubiquitous in stainless steels. Although a recent study indicated that endogenous MnCr2O4 nano-octahedra within the MnS medium give rise to local nano-galvanic cells which are responsible for the preferential dissolution of MnS, effective solutions of restraining the cells from viewpoint of electrochemistry are being tantalizingly searched. Here we report such a galvanic corrosion can be greatly resisted via bathing the steels in Cu2+-containing solutions. This chemical bath generates Cu2-δS layers on the surfaces of MnS inclusions, invalidating the nano-galvanic cells. Our study provides a low-cost approach via an atomic scale decoration to improve the pitting corrosion resistance of stainless steels in a volume-treated manner.

  17. Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

    Directory of Open Access Journals (Sweden)

    Raffi Mohammed

    2015-09-01

    Full Text Available The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy (OM and field emission scanning electron microscopy (FESEM. Energy back scattered diffraction (EBSD method was used to determine the phase analysis, grain size and orientation image mapping. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance in aerated 3.5% NaCl environment using a GillAC electrochemical system. The investigation results showed that the selected Cr–Mn–N type electrode resulted in a maximum reduction in delta-ferrite and improvement in pitting corrosion resistance of the weld zone was attributed to the coarse austenite grains owing to the reduction in active sites of the austenite/delta ferrite interface and the decrease in galvanic interaction between austenite and delta-ferrite.

  18. 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.

  19. 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.

  20. Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

    Institute of Scientific and Technical Information of China (English)

    In-Joon SON; Hiroaki NAKANO; Satoshi OUE; Shigeo KOBAYASHI; Hisaaki FUKUSHIMA; Zenji HORITA

    2009-01-01

    The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl3 and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m2 in a solution containing 1.53 mol/L H2SO4 and 0.018 5 mol/L Al2(SO4)3-16H2O at 20 ℃. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.

  1. Fouling and the inhibition of salt corrosion. [hot corrosion of superalloys

    Science.gov (United States)

    Deadmore, D. L.; Lowell, C. E.

    1980-01-01

    In an attempt to reduce fouling while retaining the beneficial effects of alkaline earth inhibitors on the hot corrosion of superalloys, the use of both additives and the intermittent application of the inhibitors were evaluated. Additions of alkaline earth compounds to combustion gases containing sodium sulfate were shown to inhibit hot corrosion. However, sulfate deposits can lead to turbine fouling in service. For that reason, dual additives and intermittant inhibitor applications were evaluated to reduce such deposit formation. Silicon in conjunction with varium showed some promise. Total deposition was apparently reduced while the inhibition of hot corrosion by barium was unimpaired. The intermittant application of the inhibitor was found to be more effective and controllable.

  2. LabVIEW 2010 Computer Vision Platform Based Virtual Instrument and Its Application for Pitting Corrosion Study.

    Science.gov (United States)

    Ramos, Rogelio; Zlatev, Roumen; Valdez, Benjamin; Stoytcheva, Margarita; Carrillo, Mónica; García, Juan-Francisco

    2013-01-01

    A virtual instrumentation (VI) system called VI localized corrosion image analyzer (LCIA) based on LabVIEW 2010 was developed allowing rapid automatic and subjective error-free determination of the pits number on large sized corroded specimens. The VI LCIA controls synchronously the digital microscope image taking and its analysis, finally resulting in a map file containing the coordinates of the detected probable pits containing zones on the investigated specimen. The pits area, traverse length, and density are also determined by the VI using binary large objects (blobs) analysis. The resulting map file can be used further by a scanning vibrating electrode technique (SVET) system for rapid (one pass) "true/false" SVET check of the probable zones only passing through the pit's centers avoiding thus the entire specimen scan. A complete SVET scan over the already proved "true" zones could determine the corrosion rate in any of the zones.

  3. Effect of Pulsed Current TIG Welding Parameters on Pitting Corrosion Behaviour of AA6061 Aluminium Alloy

    Institute of Scientific and Technical Information of China (English)

    T. Senthil Kumar; V. Balasubramanian; M. Y. Sanavullah; S. Babu

    2007-01-01

    Medium strength aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding process for aluminium alloy is frequently TIG (tungsten inert gas) welding due to its comparatively easier applicability and better economy.In the case of single pass TIG 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 use of pulsed current parameters has been found to improve the mechanical properties of the welds compared to those of continuous current welds of this alloy due to grain refinement occurring in the fusion zone. A mathematical model has been developed to predict pitting corrosion potential of pulsed current TIG welded AA6061 aluminium alloy.Factorial experimental design has been used to optimize the experimental conditions. Analysis of variance technique has been used to find out the significant pulsed current parameters. Regression analysis has been used to develop the model. Using the developed model pitting corrosion potential values have been estimated for different combinations of pulsed current parameters and the results are analyzed in detail.

  4. Evaluation of pitting corrosion of Al-Mg-Mn-Sc-Zr alloy in EXCO solution by EIS

    Institute of Scientific and Technical Information of China (English)

    PENG Yong-yi; YIN Zhi-min; LI San-hua

    2005-01-01

    In order to evaluate the degree and severity of Al-Mg-Mn-Sc-Zr alloy in exfoliation corrosion(EXCO) solution quickly and nondestructively, electrochemical impedance spectroscopy(EIS) technique was employed. The Al-Mg-Mn-Sc-Zr alloy suffers pitting corrosion in the EXCO solution. During pit incubation, the Nyquist diagram is composed of a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency. The inductive arc fades with immersion time, and the beginning of pitting corrosion and the appearance of two capacitive arcs have simultaneity. During pit propagation, the Nyquist diagram is composed of two overlapped capacitive arcs. As time goes on, two time constants are more clearly distinguished. The high frequency and low frequency capacitive arc are aroused by passive surface and new interface, respectively. An equivalent circuit is designed to fit EIS, and the experimental results and the fitted results have good correspondence. The degree and severity of pitting corrosion can be obtained by the features of EIS and comparing the fitted values of parameters at different times.

  5. The role of the interaction between oxygen and catechol in the pitting corrosion of steel in alkaline sulfide solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, S.; Kelly, R.G. [Univ. of Virginia, Charlottesville, VA (United States)

    1995-12-01

    Black liquor corrosivity is shown to depend on the interaction of the chemical species present. Specifically, an interaction between oxygen and 1,2-dihydroxybenzene compounds (catechols) in alkaline sulfide solutions leads to a distinct increase in the severity of the attack. This increased corrosivity is explained in terms of the oxidation of catechol leading to increased open circuit potentials for steel. The importance of the ratio of sulfide concentration to hydroxyl concentration in the initiation of pitting is stressed. The possible role of catechol in stabilizing metastable pits is also discussed.

  6. Equivalent Crack Size Modelling of Corrosion Pitting in an AA7050-T7451 Aluminium Alloy and its Implications for Aircraft Structural Integrity

    Science.gov (United States)

    2012-09-01

    provides a quantitative measurement of the spatial density of pits14 but there is no quantitative measurement of corrosion pit metrics without...and stress corrosion cracking in the 7075 T6 components of the RAAF C-130 Hercules...Post-Fracture Examination................................................................... 16 3.5.3 Surface Roughness Measurement

  7. Voltammetric current oscillations due to general and pitting corrosion of tantalum: Implications for electrochemical-mechanical planarization

    Energy Technology Data Exchange (ETDEWEB)

    Sulyma, Christopher M. [Department of Physics, Clarkson University, Potsdam, NY 13699-5820 (United States); Roy, Dipankar, E-mail: samoy@clarkson.ed [Department of Physics, Clarkson University, Potsdam, NY 13699-5820 (United States)

    2010-09-15

    Anodic corrosion of Ta is examined for potential applications in electrochemical-mechanical planarization (ECMP) of diffusion barriers. This strategy involves electro-oxidation of Ta in the presence of NO{sub 3}{sup -} (or Br{sup -}) to form mechanically weak surface-oxide films, followed by mechanical removal of the latter. The voltammetric currents exhibit oscillatory behaviour with frequencies that are signature attributes of localised pitting by Br{sup -} or general surface corrosion by NO{sub 3}{sup -}. SEM, voltammetry, and impedance spectroscopy are used to probe these corrosion mechanisms. Apart from their relevance for ECMP, the results also address certain fundamental aspects of pitting and general corrosion of valve metals.

  8. Inhibition of hot salt corrosion by metallic additives

    Science.gov (United States)

    Deadmore, D. L.; Lowell, C. E.

    1978-01-01

    The effectiveness of several potential fuel additives in reducing the effects of sodium sulfate-induced hot corrosion was evaluated in a cyclic Mach 0.3 burner rig. The potential inhibitors examined were salts of Al, Si, Cr, Fe, Zn, Mg, Ca, and Ba. The alloys tested were IN-100, U-700, IN-738, IN-792, Mar M-509, and 304 stainless steel. Each alloy was exposed for 100 cycles of 1 hour each at 900 C in combustion gases doped with the corrodant and inhibitor salts and the extent of attack was determined by measuring maximum metal thickness loss. The most effective and consistent inhibitor additive was Ba (NO3)2 which reduced the hot corrosion attack to nearly that of simple oxidation.

  9. Pitting corrosion in austenitic stainless steel water tanks of hotel trains

    Directory of Open Access Journals (Sweden)

    Moreno, D. A.

    2011-12-01

    Full Text Available The water storage tanks of hotel trains suffered pitting corrosion. To identify the cause, the tanks were subjected to a detailed metallographic study and the chemical composition of the austenitic stainless steels used in their construction was determined. Both the tank water and the corrosion products were further examined by physicochemical and microbiological testing. Corrosion was shown to be related to an incompatibility between the chloride content of the water and the base and filler metals of the tanks. These findings formed the basis of recommendations aimed at the prevention and control of corrosion in such tanks.

    Se han detectado problemas de corrosión por picaduras en los depósitos de agua de trenes hotel. Para identificar las causas se llevó a cabo un detallado estudio metalográfico así como de la composición química de los aceros inoxidables austeníticos utilizados en su construcción. También se realizaron estudios fisicoquímicos y microbiológicos de los productos de corrosión. Se ha encontrado que los problemas de corrosión están relacionados con la incompatibilidad entre el contenido en cloruros del agua y los metales base y de aporte de la soldadura de los tanques. En base a estos hallazgos se proponen una serie de recomendaciones encaminadas a la prevención y control de la corrosión de dichos depósitos.

  10. Role of second phase particles in pitting corrosion of 3003 Al alloy in NaCl solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.; Cheng, Y.F. [Department of Mechanical and Manufacturing Engineering, University of Calgary, AB (Canada)

    2010-03-15

    The second phase particles in 3003 aluminum (Al) alloy were characterized by scanning electron microscope, energy-dispersive X-ray analysis and X-ray diffraction techniques. The role of second phase particles in Al alloy pitting corrosion was investigated by cyclic polarization measurement, and scanning vibrating electrode technique. Results demonstrated that the second phase particles in 3003 Al alloy are mainly Al{sub x}(Fe,Mn) intermetallics, with an average diameter of about 5 {mu}m. The enrichment of Mn in second phase particles forms a galvanic cell effect relative to the adjacent Al alloy substrate. The initiation of pitting corrosion of 3003 Al alloy is the local dissolution of Al substrate around the second phase particles. When a sufficient amount of Al is dissolved away, the second phase particles drop off from the Al substrate, forming large pitting cavities that are usually linked each other. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. LabVIEW 2010 Computer Vision Platform Based Virtual Instrument and Its Application for Pitting Corrosion Study

    Directory of Open Access Journals (Sweden)

    Rogelio Ramos

    2013-01-01

    Full Text Available A virtual instrumentation (VI system called VI localized corrosion image analyzer (LCIA based on LabVIEW 2010 was developed allowing rapid automatic and subjective error-free determination of the pits number on large sized corroded specimens. The VI LCIA controls synchronously the digital microscope image taking and its analysis, finally resulting in a map file containing the coordinates of the detected probable pits containing zones on the investigated specimen. The pits area, traverse length, and density are also determined by the VI using binary large objects (blobs analysis. The resulting map file can be used further by a scanning vibrating electrode technique (SVET system for rapid (one pass “true/false” SVET check of the probable zones only passing through the pit’s centers avoiding thus the entire specimen scan. A complete SVET scan over the already proved “true” zones could determine the corrosion rate in any of the zones.

  12. Phase transition and pitting corrosion behaviour for Mo-implanted aluminium

    Institute of Scientific and Technical Information of China (English)

    张通和; 吴瑜光; 刘培英; 钱卫东

    2002-01-01

    Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of200℃, 400℃ and 500℃. Due to the high temperature and high flux of vacancies and interstitial atoms, the atomdiffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion fluxand dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysisshows thatwhen the aluminium is implanted with Mo ions at a low ion flux (25μA/cm2), the Al5Mo alloy is formed.The atomicratio of Mo/Al of the Al5Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux(50μA/cm2), the phase transition from Al5Mo to Al12Mo appears, and the latter is dominant, which is determined tobe the final phase. The ratio of Mo/Al in Al12Mo is 7.7%. Rutherford backscattering spectroscopy indicates also thatthe Mo/Al atom ratio is ~7% to ~8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al5Mo andAl12Mo are of stoichiometric composition for these alloys. The thicknesses of the Al12Mo alloy layers for Mo-implantedAl with ion doses of 3 × 1017/cm2 and 1 × 1018/cm2 are 550nm and 2000nm, respectively. The pitting corrosion potentialVp increases obviously. It is clear that due to the formation of Al12Mo alloy layer, the pitting corrosion resistance isenhanced.

  13. Effect of hot dip galvanized coating on the corrosion resistance of the external surface of reinforcement steel

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Oezlem; Topuz, Polat [Gedik University Vocational School, Istanbul (Turkey)

    2016-02-01

    Studies have been carried out to investigate the performance of hot dip galvanized coating on reinforcement corrosion. The coated and uncoated concrete specimens were subjected to accelerated corrosion to determine the time to corrosion initiation. The accelerated corrosion test results clearly showed that the specimens with hot dip galvanized coatings performed very well against reinforcement corrosion and were better than uncoated specimens.

  14. Experiment Research on Hot-Rolling Processing of Nonsmooth Pit Surface.

    Science.gov (United States)

    Gu, Yun-Qing; Fan, Tian-Xing; Mou, Jie-Gang; Yu, Wei-Bo; Zhao, Gang; Wang, Evan

    2016-01-01

    In order to achieve the nonsmooth surface drag reduction structure on the inner polymer coating of oil and gas pipelines and improve the efficiency of pipeline transport, a structural model of the machining robot on the pipe inner coating is established. Based on machining robot, an experimental technique is applied to research embossing and coating problems of rolling-head, and then the molding process rules under different conditions of rolling temperatures speeds and depth are analyzed. Also, an orthogonal experiment analysis method is employed to analyze the different effects of hot-rolling process apparatus on the embossed pits morphology and quality of rolling. The results also reveal that elevating the rolling temperature or decreasing the rolling speed can also improve the pit structure replication rates of the polymer coating surface, and the rolling feed has little effect on replication rates. After the rolling-head separates from the polymer coating, phenomenon of rebounding and refluxing of the polymer coating occurs, which is the reason of inability of the process. A continuous hot-rolling method for processing is used in the robot and the hot-rolling process of the processing apparatus is put in a dynamics analysis.

  15. Predictive Models for the Determination of Pitting Corrosion Versus Inhibitor Concentrations and Temperature for Radioactive Sludge in Carbon Steel Waste Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Mickalonis, J.I.

    1998-10-06

    Statistical models have been developed to predict the occurrence of pitting corrosion in carbon steel waste storage tanks exposed to radioactive nuclear waste. The levels of nitrite concentrations necessary to inhibit pitting at various temperatures and nitrate concentrations were experimentally determined via electrochemical polarization and coupon immersion corrosion tests. Models for the pitting behavior were developed based on various statistical analyses of the experimental data. Feed-forward Artificial Neural Network (ANN) models, trained using the Back-Propagation of Error Algorithm, more accurately predicted conditions at which pitting occurred than the logistic regression models developed using the same data.

  16. Prediction for pitting corrosion of AISI type 403 stainless steel in chloride-containing borate buffer solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yancheng [Pennsylvania State Univ. (United States); Macdonald, D.D. [Pennsylvania State Univ. (United States). Center for Electrochemical Science and Technology; Urquidi-Macdonald, M. [Pennsylvania State Univ. (United States). Engineering Science and Mechanics; Engelhardt, G.R. [OLI Systems, Inc. (United States); Dooley, R.B. [Electric Power Research Inst., Palo Alto, CA (United States). Materials and Chemistry Performance Dept.

    2007-07-15

    The prediction of pitting corrosion damage on low-pressure steam turbine (LPST) blade surfaces has been investigated experimentally and the results have been interpreted in terms of the Point Defect Model (PDM) for passivity breakdown and the nucleation of pits. Experimental relationships between the critical breakdown potential (Vc) and the chloride activity aCl- and pH have demonstrated the applicability of the PDM for describing passivity breakdown on AISI Type 403 stainless steel (SS), a commonly employed blade alloy in LPSTs, in chloride-containing borate buffer solutions. The model parameter values, as determined by optimization of the PDM on passivity breakdown data, may be used to predict the nucleation and accumulation of pitting damage on LPST blades under simulated turbine shutdown conditions. In order to evaluate the predictions, integral damage functions (IDFs) and extreme value distributions in pit depth have been measured on samples taken from failed blades recovered from the field (Texas Genco). These data are being used to test the predictions of Damage Function Analysis (DFA), which is based on the PDM and on deterministic models for pit growth and delayed repassivation. However, the success of this analysis critically depends on our ability to define the corrosion evolutionary path. (orig.)

  17. Sour and sweet corrosion of carbon steel : general or pitting or localized or all of the above?

    Energy Technology Data Exchange (ETDEWEB)

    Papavinasam, S.; Doiron, A.; Li, J.; Park, D.Y.; Liu, P. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Materials Technology Laboratory

    2009-07-01

    Carbon steel is used for 80 per cent of all refinery components in refineries, petrochemical plants and oil and gas pipelines. This paper described a model designed to predict internal pitting corrosion of carbon steel in sour and sweet environments. The effects of temperature and partial pressure of carbon dioxide (CO{sub 2}) were investigated experimentally using scanning electron microscopy (SEM) and laser profilometer analyses. Eight carbon steel coupons were placed in a high temperature high pressure rotating cage system. An autoclave was charged with CO{sub 2} and methane. Coupons were then examined using SEM and energy dispersive spectroscopy (EDS). Pit depth and density were evaluated. The obtained data were then filtered using a Gaussian filter to minimize scattering. The study showed that mass loss increased almost linearly as a function of CO{sub 2} partial pressure. An analysis of the surface layers indicated that a compact layer did not form to protect the surface from corrosion. Classical pitting corrosion processes were discussed, and the characteristics of carbon steel corrosion were outlined. 23 refs., 2 tabs., 12 figs.

  18. Synergy effects of Cu and Sn on pitting corrosion resistance of ultra-purified medium chromium ferritic stainless steel

    Science.gov (United States)

    Zhang, XiangJun; Liu, ZhenYu

    2017-03-01

    The influence of combination of Cu and Sn on pitting resistance of ultra-purified medium chromium ferritic stainless steel in 3.5 wt.% NaCl at 25°C was investigated by using electrochemical method. The results show that there is synergy effect between Cu and Sn, and the strong interaction between Cu and Sn in ferritic stainless steels clearly affects their pitting corrosion behaviour in 3.5% NaCl. A mechanism of the synergy of Cu and Sn was discussed.

  19. Acid Pit Stabilization Project (Volume 1 - Cold Testing) and (Volume 2 - Hot Testing)

    Energy Technology Data Exchange (ETDEWEB)

    G. G. Loomis (INEEL); A. P. Zdinak (MSE); M. A. Ewanic (MSE); J. J. Jessmore (INEEL)

    1998-01-01

    During the summer and fall of Fiscal Year 1997, a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Treatability Study was performed at the Idaho National Engineering and Environmental Laboratory. The study involved subsurface stabilization of a mixed waste contaminated soil site called the Acid Pit. This study represents the culmination of a successful technology development effort that spanned Fiscal Years 1994-1996. Research and development of the in situ grout stabilization technique was conducted. Hardware and implementation techniques are currently documented in a patent pending with the United States Patent and Trademark Office. The stabilization technique involved using jet grouting of an innovative grouting material to form a monolith out of the contamination zone. The monolith simultaneously provides a barrier to further contaminant migration and closes voids in the soil structure against further subsidence. This is accomplished by chemical incorporation of contaminants into less soluble species and achieving a general reduction in hydraulic conductivity within the monolith. The grout used for this study was TECT-HG, a relatively dense iron oxide-based cementitious grout. The treatability study involved cold testing followed by in situ stabilization of the Acid Pit. Volume 1 of this report discusses cold testing, performed as part of a ''Management Readiness Assessment'' in preparation for going hot. Volume 2 discusses the results of the hot Acid Pit Stabilization phase of this project. Drilling equipment was specifically rigged to reduce the spread of contamination, and all grouting was performed under a concrete block containing void space to absorb any grout returns. Data evaluation included examination of implementability of the grouting process and an evaluation of the contaminant spread during grouting. Following curing of the stabilized pit, cores were obtained and evaluated for toxicity

  20. Effect of thermal aging on pitting corrosion resistance of 16Cr - 5Ni - 1Mo precipitation hardening stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Karim, R.; Dawood, M.M.A.L.; Mahallawi, I.S.E.L.; Koussy, M.R.E.L. [Cairo University (Egypt). Dept. of Mining, Petroleum and Metallurgy

    2004-12-15

    Specimens of precipitation hardening 16-5-1 stainless steel were solution treated at 1050{sup o}C for 1 h followed by aging at temperatures in the range 400 - 750{sup o}C for various holding times (1 - 16 h). After heat treatment, two types of corrosion test (accelerated and immersion testing) were conducted in 6% ferric chloride solution. The results showed that the pitting corrosion resistance was affected by austenite content, {delta} ferrite and precipitation of molybdenum and chromium carbides. Three critical temperature ranges were identified, which were related to the phases formed: (a) high corrosion rate at 475{sup o}C ({delta} ferrite and M{sub o}2 C); (b) low corrosion rate at 550 - 625{sup o}C (reversed austenite and Laves phase); (c) intermediate corrosion rate at 750{sup o}C (Cr{sub 23} C{sub 6} and TiC). The morphology of the pitting was dependent on the form of the {delta} ferrite and carbides. (author)

  1. Effect of cold deformation on pitting corrosion of 00Cr18Mn15Mo2N0.86 stainless steel for coronary stent application.

    Science.gov (United States)

    Ren, Yibin; Zhao, Haochuan; Liu, Wenpeng; Yang, Ke

    2016-03-01

    The high nitrogen nickel-free stainless steel has offered an alternative to further improve the performance of the coronary stents, and simultaneously avoids the potential harms of nickel element. Both cold deformation and pitting corrosion are very important for coronary stents made of stainless steel. In this work, the effect of cold deformation on the pitting corrosion resistance of a high nitrogen nickel-free stainless steel (00Cr18Mn15Mo2N0.86) in 0.9% saline solution was investigated. The results showed that the pitting corrosion of the steel was nearly unchanged with increases of the cold deformation up to 50%, indicating that the higher nitrogen content can reduce the negative effect of cold deformation on the pitting corrosion resistance, which is beneficial for the long term service of coronary stents in blood vessel.

  2. Crevice corrosion {ampersand} pitting of high-level waste containers: the integration of deterministic {ampersand} probabilistic models (II)

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J.C.

    1997-10-01

    An integrated predictive model is being developed to account for the effects of localized environmental conditions in crevices on the initiation and propagation of pits. A deterministic calculation is used to estimate the accumulation of hydrogen ions (pH suppression) in the crevice solution due to the hydrolysis of dissolved metals. Pit initiation and growth within the crevice is then dealt with by either a probabilistic model, or an equivalent deterministic model. Ultimately, the role of intergranular corrosion will have to be considered. While the strategy presented here is very promising, the integrated model is not yet ready for precise quantitative predictions. Empirical expressions for the rate of penetration based upon experimental crevice corrosion data can be used in the interim period, until the integrated model can be refined. Bounding calculations based upon such empirical expressions can provide important insight into worst-case scenarios.

  3. Influence of Ta content on hot corrosion behaviour of a directionally solidified nickel base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Han, F.F. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Chang, J.X., E-mail: jxchang11s@imr.ac.cn [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Li, H.; Lou, L.H. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Zhang, J. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2015-01-15

    Highlights: • Three nickel-base superalloys containing different Ta content were subjected to Na{sub 2}SO{sub 4}-induced hot corrosion. • Ta improved the hot corrosion resistance. • Ta decreased the diffusion rate of alloying elements. • Ta promoted the formation of (Cr, Ti)TaO{sub 4} layer. - Abstract: Hot corrosion behaviour of a directionally solidified nickel base superalloy with different tantalum (Ta) addition in fused sodium sulphate (Na{sub 2}SO{sub 4}) under an oxidizing atmosphere at 900 °C has been studied. It was shown that the hot corrosion resistance was improved by increasing of Ta content. The hot corrosion kinetics of the alloy with lower Ta content deviated from parabolic law after 60 h corrosion test, whereas the corrosion kinetics of the alloy with high Ta content followed the parabolic law before 60 h and with less mass change afterwards. A detailed microstructure study using scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) was performed to investigate the corrosion products and mechanisms. The beneficial effect of Ta was found to be resulted from a Ta-enriched (Cr, Ti)TaO{sub 4} layer inside the corrosion scale, which led to the retarding of the element diffusion so as to decrease the hot corrosion kinetics.

  4. Pitting corrosion behaviour of built-up welds - Effects of welding layers and tarnish; Lochkorrosionsverhalten von Auftragschweissungen - Schweisslagen- und Oberflaecheneffekte

    Energy Technology Data Exchange (ETDEWEB)

    Heyn, A.; Schilling, K.; Boese, E.; Spieler, S.; Altendorf, S. [Otto-von-Guericke-Universitaet Magdeburg, IWW, PF 4120, 39016 Magdeburg (Germany); Burkert, A. [BAM, Berlin, Fachgruppe VII.3, Unter den Eichen 87, 12205 Berlin (Germany); Schultze, S. [LMPA Sachsen-Anhalt, Grosse Steinernetischstrasse 4, 39104 Magdeburg (Germany)

    2003-12-01

    The pitting corrosion resistance of nickel based deposition welds on a superduplex steel made by active-gas metal pulsed-arc welding was studied. Therefore the determination of the CPT (Critical Pitting Temperature) should be carried out corresponding to ASTM G 48 C. However an unexpectedly low resistance of the built-up welds also at multilayer order was noticed. After visual assessment of the examined specimens a significant effect of the surface condition was assumed. Because the CPT determination according to ASTM does not allow any statement about the corrosion process, this method was not suitable to characterize the corrosion system. For this reason a new method was applied to clarify the causes of the low corrosion resistance. This method determines the CPT with the help of the electrochemical current noise under the same conditions demanded in ASTM G 48 C. The temperature is increased continuously and the characteristic parameters of the system are recorded and evaluated objectively within short time. So it was possible to see the influence of the surface condition on the pitting corrosion behaviour of the examined specimens. The required parameters to the post-processing of the deposition welds were determined. The comparison of the results show that the surface tarnish formed after the shielded arc welding process influences the pitting corrosion resistance negatively. After its elimination the CPT could be determined in dependence of the welding layers. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Zur vergleichenden Einschaetzung der Lochkorrosionsbestaendigkeit von verschiedenen, mehrlagigen MAGp-auftraggeschweissten Nickelbasis-Schweissguetern auf einem Superduplexstahl wurden kritische Lochkorrosionstemperaturen (critical pitting temperature, CPT) nach ASTM G 48 C ermittelt. Es zeigte sich eine unerwartet niedrige Bestaendigkeit der Auftragschweissungen, als dessen Ursache ein unguenstiger Oberflaechenzustand angenommen wurde. Da die

  5. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    Science.gov (United States)

    Lowell, C. E.; Deadmore, D. L.

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  6. Effect of Laser Surface Melting on the Microstructure and Pitting Corrosion Resistance of 304L SS Weldment

    Science.gov (United States)

    Suresh, Girija; Dasgupta, Arup; Kishor, P. S. V. R. A.; Upadhyay, B. N.; Saravanan, T.; Mallika, C.; Mudali, U. Kamachi

    2017-10-01

    The manuscript presents the effect of laser surface melting (LSM) on the microstructural variations and pitting corrosion resistance of 304L SS weldment fabricated by gas tungsten arc welding of 304L SS plates using 308L SS filler wire. The weld region was examined by X-ray radiography for defect detection. LSM of 304L SS weldment was performed using Nd:YAG pulsed laser. Microstructural evaluation was carried out using optical and electron back scatter diffraction techniques. The microstructure of 304L SS base was found to be austenitic, while the weld region of 304L SS weldment contained delta ferrite distributed in austenite matrix. The microstructure of LSM 304L SS weldment was found to be homogeneous austenite matrix with sparsely distributed ferrite. Ferrite measurements showed a decrease in the percentage ferrite in the fusion zone of 304L SS weldment after LSM. A profound enhancement in the pitting corrosion resistance was observed after LSM, which could be attributed to the homogeneous microstructure and decrease in the ferrite content. Pit density was found to be higher in the heat-affected zone of the weldment. Very few pits were observed in the LSM 304L SS weldment compared to the as-weldment.

  7. Pitting corrosion of copper in aqueous solutions containing phosphonic acid as an inhibitor. Hosuhon san wo inhibita toshite fukumu suiyoekichu ni okeru do no koshiku ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Y. (Muroran Univ., Hokkaido (Japan). Graduate School); Seri, O.; Tagashira, K. (Muroran Univ., Hokkaido (Japan)); Nagata, K. (Sumitomo Light Metal Co. Ltd., Tokyo (Japan). Technical Research Lab.)

    1993-09-15

    Phosphonic acid-based inhibitors that are poured into cooling water for copper-tube circulation systems for open heat-accumulators were studied on their influence on pitting corrosion of copper. Amino trimethylene phosphonic acid (ATMP) dissolved into distilled water to 50 ppm was used for the immersion corrosion test. The corrosion-proof effect of additives such as ZnSO4, benzotriazole (BTA) was tested too. 0.5 mm thick phosphate-treated copper plates with a hole of 5 mm in diameter were used as test specimens. Pitting corrosion on the copper plate occurred when ATMP, BTA and ZnSO4 coexisted. It was proved that SO4 [sup 2-] is essential since Na2SO4 in stead of ZnSO4 induced also corrosion. The pitting took place when 0.6 ppm or more of SO4 [sup 2-] was present in a BTA-added ATMP solution. It was observed that the pitting is prone to occur with increase of SO4 [sup 2-] and the number of pitting increases. The following relationship is established when pitting corrosion occurs; E[sub b] [le] E[sub corr], where the former is a potential value at which current density shows a steep increase and the latter is an average value of spontaneous electrode potential showing a plateau. 8 refs., 11 figs., 1 tab.

  8. 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.

  9. Pitting Corrosion Characterization of Wrought Stellite Alloys in Green Death Solution with Immersion Test and Extreme Value Analysis Model

    Science.gov (United States)

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

    2014-05-01

    This article presents a study of the corrosion behavior of two wrought Stellite alloys, Stellite 6B, and Stellite 6K, in Green Death solution, utilizing the extreme value analysis (EVA) model, which is a statistics tool developed based on the Gumbel distribution. Green Death solution a typical oxidized testing solution used in industry for assessing the corrosion resistance of materials. The data of maximum pit depths are obtained from the immersion tests on these alloys for various exposure periods. The top ten maximum pit depths in each specimen surface after the immersion test are measured using a surface texture and contour measuring instrument. These data are the input parameters of the EVA model and the outcomes of the model are the extreme values (minimum thickness) required for the alloys under a given service condition. It is shown that Stellite 6K, which contains higher carbon content but smaller-size carbides, exhibits better corrosion resistance in regard to the extreme value. The results and mechanisms of Stellite 6B and Stellite 6K in Green Death solution corrosion are discussed.

  10. Experimental and numerical investigation of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by artificially produced pitting corrosion

    Science.gov (United States)

    Pippig, R.; Schmidl, E.; Steinert, P.; Schubert, A.; Lampke, T.

    2017-03-01

    In this study, the behaviour of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by the morphology and numbers of corrosion pits (defects) is presented. Since specific defect structures are not reproducible during experimental corrosion tests, metal sheets with different numbers of pits and pit shapes are produced using laser micro structuring. The defect structures are measured using laser scanning microscopy. To compare the stress states of the micro structured and real corroded metal sheets, FE-analysis is used. Afterwards, uniaxial tensile tests are carried out and critical defect parameters in terms of yield strength reduction of the investigated aluminium alloy are detected.

  11. Microstructure and pitting corrosion resistance of AA2219 Al–Cu alloy friction stir welds – Effect of tool profile

    Directory of Open Access Journals (Sweden)

    Ch Venkata Rao

    2015-06-01

    Full Text Available AA2219 Al–Cu alloy is widely used in defence and aerospace applications due to required combination of high strength-to-weight ratio and toughness. Fabrication of components used for defence always involves welding. Even though the mechanical properties of the base metal are better, but the alloy suffers from poor mechanical and corrosion properties during fusion welding. To overcome the problems of fusion welding, friction stir welding (FSW is recognized as an alternative solid state joining method aimed to improve the mechanical and corrosion properties. Tool profile is one of the important variables which affect the performance of the friction stir weld. In the present work the effect of tool profile on the microstructure and pitting corrosion of AA2219 aluminium–copper alloy was studied. Electron backscattered diffraction results established that the grain size and orientation of weld nugget of triangle profile is finer than that of conical profile. Differential scanning calorimetric results show the evidence of precipitate dissolution during FSW. It was found that the microstructure changes, such as grain size and its orientation precipitate dissolution during FSW influence the hardness and corrosion behaviour. Pitting corrosion resistance of friction stir welds of AA2219 was found to be better for triangle profile tool compared to conical profile which is attributed to material flow and strengthening precipitate morphology in various zones. Higher amount of heat generation during FSW made using triangle profile tool may be the reason for greater dissolution of strengthening precipitates in nugget zone and coarsening in thermo mechanically affected zone (TMAZ and heat affected zone (HAZ.

  12. 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.)

  13. Long-Term Corrosion Potential Behavior of Alloy 22 in Hot 5 m CaCl2 + 5 m Ca(NO3)2 Brines

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M A; Carranza, R M; Stuart, M L; Rebak, R B

    2007-02-20

    Alloy 22 is a nickel base alloy highly resistant to all forms of corrosion. In very aggressive conditions (e.g. hot concentrated chloride containing brines) Alloy 22 could suffer localized attack, namely pitting and crevice corrosion. The occurrence of localized corrosion in a given environment is governed by the values of the critical potential (E{sub crit}) for crevice corrosion and the corrosion potential (E{sub corr}) that the alloy may establish in the studied environment. If E{sub corr} is equal or higher than E{sub crit}, localized corrosion may be expected. This paper discusses the evolution of E{sub corr} of Alloy 22 specimens in 5 m CaCl{sub 2} + 5 m Ca(NO{sub 3}){sub 2} brines at 100 C and 120 C. Two types of specimens were used, polished as-welded (ASW) creviced and noncreviced specimens and as-welded plus solution heat-treated (ASW+SHT) creviced specimens. The latter contained the black annealing oxide film on the surface. Results show that, for all types of Alloy 22 specimens the E{sub corr} was higher at 120 C than at 100 C, probably because a more protective film formed at the higher temperature. Specimens with the black oxide film on the surface showed more oscillations in the potential. None of the tested specimens suffered crevice corrosion probably because of the relatively high concentration of nitrate in the electrolyte, R = [NO3]/[Cl] = 1.

  14. Chemical Composition of Apricot Pit Shells and Effect of Hot-Water Extraction

    Directory of Open Access Journals (Sweden)

    Derek B. Corbett

    2015-09-01

    Full Text Available Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS were studied in this work to assess their potential for use in a biorefinery. Hot water extraction (HWE; 160 °C, 2 h, proposed to remove easily accessible hemicelluloses, was performed to evaluate the susceptibility of APS to this mild pretreatment process. The chemical composition of APS before and after HWE (EAPS was analyzed by standard methods and 1H-NMR. A low yield of the remaining HW-extracted APS (~59% indicated that APS are highly susceptible to this pretreatment method. 1H-NMR analysis of EAPS revealed that ~77% of xylan present in raw APS was removed along with ~24% of lignin. The energy of combustion of APS was measured before and after HWE showing a slight increase due to HWE (1.61% increase. Near infrared radiation spectroscopy (NIRS, proposed as a quick non-invasive method of biomass analysis, was performed. NIRS corroborated results of traditional analysis and 1H-NMR. Determination of antioxidizing activity (AOA of APS extracts was also undertaken. AOA of organic APS extracts were shown to be more than 20 times higher than that of a synthetic antioxidizing agent.

  15. Effect of Aging on Precipitation Behavior and Pitting Corrosion Resistance of SAF2906 Super Duplex Stainless Steel

    Science.gov (United States)

    Li, Jianchun; Li, Guoping; Liang, Wei; Han, Peide; Wang, Hongxia

    2017-09-01

    The effect of aging temperature and holding time on the precipitation of secondary phases and pitting corrosion resistance of SAF2906 super duplex stainless steel was examined. Chromium nitride and σ phase were observed to preferentially precipitate at the ferrite/austenite interface. An amount of nitrides was also observed within the ferrite grain. The precipitation of chromium nitride occurred before the σ phase. The increase in aging temperature and holding time did not affect the concentration of the nitrides but increased the area fraction of the σ phase at a faster rate. The Cr2N precipitation in SAF2906 is more evident than that of the other duplex stainless steels. The variation tendency of the precipitation concentrations is primarily consistent with the prediction results of Thermo-Calc software. The electrochemical results showed that Cr2N and σ phase significantly reduced the pitting potential. Scanning electron microscope observations revealed that pits appear mainly in regions adjacent to sigma phase and Cr2N.

  16. THE USE OF COATINGS FOR HOT CORROSION AND EROSION PROTECTION IN TURBINE HOT SECTION COMPONENTS

    Directory of Open Access Journals (Sweden)

    Hayrettin AHLATCI

    1999-01-01

    Full Text Available High pressure turbine components are subjected to a wide variety of thermal and mechanical loading during service. In addition, the components are exposed to a highly oxidizing atmosphere which may contain contaminants such as sulphates, chlorides and sulphuorous gases along with erosive media. So the variety of surface coatings and deposition processes available for the protection of blade and vane components in gas turbines are summarised in this study. Coating types range from simple diffusion aluminides to modified aluminides and a CoCrAlY overlayer. The recommendations for corrosion-resistant coatings (for low temperature and high temperature hot corrosion environments are as follows: silicon aluminide and platinumchromium aluminide for different gas turbine section superalloys substrates. Platinum metal additions are used to improve the properties of coatings on turbine components. Inorganic coatings based on ceramic films which contain aluminium or aluminium and silicon are very effective in engines and gas turbines. Diffusion, overlayer and thermal barrier coatings which are deposited on superalloys gas turbine components by pack cementation, plasma spraying processes and a number of chemical vapour deposition, physical vapour deposition processes (such as electron beam, sputtering, ion plating are described. The principles underlying the development of protective coatings serve as a useful guide in the choice of coatings for other high temperature applications.

  17. Pitted Corrosion Detection of Thermal Sprayed Metallic Coatings Using Fiber Bragg Grating Sensors

    Directory of Open Access Journals (Sweden)

    Fodan Deng

    2017-02-01

    Full Text Available Metallic coatings using thermal spraying techniques are widely applied to structural steels to protect infrastructure against corrosion and improve durability of the associated structures for longer service life. The thermal sprayed metallic coatings consisting of various metals, although have higher corrosion resistance, will still corrode in a long run and may also subject to corrosion induced damages such as cracks. Corrosion and the induced damages on the metallic coatings will reduce the effectiveness of the coatings for protection of the structures. Timely repair on these damaged metallic coatings will significantly improve the reliability of protected structures again deterioration. In this paper, an inline detection system for corrosion and crack detection was developed using fiber Bragg (FBG grating sensors. Experimental results from laboratory accelerated corrosion tests showed that the developed sensing system can quantitatively detect corrosion rate of the coating, corrosion propagations, and cracks initialized in the metallic coating in real time. The developed system can be used for real-time corrosion detection of coated metal structures in field.

  18. Acceptance Criteria for Corrosion Resistance of Medical Devices: Statistical Analysis of Nitinol Pitting in In Vivo Environments

    Science.gov (United States)

    Eiselstein, Lawrence E.; Steffey, Duane; Nissan, Andrew; Corlett, Nigel; Dugnani, Roberto; Kus, Esra; Stewart, Sarah G.

    2009-08-01

    ASTM F 2129 test method nor the FDA provides any guidance as to what constitutes an acceptance criterion for the corrosion resistance of implantable medical devices. Neither provide any guidance on how many samples to test or how to handle censored data, i.e. datasets where there are only a few tests that breakdown. The development of both a statistically valid acceptance criterion for corrosion resistance and a method of evaluation would be of significant benefit to the medical device community. This study of 420 nitinol cyclic polarization tests, which builds on previous research that was presented at SMST 2007, investigates the effect of long-term exposure to simulated in vivo environments with differing degrees of aeration. This was accomplished by pre-exposing electropolished (EP) nitinol to phosphate buffered saline (PBS) at 37 °C that had been sparged with either ultra high purity nitrogen or laboratory air. Immersion times ranged from 1 h up to 30 days. A total of 290 EP samples were tested in order to obtain a reasonable number of samples with breakdown, i.e. pitted. In addition, a total of 130 mechanical polished (MP) samples were also analyzed. This data allow us to test our statistical model that was presented at SMST 2007. This model takes into account the probability of breakdown per unit of exposed surface area and, if breakdown occurs, predicts the probability that E b - E r is greater than some threshold value. Aerated PBS environments were found to have a large influence on the margin of safety against pitting in vivo. Statistical methods for treating highly right censored pitting data are presented.

  19. 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.

  20. Microstructure and pitting corrosion of armor grade AA7075 aluminum alloy friction stir weld nugget zone – Effect of post weld heat treatment and addition of boron carbide

    Directory of Open Access Journals (Sweden)

    P. Vijaya Kumar

    2015-06-01

    Full Text Available Friction stir welding (FSW of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding. In recent times FSW is being used for armor grade AA7075 aluminum alloy in defense, aerospace and marine applications where it has to serve in non uniform loading and corrosive environments. Even though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion resistance. The present work involves use of retrogression and reaging (RRA post weld heat treatment to improve the corrosion resistance of welded joints of aluminum alloys. An attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt position. The effects of peak aged condition (T6, RRA and addition of B4C nano particles on microstructure, hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been studied. Even though RRA improved the pitting corrosion resistance, its hardness was slightly lost. Significant improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.

  1. High temperature cyclic oxidation and hot corrosion behaviours of superalloys at 900°C

    Indian Academy of Sciences (India)

    Subhash Kamal; R Jayaganthan; S Prakash

    2010-06-01

    Oxidation and hot corrosion are serious problems in aircraft, marine, industrial, and land-base gas turbines. It is because of the usage of wide range of fuels coupled with increased operating temperatures, which leads to the degradation of turbine engines. To obviate these problems, superalloys, viz. Superni 75, Superni 718 and Superfer 800H superalloys (Midhani grade), are the prominent materials for the high temperature applications. It is very essential to investigate the degradation mechanism of superalloys due to oxidation and hot corrosion and substantiate the role of alloying elements for the formation of protective oxide films over the surface of the superalloys. Therefore, the present work investigates the oxidation and hot corrosion behaviour of superalloys exposed to air and molten salt (Na2SO4–60% V2O5) environment, respectively, at 900°C under cyclic conditions. The weight change measurements made on the superalloys during the experiments are used to determine the kinetics of oxidation and hot corrosion. X-ray diffraction (XRD), X-ray mapping and field emission scanning electron microscope (FESEM, FEI, Quanta 200F company) with EDAX Genesis software attachment, made in Czech Republic are used to characterize the corroded products of the superalloys. It is observed that the formation of scale rich in Cr2O3, NiO and spinel NiCr2O4 has contributed for the better oxidation and hot corrosion resistance of Superni 75; whereas relatively lesser hot corrosion resistance of Superfer 800H is due to the formation of non-protective oxides of iron and sulphides of iron and nickel. The parabolic rate constants calculated for the superalloys show that the corrosion rate is minimum in air as compared to molten salt environment.

  2. High temperature solution-nitriding and low-temperature nitriding of AISI 316: Effect on pitting potential and crevice corrosion performance

    DEFF Research Database (Denmark)

    Bottoli, Federico; Jellesen, Morten Stendahl; Christiansen, Thomas Lundin

    2017-01-01

    in a 0.1M NaCl solution and crevice corrosion immersion tests in 3wt% FeCl3 solution were studied before and after the bulk and surface treatments.Nitrogen addition in the bulk proved to have a beneficial effect on the pitting resistance of the alloy. The formation of a zone of expanded austenite...

  3. Advanced high-pressure bench-scale reactor for testing with hot corrosive gases

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Bachta, R.P.; Wangerow, J.R. (Inst. of Gas Technology, Chicago, IL (United States)); Mojtahedi, W.; Salo, K. (Enviropower Inc., Espoo (Finland))

    1994-01-01

    A bench-scale, high-pressure/high-temperature fluidized-bed reactor (HPTR) system is described that is capable of operating at a maximum temperature and pressure of 1,000 C and 30 bar in a corrosive atmosphere. The design of the unit is based on a double-shell balanced-pressure system. All the hot parts of the reactor that are wetted by the corrosive (and/or reactive) gases and the entire sampling line are constructed of inert material to prevent corrosion and loss of the reactant gases. The unit has been used for over 200 high-pressure hot coal gas desulfurization tests at 20 bars and up to 750 C without any experimental problem and with excellent sulfur balance, indicating that this reactor system is ideal for testing with reactive and corrosive gases at elevated pressures and temperatures.

  4. 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.

  5. 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)

  6. Hot corrosion performance of a NiCr coated Ni-based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sidhu, T.S.; Prakash, S.; Agrawal, R.D. [Indian Institute of Technology, Roorkee (India)

    2006-07-15

    The hot corrosion performance of high velocity oxy-fuel sprayed Ni-20Cr wire coating on a Ni-based superalloy is evaluated for 1000 h at 900{sup o}C under cyclic conditions in a coal-fired boiler. The performance of bare and Ni-20Cr coated Superni 75 is assessed via thermogravimetric data, metal thickness loss corresponding to the corrosion scale formation, scale thickness loss and the depth of internal corrosion attack. The better hot corrosion resistance of the coated alloy is mainly attributed to the formation of a thick band of chromium oxide just above the scale-substrate interface and chromium oxide stringers along the splat boundaries, as well as to the nickel oxide and the dense and uniform fine grain structure of the as sprayed coating.

  7. Optimization Of Pulsed Current Parameters To Minimize Pitting Corrosion İn Pulsed Current Micro Plasma Arc Welded Aısı 304l Sheets Using Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Kondapalli Siva Prasad

    2013-06-01

    Full Text Available Austenitic stainless steel sheets have gathered wide acceptance in the fabrication of components, which require high temperature resistance and corrosion resistance, such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industry. In case of single pass welding of thinner sections of this alloy, Pulsed Current Micro Plasma Arc Welding (PCMPAW was found beneficial due to its advantages over the conventional continuous current process. This paper highlights the development of empirical mathematical equations using multiple regression analysis, correlating various process parameters to pitting corrosion rates in PCMPAW of AISI 304L sheets in 1 Normal HCl. The experiments were conducted based on a five factor, five level central composite rotatable design matrix. A Genetic Algorithm (GA was developed to optimize the process parameters for minimizing the pitting corrosion rates.

  8. Hot-wall corrosion testing of simulated high level nuclear waste

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, G.T.; Zapp, P.E.; Mickalonis, J.I.

    1995-01-01

    Three materials of construction for steam tubes used in the evaporation of high level radioactive waste were tested under heat flux conditions, referred to as hot-wall tests. The materials were type 304L stainless steel alloy C276, and alloy G3. Non-radioactive acidic and alkaline salt solutions containing halides and mercury simulated different high level waste solutions stored or processed at the United States Department of Energy`s Savannah River Site. Alloy C276 was also tested for corrosion susceptibility under steady-state conditions. The nickel-based alloys C276 and G3 exhibited excellent corrosion resistance under the conditions studied. Alloy C276 was not susceptible to localized corrosion and had a corrosion rate of 0.01 mpy (0.25 {mu}m/y) when exposed to acidic waste sludge and precipitate slurry at a hot-wall temperature of 150{degrees}C. Type 304L was susceptible to localized corrosion under the same conditions. Alloy G3 had a corrosion rate of 0.1 mpy (2.5 {mu}m/y) when exposed to caustic high level waste evaporator solution at a hot-wall temperature of 220{degrees}C compared to 1.1 mpy (28.0 {mu}/y) for type 304L. Under extreme caustic conditions (45 weight percent sodium hydroxide) G3 had a corrosion rate of 0.1 mpy (2.5 {mu}m/y) at a hot-wall temperature of 180{degrees}C while type 304L had a high corrosion rate of 69.4 mpy (1.8 mm/y).

  9. CORROSION RESISTANCE OF HOT DIP GALVANIZED STEEL PRETREATED WITH BIS-FUNCTIONAL SILANES MODIFIED WITH NANOALUMINA

    Institute of Scientific and Technical Information of China (English)

    F.J.Shan; C.S.Liu; S.H.Wang; G.C.Qi

    2008-01-01

    The corrosion behavior of hot dip galvanized steel pretreated with bis-[triethoxy-silylpropyl]tetrasulfide (BTESPT) modified with alumina particles was studied.The corrosion resistance of the passiving films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy.The films formed on the galvanized steel substrate were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectrometry.The surface morphology of the treated hot dip galva-nized steel samples was observed by Field Emission Scanning Electron Microscope. The results show that the pretreatments on the basis of silane films modified with nanoalumina particles have reduced both anodic and cathodic current densities,and increased total impedance in the measured frequency,consequently,improving cor-rosion protection for hot dip galvanized steel during immersion in NaCl solutions compared to chromate films and silane films.

  10. Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloy

    Science.gov (United States)

    Gabb, Tim; Miller, R. A.; Sudbrack, C. K.; Draper, S. L.; Nesbitt, J.; Telesman, J.; Ngo, V.; Healy, J.

    2015-01-01

    Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 C and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 C. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. The effects of this cyclic oxidation on resistance to subsequent hot corrosion attack were examined.

  11. Corrosion of two kinds of cast steels containing chromium in hot concentrated alkaline

    Directory of Open Access Journals (Sweden)

    LI Wei

    2007-02-01

    Full Text Available A typical hot concentrated alkaline corrosion environment exists in alumina metallurgical industry, so that steel materials with outstanding alkaline corrosion resistance are strongly demanded for its processing equipment. In this paper, the corrosion resistance of two kinds of martensitic cast steels containing chromium in static 303g/L NaOH alkaline solution at 85℃ was studied through polarization and potential-time curves, corrosion weight loss and corrosion morphology analysis. Experimental results showed that protection effect by passive film of cast steel containing Cr was temporary. The low carbon steel without Cr content also exhibited chemical passivity in the same solution. The corrosion mode of the tested Cr-containing cast steel was composed of active dissolving corrosion and caustic embrittlement cracking. Dissolving corrosion was the primary mechanism for the induced weight loss, while severe caustic embrittlement cracking was secondary. With the increase of chromium content in the cast steel, the tendency of the caustic embrittlement cracking decreased, while the active dissolving corrosion increased.

  12. Corrosion of two kinds of cast steels containing chromium in hot concentrated alkaline

    Institute of Scientific and Technical Information of China (English)

    LI Wei; LIU Jun-quan; TU Xiao-hui

    2007-01-01

    A typical hot concentrated alkaline corrosion environment exists in alumina metallurgical industry, so that steel materials with outstanding alkaline corrosion resistance are strongly demanded for its processing equipment. In this paper, the corrosion resistance of two kinds of martensitic cast steels containing chromium in static 303 g/L NaOH alkaline solution at 85℃ was studied through polarization and potential-time curves, corrosion weight loss and corrosion morphology analysis. Experimental results showed that protection effect by passive film of cast steel containing Cr was temporary. The low carbon steel without Cr content also exhibited chemical passivity in the same solution. The corrosion mode of the tested Cr-containing cast steel was composed of active dissolving corrosion and caustic embrittlement cracking. Dissolving corrosion was the primary mechanism for the induced weight loss, while severe caustic embrittlement cracking was secondary. With the increase of chromium content in the cast steel, the tendency of the caustic embrittlement cracking decreased, while the active dissolving corrosion increased.

  13. 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.

  14. 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.

  15. Pitting Corrosion of Super Duplex Stainless Steel - Effect of Isothermal Heat Treament

    OpenAIRE

    Lauritsen, Christian Rene

    2016-01-01

    Super duplex stainless steels (SDSS), with a chromium content of 25 wt$\\%$, contain a duplex structure which consists of ferrite and austenite, and have a pitting resistance equivalent number (PREN) equal or higher than 40. SDSS are affected by the alloying elements, microstructure and fabrication processes. The high degree of alloying elements in SDSS can lead to formation of intermetallic precipitates and secondary phases during heat treatments. Detrimental phases, such as sigma ($\\sigma$) ...

  16. Hot corrosion monitoring of alloy 617 in molten chlorides using electrochemical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Perez, F.J.; Hierro, M.P.; Nieto, J. [Univ. Complutense de Madrid (Spain). Dept. de Ciencia de los Materiales, Facultad de Ciencias Quimicas

    2006-07-01

    Molten chloride mixtures are formed in waste incineration plants during waste firing and energy production. These mixtures are responsible for degradation processes like hot corrosion. In order to evaluate the damage of molten salt mixtures in waste incineration environments, the alloy 617 was exposed beneath a molten KCl-ZnCl{sub 2} mixture at 650 C in air. The corrosion process was monitored by electrochemical impedance spectroscopy (EIS). An extensive microscopy analysis have been done in order to correlate the electrochemical results, and to establish an electrochemical mechanism for such high temperature corrosion process. (orig.)

  17. Impact of chlorinated disinfection on copper corrosion in hot water systems

    Science.gov (United States)

    Montes, J. Castillo; Hamdani, F.; Creus, J.; Touzain, S.; Correc, O.

    2014-09-01

    In France, hot water quality control inside buildings is occasionally ensured by disinfection treatments using temperature increases or addition of sodium hypochlorite (between 0.5 ppm and 1 ppm residual free chlorine). This disinfectant is a strong oxidiser and it could interact with metallic pipes usually used in hot water systems. This work deals with the study of the impact of these treatments on the durability of copper pipes. The objective of this work was to investigate the influence of sodium hypochlorite concentration and temperature on the copper corrosion mechanism. Copper samples were tested under dynamic and static conditions of ageing with sodium hypochlorite solutions ranging from 0 to 100 ppm with temperature at 50 °C and 70 °C. The efficiency of a corrosion inhibitor was investigated in dynamic conditions. Visual observations and analytical analyses of the internal surface of samples was studied at different ageing duration. Corrosion products were characterised by X-ray diffraction and Raman spectroscopy. Temperature and disinfectant were found to considerably affect the copper corrosion mechanism. Surprisingly, the corrosiveness of the solution was higher at lower temperatures. The temperature influences the nature of corrosion products. The protection efficiency is then strongly depend on the nature of the corrosion products formed at the surface of copper samples exposed to the aggressive solutions containing different concentration of disinfectant.

  18. A Simple Approach To Assessing Copper Pitting Corrosion Tendenices and Developing Control Strategies

    Science.gov (United States)

    The objective of this research was to assess the effectiveness of a simple pipe loop system and protocol to predict localized corrosion, and to assess treatment alternatives for a drinking water that has been associated with customer complaints of pinhole leaks.

  19. Initial phase hot corrosion mechanism of gas tunnel type plasma sprayed thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yugeswaran, S. [Joining and Welding Research Institute, Osaka University, Osaka 567-0047 (Japan); Kobayashi, A., E-mail: kobayasi@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, Osaka 567-0047 (Japan); Ananthapadmanabhan, P.V. [L and PT Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2012-04-25

    Highlights: Black-Right-Pointing-Pointer Free standing TBC specimens were prepared by gas tunnel type plasma spraying with thickness of around 300-400 {mu}m. Black-Right-Pointing-Pointer 50%8YSZ + 50%La{sub 2}Zr{sub 2}O{sub 7} composite coating shows superior hot corrosion resistance. Black-Right-Pointing-Pointer Corrosive crystals structure and phase transformation was well controlled in this coating. - Abstract: The hot corrosion resistance of the top layer in TBC is one of the main constructive factors which determines the lifetime of the coatings under critical operating environments. In the present study, 8 wt% yttria stabilized zirconia (8YSZ), lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}) and equal weight percentage of its composite (50%8YSZ + 50% La{sub 2}Zr{sub 2}O{sub 7}) coatings were prepared by using gas tunnel type plasma spray torch at optimum spraying conditions. The hot corrosion performances of the above thermal barrier coatings were examined against 40 wt%V{sub 2}O{sub 5}-60 wt%Na{sub 2}SO{sub 4} corrosive ash at 1173 K for 5 h in open air atmosphere. After hot-corrosion testing, the coating surface was studied using a scanning electron microscope to observe the microstructure and X-ray diffraction techniques were used to identify the phase compositions. The results showed that LaVO{sub 4} and YVO{sub 4} are the main hot corrosion products along with the ZrO{sub 2} phase transformation from tetragonal to monoclinic phases in La{sub 2}Zr{sub 2}O{sub 7} and 8YSZ coatings respectively. The microstructure and phase formation mechanism of the hot corrosion products varied with each coating and among these, composition of 50%8YSZ + 50%La{sub 2}Zr{sub 2}O{sub 7} coating exhibited least degradation against V{sub 2}O{sub 5}-Na{sub 2}SO{sub 4} corrosive environment compared to the other coatings.

  20. Resistance of Silicon Nitride Turbine Components to Erosion and Hot Corrosion/oxidation Attack

    Science.gov (United States)

    Strangmen, Thomas E.; Fox, Dennis S.

    1994-01-01

    Silicon nitride turbine components are under intensive development by AlliedSignal to enable a new generation of higher power density auxiliary power systems. In order to be viable in the intended applications, silicon nitride turbine airfoils must be designed for survival in aggressive oxidizing combustion gas environments. Erosive and corrosive damage to ceramic airfoils from ingested sand and sea salt must be avoided. Recent engine test experience demonstrated that NT154 silicon nitride turbine vanes have exceptional resistance to sand erosion, relative to superalloys used in production engines. Similarly, NT154 silicon nitride has excellent resistance to oxidation in the temperature range of interest - up to 1400 C. Hot corrosion attack of superalloy gas turbine components is well documented. While hot corrosion from ingested sea salt will attack silicon nitride substantially less than the superalloys being replaced in initial engine applications, this degradation has the potential to limit component lives in advanced engine applications. Hot corrosion adversely affects the strength of silicon nitride in the 850 to 1300 C range. Since unacceptable reductions in strength must be rapidly identified and avoided, AlliedSignal and the NASA Lewis Research Center have pioneered the development of an environmental life prediction model for silicon nitride turbine components. Strength retention in flexure specimens following 1 to 3300 hour exposures to high temperature oxidation and hot corrosion has been measured and used to calibrate the life prediction model. Predicted component life is dependent upon engine design (stress, temperature, pressure, fuel/air ratio, gas velocity, and inlet air filtration), mission usage (fuel sulfur content, location (salt in air), and times at duty cycle power points), and material parameters. Preliminary analyses indicate that the hot corrosion resistance of NT154 silicon nitride is adequate for AlliedSignal's initial engine

  1. Studies of the Low Temperature Hot Corrosion of Uncoated Superalloys.

    Science.gov (United States)

    1981-09-01

    Corrosion of Uncoated Superal loys * EPNIQoao. qEPORT NUMUER 7. AUTHOR,.I .CONTRACT OR11 GRANT IUR. Garry 0. flewberry 9. PERPOR0111MING ORGANIZATION ...Master’s Thesis, Naval Postgraduate School, M1onterey, 7, June 1981. 13. Exell , J. R., The Substrate Effect of Active Element Hafnium in Aluminide

  2. Burner Rig Hot Corrosion of Five Ni-Base Alloys Including Mar-M247

    Science.gov (United States)

    Nesbitt, James A.; Helmink, R.; Harris, K.; Erickson, G.

    2000-01-01

    The hot corrosion resistance of four new Ni-base superalloys was compared to that of Mar-M247 by testing in a Mach 0.3 burner rig at 900 C for 300 1-hr cycles. While the Al content was held the same as in the Mar-M247, the Cr and Co levels in the four new alloys were decreased while other strengthening elements (Re, Ta) were increased. Surprisingly, despite their lower Cr and Co contents, the hot corrosion behavior of all four new alloys was superior to that of the Mar-M247 alloy. The Mar-M247 alloy began to lose weight almost immediately whereas the other four alloys appeared to undergo an incubation period of 50-150 1-hr cycles. Examination of the cross-sectional microstructures showed regions of rampant corrosion attack (propagation stage) in all five alloys after 300 1-hr cycles . This rampant corrosion morphology was similar for each of the alloys with Ni and Cr sulfides located in an inner subscale region. The morphology of the attack suggests a classic "Type I", or high temperature, hot corrosion attack.

  3. Cerium addition on pitting corrosion of (Cu50Zr50)100-2xCe2x (x=0, 1, 2 and 3) metallic glasses in seawater

    Institute of Scientific and Technical Information of China (English)

    张春芝; 王金环; 仇楠楠; 谢鲲; 李辉平

    2015-01-01

    The industrial application of metallic glass is a longstanding challenge for researchers in the field. Toward this objective, the electrochemical performance in sea water of Cu-Zr-(Ce) metallic glass with various Ce content was investigated. Cu-Zr-(Ce) me-tallic glass was fabricated by melt-spinning technique and characterized by X-ray diffraction. The corrosion resistance in seawater was then investigated by potentiodynamic polarization, immersion test, scanning electron microscopy, electron probe microanalysis, and energy dispersive spectrometer analysis. The results showed that Ce addition lowered the corrosion current density of Ce-containing Cu-Zr alloy system. The attack type changed from uniform corrosion of Cu50Zr50 metallic glasses to local one of the Ce-containing alloys. Appropriate content of Ce inhibited the selective dissolution of Cu in the pits and thus improved the corrosion resistance of the alloys.

  4. 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}.

  5. Effects of lanthanum addition on corrosion resistance of hot-dipped galvalume coating

    Institute of Scientific and Technical Information of China (English)

    YANG Dong; CHEN Jianshe; HAN Qing; LIU Kuiren

    2009-01-01

    Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated. The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% La were evaluated by various tests such as copper-accelerated acetic acid salt spray testing (CASS), immersion test in 3.5% NaCl solution, electrochemical tests including weak polarization curves and electrochemical impedance spectroscopy (EIS) tests, scanning electron microscope (SEM) test and X-ray diffraction (XRD) test. It was found that the corrosion resistance of galvalume coating could be improved by adding proper amounts of La. Meanwhile, the mechanism of the improvement of corrosion resistance by La addition was discussed.

  6. Hot corrosion of four superalloys - HA-188, S-57, IN-617, and TD-NiCrAl

    Science.gov (United States)

    Santoro, G. J.

    1979-01-01

    Cyclic oxidation and hot corrosion tests of two cobalt-base and two nickel-base alloys are reported. The alloys were exposed to maximum temperatures of 900 and 1000 C in a Mach 0.3 burner rig whose flame was doped with various concentrations of sea salt and sodium sulfate for hot corrosion tests. The test data were subjected to a regression analysis for the development of model equations relating corrosion to temperature and for the effects of salt concentration and composition on corrosion. The corrosion resistance varied with temperature, sea salt concentration, and salt composition, concluding that the S-57 cobalt-base alloy was the most hot corrosion-resistant alloy, and the TD-NiCrAl nickel-base alloy was the least resistant. However, under straight oxidation conditions, the TD-NiCrAl was most resistant, while S-57 was the least resistant alloy.

  7. Scanning Probe Investigation of Pitting Corrosion on Aluminum 5083 H131

    Science.gov (United States)

    2014-05-01

    AFM, SKPM, SEM, and EDS for AA5083 and typically iron (Fe)-rich phases are known to be local cathodes whereas silicon (Si)-containing precipitates act...performance at the U.S. Army Research Laboratory (ARL). For example, the corrosion performance of AA5083 in the neutral salt fog exposure test, ASTM...to 1200, then polished in a stepwise fashion from 9 to 3 to 1 µm using aqueous diamond suspensions (MetaDi). The final size of AA5083 substrates for

  8. Pitting corrosion resistance and bond strength of stainless steel overlay by friction surfacing on high strength low alloy steel

    Directory of Open Access Journals (Sweden)

    Amit Kumar Singh

    2015-09-01

    Full Text Available Surface modification is essential for improving the service properties of components. Cladding is one of the most widely employed methods of surface modification. Friction surfacing is a candidate process for depositing the corrosion resistant coatings. Being a solid state process, it offers several advantages over conventional fusion based surfacing process. The aim of this work is to identify the relationship between the input variables and the process response and develop the predictive models that can be used in the design of new friction surfacing applications. In the current work, austenitic stainless steel AISI 304 was friction surfaced on high strength low alloy steel substrate. Friction surfacing parameters, such as mechtrode rotational speed, feed rate of substrate and axial force on mechtrode, play a major role in determining the pitting corrosion resistance and bond strength of friction surfaced coatings. Friction surfaced coating and base metal were tested for pitting corrosion by potentio-dynamic polarization technique. Coating microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. Coatings in the as deposited condition exhibited strain-induced martensite in austenitic matrix. Pitting resistance of surfaced coatings was found to be much lower than that of mechtrode material and superior to that of substrate. A central composite design with three factors (mechtrode rotational speed, substrate traverse speed, axial load on mechtrode and five levels was chosen to minimize the number of experimental conditions. Response surface methodology was used to develop the model. In the present work, an attempt has been made to develop a mathematical model to predict the pitting corrosion resistance and bond strength by incorporating the friction surfacing process parameters.

  9. Characterization and Evaluation of Cyclic Hot Corrosion Resistance of Detonation-Gun Sprayed Ni-5Al Coatings on Inconel-718

    Science.gov (United States)

    Saladi, Sekar; Menghani, Jyoti V.; Prakash, Satya

    2015-06-01

    The high temperature hot corrosion behavior of bare and detonation-gun-sprayed Ni-5Al coatings on Ni-based superalloy Inconel-718 is comparatively discussed in the present study. Hot corrosion studies were carried out at 900 °C for 100 cycles in Na2SO4-60% V2O5 molten salt environment under cyclic heating and cooling conditions. The thermo-gravimetric technique was used to establish the kinetics of hot corrosion. X-ray diffraction, SEM/EDAX, and X-ray mapping techniques were used to analyze the hot corrosion products of bare and coated superalloys. The results indicate that Ni-5Al-coated superalloy showed very good hot corrosion resistance. The overall weight gain and parabolic rate constant of Ni-5Al-coated superalloy were less in comparison with the bare superalloy. The D-gun-sprayed Ni-5Al coating was found to be uniform, adherent, and dense in hot corrosion environment. The formation of nickel- and aluminum-rich oxide scale might have contributed for the better hot corrosion resistance of the coated superalloy.

  10. 腐蚀坑形貌对油气管道失效压力的影响%Corrosion pit morphology on the impact of oil and gas pipeline failure pressure

    Institute of Scientific and Technical Information of China (English)

    崔铭伟; 曹学文; 封子艳

    2014-01-01

    ASME B 31G规范把复杂的腐蚀坑剖面曲线简化成矩形或抛物线投影,是造成ASME B 31G规范预测结果出现保守和不稳定性的重要原因。文章采用非线性有限元方法,综合分析了腐蚀坑剖面面积和腐蚀坑形状系数对腐蚀管道失效压力的影响,提出一种新的以腐蚀坑剖面面积和腐蚀坑形状系数描述腐蚀坑形貌的B31G修正公式,实际算例表明新提出的B31G修正公式的预测结果保守性低,预测误差稳定。%The failure pressure of oil and gas pipeline with different morphology of corrosion pits was anal-ysed by using the nonlinear finite element method. The impact of the cross-section area of corrosion pit on pipeline failure pressure with the axial and circumferential corrosion was researched. The analysis showed that the cross-section area of corrosion pits seriously influenced the failure pressure of pipeline with axial corrosion, however, which was not enough to fully describe the effects of the morphology of corrosion pits on pipeline failure pressure. The research considered the effects of the morphology of corrosion pits by us-ing the cross-section area of corrosion pit and form factor of corrosion pit to descripe on pipeline failure pressure, and proposed a new B31G correction formula. The results show that forecast error and the fluctu-ation range of the error are little using the formula.

  11. Some investigations on the pitting attack of magnesium and its alloys; Contribution a l'etude de la corrosion par piqures du magnesium et de ses alliages

    Energy Technology Data Exchange (ETDEWEB)

    Blanchet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-03-01

    The pitting attack of magnesium and its alloys has been studied by means of potentio-kinetic polarisation curves; the following parameters have been considered: structural state and composition of the metal, chloride concentration and pH of the medium. The electrochemical data obtained demonstrate that when pH = 12, a localized corrosion might appear as soon as a 10{sup -3} M NaCl concentration is reached; on the other hand, when pH = 13, a much higher concentration (five times) has no effect. In the same conditions, the coupling of magnesium with various noble materials (graphite, platinum, 18/10 stainless steel) also dramatically increases its susceptibility to pitting, but only when chloride ions are present in the solution. Usual corrosion tests have confirmed these electrochemical results. A micrographic study of the pits has shown that their morphology is connected with the metallurgical state of the specimens. (author) [French] La corrosion par piqures du magnesium est etudiee a l'aide des courbes de polarisation potentiocinetiques en fonction des parametres suivants etat structural et composition du metal, concentration en chlorure et pH de la solution. De ces mesures electrochimiques on deduit qu'a pH 12, des la concentration 10{sup -3} M en NaCl, il existe un risque de corrosion localisee, tandis qu'a pH 13 une concentration cinq fois plus forte doit etre sans effet. Dans les memes conditions on montre que le couplage du magnesium avec differents elements nobles (graphite, platine, acier inoxydable 18/10) accroit fortement sa susceptibilite a l'attaque par piqures, excepte dans les solutions exemptes d'ions chlorures. Des essais classiques de corrosion dans les differentes solutions envisagees precedemment confirment les resultats de cette etude electrochimique. L'examen micrographique des piqures montre que leur morphologie est liee a l'etat metallurgique des echantillons. (auteur)

  12. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    Science.gov (United States)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  13. Hot Corrosion of Nickel-Base Alloys in Biomass-Derived Fuel Simulated Atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Leyens, C.; Pint, B.A.; Wright, I.G.

    1999-02-28

    Biomass fuels are considered to be a promising renewable source of energy. However, impurities present in the fuel may cause corrosion problems with the materials used in the hot sections of gas turbines and only limited data are available so far. As part of the Advanced Turbine Systems Program initiated by the U.S. Department of Energy, the present study provides initial data on the hot corrosion resistance of different nickel-base alloys against sodium sulfate-induced corrosion as a baseline, and against salt compositions simulating biomass-derived fuel deposits. Single crystal nickel-superalloy Rene N5, a cast NiCrAlY alloy, a NiCoCrAlY alloy representing industrially used overlay compositions, and a model {beta}NiAl+Hf alloy were tested in 1h thermal cycles at 950 C with different salt coatings deposited onto the surfaces. Whereas the NiCoCrAlY alloy exhibited reasonable resistance against pure sodium sulfate deposits, the NiCrAiY alloy and Rene N5 were attacked severely. Although considered to be an ideal alumina former in air and oxygen at higher temperatures, {beta}NiAl+Hf also suffered from rapid corrosion attack at 950 C when coated with sodium sulfate. The higher level of potassium present in biomass fuels compared with conventional fuels was addressed by testing a NiCoCrAlY alloy coated with salts of different K/Na atomic ratios. Starting at zero Na, the corrosion rate increased considerably when sodium was added to potassium sulfate. In an intermediate region the corrosion rate was initially insensitive to the K/Na ratio but accelerated when very Na-rich compositions were deposited. The key driver for corrosion of the NiCoCrAlY alloy was sodium sulfate rather than potassium sulfate, and no simple additive or synergistic effect of combining sodium and potassium was found.

  14. The inhibitive mechanisms of nitrite and molybdate anions on initiation and propagation of pitting corrosion for mild steel in chloride solution

    Science.gov (United States)

    Zhou, Yong; Zuo, Yu

    2015-10-01

    The inhibitive mechanism of NO2- and MoO42- on the initiation and propagation of pitting corrosion for mild steel in chloride solution was studied with electrochemical methods and X-ray photoelectron spectroscopy (XPS). In 0.1 M NaCl solution both the addition of 0.2 M NaNO2 and 0.2 M Na2MoO4 effectively promoted passivation of mild steel. The passive film on the steel surface formed in NaCl + NO2- solution was composed of mainly γ-Fe2O3, and the film formed in NaCl + MoO42- solution was composed of two components: one is Fe2(MoO4)3 and the other is an oxide composed of Fe and O. The film formed in NaNO2 solution has lower oxygen vacancies and larger impedance than the film formed in Na2MoO4 solution. NO2- shows better inhibition to the initiation of pitting corrosion than MoO42-, which is attributed to its strong oxidability that results in the formation of a stable γ-Fe2O3 film. However, in NaNO2 solution, once a pit forms, it is more difficult to get repassivated than the situation in Na2MoO4 solution. The main reason is due to that in a propagating pit MoO42- anions result in increased solution pH value, but conversely NO2- anions lead to a decreased solution pH value within a pit.

  15. COMPARATIVE STUDY OF THE CORROSION BEHAVIOR OF HOT DIP GALVANIZED, GALVANNEAL AND GALVALUME COATED STEELS

    Directory of Open Access Journals (Sweden)

    Álvaro Pritzel dos Santos

    2013-10-01

    Full Text Available Corrosion attack of Hot Dip Zn coatings on steels is comparatively studied. For this, the electrochemical behavior of the coatings hot dip galvanized (GI, galvanneal (GA and galvalume (Zn55Al are analyzed in chloride solutions by cyclic voltammetry and by Scanning Vibrating Electrode Technique, with and without the incidence of white light. Coatings were characterized by Scanning Electronic Microscopy and Energy Dispersive X-Ray Spectrometry. The results show that the incidence of white UV-VIS light has a minor influence on the corrosive process, although the coatings contain intermetallic phases with semiconductor nature. The tests show that among the three coatings, GA has the slowest dissolution rate, when in contact with the steel for high exposed areas of steel.

  16. Oxidation and Hot Corrosion of Gradient Thermal Barrier Coatings Prepared by EB-PVD

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermaloxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exhibitebetter resistance to not only oxidation but also hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibitesinward diffusion of O and S and outward diffusion of Al and Cr during the tests. On the other hand, an "inlaid"interface, resulting from oxidation of the Al along the columnar grains of the bond coat, enhances the adherence ofAl2O3 layer. Failure of the GTBC finally occurred by cracking at the interface between the bond coat and Al2O3layer, due to the combined effect of sulfidation of the bond coat and thermal cycling.

  17. Hot corrosion resistance of high-velocity oxyfuel sprayed coatings on a nickel-base superalloy in molten salt environment

    Science.gov (United States)

    Sidhu, T. S.; Prakash, S.; Agrawal, R. D.

    2006-09-01

    No alloy is immune to hot corrosion attack indefinitely. Coatings can extend the lives of substrate materials used at higher temperatures in corrosive environments by forming protective oxides layers that are reasonably effective for long-term applications. This article is concerned with studying the performance of high-velocity oxyfuel (HVOF) sprayed NiCrBSi, Cr3C2-NiCr, Ni-20Cr, and Stellite-6 coatings on a nickel-base superalloy at 900 °C in the molten salt (Na2SO4-60% V2O5) environment under cyclic oxidation conditions. The thermogravimetric technique was used to establish kinetics of corrosion. Optical microscope, x-ray diffraction, scanning electron microscopy/electron dispersive analysis by x-ray (SEM/EDAX), and electron probe microanalysis (EPMA) techniques were used to characterize the as-sprayed coatings and corrosion products. The bare superalloy suffered somewhat accelerated corrosion in the given environmental conditions. whereas hot corrosion resistance of all the coated superalloys was found to be better. Among the coating studied, Ni-20Cr coated superalloy imparted maximum hot corrosion resistance, whereas Stellite-6 coated indicated minimum resistance. The hot corrosion resistance of all the coatings may be attributed to the formation of oxides and spinels of nickel, chromium, or cobalt.

  18. 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.

  19. Finite Element Analysis of the Remnant Strength of the Water -cooled Wall Tubes with Different Corrosion Pit Shapes%有限元分析不同形状腐蚀坑水冷壁管的剩余强度

    Institute of Scientific and Technical Information of China (English)

    杨佳; 张轶桀; 顾天宏; 陈忠兵; 杨海松; 刘川

    2016-01-01

    ANSYS software is applied to analyze the remnant strength of the water -cooled wall tube with different corrosion pit shapes .The research results show that with cylinder corrosion pits ,when the corrosion diameter and corrosion depth reaches Ø5 mm-80% wall thickness ,Ø8 mm-70% wall thickness and Ø12 mm-60% wall thickness ,the tube can be thought of failure ;with sphere corrosion pits ,when the corrosion diameter and corrosion depth reaches 10 H-70% wall thickness ( H is the corrosion depth ) ,the tube can be thought of failure ;with rectangle corrosion pits ,when the corrosion diameter and corrosion depth reaches 6 H-60% wall thickness ,the tube can be considered as failure ;under the same size and corrosion depths of cylinder ,sphere and rectangle corrosion pits ,the tube with sphere pits is the safest and that with cylinder pits is most likely to fail .%基于ANSYS有限元软件,对含不同形状腐蚀坑水冷壁管剩余强度进行了研究。研究表明,将管壁上腐蚀坑简化为柱状,当腐蚀坑直径和腐蚀深度组合达到Ø5 mm-80%壁厚、Ø8 mm-70%壁厚、Ø12 mm-60%壁厚3种情况时,腐蚀坑直径和腐蚀深度增加则可认为腐蚀区失效;将腐蚀坑简化为球形,当腐蚀坑直径和腐蚀深度达到10 H-70%壁厚( H为腐蚀深度)时,腐蚀坑直径或深度增加则可认为腐蚀区域失效;将腐蚀坑简化为矩形,当腐蚀坑尺寸和腐蚀深度达到6 H-60%壁厚时,腐蚀深度和尺寸增加会造成腐蚀区域失效。相同尺寸和腐蚀深度的柱形坑、球形坑和矩形坑,球形坑最安全,柱形腐蚀坑最容易失效。

  20. Friction welding of a nickel free high nitrogen steel: influence of forge force on microstructure, mechanical properties and pitting corrosion resistance

    Directory of Open Access Journals (Sweden)

    Mrityunjoy Hazra

    2014-01-01

    Full Text Available In the present work, nickel free high nitrogen austenitic stainless steel specimens were joined by continuous drive friction welding process by varying the amount of forge (upsetting force and keeping other friction welding parameters such as friction force, burn-off, upset time and speed of rotation as constant at appropriate levels. The joint characterization studies include microstructural examination and evaluation of mechanical (micro-hardness, impact toughness and tensile and pitting corrosion behaviour. The integrity of the joint, as determined by the optical microscopy was very high and no crack and area of incomplete bonding were observed. Welds exhibited poor Charpy impact toughness than the parent material. Toughness for friction weld specimens decreased with increase in forge force. The tensile properties of all the welds were almost the same (irrespective of the value of the applied forge force and inferior to those of the parent material. The joints failed in the weld region for all the weld specimens. Weldments exhibited lower pitting corrosion resistance than the parent material and the corrosion resistance of the weld specimens was found to decrease with increase in forge force.

  1. Synergy between molybdenum and nitrogen on the pitting corrosion and passive film resistance of austenitic stainless steels as a pH-dependent effect

    Energy Technology Data Exchange (ETDEWEB)

    Loable, Carole, E-mail: carole.loable@lepmi.grenoble-inp.fr [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Dep. Eng. Quimica, Instituto Superior Técnico-Universidade de Lisboa, Av. Rovisco Pais, 1049 001 Lisbon (Portugal); Viçosa, Isadora N., E-mail: inogueira@poli.ufrj.br [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Mesquita, Thiago J., E-mail: Thiago.mesquita@total.com [CRU Ugitech, Avenue Paul Girod, 73403 Ugine Cedex (France); Mantel, Marc, E-mail: Marc.Mantel@ugitech.com [CRU Ugitech, Avenue Paul Girod, 73403 Ugine Cedex (France); Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Nogueira, Ricardo P., E-mail: rnogueira@pi.ac.ae [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Department of Chemical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Berthomé, Gregory, E-mail: gregory.berthome@simap.grenoble-inp.fr [Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Chauveau, Eric, E-mail: eric.chauveau@ugitech.fr [Department of Chemical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Roche, Virginie, E-mail: virginie.roche@lepmi.grenoble-inp.fr [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France)

    2017-01-15

    This paper brings up some insights upon the pH dependence of the synergistic effect of Mo and N on the localized corrosion resistance of austenitic stainless steels. The objective of this work is to study the synergetic effect of Mo and N additions on corrosion and passive film properties of austenitic grades. A comparison between Mo containing (3 wt% Mo); Mo and N containing (3 wt% Mo and 0.1% N) and free Mo or free Mo and N grades of highly controlled laboratory heats was done considering their localized corrosion resistance and oxide film formation in different aggressive conditions, from neutral to alkaline pH. The passive layer was characterized by EIS and XPS analyses. The combined effect of Mo and N on the pitting potential was confirmed to be synergistic, and not just the addition of their individual effects. Moreover, this effect was found to be pH-dependent, being very positive in acid to neutral conditions whereas it was almost inexistent in high pH. - Highlights: • Laboratory austenitic stainless steels with Mo and/or N were tested. • Mo and N acted synergistically to improve pitting resistance. • Synergistic effect is pH-dependent. • N clearly enhanced the repassivation of austenitic SS in presence of Mo.

  2. The Hot Corrosion Performance of NiCr-Cr3 C2 Cermet Coating to Boiler Tube

    Institute of Scientific and Technical Information of China (English)

    DINGZhang-xiong; TUGuo-fu

    2004-01-01

    Three kinds of NiCr-Cr3 C2 cermet coatings were designed and deposited by the subsonic velocity flame spraying, and their performances of hot corrosion performance were evaluated in comt)arison with 102G,20G boiler tube steel, FeCrAl, NiCrTi, Ni5OCr and NiCrAIMoFe-Cr3 C2 coatings, which are widely used at present for protection of boiler tubes. Meanwhile, the influence of sealer on the hot corrosion resistance of warious coatings and the mechanisms of coating corrosion were explored.

  3. Crevice corrosion and pitting of high-level waste containers: a first step towards the integration of deterministic and probabilistic models

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J. C., LLNL

    1997-07-01

    An integrated predictive model is being developed to account for the effects of localized environmental conditions in crevices on pit initiation and propagation. A deterministic calculation is used to estimate the accumulation of hydrogen ions in the crevice solution due to equilibrium hydrolysis reactions of dissolved metal. Pit initiation and growth within the crevice is dealt with by either a stochastic probability model, or an equivalent deterministic model. While the strategy presented here is very promising, the integrated model is not yet ready for accurate quantitative predictions. Empirical expressions for the rate of penetration based upon experimental crevice corrosion data should be used in the interim period, until the integrated model can be refined. Both approaches are discussed.

  4. The Role of Nanostructured Al2O3 Layer in Reduction of Hot Corrosion Products in Normal YSZ Layer

    Directory of Open Access Journals (Sweden)

    Mohammadreza Daroonparvar

    2013-01-01

    Full Text Available YVO4 crystals and monoclinic ZrO2 are known as hot corrosion products that can considerably reduce the lifetime of thermal barrier coatings during service. The hot corrosion resistance of two types of air plasma sprayed thermal barrier coating systems was investigated: an Inconel 738/NiCrAlY/YSZ (yttria-stabilized zirconia and an Inconel 738/NiCrAlY/YSZ/nano-Al2O3 as an outer layer. Hot corrosion test was accomplished on the outer surface of coatings in molten salts (45% Na2SO4 + 55% V2O5 at 1000°C for 52 hour. It was found that nanostructured alumina as outer layer of YSZ/nano-Al2O3 coating had significantly reduced the infiltration of molten salts into the YSZ layer and resulted in lower reaction of fused corrosive salts with YSZ, as the hot corrosion products had been substantially decreased in YSZ/nano-Al2O3 coating in comparison with normal YSZ coating after hot corrosion process.

  5. Failure of a MEA reclaimer tube bundle due to corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Shaban, H.; Abdo, M.S.E.; Lal, D.P.

    1988-08-01

    The removal of sulphur compounds from natural gas used in ammonia production is carried out by scrubbing with monoethanol amine (MEA). To avoid build up of corrosion and degradation products, a portion of the circulating MEA solution is passed through a reclaimer. This is essentially a kettle-type reboiler with a tube bundle made of 316L stainless steel. Occasional failures of the tube bundle due to pitting corrosion have been reported. It is suggested that the excessive pitting corrosion observed on the upper rows of the tube bundle could be partly due to high steam temperature but mainly due to the liquid level falling below the tubes leaving an accumulation of corrosive degradation products on the exposed surfaces, normally these corrosive products remain diluted in the MEA solution and cause little corrosion of the covered tubes. Their concentration on the dry upper layers of the hot metal tubes, however, leads to excessive corrosion. (U.K.).

  6. High temperature corrosion of advanced ceramic materials for hot-gas filters and heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Kupp, E.R.; Trubelja, M.F.; Spear, K.E.; Tressler, R.E. [Pennsylvania State Univ., University Park, PA (United States)

    1995-08-01

    Experimental corrosion studies of hot gas filter materials and heat exchanger materials in oxidizing combustion environments have been initiated. Filter materials from 3M Co. and DuPont Lanxide Composites Inc. are being tested over a range of temperatures, times and gas flows. It has been demonstrated that morphological and phase changes due to corrosive effects occur after exposure of the 3M material to a combustion environment for as little as 25 hours at 800{degrees}C. The study of heat exchanger materials has focused on enhancing the corrosion resistance of DuPont Lanxide Dimox{trademark} composite tubes by adding chromium to its surfaces by (1) heat treatments in a Cr{sub 2}O{sub 3} powder bed, or (2) infiltrating surface porosity with molten chromium nitrate. Each process is followed by a surface homogenization at 1500{degrees}C. The powder bed method has been most successful, producing continuous Cr-rich layers with thicknesses ranging from 20 to 250 {mu}m. As-received and Cr-modified DuPont Lanxide Dimox{trademark} samples will be reacted with commonly encountered coal-ash slags to determine the Cr effects on corrosion resistance.

  7. Microstructural, mechanical, corrosion and cytotoxicity characterization of the hot forged FeMn30(wt.%) alloy.

    Science.gov (United States)

    Čapek, Jaroslav; Kubásek, Jiří; Vojtěch, Dalibor; Jablonská, Eva; Lipov, Jan; Ruml, Tomáš

    2016-01-01

    An interest in biodegradable metallic materials has been increasing in the last two decades. Besides magnesium based materials, iron-manganese alloys have been considered as possible candidates for fabrication of biodegradable stents and orthopedic implants. In this study, we prepared a hot forged FeMn30 (wt.%) alloy and investigated its microstructural, mechanical and corrosion characteristics as well as cytotoxicity towards mouse L 929 fibroblasts. The obtained results were compared with those of iron. The FeMn30 alloy was composed of antiferromagnetic γ-austenite and ε-martensite phases and possessed better mechanical properties than iron and even that of 316 L steel. The potentiodynamic measurements in simulated body fluids showed that alloying with manganese lowered the free corrosion potential and enhanced the corrosion rate, compared to iron. On the other hand, the corrosion rate of FeMn30 obtained by a semi-static immersion test was significantly lower than that of iron, most likely due to a higher degree of alkalization in sample surrounding. The presence of manganese in the alloy slightly enhanced toxicity towards the L 929 cells; however, the toxicity did not exceed the allowed limit and FeMn30 alloy fulfilled the requirements of the ISO 10993-5 standard.

  8. Mechanical properties and corrosion resistance of hot extruded Mg–2.5Zn–1Ca alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dexue, E-mail: dexeliu@hotmail.com [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States); Guo, Chenggong; Chai, Liqiang [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Sherman, Vincent R. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States); Qin, Xiaoqiong; Ding, Yutian [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Meyers, Marc A. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States)

    2015-05-15

    Highlights: • MgZnCa alloy was extruded into precise microtube for resorbable stent applications. • Interconnection between micro-structure and corrosion properties was revealed. • Both strength and ductility were simultaneously improved by processing sequence. • Better corrosion resistance in PBS solution was achieved after grain refining. - Abstract: It is demonstrated that the mechanical properties and corrosion resistance of Mg–2.5 wt%Zn–1 wt%Ca alloy are enhanced by the microstructural changes imparted by hot extrusion. A processing procedure is developed to form hollow tubes with an outer diameter of ∼2.0 mm and wall thickness of ∼0.1 mm, which is well suited for subsequent stent manufacturing. The influence of thermal and mechanical processing on corrosion and plasticity was found to be associated with grain-size reduction and the redistribution of intermetallic particles within the microstructure, providing significant improvement of performance over the cast alloy. Observation of the fracture surfaces reveals a mode transition from brittle (cast) to ductile (processed). Enhanced mechanical properties and decreased resorption rate represent significantly improved performance of this alloy after the novel processing sequence. Based on the improved properties, the produced Mg alloy is more suitable for practical in vivo applications.

  9. Vanadate-Sulfate Melt Thermochemistry Relating to Hot Corrosion of Thermal Barrier Coatings.

    Science.gov (United States)

    2007-11-02

    ship propulsion or electricity generation), such TBCs may be corroded by molten vanadate-sulfate deposits from fuel impurities. This Report provides a synopsis of vanadate-sulfate thermochemistry relating to TBC hot corrosion, and summarizes research conducted on this topic at the Naval Research Laboratory. The interactions of Na2O, V2O5 and SO3, the melt components which determine the composition of the vanadate-sulfate deposits, were examined and clarified. Vanadate-sulfate melts were shown to be nonideal rather than ideal a point of some contention in the past

  10. Image analysis of corrosion pit initiation on ASTM type A240 stainless steel and ASTM type A 1008 carbon steel

    Science.gov (United States)

    Nine, H. M. Zulker

    The adversity of metallic corrosion is of growing concern to industrial engineers and scientists. Corrosion attacks metal surface and causes structural as well as direct and indirect economic losses. Multiple corrosion monitoring tools are available although those are time-consuming and costly. Due to the availability of image capturing devices in today's world, image based corrosion control technique is a unique innovation. By setting up stainless steel SS 304 and low carbon steel QD 1008 panels in distilled water, half-saturated sodium chloride and saturated sodium chloride solutions and subsequent RGB image analysis in Matlab, in this research, a simple and cost-effective corrosion measurement tool has identified and investigated. Additionally, the open circuit potential and electrochemical impedance spectroscopy results have been compared with RGB analysis to gratify the corrosion. Additionally, to understand the importance of ambiguity in crisis communication, the communication process between Union Carbide and Indian Government regarding the Bhopal incident in 1984 was analyzed.

  11. 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)

  12. 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)

  13. Evaluation of hot corrosion behaviour of HVOF sprayed NiCrAl coating on superalloys at 900 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Mahesh, R.A. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, IIT Roorkee Campus, Roorkee 247667, Uttarakhand (India); Jayaganthan, R. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, IIT Roorkee Campus, Roorkee 247667, Uttarakhand (India)], E-mail: rjayafmt@iitr.ernet.in; Prakash, S. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, IIT Roorkee Campus, Roorkee 247667, Uttarakhand (India)

    2008-10-15

    In the present investigation, NiCrAl coating was deposited on Ni- and Fe-based superalloy substrates by using high velocity oxy-fuel (HVOF) process to study the hot corrosion behaviour in molten salt (Na{sub 2}SO{sub 4}-60% V{sub 2}O{sub 5}) environment at 900 deg. C under cyclic conditions. The mass gain measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopic analysis (SEM/EDS) and X-ray mapping techniques were used to analyse the corrosion products. The bare superalloys experienced higher weight gain. The NiCrAl-coated Superni 750 alloy (SN 750) provided a better protection among the coated superalloys investigated. The formation of oxides and spinels of nickel, chromium and aluminum may be contributing better resistance to hot corrosion.

  14. 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.

  15. Hot Corrosion Studies of HVOF-Sprayed Coating on T-91 Boiler Tube Steel at Different Operating Temperatures

    Science.gov (United States)

    Bhatia, Rakesh; Singh, Hazoor; Sidhu, Buta Singh

    2013-11-01

    The aim of the present work is to investigate the usefulness of high velocity oxy fuel-sprayed 75% Cr3C2-25% (Ni-20Cr) coating to control hot corrosion of T-91 boiler tube steel at different operating temperatures viz 550, 700, and 850 °C. The deposited coatings on the substrates exhibit nearly uniform, adherent and dense microstructure with porosity less than 2%. Thermogravimetry technique is used to study the high temperature hot corrosion behavior of uncoated and coated samples. The corrosion products of the coating on the substrate are analyzed by using XRD, SEM, and FE-SEM/EDAX to reveal their microstructural and compositional features for the corrosion mechanisms. It is found that the coated specimens have shown minimum weight gain at all the operating temperatures when compared with uncoated T-91 samples. Hence, coating is effective in decreasing the corrosion rate in the given molten salt environment. Oxides and spinels of nickel-chromium may be the reason for successful resistance against hot corrosion.

  16. The Effect of La on the Microstructure and Corrosion-resistance of Hot-dipped Aluminizing Steel

    Institute of Scientific and Technical Information of China (English)

    WENJiu-ba; ZHANGWei; LIXiao-yuan; LIQuan-an

    2004-01-01

    The effect of the content of rare-earth La on the microstructure and corrosion-resistance of hot-dipped aluminum was investigated in this paper. The results show that, under the same technology conditions, the thickness of hot-dipped aluminizing layer by adding the appropriate content of rare-earth La is about 2-3 times as much as that without rare-earth La, and the microstructure of hot-dipped aluminizing layer has also greatly changed ,and a great deal of phase Fe3A1 waspreci pitated along the boundary of a phase. The corrosion resistance of the hot-dipped layer with rare-earth is greatly increased.

  17. The Effect of La on the Microstructure and Corrosion-resistance of Hot-dipped Aluminizing Steel

    Institute of Scientific and Technical Information of China (English)

    WEN Jiu-ba; ZHANG Wei; LI Xiao-yuan; LI Quan-an

    2004-01-01

    The effect of the content of rare-earth La on the microstructure and corrosion-resistance of hot-dipped aluminum was investigated in this paper. The results show that, under the same technology conditions, the thickness of hot-dipped aluminizing layer by adding the appropriate content of rare-earth La is about 2~3 times as much as that without rare-earth La, and the microstructure of hot-dipped aluminizing layer has also greatly changed ,and a great deal of phase Fe3Al was precipitated along the boundary of α phase. The corrosion resistance of the hot-dipped layer with rare-earth is greatly increased.

  18. PITTING CORROSION IN EROSIVE CONDITION OF AGED 550°C CU10NI-3AL-1,3FE ALLOY IN 0,01 M NA2 SO4

    Directory of Open Access Journals (Sweden)

    Rodrigo Nascimento Liberto

    2012-09-01

    Full Text Available This study evaluates the effect of aging at 550°C on pitting corrosion of Cu10Ni-3Al-1.3Fe alloy, after potentiodynamic polarization test in 0.01 M Na2 SO4 in erosive condition. Cold rolled sheet specimens were solution treated at 900°C for 1 hour, and aged at 550°C until 1,032 hours. The investigation was carried out by potentiodynamic polarization in electrolyte consisted of 0.01 M Na2 SO4 with 10 wt. (% of Al2 O3 abrasive particles. After the polarization tests, specimens were analyzed by optical microscopy and scanning electron microscopy techniques to examine the morphology of the corroded regions. Result show that all samples present a passivity break potential (Eq that characterizes the initiation of pitting corrosion. However, it is not observed any significant change in the value of passivity break potential as a function of aging time. The mechanism of pitting corrosion in the studied alloys can be the passivity breakdown by the action of sulfate ion, followed by growth of pit by galvanic action or dissolution of the copper in cupric and cuprous ions and membrane formation of cuprous oxide over the pit

  19. Burn Pits

    Science.gov (United States)

    ... Enter ZIP code here Enter ZIP code here Burn Pits Burn Pits Registry Studies Photo: U.S. Department ... the health of deployed Veterans. Health effects from burn pit smoke Toxins in burn pit smoke may ...

  20. Comparison of anti-corrosive properties between hot alkaline nitrate blackening and hydrothermal blackening routes

    Energy Technology Data Exchange (ETDEWEB)

    Fattah-alhosseini, A. [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Yazdani Khan, H., E-mail: hamid.yazdanikhan@gmail.com [Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of); Heidarpour, A. [Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, 65155-579 (Iran, Islamic Republic of)

    2016-08-15

    In this study, the oxide films were formed on carbon steel by using hot alkaline nitrate and hydrothermal treatments. A dense and protective oxide film was obtained by hydrothermal method due to application of high pressure and by increasing solution temperature from boiling temperature (155 °C) to 250 °C. Oxide films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical tests including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These analyses showed that the magnetite film which was formed on carbon steel surface by hydrothermal treatment offers the best resistance in 3.5 wt.% NaCl solution. Although thicker oxide film could be obtained via hot alkaline nitrate black oxidizing, corrosion resistance was lower as a result of being highly porous and the presence of hematite. - Highlights: • Oxide films have been formed on steel by using of hot alkaline nitrate and hydrothermal treatments. • A dense and protective oxide film was obtained by hydrothermal treatment. • SEM micrographs showed that a dense and protective oxide film was obtained by hydrothermal treatment. • Film formed by hydrothermal treatment could have the best resistance in 3.5 wt.% NaCl solution.

  1. Hot Corrosion Behaviour of Detonation Gun Sprayed Al2O3-40TiO2 Coating on Nickel Based Superalloys at 900°C

    Directory of Open Access Journals (Sweden)

    N. K. Mishra

    2014-01-01

    Full Text Available Hot corrosion is the major degradation mechanism of failure of boiler and gas turbine components. These failures occur because of the usage of wide range of fuels such as, coal and oil at the elevated temperatures. Nickel based superalloys having excellent mechanical strength and creep resistance at elevated temperature are used under such environment but they lack resistance to hot corrosion at high temperature. To overcome these problems hot corrosion resistant coatings are deposited on these materials. In the current investigation Al2O3-40%TiO2 powder has been deposited on Superni 718 and AE 435 superalloys by Detonation Gun method. The hot corrosion performance of Al2O3-40%TiO2 coated as well as uncoated Superni 718 and AE 435 alloys has been evaluated in aggressive environment Na2SO4-82%Fe2(SO43 under cyclic conditions at an elevated temperature of 900°C. The kinetics of the corrosion is approximated by weight change measurements made after each cycle for total duration of 50 cycles. Scanning electron microscopy was used to characterize the hot corrosion products. The coated samples imparted better hot corrosion resistance than the uncoated ones. The AE 435 superalloy performed better than Superni 718 for hot corrosion in a given environment.

  2. 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.

  3. Hot Corrosion Behavior of Arc-Sprayed Highly Dense NiCr-Based Coatings in Chloride Salt Deposit

    Science.gov (United States)

    Qin, Enwei; Yin, Song; Ji, Hua; Huang, Qian; Liu, Zekun; Wu, Shuhui

    2017-03-01

    To make cities more environmentally friendly, combustible wastes tend to be incinerated in waste-to-energy power plant boilers. However, release of chlorine gas (Cl2) during incineration causes serious problems related to hot corrosion of boiler tubes and poses a safety threat for such plants. In this study, a pseudo-de Laval nozzle was employed in a twin-wire arc spray system to enhance the velocity of in-flight particles. Highly dense NiCr-based coatings were obtained using the modified nozzle gun. The coating morphology was characterized by optical microscopy and scanning electron microscopy, and hot corrosion testing was carried out in a synthetic molten chloride salt environment. Results showed that the dense NiCr-based coatings exhibited high resistance against corrosion by chlorine, which can be related to the typical splat lamellar microstructure and chemical composition as well as minor alloying elements such as Ti and Mo.

  4. Hot Corrosion Behavior of Arc-Sprayed Highly Dense NiCr-Based Coatings in Chloride Salt Deposit

    Science.gov (United States)

    Qin, Enwei; Yin, Song; Ji, Hua; Huang, Qian; Liu, Zekun; Wu, Shuhui

    2017-04-01

    To make cities more environmentally friendly, combustible wastes tend to be incinerated in waste-to-energy power plant boilers. However, release of chlorine gas (Cl2) during incineration causes serious problems related to hot corrosion of boiler tubes and poses a safety threat for such plants. In this study, a pseudo-de Laval nozzle was employed in a twin-wire arc spray system to enhance the velocity of in-flight particles. Highly dense NiCr-based coatings were obtained using the modified nozzle gun. The coating morphology was characterized by optical microscopy and scanning electron microscopy, and hot corrosion testing was carried out in a synthetic molten chloride salt environment. Results showed that the dense NiCr-based coatings exhibited high resistance against corrosion by chlorine, which can be related to the typical splat lamellar microstructure and chemical composition as well as minor alloying elements such as Ti and Mo.

  5. 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.

  6. Effect of Mg content on microstructure and corrosion behavior of hot dipped Zn–Al–Mg coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Caizhen; Lv, Haibing [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Zhu, Tianping [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand); Zheng, Wanguo [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Yuan, Xiaodong, E-mail: xdyuan@caep.cn [Research Centre of Laser Fusion, CAEP, P.O.Box 919-988-5, Mianyang, Sichuan 621900 (China); Gao, Wei, E-mail: w.gao@auckland.ac.nz [Department of Chemical and Materials Engineering, The University of Auckland, PB 92019, Auckland 1142 (New Zealand)

    2016-06-15

    In this article, Zn–Al–Mg coatings were prepared by hot dipping method. The surface morphology, cross–section microstructure, microhardness, composition, corrosion behaviour of ZAM coatings were investigated by using X–ray diffraction (XRD), Optical microscope, Environmental scanning electron microscopy equipped with EDS (FESEM–EDS), Microhardness tester and Electrochemical analysis respectively. Corrosion test was also performed in a standard salt fog spray chamber. Microstructure studies indicates that Zn grain size was refined and eutectic areas at Zn grain boundary areas increased with increasing Mg content. ZA5M1.5 and ZA5M2 coatings have two distinct layers. Mg tends to exist in the outer layer while Al is in the inner layer. The inner layer is composed of Al{sub 5}Fe{sub 2}Zn{sub 0.4} intermetallic, which may to contribute to the microhardness. The outer layer is Zn grains surrounded by Zn–Mg etutectics, which may improve the corrosion resistance. The microhardness is more than 700 HV{sub 50g} for Al-rich layer and around 151 HV{sub 25g} for Mg-rich layer. The improved corrosion resistance of Zn–5%Al-1.5%Mg coating comes from the corrosion product of flocculent type simonkolleite, which prolongs the micro-path and impedes the movement of O{sub 2} and H{sub 2}O, ultimately retards the overall corrosion process. - Highlights: • Two-layer structured Zn–Al–Mg coatings were prepared by hot dipping method. • Mg exists in the outer layer while Al exists in the inner layer of Zn–Al–Mg coating. • Zn–Al–Mg coating has better protective ability than Zn and Zn–Al coatings. • The Mg-modified simonkolleite is the reason of the enhanced corrosion resistance.

  7. Improving hot corrosion resistance of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with enamel coating

    Science.gov (United States)

    Pambudi, Muhammad Jajar; Basuki, Eddy Agus; Prajitno, Djoko Hadi

    2017-01-01

    TiAl intermetallic alloys have attracted great interest among aerospace industry after successful utilization in low pressure turbine blades of aircraft engine which makes dramatic weight saving up to 40% weight saving. However, poor oxidation and corrosion resistance at temperatures above 800°C still become the drawbacks of this alloys, making the development of protective coatings to improve the resistance is important. This study investigates the hot corrosion behavior of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with and without enamel coating using immersion test method in molten salt of 85%-wt Na2SO4 and 15%-wt NaCl at 850°C. The results show after 50 hours of hot corrosion test, bare alloy showed poor hot corrosion resistance due to the formation of non-protective Al2O3+TiO2 mixed scale at the surface of the alloy. Improvement of hot corrosion resistance was obtained in samples protected with enamel coating, indicated by significant decreasing in mass change (mg/cm2) by 98.20%. Enamel coating is expected to has the capability in suppressing the diffusion of oxygen and corrosive ions into the substrate layer, and consequently, it improves hot corrosion resistance of the alloy. The study showed that enamel coatings have strong adherent to the substrate and no spallation was observed after hot corrosion test. Nevertheless, the dissolution of oxides components of the enamel coating into the molten salts was observed that lead enamel coating degradation. This degradation is believed involving Cl- anion penetration into the substrate through voids in the coating that accelerates the corrosion of the two phases α2-Ti3Al/γ-TiAl alloy. Even though further observations are needed, it appears that enamel coating could be a promising protective coating to increase hot corrosion resistance of TiAl intermetallic alloys.

  8. Automated Methods Of Corrosion Measurements

    DEFF Research Database (Denmark)

    Bech-Nielsen, Gregers; Andersen, Jens Enevold Thaulov; Reeve, John Ch

    1997-01-01

    The chapter describes the following automated measurements: Corrosion Measurements by Titration, Imaging Corrosion by Scanning Probe Microscopy, Critical Pitting Temperature and Application of the Electrochemical Hydrogen Permeation Cell.......The chapter describes the following automated measurements: Corrosion Measurements by Titration, Imaging Corrosion by Scanning Probe Microscopy, Critical Pitting Temperature and Application of the Electrochemical Hydrogen Permeation Cell....

  9. High temperature corrosion of advanced ceramic materials for hot gas filters and heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Crossland, C.E.; Shelleman, D.L.; Spear, K.E. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1996-08-01

    A vertical flow-through furnace has been built to study the effect of corrosion on the morphology and mechanical properties of ceramic hot gas filters. Sections of 3M Type 203 and DuPont Lanxide SiC-SiC filter tubes were sealed at one end and suspended in the furnace while being subjected to a simulated coal combustion environment at 870{degrees}C. X-ray diffraction and electron microscopy is used to identify phase and morphology changes due to corrosion while burst testing determines the loss of mechanical strength after exposure to the combustion gases. Additionally, a thermodynamic database of gaseous silicon compounds is currently being established so that calculations can be made to predict important products of the reaction of the environment with the ceramics. These thermodynamic calculations provide useful information concerning the regimes where the ceramic may be degraded by material vaporization. To verify the durability and predict lifetime performance of ceramic heat exchangers in coal combustion environments, long-term exposure testing of stressed (internally pressurized) tubes must be performed in actual coal combustion environments. The authors have designed a system that will internally pressurize 2 inch OD by 48 inch long ceramic heat exchanger tubes to a maximum pressure of 200 psi while exposing the outer surface of the tubes to coal combustion gas at the Combustion and Environmental Research Facility (CERF) at the Pittsburgh Energy and Technology Center. Water-cooled, internal o-ring pressure seals were designed to accommodate the existing 6 inch by 6 inch access panels of the CERF. Tubes will be exposed for up to a maximum of 500 hours at temperatures of 2500 and 2600{degrees}F with an internal pressure of 200 psi. If the tubes survive, their retained strength will be measured using the high temperature tube burst test facility at Penn State University. Fractographic analysis will be performed to identify the failure source(s) for the tubes.

  10. Effect of Annealing Temperature on the Corrosion Protection of Hot Swaged Ti-54M Alloy in 2 M HCl Pickling Solutions

    Directory of Open Access Journals (Sweden)

    El-Sayed M. Sherif

    2017-01-01

    Full Text Available The corrosion of Ti-54M titanium alloy processed by hot rotary swaging and post-annealed to yield different grain sizes, in 2 M HCl solutions is reported. Two annealing temperatures of 800 °C and 940 °C, followed by air cooling and furnace cooling were used to give homogeneous grain structures of 1.5 and 5 μm, respectively. It has been found that annealing the alloy at 800 °C decreased the corrosion of the alloy, with respect to the hot swaged condition, through increasing its corrosion resistance and decreasing the corrosion current and corrosion rate. Increasing the annealing temperature to 940 °C further decreased the corrosion of the alloy.

  11. Growth and corrosion resistance of molybdate modified zinc phosphate conversion coatings on hot-dip galvanized steel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The modified zinc phosphate conversion coatings(ZPC) were formed on hot-dip galvanized(HDG) steel when 1.0 g/L sodium molybdate were added in a traditional zinc phosphate solution. The growth performance and corrosion resistance of the modified ZPC were investigated by SEM, open circuit potential(OCP), mass gain, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) measurements and compared with those of the traditional ZPC. The results show that if sodium molybdate is added in a traditional zinc phosphate solution, the nucleation of zinc phosphate crystals is increased obviously; zinc phosphate crystals are changed from bulky acicular to fine flake and a more compact ZPC is obtained. Moreover, the mass gain and coverage of the modified ZPC are also boosted. The corrosion resistance of ZPI is increased with an increase in coverage, and thus the corrosion protection ability of the modified ZPC for HDG steel is more outstanding than that of the traditional ZPC.

  12. A multiple linear regression analysis of hot corrosion attack on a series of nickel base turbine alloys

    Science.gov (United States)

    Barrett, C. A.

    1985-01-01

    Multiple linear regression analysis was used to determine an equation for estimating hot corrosion attack for a series of Ni base cast turbine alloys. The U transform (i.e., 1/sin (% A/100) to the 1/2) was shown to give the best estimate of the dependent variable, y. A complete second degree equation is described for the centered" weight chemistries for the elements Cr, Al, Ti, Mo, W, Cb, Ta, and Co. In addition linear terms for the minor elements C, B, and Zr were added for a basic 47 term equation. The best reduced equation was determined by the stepwise selection method with essentially 13 terms. The Cr term was found to be the most important accounting for 60 percent of the explained variability hot corrosion attack.

  13. Layer texture of hot-rolled BCC metals and its significance for stress-corrosion cracking of main gas pipelines

    Science.gov (United States)

    Perlovich, Yu. A.; Isaenkova, M. G.; Krymskaya, O. A.; Morozov, N. S.

    2016-10-01

    Based on data of X-ray texture analysis of hot-rolled BCC materials it was shown that the layerwise texture inhomogeneity of products is formed during their manufacturing. The effect can be explained by saturation with interstitial impurities of the surface layer, resulting in dynamical deformation aging (DDA). DDA prevents the dislocation slip under rolling and leads to an increase of lattice parameters in the external layer. The degree of arising inhomogeneity correlates with the tendency of hot-rolled sheets and obtained therefrom tubes to stress-corrosion cracking under exploitation, since internal layers have a compressive effect on external layers, and prevents opening of corrosion cracks at the tube surface.

  14. 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.

  15. LWRS Fuels Pathway: Engineering Design and Fuels Pathway Initial Testing of the Hot Water Corrosion System

    Energy Technology Data Exchange (ETDEWEB)

    Dr. John Garnier; Dr. Kevin McHugh

    2012-09-01

    The Advanced LWR Nuclear Fuel Development R&D pathway performs strategic research focused on cladding designs leading to improved reactor core economics and safety margins. The research performed is to demonstrate the nuclear fuel technology advancements while satisfying safety and regulatory limits. These goals are met through rigorous testing and analysis. The nuclear fuel technology developed will assist in moving existing nuclear fuel technology to an improved level that would not be practical by industry acting independently. Strategic mission goals are to improve the scientific knowledge basis for understanding and predicting fundamental nuclear fuel and cladding performance in nuclear power plants, and to apply this information in the development of high-performance, high burn-up fuels. These will result in improved safety, cladding, integrity, and nuclear fuel cycle economics. To achieve these goals various methods for non-irradiated characterization testing of advanced cladding systems are needed. One such new test system is the Hot Water Corrosion System (HWCS) designed to develop new data for cladding performance assessment and material behavior under simulated off-normal reactor conditions. The HWCS is capable of exposing prototype rodlets to heated, high velocity water at elevated pressure for long periods of time (days, weeks, months). Water chemistry (dissolved oxygen, conductivity and pH) is continuously monitored. In addition, internal rodlet heaters inserted into cladding tubes are used to evaluate repeated thermal stressing and heat transfer characteristics of the prototype rodlets. In summary, the HWCS provides rapid ex-reactor evaluation of cladding designs in normal (flowing hot water) and off-normal (induced cladding stress), enabling engineering and manufacturing improvements to cladding designs before initiation of the more expensive and time consuming in-reactor irradiation testing.

  16. Study on the Pitting Corrosion Behavior of Super 13Cr Casing and Tubing Steel%超级13Cr油套管钢的点蚀行为研究

    Institute of Scientific and Technical Information of China (English)

    张国超; 林冠发; 张涓涛

    2013-01-01

    石油管材的点蚀穿孔是管材失效的主要原因,采用电化学测试和化学浸泡的方法,研究了超级13Cr油套管钢的点蚀行为,旨在为超级13Cr钢的研究开发提供依据.结果表明,Cl-和温度是影响超级13Cr钢点蚀发生的主要原因,材料的点蚀敏感性均随Cl-浓度和温度的升高而增加;电化学和化学浸泡两种方法测定的临界点蚀温度(CPT)分别为40.5℃和37.5℃,相差3℃.当温度低于CPT时,13Cr钢处于破钝和再钝化的平衡状态,材料表面形成少、小而浅的点蚀坑;当温度高于CPT时,13Cr钢表面则形成多、大而深的点蚀坑,点蚀全面发生.%The pitting corrosion is the main reason for the failure of petroleum tubular goods.In this article,by the electrochemical test and chemical immersion method,it studied the pitting corrosion behavior of super 13Cr casing and tubing steel to provide the basis for research and development.The results showed that Cl-and temperature are the main influence factors for pitting corrosion of super 13Cr,with Cl-concentration and temperature increasing,the pitting corrosion sensitivity increases.The critical pitting temperature is respectively 40.5 ℃ and 37.5 ℃,by the electrochemical test and chemical immersion method,the difference is 3 ℃.When the temperature is below the CPT,13Cr steel is in equilibrium state of breaking inactivation and repassivation,few,small and shallow pitting dents form on material surface; when the temperature is above CPT,many,big and deep dents appear,so the pitting entirely happen.

  17. PITTING CORROSION OF X70 PIPELINE STEEL IN THE SIMULATED WET STORAGE ENVIRONMENT%X70钢在模拟潮湿存储环境中的点蚀行为

    Institute of Scientific and Technical Information of China (English)

    刘智勇; 董超芳; 贾志军; 李晓刚

    2011-01-01

    Pitting mechanism and behaviour of X70 pipeline steel in humid storage environ ments were investigated using electrochemical polarization curves, electrochemical impedance spec trums (EIS), immersing corrosion tests and corrosion morphology observation through SEM. It was demonstrated that pitting of X70 pipeline steel occurred in simulated moist storage environments, for which the corrosive substances came from the residual species in laminar cooling water introduced during steel manufacture processes. HCO3- and NOJ are passivating agents, Cl- and SO42- would destroyed the passivation layer, which could lead to pitting. In solution with 0.5 mol/L NaHCO3, 0.02 mol/L Cl- was enough to break the passivation layer. Cl- concentration is a key factor for pit ting initiation and propagation. When the Cl- concentration was relatively low, pitting could initiate but was hard to grow up. When the Cl- concentration was moderate (about 0.149 mol/L), pitting sensitivity was the highest because pitting was easy to grow up. However, if the concentration of Cl-was too high, uniform corrosion occurred.%应用电化学极化技术、电化学阻抗谱、模拟浸泡实验,研究了X70钢在模拟潮湿存储环境中点蚀的发生机制及规律.结果表明,X70钢在模拟潮湿存储环境中可以发生点蚀,导致点蚀发生的腐蚀介质来自于层流冷却水中的腐蚀性物质,其中HCO-3和NO-3是致钝剂,而Cl-和SO42-可破坏钝化膜,促进点蚀发生.在0.5 mol/L的NaHCO3介质中当Cl-浓度达到0.02 mol/L时钝化膜即失去保护性.CI-浓度是影响点蚀的萌生和发展的关键因素,当其浓度较低时点蚀容易形核,但仅有少数能够长大;而当其浓度适中(约0.149 mol/L)时点蚀敏感性最高,点蚀容易长大;当其浓度过高时发生均匀腐蚀,点蚀难以长大.

  18. THERMODYNAMICS OF LOW-TEMPERATURE (700-850{degree}C) HOT CORROSION

    Energy Technology Data Exchange (ETDEWEB)

    Misra, A. K.; Whittle, D. P.; Worrell, W. L.

    1980-09-01

    Existing phase diagrams in the systems Na{sub 2}SO{sub 4} - MSO}{sub 4} (M=Ni, Co) and Na{sub 2}SO{sub 4} - M{sub 2}(SO{sub 4}){sub 3} (M=Al, Fe, Cr) have been used to calculate the thermodynamic properties of the molten sulfate systems. The calculated thermodynamic data show satisfactory agreement with most of the available experimental observations. The calculations have shown that the activity of Al{sub 2}(SO{sub 4}){sub 3} and Fe{sub 2}(SO{sub 4}){sub 3} in the melt can be lowered to such an extent that liquid sulfate solutions can be formed at P{sub SO{sub 3}} levels that are prevalent in marine gas turbine operations, and this has been explained on the basis of complex formation in the melt. Thermodynamic analysis of the interaction of the Na{sub 2}SO{sub 4} - MSO{sub 4} (M=Co, Ni) melt with protective oxides Al{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} has demonstrated the vulnerability of Al-containing alloys to hot corrosion attack.

  19. Evaluation of Thermal Barrier Coatings Exposed to Hot Corrosion Environment by Impedance Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LIU Chao; HUANG Hui; NI Liyong; ZHOU Chungen

    2011-01-01

    In this investigation,impedance spectroscopy(IS) is used,as a non-destructive tool,to examine the hot corrosion behavior of thermal barrier coatings(TBCs) exposed to a mixture of 25wt% NaC1 and 75wt% Na2SO4.The results show that the thermally grown oxide(TGO) formed along the top coat/bond coat interface is a mixed oxide layer,i.e.Cr2O3,(Ni,Co)(Cr,Al)2O4 spinel and NiO.The growth of TGO layer appears to follow the parabolic law.The resistance of TGO increases due to the increase of thickness when the number of cycles is less than 110.While for more than 110 cycles,the resistance of TGO decreases with the increase of porosity of TGO layer,even though the thickness of TGO layer increases.The nucleation and propagation of cracks within top coat increase the electrical resistance of top coat.The parameters in equivalent circuit could be used to characterize the degradation of TBCs.

  20. Chemical reactions involved in the initiation of hot corrosion of IN-738

    Science.gov (United States)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1984-01-01

    Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions; Cr203 + 2 Na2S04(1) + 3/2 02 yields 2 Na2Cr04(1) + 2 S03(g)n TiO2 + Na2S04(1) yields Na20(T102)n + 503(g)n T102 + Na2Cro4(1) yields Na2(T102)n + Cr03(g).

  1. High temperature corrosion of hot-dip aluminized steel in Ar/1%SO2 gas

    Science.gov (United States)

    Abro, Muhammad Ali; Lee, Dong Bok

    2017-01-01

    Carbon steels were hot-dip aluminized in Al or Al-1at%Si baths, and corroded in Ar/1%SO2 gas at 700-800 °C for up to 50 h. The aluminized layers consisted of not only an outer Al(Fe) topcoat that had interdispersed needle-like Al3Fe particles but also an inner Al-Fe alloy layer that consisted of an outer Al3Fe layer and an inner Al5Fe2 layer. The Si addition in the bath made the Al(Fe) topcoat thin and nonuniform, smoothened the tongue-like interface between the Al-Fe alloy layer and the substrate, and increased the microhardness of the aluminized layer. The aluminized steels exhibited good corrosion resistance by forming thin α-Al2O3 scales, along with a minor amount of iron oxides on the surface. The interdiffusion that occurred during heating made the aluminized layer thick and diffuse, resulting in the formation of Al5Fe2, AlFe and AlFe3 layers. It also smoothened the tongue-like interface, and decreased the microhardness of the aluminized layer. The non-aluminized steel formed thick, nonadherent, nonprotective (Fe3O4, FeS)-mixed scales.

  2. Corrosion rate of construction materials in hot phosphoric acid with the contribution of anodic polarization

    DEFF Research Database (Denmark)

    Kouril, M.; Christensen, Erik; Eriksen, S.;

    2011-01-01

    ). Several grades of stainless steels were tested as well as tantalum, niobium, titanium, nickel alloys and silicon carbide. The corrosion rate was evaluated by means of mass loss at free corrosion potential as well as under various levels of polarization. The only corrosion resistant material in 85...

  3. Hot corrosion behaviour of Fe-Al based intermetallic in molten NaVO{sub 3} salt

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa-Medina, M.A. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte No. 152, Col. San Bartolo Atepehuacan, C.P. 07730 Mexico, D.F. (Mexico)], E-mail: maespin@imp.mx; Carbajal-De la Torre, G. [Facultad de Ingenieria Mecanica, UMSNH, Santiago Tapia 403 Col. Centro, C.P. 58098 Morelia, Michoacan (Mexico); Liu, H.B. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte No. 152, Col. San Bartolo Atepehuacan, C.P. 07730 Mexico, D.F. (Mexico); Martinez-Villafane, A. [CIMAV, Complejo Industrial Chihuahua, Chihuahua (Mexico); Gonzalez-Rodriguez, J.G. [CIMAV, Complejo Industrial Chihuahua, Chihuahua (Mexico); UAEM-CIICAP, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos (Mexico)

    2009-06-15

    The hot corrosion of sprayed Fe-40 (at.%)Al intermetallic alloy with additions of boron and alumina whiskers in molten NaVO{sub 3} at 700 deg. C has been evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy, EIS, techniques. For short exposure times, the corrosion mechanism under these conditions was observed to be controlled by an activation process, whereas for longer exposure times, the corrosion process was under diffusion control due to the growing of an Al{sub 2}O{sub 3} oxide scale, which made the diffusion of both reducing and oxidizing species through the scale to the alloy or scale surfaces more difficult. Equivalent electric model used to simulate the EIS data showed that a finite length Warburg diffusion could properly characterize the diffusion process, which confirmed the formation of a compact corrosion product scales containing rich aluminium oxide. Thus, the corrosion process was under diffusion control of aggressive ions through the formed scale. The electrochemical study was complemented by scanning electronic microscopy characterization and micro chemical analysis.

  4. Wear resistance and hot corrosion behaviour of laser cladding Co-based alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    2Cr13 stainless steel was surface cladded with Co-based alloy using a high power carbon dioxide laser. The microstructure, wear resistance and corrosion properties of the clad layer were investigated. It is found that the high temperature corrosion behavior and wearing resistant property of the clad layer are 3 and 2.5 times higher than those of the parent metal. Under the high temperature molten lead sulphate salt corrosion condition, the clad layer fails by spalling which is caused by intergrannular corrosion within the clad layer. The fine dendritic structure and the oxide help to retard the penetration of the sulphur ion that induces the intergrannular corrosion.

  5. Effect of Annealing Temperature on the Corrosion Protection of Hot Swaged Ti-54M Alloy in 2 M HCl Pickling Solutions

    OpenAIRE

    El-Sayed M. Sherif; Ehab A. El Danaf; Hany S. Abdo; Sherif Zein El Abedin; Hasan Al-Khazraji

    2017-01-01

    The corrosion of Ti-54M titanium alloy processed by hot rotary swaging and post-annealed to yield different grain sizes, in 2 M HCl solutions is reported. Two annealing temperatures of 800 °C and 940 °C, followed by air cooling and furnace cooling were used to give homogeneous grain structures of 1.5 and 5 μm, respectively. It has been found that annealing the alloy at 800 °C decreased the corrosion of the alloy, with respect to the hot swaged condition, through increasing its corrosion resis...

  6. Erosion-corrosion resistance of electroplated Co-Pd film on 316L stainless steel in a hot sulfuric acid slurry environment

    Science.gov (United States)

    Li, Sirui; Zuo, Yu; Ju, Pengfei

    2015-03-01

    A Co-Pd film was deposited on 316L stainless steel by electroplating. The erosion-corrosion behavior of the Co-Pd plated samples in hot sulfuric acid solution with SiO2 particles was investigated. The results showed that there was a significant synergistic effect between erosion and corrosion. At higher stirring speed, even in such strong corrosive environment the erosion-corrosion rate of Co-Pd plated samples was controlled mainly by the erosion resistance. The erosion-corrosion resistance of pure Pd plated sample decreased rapidly with increasing stirring speed, whereas that of Co-Pd plated sample kept almost stable under the tested conditions due to the high micro-hardness and good corrosion resistance of the film.

  7. Computational Thermodynamic Modeling of Hot Corrosion of Alloys Haynes 242 and HastelloyTM N for Molten Salt Service in Advanced High Temperature Reactors

    Energy Technology Data Exchange (ETDEWEB)

    V. Glazoff, Michael; Charit, Indrajt; Sabharwall, Piyush

    2014-09-17

    An evaluation of thermodynamic aspects of hot corrosion of the superalloys Haynes 242 and HastelloyTM N in the eutectic mixtures of KF and ZrF4 is carried out for development of Advanced High Temperature Reactor (AHTR). This work models the behavior of several superalloys, potential candidates for the AHTR, using computational thermodynamics tool (ThermoCalc), leading to the development of thermodynamic description of the molten salt eutectic mixtures, and on that basis, mechanistic prediction of hot corrosion. The results from these studies indicated that the principal mechanism of hot corrosion was associated with chromium leaching for all of the superalloys described above. However, HastelloyTM N displayed the best hot corrosion performance. This was not surprising given it was developed originally to withstand the harsh conditions of molten salt environment. However, the results obtained in this study provided confidence in the employed methods of computational thermodynamics and could be further used for future alloy design efforts. Finally, several potential solutions to mitigate hot corrosion were proposed for further exploration, including coating development and controlled scaling of intermediate compounds in the KF-ZrF4 system.

  8. Adaptability Evaluation of 316L Stainless Steel Based on Pitting Corrosion in Acid Gas Field%基于点蚀的316L不锈钢在酸性气田环境中的适应性评价

    Institute of Scientific and Technical Information of China (English)

    鲍明昱; 任呈强; 郑云萍; 杜磊; 鲜宁; 姜放; 郭小阳

    2016-01-01

    国内外酸性气田的开发使腐蚀环境越来越苛刻,为满足气液混输的工艺要求,发展了耐蚀合金/碳钢的双金属复合管技术。316L不锈钢被广泛用于双金属管的内衬,在含H2 S和CO2环境中腐蚀速率很低,然而在高含Cl-的溶液中,316L不锈钢容易出现点蚀而诱发集输管线失效,为此,就316L不锈钢在酸性气田集输环境中的点蚀进行评述。讨论了影响316 L不锈钢点蚀的材质因素,Mn和Fe的硫化物及Mg、Al、Ca的氧化物等两种夹杂物均能促进钝化膜的溶解而引起点蚀;分析了316L不锈钢点蚀的H2 S、CO2、温度、Cl-浓度和pH值等环境的适应性条件,发现H2 S环境比CO2环境更容易发生点蚀,H2 S和CO2对点蚀发生存在协同机制,温度升高、Cl-浓度增加和酸性介质均会增加316L不锈钢点蚀的敏感性。为进一步优化选材原则,需重点加强环境因素的协同机制、环境适应性的边界条件、点蚀发展的动力学以及新的标准研究。%The corrosion conditions become more and more severe due to the rapid development of acid gas field.In order to meet the requirements of gas-liquid mixed transportation technology,bimetal-lined pipe composed of anti-corrosion alloy and carbon steel has been manufactured.316L stainless steel has been widely used for the liner of the bimetal-lined pipe because of the low corrosion rate in the H2 S and CO2 environments.However,316L stainless steel has potential failure risk,which is attributed to the pitting corrosion in the solution containing Cl-.Therefore, the pitting corrosion of 316L stainless steel in acid gas field is commented.The material factors affecting the pitting corrosion of 316L stainless steel are discussed.Both the sulfide of manganese,iron and the oxide of magnesium,alu-minum,calcium can promote the local dissolution of the passive film and further cause pitting corrosion.The environ-mental adaptability conditions

  9. 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.

  10. Hot Corrosion Behavior of Sputtered Nanocrystalline Coating with Yttrium Addition at 900 °C

    Directory of Open Access Journals (Sweden)

    Wei Jiang

    2014-04-01

    Full Text Available The high temperature corrosion behavior of sputtered nanocrystalline K38 coating with and without yttrium addition under mixed molten salt film in air was investigated. Accelerated corrosion occurred on the coating without yttrium (Y addition locally after 60 h exposure at 900 °C, which resulted in negative weight gain in kinetics. A uniform and protective alumina scale formed on surface of the coating containing yttrium in comparison. Y enriched particle as corrosion product was observed on the top of alumina scale. The results indicated the beneficial influence of Y on the chemical stability of the protective scale in the presence of chloride. The mechanism was discussed.

  11. Aging influence in the pitting corrosion of a stainless steel in marine media: role of the sulfato-reducing bacteria; Influence du vieillissement dans la corrosion par piqures d'un acier inoxydable en milieu marin: role des bacteries sulfato-reductrices

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, J

    1993-10-15

    In order to detect and measure the activity of the desufavibrio vulgaris bacteria in seawater towards the pitting corrosion of a stainless steel, electrochemical techniques (polarization curves, impedance diagrams, multi-pits) and surface analysis techniques (luminescent discharge spectroscopy,...) have been carried out. In order to separate biological and chemical parameters, several media have been used: synthetical or natural seawater. The obtained results reveal the specific role of the studied bacteria on the alterations of behavior of the stainless steels corrosion resistance; indeed, there is a competition between two opposed processes: -the reinforcement of the passive film by the OH{sup -} of water and -the de-passivation by the formed sulfur species. (O.M.)

  12. Corrosion Fatigue of Austenitic Stainless Steel in Different Hot Chloride Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Visser, A.; Mori, G.; Panzenboeck, M. [Montanuniversitaet Leoben, Leoben (Austria); Pippan, R. [Erich Schmid Institute of Materials Science, Austrian Academy of Science, Leoben (Austria)

    2015-08-15

    Austenitic stainless steel was investigated under cyclic loading in electrolytes with different chloride contents and pH and at different temperatures. The testing solutions were 13.2 % NaCl (80,000 ppm Cl-) at 80 °C and 43 % CaCl{sub 2} (275,000 ppm Cl-) at 120 °C. In addition to S-N curves in inert and corrosive media, the fracture surfaces were investigated with a scanning electron microscope (SEM) to analyse the type of attack. The experimental results showed that a sharp decrease in corrosion fatigue properties can be correlated with the occurrence of stress corrosion cracking. The correlation of occurring types of damage in different corrosion systems is described.

  13. Evaluation of hot corrosion behaviour of HVOF sprayed Ni-5Al and NiCrAl coatings in coal fired boiler environment

    Energy Technology Data Exchange (ETDEWEB)

    Mahesh, R.A.; Jayaganthan, R.; Prakash, S. [VA Tech EWF Pvt Ltd., Prithla (India)

    2010-08-15

    Hot corrosion was recognised as a serious problem in connection with the degradation of fireside boiler tubes in coal fired steam generating plants. It is one of the most deleterious forms of surface degradation which can lead to the loss of mechanical strength and catastrophic failure of structural and engineering components. In the present investigation, an attempt has been made to evaluate the hot corrosion behaviour of high velocity oxyfuel (HVOF) sprayed Ni-5Al and NiCrAl coatings on iron based superalloy in an actual coal fired boiler environment. The coated specimens were hung in the low temperature superheater zone (about 700{sup o}C) of a coal fired boiler. The studies were carried out for 10 cycles each cycle consisting of exposing the coated specimens for 100 h followed by 1 h cooling to ambient conditions. NiCrAl coated specimen provided better resistance to hot corrosion than Ni-5Al coated specimen in the given environment.

  14. Effect of Sputtered TiAICr Coatings on Oxidation and Hot Corrosion Resistance of Ti-24Al-14Nb-3V

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of sputtered Ti-50Al-10Cr and Ti-50Al-20Cr coatings on both isothermal and cyclic oxidation resistance at 800~900°C and hot corrosion resistance at 850°C of Ti-24Al-14Nb3V was investigated. Results indicated that Ti-24Al-14Nb-3V alloys exhibited poor oxidation resistance due to the formation of Al2O3+TiO2+AlNbO4 mixed scales in air at 800~900°C and poor hot corrosion resistance due to the spallation of scales formed in Na2SO4+K2SO4 melts at 850°C. Both Ti-S0Al-10Cr and Ti-50Al-20Cr coatings remarkably improved the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy.

  15. Hot corrosion behavior of nanostructured Gd2O3 doped YSZ thermal barrier coating in presence of Na2SO4 + V2O5 molten salts

    Directory of Open Access Journals (Sweden)

    Yixiong Wang

    2017-08-01

    Full Text Available Nickel-based superalloy DZ125 was first sprayed with a NiCrAlY bond coat and followed with a nanostructured 2 mol% Gd2O3−4.5 mol% Y2O3-ZrO2 (2GdYSZ topcoat using air plasma spraying (APS. Hot corrosion behavior of the as-sprayed thermal barrier coatings (TBCs were investigated in the presence of 50 wt% Na2SO4 + 50 wt% V2O5 as the corrosive molten salt at 900 °C for 100 h. The analysis results indicate that Gd doped YVO4 and m-ZrO2 crystals were formed as corrosion products due to the reaction of the corrosive salts with stabilizers (Y2O3, Gd2O3 of zirconia. Cross-section morphology shows that a thin layer called TGO was formed at the bond coat/topcoat interface. After hot corrosion test, the proportion of m-ZrO2 phase in nanostructured 2GdYSZ coating is lower than that of nano-YSZ coating. The result reveals that nanostructured 2GdYSZ coating exhibits a better hot corrosion resistance than nano-YSZ coating.

  16. The Pitting Corrosion Rate Of Super13Cr、15Cr Stainless Steel Under Oil Field Acidizing Environment%油田酸化环境下超级13Cr、15Cr不锈钢的点蚀速率研究

    Institute of Scientific and Technical Information of China (English)

    宋文文; 金伟; 耿海龙; 杜金楠; 高文祥

    2016-01-01

    本文研究了超级13Cr和15Cr马氏体不锈钢分别在120℃和95℃全程酸化(鲜酸+残酸)实验中的耐点蚀性能。结果表明:超级13Cr和15Cr不锈钢在120℃条件下的点蚀速率分别为1.59mm/a和1.35mm/a;在95℃条件下的点蚀速率分别为6.55mm/a 和2.60mm/y;95℃条件下两种材质的点蚀速率高于120℃条件下的点蚀速率;在两种腐蚀条件下15Cr较13Cr表现出更优异的耐点蚀性能。%This paper studied the pitting corrosion resistance performance of super 13Cr and 15Cr stainless steel under the entire acidizing (fresh acid + residual acid) experiment at 120℃ and 95℃.The results showed that pitting corrosion rates of super 13Cr and 15Cr stainless steel were 1.59 mm/a and 1.35mm/aat 120℃; The pitting corrosion rates of super 13Cr and 15Cr stainless steel were 6.5mm/a and 2.6mm/aat 95℃;The pitting corrosion rates of the two materialsat 95℃ were higher than pitting corrosion rates at 120℃;The pitting corrosion resistance of super 15Cr was better than 13Cr stainless steel in the two corrosion conditions.

  17. Na2SO4- and NaCl- Induced Hot Corrosion Behaviors of a Nickel-Base Superalloy with Aluminide Diffusion Coating

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hot-corrosion behaviors of nickel-base superalloy and aluminide diffusion coating have been investigated in conditions of contents of Na2SO4 and NaCl molten salts at 900℃ by means of XRD and SEM.Hot-corrosion scale of the superalloy and aluminide diffusion coating were analyzed and their surface morphologies were observed.The results demonstrate that both coated and uncoated specimens are not susceptible to various contents of NaCl.That may be resulted from the Al2O3 scale formation.Growth stress was characterized by the formation of convoluted scales.

  18. Corrosion behavior of Ni-base superalloys in a hot molten salt

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Soo Haeng; Kang, Dae Seong; Hong, Sun Seok; Hur, Jin Mok; Lee, Han Soo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-09-15

    The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which results in a chemically aggressive environment that is too corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Inconel 713LC, Inconel MA 754, Nimonic 80A and Nimonic 90 in the molten salt LiCl-Li{sub 2}O under an oxidizing atmosphere was investigated at 650 .deg. C for 72-216 hrs. Inconel 713LC alloy showed the highest corrosion resistance among the examined alloys. Corrosion products of Inconel 713LC were Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and NiO, and those of Inconel MA 754 were Cr{sub 2}O{sub 3} and Li{sub 2}Ni{sub 8}O{sub 10} while Cr{sub 2}O{sub 3}, LiFeO{sub 2}, (Cr, Ti){sub 2}O{sub 3} and Li{sub 2}Ni{sub 8}O{sub 10} were produced from Nimonic 80A. Also, corrosion products of Nimonic 90 were found to be Cr{sub 2}O{sub 3}, (Cr, Ti){sub 2}O{sub 3}, LiAlO{sub 2} and CoCr{sub 2}O{sub 4}. Inconel 713LC showed local corrosion behavior and Inconel MA 754, Nimonic 80A, Nimonic 90 showed uniform corrosion behavior.

  19. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    Science.gov (United States)

    Lowell, C. E.; Deadmore, D. L.; Whittenberger, J. D.

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  20. Development of Exterior Anti-corrosion Coating Production Line for Large Diameter Hot Bent Pipes

    Institute of Scientific and Technical Information of China (English)

    JiaoRuyi; ZhangYing

    2004-01-01

    The epoxy powder exterior anti-corrosion coating production line for bent pipes with a single (double) course production is a technologically advanced bent pipe anti-corrosion method with cost efficiency, environment friendliness and stable coating quality. The quality of the coating on the bent pipe fully meets the requirements of the current national and industrial standards. The application of the technology has filled the gap in the bent pipe anti-corrosion coating area of China, and leads the world technologically. With this technology the coating quality of the bent pipe has greatly improved, resulting in significant social and economic benefits. With the use of the technology in various large scale pipeline projects such as the “West to East Gas Pipeline Project”, it will exhibite a greater potential in the future pipeline projects with a broad application prospect.

  1. A study on the mechanism of stress corrosion cracking of duplex stainless steels in hot alkaline-sulfide solution

    Science.gov (United States)

    Chasse, Kevin Robert

    Duplex stainless steels (DSS) generally have superior strength and corrosion resistance as compared to most standard austenitic and ferritic stainless grades owing to a balanced microstructure of austenite and ferrite. As a result of having favorable properties, DSS have been selected for the construction of equipment in pulp and paper, chemical processing, nuclear, oil and gas as well as other industries. The use of DSS has been restricted in some cases because of stress corrosion cracking (SCC), which can initiate and grow in either the ferrite or austenite phase depending on the environment. Thorough understanding of SCC mechanisms of DSS in chloride- and hydrogen sulfide-containing solutions has been useful for material selection in many environments. However, understanding of SCC mechanisms of DSS in sulfide-containing caustic solutions is limited, which has restricted the capacity to optimize process and equipment design in pulp and paper environments. Process environments may contain different concentrations of hydroxide, sulfide, and chloride, altering corrosion and SCC susceptibility of each phase. Crack initiation and growth behavior will also change depending on the relative phase distribution and properties of austenite and ferrite. The role of microstructure and environment on the SCC of standard grade UNS S32205 and lean grade UNS S32101 in hot alkaline-sulfide solution were evaluated in this work using electrochemical, film characterization, mechanical testing, X-ray diffraction, and microscopy techniques. Microstructural aspects, which included residual stress state, phase distribution, phase ratio, and microhardness, were related to the propensity for SCC crack initiation in different simulated alkaline pulping liquors at 170 °C. Other grades of DSS and reference austenitic and superferritic grades of stainless steel were studied using exposure coupons for comparison to understand compositional effects and individual phase susceptibility

  2. Study of Pitting Morphology Fractal Characteristic of Corroded Surface of 304 Stainless Steel in FeCl3 Environment

    Institute of Scientific and Technical Information of China (English)

    张玮; 梁成浩

    2004-01-01

    Experiments were performed to study the pitting corrosion morphology of 304 stainless steel exposed to FeCl3 environments and SEM micrographs of the pitting corrosion morphology were obtained. The image processing technique combining with the fractal method was employed to analyze these pitting corrosion images and the self-similarity of pits morphology was observed. It indicates that fractal characteristics exist in pitting corrosion of 304 stainless steel. The self-similarity and complexity of the pitting morphology phenomenon were described in terms of fractal dimension which can also be an important parameter related to characterize pitting morphology qualitatively and quantitatively.

  3. 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

  4. Aluminizing and boroaluminizing treatments of Mar-M247 and their effect on hot corrosion resistance in Na2SO4-NaCl molten salt

    Science.gov (United States)

    Cho, J. H.; Kim, T. W.; Son, K. S.; Yoon, J. H.; Kim, H. S.; Leisk, G. G.; Mitton, D. B.; Latanision, R. M.

    2003-06-01

    The effect of surface modifications of Mar-M247 superalloy on hot corrosion resistance was examined in Na2SO4-NaCl molten salt. The Mar-M247 was aluminized and boroaluminized by pack cementation in Ar and underwent a cyclic hot corrosion test in Na2SO4-NaCl molten salt. The XRD results showed that a Ni2Al3 phase was formed between the aluminized layer and the substrate when the surface modification temperature was below 1273 K. However, a NiAl phase formed when the temperature was above 1273 K. The intensity of the XRD peak in the NiAl phase increased after post heat treatment. Hot corrosion resistance increased for the specimens containing NiAl rather than Ni2Al3 phase. The ductile NiAl phase suppressed the potential for crack initiation during thermal cycling. Post heat treatment increased the corrosion resistance of the aluminized layer for Mar-M247, which underwent surface modification at 1273 K and above. In the boroaluminized Mar-M247 specimens, corrosion resistance decreased as a result of the blocking of outward diffusion of Cr by boron and decreased cohesion between the oxide scale and the aluminized layer during thermal cycling.

  5. Corrosion Failures in Marine Environment

    Directory of Open Access Journals (Sweden)

    R. Krishnan

    1985-04-01

    Full Text Available This paper gives a brief description of typical marine environments and the most common form of corrosion of materials used in this environment. Some typical case histories of failures pertaining to pitting, bimetallic corrosion, dealloying, cavitation and stress corrosion cracking are illustrated as typical examples of corrosion failures.

  6. The effects of pitting on fatigue crack nucleation in 7075-T6 aluminum alloy

    Science.gov (United States)

    Ma, LI; Hoeppner, David W.

    1994-01-01

    A high-strength aluminum alloy, 7075-T6, was studied to quantitatively evaluate chemical pitting effects of its corrosion fatigue life. The study focused on pit nucleation, pit growth, and fatigue crack nucleation. Pitting corrosion fatigue experiments were conducted in 3.5 percent NaCl aqueous solution under constant amplitude sinusoidal loading at two frequencies, 5 and 20 Hz. Smooth and unnotched specimens were used in this investigation. A video recording system was developed to allow in situ observation of the surface changes of the specimens during testing. The results indicated that pitting corrosion considerably reduces the fatigue strength by accelerating fatigue crack nucleation. A metallographic examination was conducted on the specimens to evaluate the nature of corrosion pits. First, the actual shapes of the corrosion pits were evaluated by cross-sectioning the pits. Secondly, the relation between corrosion pits and microstructure was also investigated. Finally, the possibility of another corrosion mechanism that might be involved in pitting was explored in this investigation. The fractography of the tested specimens showed that corner corrosion pits were responsible for fatigue crack nucleation in the material due to the associated stress concentration. The pits exhibited variance of morphology. Fatigue life for the experimental conditions appeared to be strongly dependent on pitting kinetics and the crack nucleation stage.

  7. The composition of the boundary region of MnS inclusions in stainless steel and its relevance in triggering pitting corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Schmuki, P.; Hildebrand, H.; Friedrich, A.; Virtanen, S

    2005-05-01

    Recently, controversy has arisen on the presence of a Cr-depleted zone around MnS inclusions in stainless steels and the relevance of such zones to pit initiation events. In the present work, we use a scanning Auger microscope (SAM) combined with simple pitting immersion tests to elucidate this question in more detail. The SAM analysis of 27 inclusions of a high S-containing DIN 1.4305 stainless steel indicated no Cr-depletion at the inclusion/matrix-interface with a lateral resolution of {+-}20 nm. A scanning electron microscope (SEM) characterization of the sample surface after an exposure to 10% FeCl{sub 3} solution shows that pitting attack in all cases initiates at inclusion sites. Different pit initiation morphologies were observed (inside the inclusion, around the inclusion, mixed attack morphology). However, even the attack morphology 'around an inclusion' cannot be ascribed to Cr depletion at the inclusion. Although in special cases (special composition or heat treatment history of the steel) a Cr-depleted may be induced at the matrix/inclusion-interface, the present work shows that this approach does not generally hold and therefore the presence of such a depletion zone cannot be the general explanation for pitting of stainless steels in the vicinity of inclusions.

  8. The Pits

    Science.gov (United States)

    2006-01-01

    8 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a pit chain on the lower, northern flank of the giant martian volcano, Arsia Mons. Pits such as these commonly form as a result of collapse of surface materials into a subsurface void, possibly along a fault or into an old lava tube. The layered material, exposed near the top of several of the pits, is shedding house-sized boulders which can be seen resting on the sloping sidewalls and floors of many of the pits. Location near: 6.7oS, 120.1oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer

  9. Ultimate Strength of Ship Structural Plate with Pitting Corrosion Damnification Under Uniaxial Compression%点蚀损伤船体板格单轴压缩极限强度

    Institute of Scientific and Technical Information of China (English)

    张岩; 黄一

    2016-01-01

    为了能够简单准确地计算服役期内点蚀损伤船体板格的极限强度,选择腐蚀体积为点蚀损伤板的主要评估参数,结合实际船体板格的腐蚀损伤特点,采用有限元数值计算方法,分析点蚀坑形状、有限元单元类型、蚀坑分布和蚀坑深度对板极限强度的影响,以及板的初始柔度、初始变形、长宽比和板边缘线性载荷因子对板极限强度折减因子的影响,并利用回归分析方法,建立了基于腐蚀体积的点蚀损伤船体板格极限强度折减因子的计算公式.结果表明,整套公式的计算结果与有限元计算结果的相对误差仅有极少量在5%,~6%,之间,绝大部分在5%,以内,可用于服役期内点蚀损伤船体板格的安全评估.%To simply and accurately calculate the ultimate strength of ship structural plates with corrosion damnifica-tion during the service lives of ships,the corrosion volume loss was used as the most important assessment parameter of the plate with corrosion damnification.On the basis of the characteristics of the actual hull structural plates,the effects of some parameters(the shape of pits,the type of finite elements,the distribution of pits and the depth of pits)on the ultimate strength and the effects of some parameters(the initial slenderness,the initial geometric deflec-tion and the aspect of plates and the linear load factors at the plate edges)on ultimate strength reduction factor were studied by the nonlinear finite element analyses.The ultimate strength reduction factor formulae based on the corro-sion volume loss were obtained by regression analysis approach.The results show that most of the relative errors be-tween the calculating value by the formulae and finite element analysis result are below 5%, and only very few is 5%,—6%,.The formulae can be used in the safety assessment of ship structural plates with pitting corrosion damnifi-cation during their service lives.

  10. Effect of enamel coating on long-term oxidation and hot corrosion behavior of Ti-24Al-17Nb-0.5Mo alloys

    Institute of Scientific and Technical Information of China (English)

    ZHENG De-you; XIONG Yu-ming; ZHU Sheng-long; WANG Fu-hui

    2004-01-01

    The effect of enamel coating on long-term isothermal oxidation at 700 ℃ and cyclic oxidation at 800 ℃ in air and hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo in 75% (Na2SO4 + K2SO4 ) + 25% NaCl (mass fraction) molten mixed salts at 700 ℃ was investigated. The results indicate that Ti-24Al-17Nb-0.5Mo alloy exhibits relatively poor long-term oxidation resistance due to the formation of Al2O3 + TiO2 + Nb2O5 mixed scales and poor hot corrosion resistance due to the spallation of scales formed in molten (Ns, K)2 SO4 +NaCl. Enamel coating can effectively protect Ti-24Al-17Nb-0.5Mo alloy from long-term oxidation at high temperature in air and remarkably improve the hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo alloy, and can act as the barrier to suppress the migration of oxygen and corrosive ions into the substrate.

  11. 点蚀损伤船体结构板的极限剪切屈曲强度研究%Ultimate shear strength of ship structural plate with pitting corrosion damnification

    Institute of Scientific and Technical Information of China (English)

    张岩; 黄一; 刘刚

    2013-01-01

    Corrosion-caused thickness loss makes the ultimate strength of ship structural plates degraded significantly. An assessing method for ultimate strength of ship hull plate with corrosion damnification un-der edge shear loading based on corroded volume loss is proposed by theoretical deduction and finite ele-ment analysis. The models which are in accord with the actual ship hull plate are obtained. The quantita-tive assessment formulae are obtained by statistics approach according to the data that come from the non-linear finite element analyses of a series of the setting models by changing the plate thickness, the number, the diameter and the distribution of the pits. It is found out that the proposed corroded volume loss based ultimate strength assessment formulae can accurately predict the ultimate buckling strength of the pitted plate under the shear loading. Moreover, the formulae are applicable for reliability or risk assessment of the actual ship panels with pitting corrosion wastage of the sea-going steel ships during their service lives.%  腐蚀损伤导致船体结构板的极限承载能力大幅度下降。文章采用腐蚀体积描述板的点蚀损伤程度,模拟船体结构板的点蚀损伤形态,在点蚀损伤板模型中变化板的厚度、点蚀数目、点蚀直径以及点蚀分布等要素,实施系列有限元数值模拟计算,在进行理论分析的基础上,采用统计学方法,建立了点蚀损伤板极限剪切屈曲强度的评估方法,得到了点蚀损伤板极限剪切屈曲强度的计算公式。从而确立了基于腐蚀体积的点蚀损伤船体结构板极限剪切屈曲强度的评价技术,可为在役海船点蚀损伤后的安全性评估提供有效的技术手段。

  12. Scanning reference electrode techniques in localized corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Isaacs, H.S.; Vyas, B.

    1979-04-01

    The principles, advantages, and implementations of scanning reference electrode techniques are reviewed. Data related to pitting, intergranular corrosion, welds and stress corrosion cracking are presented. The technique locates the position of localized corrosion and can be used to monitor the development of corrosion and changes in the corrosion rate under a wide range of conditions.

  13. Protection of carbon steel against hot corrosion using thermal spray Si- and Cr-base coatings

    Science.gov (United States)

    Porcayo-Calderon, J.; Gonzalez-Rodriguez, J. G.; Martinez, L.

    1998-02-01

    A Fe75Si thermal spray coating was applied on the surface of a plain carbon steel baffle plate. Beneath this coating, a Ni20Cr coating was applied to give better adherence to the silicon coating. The baffle was installed in the high-temperature, fireside, corrosion zone of a steam generator. At the same time, an uncoated 304 stainless steel baffle was installed nearby for comparison. For 13 months the boiler burned heavy fuel oil with high contents of vanadium. The samples were studied employing scanning electron microscopy, x-ray microanalysis, and x-ray diffraction techniques. After that, it was possible to inspect the structural state of the components, and it was found that the stainless steel baffle plates were destroyed almost completely by corrosion, whereas the carbon steel coated baffle plate did not suffer a significant attack, showing that the performance of the thermal spray coating was outstanding and that the coating was not attacked by vanadium salts of the molten slag.

  14. Influence of liquid surface segregation on the pitting corrosion behavior of semi-solid metal high pressure die cast alloy F357

    CSIR Research Space (South Africa)

    Moller, H

    2009-01-01

    Full Text Available Semi-solid metal processing results in liquid segregation at the surface of the components. The pitting behaviour of this surface layer of semi-solid metal processed alloy F357 was compared with the centre (or bulk) of cast plates in 3.5% Na...

  15. Studies on the impact, detection, and control of microbiology influenced corrosion related to pitting failures in the Russian oil and gas industry. Final CRADA report.

    Energy Technology Data Exchange (ETDEWEB)

    Ehst, D.

    2006-09-30

    The objectives of the Project are: (1) to design effective anti-corrosion preparations (biocides, inhibitors, penetrants and their combinations) for gas- and oil-exploration industries; (2) to study a possibility of development of environmentally beneficial ('green') biocides and inhibitors of the new generation; (3) to develop chemical and microbiological methods of monitoring of sites at risk of corrosion; and (4) to evaluate potentialities in terms of technology, raw materials and material and technical basis to set up a production of effective anti-corrosion preparations of new generation in Russia. During the four years of the project 228 compounds and formulations were synthesized and studied in respect to their corrosion inhibiting activity. A series of compounds which were according to the Bubble tests more efficient (by a factor of 10-100) than the reference inhibitor SXT-1102, some possessing the similar activity or slightly better activity than new inhibitor ??-1154? (company ONDEO/Nalco). Two synthetic routes for the synthesis of mercaptopyrimidines as perspective corrosion inhibitors were developed. Mercaptopyrimidine derivatives can be obtained in one or two steps from cheap and easily available precursors. The cost for their synthesis is not high and can be further reduced after the optimization of the production processes. A new approach for lignin utilization was proposed. Water-soluble derivative of lignin can by transformed to corrosion protective layer by its electropolymerization on a steel surface. Varying lignosulfonates from different sources, as well as conditions of electrooxidation we proved, that drop in current at high anodic potentials is due to electropolymerization of lignin derivative at steel electrode surface. The electropolymerization potential can be sufficiently decreased by an increase in ionic strength of the growing solution. The lignosulfonate electropolymerization led to the considerable corrosion protection

  16. Effects of cold work on stress corrosion cracking of type 316L stainless steel in hot lithium hydroxide solution

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, J.H.; Bogaerts, W.F. (Univ. of Leuven (Belgium). Dept. of Metallurgy and Materials Engineering)

    1993-07-01

    Lithium hydroxide (LiOH) has ben chose as the lithium compound to be used in the Aqueous Lithium Salt Blanket (ALSB) concept that has been proposed as a possible driver blanket for the Next European Torus (NET), the next generation of fusion testing devices in Europe, as well as for the International Thermonuclear Experimental Reactor program (ITER). The stress corrosion cracking (SCC) behavior of cold-worked AISI type 316L stainless steel (SS) in a concentrated lithium salt solution at elevated temperature was investigated. Using the slow strain rate technique, SCC experiments were carried out on 20% and 40% cold-worked materials in a solution of 10g lithium hydroxide and 100 cm[sup 3]H[sub 2]O at 95C under conditions with controlled electrochemical potential. Observation of the fracture surfaces by scanning electron microscope indicated the SCC behavior of the cold-worked steel was essentially different from that of the solution-annealed steel. A ductile fracture of cold-worked samples occurred under open-circuit conditions ([approximately][minus]280 mV) and at 200 mV. Slight intergranular attack was found in the region near the surface of cold-worked specimens when the electrochemical potential was controlled at [minus]120 mV. SCC was observed when the experiments were conducted at +100mV. Intergranular stress corrosion cracking (IGSCC) of solution-annealed material changed into a mixed SCC mode, or a dominant transgranular SCC (TGSCC) with an increase of cold work to 20% and 40%. Compared to the SCC behavior of the solution-annealed 316L, the results showed cold work improved significantly the resistance of 316L SS to IGSCC in the hot LiOH environment. Susceptibility to TGSCC of cold-worked 316L SS increased with increasing extent of cold working. These effects were reviewed with respect to electrochemical and microstructural phenomena.

  17. Studies on Hot Corrosion of the 2.25 Cr-1Mo Boiler Tube Steel and Its Weldments in the Molten Salt Na2SO4-60 pct V2O5 Environment

    Science.gov (United States)

    Kumar, Ravindra; Tewari, V. K.; Prakash, S.

    2007-01-01

    Hot corrosion is mainly due to the dissolution of protective oxides in the molten salt at the metal surface and their reprecipitation at some other sites as nonprotective porous mass. The hot corrosion attack along the grain boundaries leading to subsurface precipitation of oxides and sulfides also contributes to weakening of material. Ferritic steel with 2.25Cr 1Mo is used widely as a candidate material in the steam generating system of power plants. Hot corrosion studies were conducted on 2.25Cr-1Mo unwelded as well as welded steel specimens with molten salt coated after exposure at 900 °C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion X-ray diffraction (XRD); scanning electron microscopy/energy-dispersive analysis (SEM/EDAX) was used to analyze the corrosion products.

  18. Methodology Using Inverse Methods for Pit Characterization in Multilayer Structures

    Science.gov (United States)

    Aldrin, John C.; Sabbagh, Harold A.; Sabbagh, Elias H.; Murphy, R. Kim; Concordia, Michael; Judd, David R.; Lindgren, Eric; Knopp, Jeremy

    2006-03-01

    This paper presents a methodology incorporating ultrasonic and eddy current data and NDE models to characterize pits in first and second layers. Approaches such as equivalent pit dimensions, approximate probe models, and iterative inversion schemes were designed to improve the reliability and speed of inverse methods for second layer pit characterization. A novel clutter removal algorithm was developed to compensate for coherent background noise. Validation was achieved using artificial and real pitting corrosion samples.

  19. Tribological and corrosion behaviors of warm- and hot-rolled Ti-13Nb-13Zr alloys in simulated body fluid conditions

    Directory of Open Access Journals (Sweden)

    Lee T

    2015-10-01

    Full Text Available Taekyung Lee,1 Eshaan Mathew,2 Santhosh Rajaraman,2 Geetha Manivasagam,2 Ashok Kumar Singh,3 Chong Soo Lee4 1Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA; 2Centre for Biomaterials Science and Technology, School for Mechanical and Building Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu, India; 3Defense Metallurgical Research Laboratory, Hyderabad, India; 4Graduate Institute of Ferrous Technology (GIFT, Pohang University of Science and Technology (POSTECH, Pohang, Republic of Korea Abstract: Development of submicrocrystalline structure in biomedical alloy such as Ti-13Nb-13Zr (in wt% through warm-rolling process has been found to enhance mechanical properties compared to conventional thermomechanical processing routes including hot-rolling process. The present study investigated the tribological and corrosion behaviors of warm-rolled (WR and hot-rolled Ti-13Nb-13Zr alloys which have not been studied to date. Both tribological and corrosion experiments were carried out in simulated body fluid conditions (Hank’s solution at 37°C based on the fact that the investigated alloys would be used in a human body as orthopedic implants. The WR Ti-13Nb-13Zr demonstrated a submicrocrystalline structure that provided a significant enhancement in hardness, strength, and corrosion resistance. Meanwhile, there was no notable difference in wear resistance between the WR and hot-rolled samples despite the different microstructure and hardness. The present study confirmed the enormous potential of WR Ti-13Nb-13Zr with not only great mechanical properties but also high corrosion resistance in the simulated body fluid. Keywords: titanium alloy, multi-pass caliber-rolling, grain refinement, tribology, corrosion

  20. Effect of Al Hot-Dipping on High-Temperature Corrosion of Carbon Steel in N2/0.1% H2S Gas

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Abro

    2016-02-01

    Full Text Available High-temperature corrosion of carbon steel in N2/0.1% H2S mixed gas at 600–800 °C for 50–100 h was studied after hot-dipping in the aluminum molten bath. Hot-dipping resulted in the formation of the Al topcoat and the Al-Fe alloy layer firmly adhered on the substrate. The Al-Fe alloy layer consisted primarily of a wide, tongue-like Al5Fe2 layer and narrow Al3Fe layer. When corroded at 800 °C for 100 h, the Al topcoat partially oxidized to the protective but non-adherent α-Al2O3 layer, and the interdiffusion converted the Al-Fe alloy layer to an (Al13Fe4, AlFe3-mixed layer. The interdiffusion also lowered the microhardness of the hot-dipped steel. The α-Al2O3 layer formed on the hot-dipped steel protected the carbon steel against corrosion. Without the Al hot-dipping, the carbon steel failed by forming a thick, fragile, and non-protective FeS scale.

  1. Effects of X-rays Radiation on AISI 304 Stainless Steel Weldings with AISI 316L Filler Material: A Study of Resistance and Pitting Corrosion Behavior

    Directory of Open Access Journals (Sweden)

    Francisco Javier Cárcel-Carrasco

    2016-04-01

    Full Text Available This article investigates the effect of low-level ionizing radiation, namely X-rays, on the micro structural characteristics, resistance, and corrosion resistance of TIG-welded joints of AISI 304 austenitic stainless steel made using AISI 316L filler rods. The welds were made in two different environments: natural atmospheric conditions and a closed chamber filled with inert argon gas. The influence of different doses of radiation on the resistance and corrosion characteristics of the welds is analyzed. Welded material from inert Ar gas chamber TIG showed better characteristics and lesser irradiation damage effects.

  2. The effect of zinc bath temperature on the morphology, texture and corrosion behaviour of industrially produced hot-dip galvanized coatings

    Directory of Open Access Journals (Sweden)

    A. Bakhtiari

    2014-03-01

    Full Text Available The purpose of this work is to identify the influence of zinc bath temperature on the morphology, texture and corrosion behavior of hot-dip galvanized coatings. Hot-dip galvanized samples were prepared at temperature in the range of 450-480 °C in steps of 10 °C, which is the conventional galvanizing temperature range in the galvanizing industries. The morphology of coatings was examined with optical microscopy and scanning electron microscopy (SEM. The composition of the coating layers was determined using energy dispersive spectroscopy (EDS analysis. The texture of the coatings was evaluated using X-ray diffraction. Corrosion behavior was performed using salt spray cabinet test and Tafel extrapolation test. From the experimental results, it was found that increasing the zinc bath temperature affects the morphology of the galvanized coatings provoking the appearance of cracks in the coating structure. These cracks prevent formation of a compact structure. In addition, it was concluded that (00.2 basal plane texture component was weakened by increasing the zinc bath temperature and, conversely, appearance of (10.1 prism component, (20.1 high angle pyramidal component and low angle component prevailed. Besides, coatings with strong (00.2 texture component and weaker (20.1 components have better corrosion resistance than the coatings with weak (00.2 and strong (20.1 texture components. Furthermore, corrosion resistance of the galvanized coatings was decreased by increasing the zinc bath temperature.

  3. Studies on the impact, detection, and control of microbiology influenced corrosion related to pitting failures in the Russian oil and gas industry. Final CRADA report.

    Energy Technology Data Exchange (ETDEWEB)

    Ehst, D.

    2006-09-30

    The objectives of the Project are: (1) to design effective anti-corrosion preparations (biocides, inhibitors, penetrants and their combinations) for gas- and oil-exploration industries; (2) to study a possibility of development of environmentally beneficial ('green') biocides and inhibitors of the new generation; (3) to develop chemical and microbiological methods of monitoring of sites at risk of corrosion; and (4) to evaluate potentialities in terms of technology, raw materials and material and technical basis to set up a production of effective anti-corrosion preparations of new generation in Russia. During the four years of the project 228 compounds and formulations were synthesized and studied in respect to their corrosion inhibiting activity. A series of compounds which were according to the Bubble tests more efficient (by a factor of 10-100) than the reference inhibitor SXT-1102, some possessing the similar activity or slightly better activity than new inhibitor ??-1154? (company ONDEO/Nalco). Two synthetic routes for the synthesis of mercaptopyrimidines as perspective corrosion inhibitors were developed. Mercaptopyrimidine derivatives can be obtained in one or two steps from cheap and easily available precursors. The cost for their synthesis is not high and can be further reduced after the optimization of the production processes. A new approach for lignin utilization was proposed. Water-soluble derivative of lignin can by transformed to corrosion protective layer by its electropolymerization on a steel surface. Varying lignosulfonates from different sources, as well as conditions of electrooxidation we proved, that drop in current at high anodic potentials is due to electropolymerization of lignin derivative at steel electrode surface. The electropolymerization potential can be sufficiently decreased by an increase in ionic strength of the growing solution. The lignosulfonate electropolymerization led to the considerable corrosion protection

  4. Hot corrosion evaluation of aluminide coated superalloys in support of an ASTM Round Robin program

    Science.gov (United States)

    Santoro, G.

    1975-01-01

    Commercial aluminized coatings on substrates were hot corroded at 900 C in a 0.3 Mach burner rig with 5 ppm synthetic sea salt and at two cycling frequencies. Extensive post-exposure examinations were conducted on the corroded specimens such as metallography, X-ray diffraction, scanning electron microscopy, microprobe raster scans, and spectrographic analyses. Thermodynamic calculations were made of the equilibrium burner flame composition and the calculations were compared to the experimental findings. It was found that localized spalling of the coatings preceded coating failure. It is suggested that the spalling of the coatings is due to the formation of localized stresses caused by the depletion of chromium and aluminum in the coating or the enrichment of the coating with sulfur. For the materials and test conditions investigated, it was found that coating life is dependent only upon the initial coating thickness and not on the type of aluminized coating, the substrate, or the cycle frequency.

  5. Hot Corrosion Studies of Detonation-Gun-Sprayed NiCrAlY + 0.4 wt.% CeO2 Coated Superalloys in Molten Salt Environment

    Science.gov (United States)

    Kamal, Subhash; Jayaganthan, R.; Prakash, Satya

    2011-08-01

    Rare earth oxide (CeO2) has been incorporated in NiCrAlY alloy and hot corrosion resistance of detonation-gun-sprayed NiCrAlY + 0.4 wt.% CeO2 coatings on superalloys, namely, superni 75, superni 718, and superfer 800H in molten 40% Na2SO4-60% V2O5 salt environment were investigated at 900 °C for 100 cycles. The coatings exhibited characteristic splat globular dendritic structure with diameter similar to the original powder particles. The weight change technique was used to establish corrosion kinetics. X-ray diffraction (XRD), field emission scanning electron microscopy/energy-dispersive analysis (FE-SEM/EDAX), and x-ray mapping techniques were used to analyze the corrosion products. Coated superfer 800H alloy showed the highest corrosion resistance among the examined superalloys. CeO2 was found to be distributed in the coating along the splat boundaries, whereas Al streaks distributed non-uniformly. The main phases observed for the coated superalloys are oxides of Ni, Cr, Al, and spinels, which are suggested to be responsible for developing corrosion resistance.

  6. 探究电化学极化方法加速超级13Cr,15Cr不锈钢点蚀的发生和发展%The ExploringOf Accelerating Occurrence And Development Of Pitting Corrosion On Super13Cr,15Cr Stainless Steel By Electrochemical Polarization

    Institute of Scientific and Technical Information of China (English)

    李岩; 姜锐; 王华; 张旭; 周梦秋

    2016-01-01

    In corrosion medium, the pitting of 13Cr and 15Cr stainless steel has certain induction period. The method of electrochemical polarization was used to shorten the induction period of stainless steel in oilifeld produced water environment and accelerated the occurrence and growth of pitting. Studies showed that the pitting potential and the pitting depth proved that the corrosion resistance of the 15Cr stainless steelwas better than the 13Cr stainless steel; the electrochemical polarization method could accelerate pitting occurrence and development of super 13Cr and 15Cr stainless steel.%在腐蚀介质中,超级13Cr和15Cr不锈钢点蚀的发生存在一定的诱导期,本文采用电化学极化的方法缩短不锈钢在油田采出水环境下的点蚀诱导期,加速点蚀的发生和发展。研究表明:点蚀电位和点蚀深度的测量结果均证实了15Cr不锈钢的耐蚀性优于13Cr不锈钢;电化学极化方法可以加速超级13Cr和15Cr不锈钢点蚀的发生和发展。

  7. Pitting corrosion protection of low nickel stainless steel by electropolymerized conducting polymer coating in 0.5 M NaCl solution

    Indian Academy of Sciences (India)

    T Dhanabal; G Amirthaganesan; J Ravichandran

    2011-06-01

    Conducting polymers of polyaniline (PANi) and poly(o-phenylenediamine) (PoPD) were electropolymerized by cyclic voltammetric technique on low nickel stainless steel (LN SS) in H2SO4 solution containing aniline and -phenylenediamine monomers. The coatings were characterized by Fourier transform infrared spectroscopy, UV-visible and scanning electron microscopic techniques and the results are discussed. The corrosion protective properties of PANi and PoPD coatings on LN SS in 0.5 M NaCl were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The potentiodynamic polarization and electrochemical impedance spectroscopic results indicate that the PoPD coating inhibits the corrosion of LN SS in 0.5 M NaCl solution more effectively than PANi.

  8. Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation

    Science.gov (United States)

    Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei

    2016-03-01

    Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as

  9. Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation.

    Science.gov (United States)

    Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei

    2016-04-14

    Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.

  10. Environmental and Geometrical Conditions to Sustain Crevice Corrosion in Alloy 22

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-11-10

    Alloy 22 (N06022) is highly resistant to localized corrosion. Under aggressive environmental conditions Alloy 22 may be susceptible to crevice corrosion in hot chloride (Cl{sup -}) solutions. The objective of the present work was to explore the environmental and geometrical conditions for crevice corrosion to occur. Electrochemical tests were performed using PCA and prismatic mill annealed Alloy 22 specimens in chloride solutions. Crevice corrosion current density was found to be a function of applied potential. i{sub CREV} values ranged from 40 {micro}A/cm{sup 2} to 20 mA/cm{sup 2}. Such low values of current density explained the absence of pitting corrosion in Alloy 22 at any potential. Decreasing of the effective diffusion distance in a propagating crevice is thought to cause crevice corrosion stifling or repassivation after long anodic polarization. Crevice corrosion breakdown potential is expected to decrease with potential scan rate, approaching repassivation potential for low scan rates. The lowest corrosion potential of Alloy 22 in hydrochloric acid solutions at which active corrosion exists was proposed as the lowest possible repassivation potential for crevice corrosion.

  11. 非标件压力管道加厚弯头凹坑腐蚀超声相控阵检测的应用%The Application of Pits Corrosion of Nonstandard Pressure Pipeline Thickening Elbow Using Ultrasonic Phased Array Technology

    Institute of Scientific and Technical Information of China (English)

    康小伟; 何仁洋; 黄辉; 陈金忠

    2013-01-01

    本文应用超声波相控阵技术,对非标件的压力管道加厚弯头凹坑腐蚀减薄进行了检测。检测发现,加厚弯头因其内部凹槽腐蚀特殊性,普通超声波测厚无法完成,而相控阵技术因其探头晶片聚焦功能可实现对加厚弯头腐蚀凹坑的识别,相控阵检测图像信号清晰完整,最后对检测有异常信号的弯头进行解剖,发现相控阵检测的缺陷信号与非标件弯头凹坑缺陷相符合,为今后检测非标件压力管道加厚弯头内部凹坑缺陷提供了有效的技术支持。%In this paper, a nonstandard parts of pressure pipeline thickening elbow pits corrosion were detected by ultrasonic phased array technology. Ordinary ultrasonic testing can’t be completed because of thickening elbow’s internal pit corrosion particularity. However, phased array probe chip’s focus function can detect thickening elbow pits corrosion. Phased array detection’s picture and signal were clear and complete. Finally, elbows which phased array signal was abnormal were dissected. It found that phased array defect’s signal and the nonstandard parts elbow pit defects were same. Phased array technology provide effective technical support for internal pit defects of nonstandard parts pressure pipeline thickening elbow in the future.

  12. OPTIMAL DESIGN OF DEEP FOUNDATION PIT CONSTRUCTION PROJECT IN WUHAN

    OpenAIRE

    Nguyen Xuan Loi, Wu Li*, Nguyen Khanh Tung

    2016-01-01

    Deep foundation pit construction project is one of hot and difficult problems in rock soil engineering. How to control the deformation of the pits effectively and economically is what we all want. Retaining structure deformation of foundation pit is an important factor on the deformation of foundation pit. Reference of domestic and foreign research and the experience of similar projects, combined with the characteristics of Wuhan project, calculation, analyses and compared two design options ...

  13. Evaluation of the susceptibility to pitting corrosion of steel api 5L x42 exposed to solutions containing chloride ions and CO{sub 2} by electrochemical noise measurements; Evaluacion de la susceptibilidad a la corrosion por picado del acero api 5l x42 expuesto a un ambiente con cloruros y CO{sub 2} mediante la tecnica de ruido electroquimico

    Energy Technology Data Exchange (ETDEWEB)

    Pena-Ballesteros, D.; Rodriguez-Vanegas, N.; Anteliz, C.; Sarmiento Klapper, H.

    2011-07-01

    The concentration of chloride ions and the partial pressure of CO{sub 2} play an important role in the degradation of low-carbon steels used for the construction of pipelines in oil and gas industry. In order to evaluate the susceptibility of carbon steel API 5L X42 to pitting corrosion electrochemical noise and linear polarization resistance measurements were carried out in aqueous solutions containing chloride ions and CO{sub 2}. The concentration of chloride ions was varied between, 10000 and 18000 ppm, and the CO{sub 2} partial pressure between 10 psi and 18 psi. Experimental results pointed out that the formation of protective layer, consisting mainly of FeCO{sub 3}, depends on the partial pressure of CO{sub 2} in the system. Nevertheless, the stability of this layer was considerably affected by increasing the concentration of chloride ions causing that localized corrosion has taken place in some areas of the surface of API 5L X42, which were detected by electrochemical noise technique. (Author) 10 refs.

  14. Evaluation of hot corrosion protection of Cr-Al and CoNiCrAlY on IN-738LC

    Energy Technology Data Exchange (ETDEWEB)

    Khajavi, M.R. [Niroo Research Institute - Chemistry and Materials Research Center - Metallurgy Dept. End of Pounak-e-Bakhtari, P.O.Box 14665-517, Post Code 1468617151, Blvd., Shahrak-e-Gharb, Tehran (Iran)]|[Shiraz University - Materials Science and Engineering Department, Engineering School, Shiraz University, Shiraz (Iran); Pasha, A. [Niroo Research Institute - Chemistry and Materials Research Center - Metallurgy Dept. End of Pounak-e-Bakhtari, P.O.Box 14665-517, Post Code 1468617151, Blvd., Shahrak-e-Gharb, Tehran (Iran); Shariat, M.H. [Shiraz University - Materials Science and Engineering Department, Engineering School, Shiraz University, Shiraz (Iran)

    2004-07-01

    A program was conducted to evaluate the relative corrosion resistance of CoNiCrAlY and Chromium modified Aluminide on IN738-LC, used for turbine blades. The corrosion experiments were performed in a laboratory tube furnace. The microstructure of coatings was characterized by using optical and scanning electron microscopy techniques. The results indicated that at a temperature of 800 deg. C the CoNiCrAlY is more protective than Cr-Al coating. (authors)

  15. Performance of high-velocity oxyfuel-sprayed coatings on an Fe-based superalloy in Na2SO4-60%V2O5 environment at 900 °C part II: Hot corrosion behavior of the coatings

    Science.gov (United States)

    Sidhu, T. S.; Prakash, S.; Agrawal, R. D.

    2006-02-01

    NiCrBSi, Cr3C2-NiCr, Ni-20Cr, and Stellite-6 coatings were deposited on an Fe-based superalloy by the high-velocity oxyfuel (HVOF) thermal spray process. The hot corrosion behavior of the coatings in an aggressive environment of Na2SO4-60%V2O5 at 900 °C under cyclic conditions was studied. The thermogravimetric technique was used to establish the kinetics of corrosion. X-ray diffraction, scanning electron microscopy/energy-dispersive x-ray and electron probe microanalysis techniques were used to analyze the corrosion products. Hot corrosion resistances of all the coatings were found to be better than the uncoated superalloy. The Ni-20Cr coating was found to be the most protective, followed by Cr3C2-NiCr coatings. The Ni-20Cr coating had reduced the mass gain by 90% of that gained by the uncoated superalloy. The hot corrosion resistance shown by the Cr3C2-NiCr coating was slightly better compared with the NiCrBSi coating; however, both of the coatings performed better than the Stellite-6 coating. The Stellite-6 coating was the least effective among the coatings studied, but it was still successful in decreasing the mass gain to about one fourth compared with the uncoated superalloy. The formation of oxides and spinels of nickel, chromium, or cobalt may be contributing to the development of hot corrosion resistance in the coatings. This article focuses on the hot corrosion behavior of HVOF coatings. The characterization of these coatings has been presented in part I included in this issue.

  16. Corrosion of Metal-Matrix Composites with Aluminium Alloy Substrate

    Directory of Open Access Journals (Sweden)

    B. Bobic

    2010-03-01

    Full Text Available The corrosion behaviour of MMCs with aluminium alloy matrix was presented. The corrosion characteristics of boron-, graphite-, silicon carbide-, alumina- and mica- reinforced aluminium MMCs were reviewed. The reinforcing phase influence on MMCs corrosion rate as well as on various corrosion forms (galvanic, pitting, stress corrosion cracking, corrosion fatique, tribocorrosion was discussed. Some corrosion protection methods of aluminium based MMCs were described

  17. Protective Effect of the Sputtered TiAlCrAg Coating on the High-Temperature Oxidation and Hot Corrosion Resistance of Ti-Al-Nb Alloy

    Institute of Scientific and Technical Information of China (English)

    Yanjun XI; Fuhui WANG; Lianlong HE

    2004-01-01

    The effect of a sputtered Ti-48Al-8Cr-2Ag (at. pct) coating on the oxidation resistance of the cast Ti-46.5Al-5Nb (at. pct) alloy was investigated in air at 1000~1100℃. Hot corrosion in molten 75 wt pct Na2SO4+25 wt pct K2SO4 was investigated at 900℃. The scale on the cast TiAlNb tends to spall in air, while the scale on coating is very adherent. The sputtered Ti-48Al-8Cr-2Ag coating remarkably improved high temperature oxidation resistance of the cast Ti-46.5Al-5Nb alloy because of the formation of an adherent Al2O3 scale. Due to the inward diffusion of Cr,Kirkendall voids were found at the coating/substrate interface. TiAlCrAg coating provided excellent hot corrosion resistance for TiAlNb alloy in molten 75 wt pct Na2SO4+25 wt pct K2SO4 at 900℃ due to the formation of a continuous Al2O3 scale.

  18. Corrosion studies in brines of the Salton Sea Geothermal Field

    Energy Technology Data Exchange (ETDEWEB)

    Carter, J.P.; McCawley, F.X.; Cramer, S.D.; Needham, P.B. Jr.

    1979-01-01

    Toward the goal of maximizing minerals and metals recovery from domestic resources, the Bureau of Mines, U.S. Department of the Interior, has conducted in situ corrosion studies at the Salton Sea Known Geothermal Resources Area (KGRA) in the Imperial Valley, Calif., to evaluate and characterize materials of construction for geothermal resources recovery plants. General-, pitting, and crevice-corrosion characteristics of 13 commercially available alloys were investigated for periods of 15 and 30 days in seven process environments expected to be found in typical geothermal resources plants. Stainless steel alloy 29-4, Inconel 625, and the Hastelloys G, S, and C-276 were the most resistant to general corrosion, did not pit, and exhibited little susceptibility to crevice corrosion. Stainless steel alloys 430, E-Brite 26-1, and 6X had low general corrosion rates, but pitted and were susceptible to crevice corrosion. Stainless steel alloy 316 L had a low corrosion rate, but corroded intergranularly, pitted, and was susceptible to crevice corrosion and to stress-corrosion cracking. Titanium--1.5 nickel and TiCode-12 had low corrosion rates, did not pit, and were not susceptible to crevice corrosion. Carbon and 4130 steels had high corrosion rates, pitted, and had high susceptibilities to crevice corrosion. The major scale-forming mineral on the corrosion samples in most of the process environments studied was galena mixed with lesser amounts of other minerals.

  19. CORROSION ISSUES ASSOCIATED WITH AUSTENITIC STAINLESS STEEL COMPONENTS USED IN NUCLEAR MATERIALS EXTRACTION AND SEPARATION PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    Mickalonis, J.; Louthan, M.; Sindelar, R.

    2012-12-17

    This paper illustrated the magnitude of the systems, structures and components used at the Savannah River Site for nuclear materials extraction and separation processes. Corrosion issues, including stress corrosion cracking, pitting, crevice corrosion and other corrosion induced degradation processes are discussed and corrosion mitigation strategies such as a chloride exclusion program and corrosion release testing are also discussed.

  20. Pattern recognition model to estimate intergranular stress corrosion cracking (IGSCC) at crevices and pit sites of 304 SS in BWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Urquidi-Macdonald, Mirna [Penn State University, 212 Earth-Engineering Science Building, University Park, PA 16801 (United States)

    2004-07-01

    Many publications have shown that crack growth rates (CGR) due to intergranular stress corrosion cracking (IGSCC) of metals is dependent on many parameters related to the manufacturing process of the steel and the environment to which the steel is exposed. Those parameters include, but are not restricted to, the concentration of chloride, fluoride, nitrates, and sulfates, pH, fluid velocity, electrochemical potential (ECP), electrolyte conductivity, stress and sensitization applied to the steel during its production and use. It is not well established how combinations of each of these parameters impact the CGR. Many different models and beliefs have been published, resulting in predictions that sometimes disagree with experimental observations. To some extent, the models are the closest to the nature of IGSCC, however, there is not a model that fully describes the entire range of observations, due to the difficulty of the problem. Among the models, the Fracture Environment Model, developed by Macdonald et al., is the most physico-chemical model, accounting for experimental observations in a wide range of environments or ECPs. In this work, we collected experimental data on BWR environments and designed a data mining pattern recognition model to learn from that data. The model was used to generate CGR estimations as a function of ECP on a BWR environment. The results of the predictive model were compared to the Fracture Environment Model predictions. The results from those two models are very close to the experimental observations of the area corresponding to creep and IGSCC controlled by diffusion. At more negative ECPs than the potential corresponding to creep, the pattern recognition predicts an increase of CGR with decreasing ECP, while the Fracture Environment Model predicts the opposite. The results of this comparison confirm that the pattern recognition model covers 3 phenomena: hydrogen embrittlement at very negative ECP, creep at intermediate ECP, and IGSCC

  1. 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.

  2. Construction of an external electrode for determination of electrochemical corrosion potential in normal operational conditions of an BWR type reactor for hot cells; Construccion de un electrodo externo para determinacion del potencial de corrosion electroquimico en condiciones normales de operacion de un reactor tipo BWR para celdas calientes

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar T, J.A.; Rivera M, H.; Hernandez C, R. [Departamento de Sintesis y Caracterizacion de Materiales, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2001-07-01

    The behavior of the corrosion processes at high temperature requires of external devices that being capable to resist a temperature of 288 Centigrade and a pressure of 80 Kg/cm{sup 2}, to give stable and reproducible results of some variable and resisting physically and chemically the radiation. The external electrode of Ag/AgCl fulfils all the requirements in the determination of the electrochemical corrosion potential under normal operational conditions of a BWR type reactor in hot cells. (Author)

  3. Detection of microbiologically influenced corrosion by electrochemical noise transients

    NARCIS (Netherlands)

    Homborg, A.M.; Morales, C.F. Leon; Tinga, Tiedo; de Wit, J.H.W.; Mol, J.M.C.

    2014-01-01

    This work investigates the electrochemical processes involved in pitting corrosion induced by microbiologically influenced corrosion by using time-resolved instantaneous frequency information of electrochemical current noise (ECN) transients obtained from Hilbert spectra. In addition to the

  4. Corrosion evaluation technology

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Uh Chul; Han, Jeong Ho; Nho, Kye Ho; Lee, Eun Hee; Kim, Hong Pyo; Hwang, Seong Sik; Lee, Deok Hyun; Hur, Do Haeng; Kim, Kyung Mo

    1997-09-01

    A multifrequency ACPD system was assembled which can measure very small crack. Stress corrosion cracking test system with SSRT operating high temperature was installed. Stress corrosion cracking test of newly developed alloy 600 and existing alloy 600 was carried out in steam atmosphere of 400 deg C. No crack was observed in both materials within a test period of 2,000 hrs. Corrosion fatigue test system operating at high temperature was installed in which fatigue crack was measured by CDPD. Lead enhanced the SCC of the Alloy 600 in high temperature water, had a tendency to modify a cracking morphology from intergranular to transgranular. Pit initiation preferentially occurred at Ti-rich carbide. Resistance to pit initiation decreased with increasing temperature up to 300 deg C. Test loop for erosion corrosion was designed and fabricated. Thin layer activation technique was very effective in measuring erosion corrosion. Erosion corrosion of a part of secondary side pipe was evaluated by the Check Family Codes of EPRI. Calculated values of pipe thickness by Check Family Codes coincided with the pipe thickness measured by UT with an error of {+-} 20%. Literature review on turbine failure showed that failure usually occurred in low pressure turbine rotor disc and causes of failure are stress corrosion cracking and corrosion fatigue. (author). 12 refs., 20 tabs., 77 figs.

  5. Studies on Hot Corrosion of the Microstructurally Different Regions of 2.25Cr-1Mo (T22) Boiler Tube Steel Weldment

    Science.gov (United States)

    Kumar, Ravindra; Tewari, V. K.; Prakash, Satya

    2009-10-01

    This study examines the effect of microstructurally different regions on the hot corrosion of tungsten inert gas weldment in 2.25Cr-1Mo (T22) boiler tube steel. Various regions of weldment were oxidized in molten salt Na2SO4-60% V2O5 environment at 900 °C. The base metal was found to oxidize at much higher rates than the weld metal and the heat-affected zone. Oxide scales formed in the three regions were compared by scanning electron microscopy with energy dispersive of X-ray analysis, X-ray diffraction pattern, and electron probe microanalysis. The research investigates the formation of inner scales with free Cr over the HAZ.

  6. Experimental Studies of the Formation/Deposition of Sodium Sulfate in/from Combustion Gases. [hot corrosion in gas turbine engines

    Science.gov (United States)

    Rosner, D. E.

    1978-01-01

    Processes related to the hot corrosion of gas turbine components were examined in two separate investigations. Monochromatic laser light was used to probe condensation onset and condensate film growth (via interference of reflected light) on electrically heated ribbons immersed in seeded, flat flame combustion product gases. Boron trichloride is used as the seed gas in these preliminary experiments conducted to obtain precise measurements of the dew point/deposition rates. Because of the importance of gaseous Na(g) as a precursor to NaSO4 formation, the kinetics and mechanisms of the heterogeneous reaction H(g) + NaCl(s) yields Na(g) + HCl(g) was studied using atomic absorption spectroscopy combined with microwave discharge-vacuum flow reactor techniques at moderate temperatures. Preliminary results indicate the H-atom attack of solid NaCl vaporization is negligible; hence the corresponding gas phase (homogeneous) reaction no role in the observed Na(g) production.

  7. Development and Testing of an Anti-Scale/Corrosion Resistant Coating for Domestic Hot Water Heat Exchangers

    Science.gov (United States)

    1990-12-01

    Fort Bragg 23 10 Closeup of Scale- Incrusted Heat Exchanger Tube Bundle from Fort Bragg 24 11 Removal of Heat Exchanger Tube Bundle from Bldg 421, Fort...or vertical cylindrical tank (Figure 3). The tube bundle is usually made of copper or a copper alloy, and the tank is usually steel with a cement ...side of the solid barrier. The fouling factor includes the effects of corrosion and scale incrustation , and also the effect of protective coatini-s such

  8. Accelerated corrosion test and corrosion failure distribution model of aircraft structural aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    LIU Wen-lin; MU Zhi-tao; JIN Ping

    2006-01-01

    Based on corrosion damage data of 10 years for a type of aircraft aluminum alloy, the statistical analysis was conducted by Gumbel, Normal and two parameters Weibull distribution function. The results show that aluminum alloy structural member has the corrosion history of pitting corrosion-intergranular corrosion-exfoliation corrosion, and the maximum corrosion depth is in conformity to normal distribution. The accelerated corrosion test was carried out with the complied equivalent airport accelerated environment spectrum. The corrosion damage failure modes of aluminum alloy structural member indicate that the period of validity of the former protective coating is about 2.5 to 3 years, and that of the novel protective coating is about 4.0 to 4.5 years. The corrosion kinetics law of aluminum spar flange was established by fitting corrosion damage test data. The law indicates two apparent corrosion stages of high strength aluminum alloy section material: pitting corrosion and intergranular corrosion/exfoliation corrosion.The test results agree with the statistical fit result of corrosion data collected from corrosion member in service. The fractional error is 5.8% at the same calendar year. The accelerated corrosion test validates the corrosion kinetics law of aircraft aluminum alloy in service.

  9. Materials selection and corrosion problems

    Energy Technology Data Exchange (ETDEWEB)

    Cornet, I.; Greif, R.; Treseder, R.S.

    1974-06-28

    Data tabulated for chemical composition of geothermal waters are presented for four areas of interest in Nevada: Beowawe steam well and Beowawe Hot Spring, Buffalo Valley Hot Springs, Kyle Hot Springs, and Leach Hot Springs. Material recommendations were prepared for the Nevada geothermal well. A detailed field corrosion test program planned for the Nevada test well is included. A progress report is presented for a laboratory research program on velocity effects in corrosion. (MHR)

  10. Susceptibility of two types of low-alloy hull steels to pit initiation

    Institute of Scientific and Technical Information of China (English)

    Jianmin Wang; Xuequn Chen; Guomin Li

    2004-01-01

    Four low-alloy hull steels with different alloy elements were selected. Their susceptibility to pitting corrosion was compared by means of electrochemical polarization test. The inclusions in the steels and their pitting corrosion characteristics were studied by an electron probe micro-analyzer (EPMA). The results indicate that some inclusions are the main sources of pitting corrosion.The susceptibility of nickel-chromium steel to pit initiation is less than that of manganese steel. Under the same conditions, nickelchromium steel is easier to passivate than manganese steel, and the passive films on nickel-chromium steel surface are more stable than that on manganese steel. In low-alloy steels, the higher the contents of nickel and chromium, the lower the critical passive pH value. In the same kind of steel, multi-phase inclusions containing sulfide are easier to initiate pitting corrosion than other inclusions.

  11. Localized corrosion of copper alloys in China seawater for 16 years

    Institute of Scientific and Technical Information of China (English)

    赵月红; 林乐耘; 崔大为

    2004-01-01

    The regulation of localized corrosion of 2 kinds of copper and 17 kinds of copper alloys exposed in seawater of Qingdao, Zhoushan, Yulin and Xiamen for 16 years has been studied. Results show that during immersion copper alloys suffer from pitting corrosion due to high temperature and marine living adhesion at Yulin, and to the higher velocity of seawater containing sand at Zhoushan. However, the seawater of Xiamen inhibits the pitting corrosion of copper alloys. No pitting corrosion is observed on copper alloy plates tested there. The copper alloys suffer from more serious pitting corrosion in the tide zone than that in the immersion zone at Qingdao after long time exposure.

  12. Effects of selected water chemistry variables on copper pitting propagation in potable water

    Energy Technology Data Exchange (ETDEWEB)

    Ha Hung, E-mail: hmh2n@virginia.edu [Center for Electrochemical Science and Engineering, Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA (United States); Taxen, Claes [SWEREA-KIMAB, Stockholm (Sweden); Williams, Keith [Department of Physics, University of Virginia, Charlottesville, VA (United States); Scully, John [Center for Electrochemical Science and Engineering, Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA (United States)

    2011-07-01

    Highlights: > The effects of water composition on pit propagation kinetics on Cu were separated from pit initiation and stabilization using the artificial pit method in a range of dilute HCO{sub 3}{sup -}, SO{sub 4}{sup 2-} and Cl{sup -}-containing waters. > The effective polarization and Ohmic resistance of pits were lower in SO4{sup 2-}-containing solutions and greater in Cl{sup -}-containing solutions. > Relationship between the solution composition and the corrosion product identity and morphology were found. > These, in turn controlled the corrosion product Ohmic resistance and subsequently the pit growth rate. - Abstract: The pit propagation behavior of copper (UNS C11000) was investigated from an electrochemical perspective using the artificial pit method. Pit growth was studied systematically in a range of HCO{sub 3}{sup -}, SO{sub 4}{sup 2-} and Cl{sup -} containing-waters at various concentrations. Pit propagation was mediated by the nature of the corrosion products formed both inside and over the pit mouth (i.e., cap). Certain water chemistry concentrations such as those high in sulfate were found to promote fast pitting that could be sustained over long times at a fixed applied potential but gradually stifled in all but the lowest concentration solutions. In contrast, Cl{sup -} containing waters without sulfate ions resulted in slower pit growth and eventual repassivation. These observations were interpreted through understanding of the identity, amount and porosity of corrosion products formed inside and over pits. These factors controlled their resistive nature as characterized using electrochemical impedance spectroscopy. A finite element model (FEM) was developed which included copper oxidation kinetics, transport by migration and diffusion, Cu(I) and Cu(II) solid corrosion product formation and porosity governed by equilibrium thermodynamics and a saturation index, as well as pit current and depth of penetration. The findings of the modeling were

  13. Pit Water Storage Ottrupgaard

    DEFF Research Database (Denmark)

    Heller, Alfred

    2000-01-01

    The pit water storage, a seasonal thermal storage, was built in 1993 with floating lid and hybrid clay-polymer for pit lining. The storage was leaking severe and solutions were to be found. In the paper solutions for pit lining and floating lids are discussed, cost estimations given and coming...

  14. Pit Water Storage Ottrupgaard

    DEFF Research Database (Denmark)

    Heller, Alfred

    2000-01-01

    The pit water storage, a seasonal thermal storage, was built in 1993 with floating lid and hybrid clay-polymer for pit lining. The storage was leaking severe and solutions were to be found. In the paper solutions for pit lining and floating lids are discussed, cost estimations given and coming...

  15. Review of studies on corrosion of magnesium alloys

    Institute of Scientific and Technical Information of China (English)

    ZENG Rong-chang; ZHANG jin; HUANG Wei-jiu; W. DIETZEL; K. U. KAINER; C. BLAWERT; KE Wei

    2006-01-01

    This review provided some recent progress of the research on corrosion mechanisms of magnesium and its alloys and a basis for follow-on research. Galvanic corrosion,pitting corrosion,intergranular corrosion (IGC),filiform corrosion,crevice corrosion,stress corrosion cracking (SCC),and corrosion fatigue (CF) were discussed. The influence of metallurgical factors such as alloying elements,microstructure and secondary phases,processing factors such as heat treatment and weld,and environmental factors including temperature,relative humidity,solution pH values and concentration on corrosion were discussed. In particular,a mechanism of pitting corrosion caused by AlMn particles was proposed. The corrosion properties of AZ91D weld material were investigated.

  16. Multicomponent Oxide Systems for Corrosion Protection.

    Science.gov (United States)

    1980-11-15

    and Si(OEt) 4 are somewhat lpss corrosive to aluminum than is SiCI 4 alone, although some pitting occurs for slow hydrolysis after coating by solutions...humidity (x) 86 A𔃻 determinants of corrosion resistance. The magnesium-silicon- aluminum alloy AA 6061 is generally considered to have good corrosion ... 6061 ), the corrosion resistance exceeded that of the chromate coatings. The feasibilityof the basic approach taken here has been validated. It

  17. Hot corrosion performance of LVOF sprayed Al2O3–40% TiO2 coating on Superni 601 and Superco 605 superalloys at 800 and 900°C

    Indian Academy of Sciences (India)

    N K Mishra; S B Mishra

    2015-12-01

    Al2O3–40% TiO2 coating is deposited on Superni 601 and Superco 605 superalloys by low-velocity oxy-fuel (LVOF) process. LVOF sprayed coating is characterized for surface roughness, microhardness, scanning electron microscopy and X-ray diffraction analysis. Hot corrosion of the coated and uncoated superalloys have been evaluated in an aggressive environment of Na2SO4–82% Fe2(SO4)3 under cyclic conditions at temperatures of 800 and 900°C. The microhardness and surface roughness values of the as-sprayed coatings are found to be in the range of 742–946 Hv and 14.40–14.80 m, respectively. Al2O3–40% TiO2 coating on both the superalloys has indicated protective behaviour during hot corrosion studies.

  18. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    Science.gov (United States)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  19. Modeling and simulation of pit chemistry of 304 austenitic stainless steel under applied stress in sodium chloride solution

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yuhui, E-mail: yhhuang@ecust.edu.cn [Key Laboratory of Pressure Systems and Safety, MOE, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China); Tu, Shan-Tung; Xuan, Fu-Zhen [Key Laboratory of Pressure Systems and Safety, MOE, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2013-04-15

    Highlights: ► A corrosion model was developed to simulate a stressed metal surface with a pit. ► The stress state in the pit bottom was coupled with the local corrosion environment. ► An analytical expression was established for current density of deformed pit surface. ► Local deformation had a strong effect on potential and species concentration in pits. -- Abstract: A mathematical model for simulating the active dissolution of a pit on stressed metal surface had been developed. Based on active dissolution mechanism, dissolution current density on the pit surface was assumed and extended through accounting for the thermal activation energy and the multiaxial stress state in pit bottom. The influence of applied tensile stress, pit radius and temperature was addressed. The distribution of solution potential and species concentration was predicted for different applied tensile stresses based on finite element calculations.

  20. Dermoscopy of Pitted Keratolysis

    Directory of Open Access Journals (Sweden)

    Lauren L. Lockwood

    2010-08-01

    Full Text Available Irritated hyperhidrotic soles with multiple small pits are pathognomonic for pitted keratolysis (PK. Here we show the dermatoscopic view of typical pits that can ensure the diagnosis. PK is a plantar infection caused by Gram-positive bacteria, particularly Corynebacterium. Increases in skin surface pH, hyperhidrosis, and prolonged occlusion allow these bacteria to proliferate. The diagnosis is fundamentally clinical and treatment generally consists of a combination of hygienic measures, correcting plantar hyperhidrosis and topical antimicrobials.

  1. Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

    Directory of Open Access Journals (Sweden)

    Yongfang Huang

    2017-04-01

    Full Text Available For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ and pit depth (d with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively.

  2. Effect of chromium on the corrosion resistance of aluminide coatings on nickel and nickel-based substrates

    Energy Technology Data Exchange (ETDEWEB)

    Godlewski, K.; Godlewska, E.

    1987-04-01

    The aluminide and Cr-Al diffusion coatings on nickel and the nickel-based alloy EI 867 obtained by a two-step pack cementation technique were subjected to various corrosion tests consisting of oxidation under thermal cycling conditions as well as isothermal oxidation in the presence of fused Na/sub 2/SO/sub 4/. The presence of chromium in the surface layer of aluminide coatings had a beneficial effect on their resistance to oxidation in that the oxide layer formed was less prone to spallation. This type of coating microstructure also appeared to be advantageous with respect to hot corrosion since pitting, which is typical of the degradation of aluminide coatings, was not observed. It is postulated that the chromium-enriched zone acts as a barrier to the oxidation of refractory metals (molybdenum, tungsten and vanadium) present in somewhat deeper coating layers in the form of carbide or intermetallic phases, thus preventing the onset of catastrophic corrosion.

  3. Corrosion of mild steel and stainless steel by marine Vibrio sp.

    Digital Repository Service at National Institute of Oceanography (India)

    PrabhaDevi; Wagh, A.B.

    Microbially induced corrosion (MIC) of stainless steel and mild steel coupons exposed to media with and without a bacterial culture Vibrio sp. was studied using Scanning Electron Microscope (SEM). Pitting type of corrosion was noticed which was more...

  4. Recognition and Analysis of Corrosion Failure Mechanisms

    Directory of Open Access Journals (Sweden)

    Steven Suess

    2006-02-01

    Full Text Available Corrosion has a vast impact on the global and domestic economy, and currently incurs losses of nearly $300 billion annually to the U.S. economy alone. Because of the huge impact of corrosion, it is imperative to have a systematic approach to recognizing and mitigating corrosion problems as soon as possible after they become apparent. A proper failure analysis includes collection of pertinent background data and service history, followed by visual inspection, photographic documentation, material evaluation, data review and conclusion procurement. In analyzing corrosion failures, one must recognize the wide range of common corrosion mechanisms. The features of any corrosion failure give strong clues as to the most likely cause of the corrosion. This article details a proven approach to properly determining the root cause of a failure, and includes pictographic illustrations of the most common corrosion mechanisms, including general corrosion, pitting, galvanic corrosion, dealloying, crevice corrosion, microbiologically-influenced corrosion (MIC, corrosion fatigue, stress corrosion cracking (SCC, intergranular corrosion, fretting, erosion corrosion and hydrogen damage.

  5. Hanford double shell waste tank corrosion studies - final report FY2014

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, B. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Fuentes, R. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hicks, K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-12-19

    SRNL tasks for FY14 included studies to evaluate the susceptibility of carbon steel to vapor space corrosion (VSC), liquid-air interface (LAI) corrosion, and pitting corrosion. Additionally, SRNL evaluated the susceptibility of carbon steel to pitting corrosion under buffered waste conditions, with the objective of determining the adequate amount of inhibitor (e.g., nitrite) necessary to mitigate pitting corrosion. Other CPP experiments were performed in historical waste simulants and the results were compared to previously gathered results. The results of these activities were utilized to assess the robustness of the standardized CPP protocol

  6. Pit initiation on nitinol in simulated physiological solutions.

    Science.gov (United States)

    Pound, Bruce G

    2017-08-21

    Inclusions appear to play a crucial role in the initiation of pitting on nitinol, but the reason remains unclear. Furthermore, it has not been established whether the type of inclusion is a central factor. In this study, potentiodynamic polarization together with scanning electron microscopy and energy dispersive X-ray spectroscopy were used to provide more insight into the initiation of pits on electropolished nitinol wire. Corrosion was limited to a single primary pit on each of the few wire samples that exhibited breakdown. The pit contained numerous Ti2 NiOx inclusions, but secondary pits that developed within the primary pit provided evidence that these inclusions were the sites of pit initiation. Although several theories have been proposed to account for pit initiation at inclusions in mechanically polished and electropolished nitinol, titanium depletion in the adjacent alloy matrix appears to provide the most viable explanation. The key factor appears to be the size of the inclusion and therefore the extent of titanium depletion in the alloy matrix. The type of inclusion evidently plays a secondary role at most. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

  7. Corrosion Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Weldingh, Jakob; Olsen, Flemmming Ove

    1997-01-01

    In this paper the corrosion properties of laser welded AISI 316L stainless steel are examined. A number of different welds has been performed to test the influence of the weld parameters of the resulting corrosion properties. It has been chosen to use the potential independent critical pitting...... temperature (CPT) test as corrosion test. The following welding parameters are varied: Welding speed, lsser power, focus point position and laser operation mode (CW or pulsed)....

  8. Study of the properties of plasma deposited layers of nickel-chrome-aluminium-yttrium coatings resistant to oxidation and hot corrosion

    Directory of Open Access Journals (Sweden)

    Mihailo R. Mrdak

    2012-04-01

    Full Text Available The aim of this study was to examine the properties of Ni22Cr10Al1Y layers in order to obtain optimal structural - mechanical properties with the optimization of depositing parameters. Powder was deposited by the atmospheric plasma spray (APS process with the current intensity of 600, 700 and 800A, with a corresponding plasma gun power supply of 22KW, 34KW and 28KW. The evaluation of the Ni22Cr10Al1Y coating layers was made on the basis of their microhardness, tensile strength and microstructure performance. The best performance was obtained in the layers deposited with 800A and the 34KW plasma gun power supply. The coating with the best characteristics was tested to oxidation in the furnace for heat treatment without a protective atmosphere at 1100°C for one hour. The examination of the morphology of Ni22Cr10Al1Y powder particles was carried out on the SEM (Scanning Electron Microscope as well as the EDS analysis of the best layers. The microstructure of the deposited coating layers was examined with a light microscope. The microstructure analysis was performed according to the TURBOMECA standard. The mechanical properties of layers were evaluated by the method HV0.3 for microhardness and by tensile testing for bond strength. The research has shown that plasma gun power supply significantly affects the mechanical properties and microstructure of coatings that are of crucial importance for the protection of components exposed to high temperature oxidation and hot corrosion.

  9. Research on the Corrosion Resistance of Hot Dip Galvanized Coating in Simulated Hot and Humid Acidic Atmospheric Environment%热镀锌层在模拟湿热酸性大气环境中的耐蚀性研究

    Institute of Scientific and Technical Information of China (English)

    刘胜林; 孙亮; 袁毅; 卢才

    2015-01-01

    目的:研究Q420钢表面热镀锌工艺中,Zn和Zn-Al-Ni-RE合金镀层在酸性铜离子加速盐雾试验条件下的耐蚀性能。方法 Q420钢表面预处理后进行热镀锌,根据GB6460—1986进行铜加速醋酸盐雾腐蚀试验,对比纯Zn镀层与Zn-Al-Ni-RE合金镀层的耐蚀性。结果 Ni,RE等元素的加入使镀层表面光亮,组织更加细密。在酸性铜离子加速实验进行到192 h时,纯锌镀层的腐蚀质量损失是合金镀层的2.7倍;72 h后纯锌镀层出现红锈,120 h后合金镀层出现红锈,说明Zn-Al-Ni-RE合金镀层比纯Zn镀层更耐腐蚀。结论通过适量添加Al,Ni与稀土元素,能使Q420钢合金镀层的耐蚀性能大幅度提高。%Objective To study the corrosion resistance of hot dip galvanized pure Zn and Zn-Al-Ni-RE alloy coatings of high-strength steel Q420 under the acidic and copper accelerated salt spray corrosion condition. Methods On the basis of surface pre-treatment, the Q420 steel was treated by hot dip galvanizing. Copper accelerated acetic acid salt spray corrosion test was carried out according to GB 6460—1986, and the corrosion resistance of the pure Zn coating and Zn-Al-Ni-RE coating was compared. Results With the addition of Ni, RE and other elements, the coating surface was bright and the microstructure became finer. After 192 h, the corrosion weight loss of pure zinc coating was 2. 7 times higher than the corrosion weight loss of Zn-Al-Ni-RE alloy coatings un-der the acidic and copper accelerated salt spray corrosion condition. Pure zinc coating showed red rust after 72 h, while Zn-Al-Ni-RE alloy coating showed red rust after 120 h, so Zn-Al-Ni-RE alloy coating was more corrosion resistant than the pure Zn coating. Conclusion By means of adding nickel aluminum elements and rare earth elements, the corrosion resistance of alloy coating was greatly improved.

  10. Final Report for the Erosion-Corrosion Anaysis of Tank 241-AW-02E Feed Pump Pit Jumpers B-2 and 1-4 Removed from Service in 2013

    Energy Technology Data Exchange (ETDEWEB)

    Page, Jason S.

    2014-04-07

    This document is the final report summarizing the results in the examination of two pipe sections (jumpers) from the tank 241-AW-02E feed pump pit in the 241-AW tank farm. These pipe section samples consisted of jumper AW02E-WT-J-[B – 2] and jumper AW02E-WT-J-[1 – 4]. For the remainder of this report, these jumpers will be referred to as B – 2 and 1 – 4.

  11. Corrosion behaviour of the welded steel sheets used in automotive industry

    Directory of Open Access Journals (Sweden)

    D. Katundi

    2010-02-01

    Full Text Available Purpose: of this paper is to characterise the corrosion resistance in the steel sheets (Hot dip galvanizing of steel sheets used in automotive industry. In fact, corrosion of automotive components by road salt is a widely known problem. The different parts under the car body and the interior surface of body panels suffer easily from the corrosive products deposited on roads and used mainly to melt snow. A comparison in a chemical investigation of the corrosion rate for base metals (without welding and welded steel is required. Therefore, conformity will be accomplished between the corrosion phenomena in simulated corrosion tests and those in actual cars.Design/methodology/approach: Simulated corrosion tests, wet/humidity test and hot dust/dry cycle talk test carried on in laboratory conditions was investigated quantitatively. Dynamic behaviour of the corroded specimens have been tested dynamically to simulate under the crash test conditions.Findings: Studies carried out on the vast corroded samples have shown that the pitting corrosion damage and crack initiation sites have began and propagated generally in the HAZ in the welded steel sheets (Tailored welded blanks - TWB.Research limitations/implications: This paper contains partially results of a common research project. Some limitations exist in application of hot dust/dry cycle talk to the real open air test conditions. All of these results were carried out in the laboratory conditions.Practical implications: The problem is of extreme importance to all academic, scientific, manufacturing, maintenance and industrial societies. The outcome of the proposed study will contribute to the industrial application of ARCELOR-MITTAL. The proposed study will be benefit not only for the car industry and steel makers, but also important for the other industrial applications. The proposed research can be employed in a broad range of applications in oil and natural gas industries. This project will promote

  12. Research on Pitting Corrosion-resistant of Stainless Steel/Carbon Steel Welding Jiont%不锈钢/碳钢复合钢板焊接接头耐点蚀性能研究

    Institute of Scientific and Technical Information of China (English)

    贡志林

    2015-01-01

    The corrosion resistance of bade metal, weld and heat affected zone of stainless steel-carbon steel laminated composite material in 3. 5% NaCl solution, 30% CH3 COOH solution, 60% CH3 COOH solution and 98%CH3 COOH solution was studied respectively through electrochemical test. It was obtained that the corrosion resistance of weld was the better then the base metal, but the corrosion resistance of heat affected zone was the worst. Besides, in the four solution base metal and weld showed poor corrosion resistance in 3. 5%NaCl solution. A theoretical and experimental foundation for stainless steel-carbon steel laminated composite material was supplied.%采用电化学测试方法评价了不锈钢复合板母材、焊缝及热影响区在3.5%NaCl溶液、30%CH3 COOH溶液、60%CH3 COOH溶液、98%CH3 COOH溶液中的耐点蚀性能。结果显示在以上各种溶液中焊缝的抗腐蚀性能最优、母材其次而热影响区抗腐蚀性能最弱。此外在这四种溶液中母材跟焊区在3.5%NaCl溶液溶液中的耐腐蚀性能最弱。

  13. IntegralitU Assessment for Corrosion Defects in Hot-bend Pipe for Natural Gas Transmission Pipelines%天然气输送管道热弯钢管腐蚀缺陷的完整性评价

    Institute of Scientific and Technical Information of China (English)

    张忠秀; 安立芬; 陶爱莲; 陈利华

    2011-01-01

    为了评价天然气输送管道热弯钢管腐蚀缺陷的完整性,分别对热弯钢管及含腐蚀热弯钢管进行了有限元分析(FEA).对热弯钢管有限元分析的结果表明,应变在拉伸区域轴向为正值,在压缩区域轴向为负值,而径向应变分布却与此相反,且钢管的壁厚和应变与弯曲角无关.通过对不同壁厚、平均壁厚、含对称腐蚀缺陷以及含非对称腐蚀缺陷热弯钢管爆破压力的预测及对比,得出了将弯曲系数和平均壁厚引入用于直钢管完整性评价的 PCORRC方程,可以合理预测出有腐蚀缺陷热弯钢管的爆破压力的结论.%In order to assess integrality of hot-bend pipe corrosion defects for natural gas transmission pipeline, finite element analysis (FEA) was separately performed to hot-bend pipe and corrosive hot-bend pipe. The results showed that strain value is positive in axial tensile area,it is negative in axial compress area,while longitudinal strain distribution is in contrast, and thickness is not relevant to strain and bending angle. Through prediction and contrast to 4 kinds of bursting pressure of hot-bend pipe, different thickness, average thickness, symmetry corrosive defects and asymmetry corrosive defects, it can obtain PCORIRC equation which applied bend coefficient and average wall thickness to straight steel pipe structural integrity assessment, and can get bursting pressure through reasonable prediction.

  14. 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)

  15. Accelerated corrosion testing results for specimens containing uncoated reinforcing steel and corrosion inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Kondratova, I. L.; Montes, P.; Bremner, T. W. [New Brunswick Univ., Dept, of Civil Engineering, Fredericton, NB (Canada)

    2000-07-01

    Concrete mixtures (water-cement ratios of 0.25, 0.40. or 0.60) containing uncoated reinforcing bars with a simulated crack, formed transverse to the axis of the bar, and with three commercial corrosion inhibitors added for corrosion protection (organic corrosion inhibitor,calcium nitrate-based corrosion inhibitor, and migratory corrosion inhibitor), were tested for corrosion damage. The objective was to evaluate the effectiveness of the different corrosion inhibitors in uncracked and cracked concrete slabs in a simulated marine environment. The specimens were placed in an accelerated exposure cabinet with four cycles of wetting and drying per day in simulated seawater, and corrosion rates measured using the linear polarization technique. Water-soluble chloride content in the rebars was analyzed at the end of the exposure period. The three corrosion inhibitors were found to show a wide variation in performance. There was a direct correlation between their effectiveness and addition rate. All three appeared to be more effective in reducing corrosion rate in a higher water-to-cement ratio concrete. Consistent performance was provided only by calcium nitrate at an addition rate of 25 litre/cu m of concrete, with water-to-cement ratios of 0.60 and 0.40. Pitting corrosion was observed in all pre-cracked high performance concrete specimens; the depth of the pit tended to be deeper when a corrosion inhibitor was used. 6 refs., 6 tabs., 6 figs.

  16. Furniture Rack Corrosion Coupon Surveillance - 2012 Update

    Energy Technology Data Exchange (ETDEWEB)

    Mickalonis, J. I.; Murphy, T. R.; Berry, C. J.

    2012-10-01

    Under the L Basin corrosion surveillance program furniture rack coupons immersed for 14 years (FY2009 coupons) and 16 years (FY2011 coupons) were analyzed and the results trended with coupons exposed for shorter times. In addition, a section harvested from an actual furniture rack that was immersed for 14 years was analyzed for pitting in the weld and heat-affected-zone (HAZ) regions. The L Basin operations maintained very good water quality over the entire immersion period for these samples. These results for FY2009 and FY2011 coupons showed that the average pit depths for the 6061 and 6063 base metal are 1 and 2 mils, respectively, while those for the weld and HAZ are 3 and 4 mils, respectively. The results for the weld and HAZ regions are similar to coupons removed during the period of FY2003 to FY2007. These similarities indicate that the pit development occurred quickly followed by slow kinetics of increase in pit depth. For the actual furniture rack sample average pits of 5 and 2 mils were measured for the HAZ and weld, respectively. These results demonstrate that pitting corrosion of the aluminum furniture racks used to support the spent fuel occurs in waters of good quality. The corrosion kinetics or pit depth growth rate is much less that 1 mil/year, and would not impact long-term use of this material system for fuel storage racks in L Basin if good water quality is maintained.

  17. Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

    Directory of Open Access Journals (Sweden)

    P. Vijaya Kumar

    2015-12-01

    It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged (T6 condition but the welds showed poor corrosion resistance. The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment. The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.

  18. Lava Tube Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in the southern hemisphere of Mars. They are likely lava tube collapse pits related to flows from Hadriaca Patera. Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D

  19. Ascraeus Mons Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found on the flank of Ascraeus Mons. The pits and channels are all related to lava tube formation and emptying. Image information: IR instrument. Latitude 8, Longitude 253.9 East (106.1 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal

  20. Selectable-Tip Corrosion-Testing Electrochemical Cell

    Science.gov (United States)

    Lomness, Janice; Hintze, Paul

    2008-01-01

    The figure depicts aspects of an electrochemical cell for pitting- corrosion tests of material specimens. The cell is designed to generate a region of corrosion having a pit diameter determined by the diameter of a selectable tip. The average depth of corrosion is controlled by controlling the total electric charge passing through the cell in a test. The cell is also designed to produce minimal artifacts associated with crevice corrosion. There are three selectable tips, having diameters of 0.1 in. (0.254 cm), 0.3 in. (0.762 cm), and 0.6 in. (1.524 cm), respectively.

  1. Impact of biofouling on corrosion resistance of reinforced concrete

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, B.T.; Gajendragad, M.R.; Ranganna, G.; Wagh, A.B.; Sudhakaran, T.

    the structure from deterioration; a nonuniform deposit can lead to severe localized pitting corrosion. To study this cylindrical reinforced concrete electrodes were exposed to seawater. They were periodically removed and examined for the presence of fouling...

  2. Effect of Cl– on the corrosive wear of AISI 321 stainless steel in H2SO4 solution

    Indian Academy of Sciences (India)

    Yanliang Huang; Xiaoxia Jiang; Sizuo Li

    2003-06-01

    The effect of Cl– on the corrosive wear behaviour of AISI 321 stainless steel in H2SO4 solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly lowered by Cl–, while above which is increased. At natural potential there are more pits at low load than that at a higher one in the wear tracks and the pits are also deeper. The load bearing capacity is lowered by Cl– at passive region and then the corrosive wear rate increased.

  3. Characterization of Corrosion Product Layers from CO2 Corrosion of 13Cr Stainless Steel in Simulated Oilfield Solution

    Science.gov (United States)

    Yin, Z. F.; Wang, X. Z.; Liu, L.; Wu, J. Q.; Zhang, Y. Q.

    2011-10-01

    The influence of temperature and flow rate on the characterization and mechanisms of corrosion product layers from CO2 corrosion of 13Cr stainless steel was carried out in simulated oilfield solution. Cyclic potentiodynamic polarization method as well as weight loss tests in autoclave were utilized to investigate pitting corrosion behavior at various temperatures. Weight loss tests were performed at 100 and 160 °C under dynamic and static flow conditions. At the same time, the significant pitting parameters such as E corr, E pit, E pp, ∆ E, and I pass in cyclic polarization curves at various temperatures were analyzed and compared for revealing the pitting behavior of 13Cr stainless steel. The surface measurement techniques such as SEM, XRD, and XPS were used to detect the corrosion product layers. The results showed that both temperature and flow rate had significant effects on characterization of corrosion product layers or passive films formed on 13Cr stainless steel in CO2 corrosion system. At high temperature, lots of pits were formed at the localized corrosion areas of metal surfaces. Corrosion rates under the condition of 5 m/s were higher than those under the static condition regardless of the test temperatures.

  4. The oxidation and corrosion of ODS alloys

    Science.gov (United States)

    Lowell, Carl E.; Barrett, Charles A.

    1990-01-01

    The oxidation and hot corrosion of high temperature oxide dispersion strengthened (ODS) alloys are reviewed. The environmental resistance of such alloys are classified by oxide growth rate, oxide volatility, oxide spalling, and hot corrosion limitations. Also discussed are environmentally resistant coatings for ODS materials. It is concluded that ODS NiCrAl and FeCrAl alloys are highly oxidation and corrosion resistant and can probably be used uncoated.

  5. Effect of Deleterious Phases on Corrosion Resistance of Duplex Stainless Steel (2205

    Directory of Open Access Journals (Sweden)

    AbdulKadar M. Godil

    2013-07-01

    Full Text Available Duplex stainless steel is a Ferritic(BCC-Austenitic(FCC steel, covers the advantages of both Austenitic and Ferritic Stainless steels. They having good mechanical and corrosion resistance properties are widely used in many industries like chemical plants, refineries for critical equipments such as pressure vessels, heatexchangers, water heaters. Major problem occurs with duplex steels when they are worked or heated above about temperature of 280°C. Detrimental phases like Sigma, Chi, Laves and Alpha prime form when the Duplex steels are treated above this temperature and they retard the properties of Duplex stainless steels. They also cause embrittlement above temperature of 475°C called “475°C embrittlement”. During welding of duplex steels, Secondary austenite also forms, which is also one of the harmful phases in duplex steels. Among all of these phases, Sigma (σ is extremely harmful to the corrosion resistance of steel. Due to these limitations duplexgrades are not used above certain temperature ranges. In this experimental work a plate of duplex grade 2205 in hot worked condition was procured from TCR Advanced Engineering Pvt. Ltd., GIDC, Vadodara. Initially chemical composition of the plate was checked with emission spectrometer, tensile test and hardness tests werecarried out for comparing with the standard data. As there was no Sigma phase detected when tested with ASTM 930 in the received sample, Sigma phase was intentionally produced by giving heat treatment in the range of 700-850°C. Sigma phases were quantified with ASTM 930 practice A, by electrolytic etching with 40% NaOH. The effect of Sigma phase on corrosion resistance was measured by ASTM G48. The pitting corrosion resistance was evaluated in terms of average pit depth and overall corrosion rate.

  6. Alba Patera Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This image of the Alba Patera region has both lava tube collapse pits (running generally east/west) and subsidence related collapse within structural grabens. Image information: IR instrument. Latitude 26.9, Longitude 256.5 East (103.5 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  7. Sulci Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This is the Noctis Labyrinthus region of Mars. These collapse pits are forming along structural fractures that are allowing the release of volatiles from the subsurface. This is believed to be the way that chaos terrain forms on Mars. This area represents the early stage of chaos formation. Image information: VIS instrument. Latitude -12.6, Longitude 264 East (96 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project

  8. Tharsis Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found within the extensive lava flows of the Tharsis region. They are related to lava tubes, likely coming from Ascraeus Mons. Image information: VIS instrument. Latitude 22.8, Longitude 266.8 East (93.2 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington

  9. Tractus Catena Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in graben located in Tractus Catena. These features are related to subsidence after magma chamber evacuation of Alba Patera. Image information: VIS instrument. Latitude 35.8, Longitude 241.7 East (118.3 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  10. Understanding the corrosion phenomena to organize the nondestructive evaluation programs in the nuclear power plants; Connaitre les phenomenes de corrosion pour organiser les programmes d'end dans les centrales nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Berge, J.Ph. [Federation Europeenne de Corrosion, 75 - Paris (France); Samman, J. [Electricite de France (EDF), Div. du Production Nucleaire, 75 - Paris (France)

    2001-07-01

    The french nuclear power plants used PWR which components revealed many corrosion defects of different shapes as stress corrosion cracks or pits. Understanding the corrosion processes will help the inspection of in service power plants. The following examples describe some corrosion cases and present the corresponding developed control methods: corrosion on condenser, secondary circuit pipes and corrosion-erosion, steam generator pipes, vessels head penetration. (A.L.B.)

  11. Effect of Temperature and Cl-Concentration on Pitting of 2205 Duplex Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    DONG Chaofang; LUO Hong; XIAO Kui; SUN Ting; LIU Qian; LI Xiaogang

    2011-01-01

    The electrochemical behaviors of 2205 duplex stainless steel in NaCl solution with different temperatures and concentrations were studied by gravimetric tests,potentiodynamic polarization,electrochemical impedance spectroscopy and scanning electron microscopy.The experimental results show that temperature and chloride concentration have a great influence on the pitting resistance of 2205 duplex stainless steels.They not only effect the corrosion rate of pitting,but also change the shape of the pits.When NaCl solution was in low concentration and temperature below the critical pitting temperature,pits were very small and scattered with hemisphere-like shape.On the contrary,the pits of 2205 duplex stainless steel were large and sometimes had a lacy cover when the NaCl concentration was higher and the temperature was 70℃.

  12. 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.

  13. PIT Coating Requirements Analysis

    Energy Technology Data Exchange (ETDEWEB)

    MINTEER, D.J.

    2000-10-20

    This study identifies the applicable requirements for procurement and installation of a coating intended for tank farm valve and pump pit interior surfaces. These requirements are intended to be incorporated into project specification documents and design media. This study also evaluates previously recommended coatings and identifies requirement-compliant coating products.

  14. Pitting Behavior of L415 Pipeline Steel in Simulated Leaching Liquid Environment

    Science.gov (United States)

    Wan, H. X.; Yang, X. J.; Liu, Z. Y.; Song, D. D.; Du, C. W.; Li, X. G.

    2016-12-01

    The corrosion behavior and laws of the west-east gas pressure pipeline of L415 steel were studied in simulated leaching liquid. The failure of the L415 steel during the pressure testing process was investigated using electrochemical polarization, electrochemical impedance spectroscopy, and immersion test. The corrosion rate of the L415 steel increased with ion concentration in the leaching liquid. This rate reached about 0.8 mm a-1 and belonged to the severe corrosion grade. Pitting corrosion was observed in various simulated solutions with different aggressive species concentrations. The original ion concentration in the leaching liquid (1×) is the key factor influencing pitting initiation and development. Pitting showed easy nucleation, and its growth rate was relatively slow, in the basic simulating solution of the leach liquid (i.e., the ion content is compactable to the real condition in the rust on the inner steel pipe surface). Pitting was also highly sensitive and easily grew in the solution with doubled ion concentration in the basic simulating solution (2×). A uniform corrosion, instead of pitting, mainly occurred when the ion concentration was up to 10× of the basic solution.

  15. 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.

  16. Fouling corrosion in aluminum heat exchangers

    Directory of Open Access Journals (Sweden)

    Su Jingxin

    2015-06-01

    Full Text Available Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum coupons covered with a layer of artificial fouling in a humid atmosphere by their weight loss, Tafel plots, electrochemical impedance spectroscopy (EIS, and scanning electron microscope (SEM observations. The results reveal that chloride is one of the major elements found in the fouling which damages the passive film and initiates corrosion. The galvanic corrosion between the metal and the adjacent carbon particles accelerates the corrosive process. Furthermore, the black carbon favors the moisture uptake, and gives the dissolved oxygen greater chance to migrate through the fouling layer and form a continuous diffusive path. The corrosion rate decreasing over time is conformed to electrochemistry measurements and can be verified by Faraday’s law. The EIS results indicate that the mechanism of corrosion can be interpreted by the pitting corrosion evolution mechanism, and that pitting was observed on the coupons by SEM after corrosive exposure.

  17. Migrating corrosion inhibitor blend for reinforced concrete: Part 1 -- Prevention of corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Elsener, B.; Buechler, M.; Stalder, F.; Boehni, H.

    1999-12-01

    The efficiency of a migrating corrosion inhibitor in preventing corrosion of mild steel was investigated in saturated calcium hydroxide (Ca[OH]{sub 2}) solutions and in mortar. The protective effect of the inhibitor against pitting corrosion caused by chloride attack and against uniform corrosion as a result of carbonation was determined. Results showed that high concentrations ({approx}10%) allowed the inhibition of pitting corrosion tritiation in solution containing 1 M/L sodium chloride (NaCl). However, inhibiting properties can be lost by evaporation of the volatile constituent of the inhibitor or by the precipitation of the nonvolatile fraction of the inhibitor in presence of calcium ions. Addition of the inhibitor blend to mortar yielded a retardation of the corrosion initiation in the case of chloride-induced corrosion, but o significant reduction in corrosion rate. No effect was found in carbonated samples, and no influence on the corrosion rate was detected. Additionally, the estimation of the extent of the retarding effect on corrosion initiation on real structures was difficult, as the inhibitor was found to evaporate from the mortar. This evaporation resulted in a loss of inhibiting properties. Hence, the long-term efficiency of the inhibitor could not be guaranteed.

  18. Effects of Variations in Salt-Spray Conditions on the Corrosion Mechanisms of an AE44 Magnesium Alloy

    Directory of Open Access Journals (Sweden)

    Holly J. Martin

    2010-01-01

    Full Text Available The understanding of how corrosion affects magnesium alloys is of utmost importance as the automotive and aerospace industries have become interested in the use of these lightweight alloys. However, the standardized salt-spray test does not produce adequate corrosion results when compared with field data, due to the lack of multiple exposure environments. This research explored four test combinations through three sets of cycles to determine how the corrosion mechanisms of pitting, intergranular corrosion, and general corrosion were affected by the environment. Of the four test combinations, Humidity-Drying was the least corrosive, while the most corrosive test condition was Salt Spray-Humidity-Drying. The differences in corrosivity of the test conditions are due to the various reactions needed to cause corrosion, including the presence of chloride ions to cause pit nucleation, the presence of humidity to cause galvanic corrosion, and the drying phase which trapped chloride ions beneath the corrosion by-products.

  19. Controlled-Release Microcapsules for Smart Coatings for Corrosion Applications

    Science.gov (United States)

    2008-01-01

    Corrosion is a serious problem that has enormous costs and serious safety implications. Localized corrosion, such as pitting, is very dangerous and can cause catastrophic failures. The NASA Corrosion Technology Laboratory at Kennedy Space Center is developing a smart coating based on pH-sensitive microcapsules for corrosion applications. These versatile microcapsules are designed to be incorporated into a smart coating and deliver their core content when corrosion starts. Corrosion indication was the first function incorporated into the microcapsules. Current efforts are focused on incorporating the corrosion inhibition function through the encapsulation of corrosion inhibitors into water core and oil core microcapsules. Scanning electron microscopy (SEM) images of encapsulated corrosion inhibitors are shown.

  20. Synthetic seawater as stress-corrosion test medium

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1980-01-01

    Seawater minimizes pitting corrosion of aluminum-alloy test samples. Of three corrosion-inhibiting methods evaluated using (a) chromate inhibitors in saltwater, (b) surface treating sample via anodizing or alodine treatment, and (c) synthetic seawater, synthetic seawater was most effective test medium, since it is more uniform than fresh seawater.

  1. Coupon Surveillance For Corrosion Monitoring In Nuclear Fuel Basin

    Energy Technology Data Exchange (ETDEWEB)

    Mickalonis, J. I.; Murphy, T. R.; Deible, R.

    2012-10-01

    Aluminum and stainless steel coupons were put into a nuclear fuel basin to monitor the effect of water chemistry on the corrosion of fuel cladding. These coupons have been monitored for over ten years. The corrosion and pitting data is being used to model the kinetics and estimate the damage that is occurring to the fuel cladding.

  2. Corrosion of surface defects in fine wires.

    Science.gov (United States)

    Rentler, R M; Greene, N D

    1975-11-01

    Defects were observed on the surfaces of various fine diameter wires commonly used in biomedical applications. These surface irregularities were viewed at high magnifications using a scanning electron microscope which has a much greater depth of field than normal light microscopy. Defects include scratches, pits, and crevices, which are the result of commercial wire drawing practices. Corrosion test results show that imperfections can serve as sites for localized corrosion attack which could lead to premature failures.

  3. Field corrosion characterization of soil corrosion of X70 pipeline steel in a red clay soil

    Institute of Scientific and Technical Information of China (English)

    Shengrong Wang; Cuiwei Dun; Xiaogang Li; Zhiyong Liunn; Min Zhu; Dawei Zhang

    2015-01-01

    The corrosion behavior of X70 pipeline steel buried in red soil environment has been studied. The surface morphology and elemental distribution were determined by scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The corrosion kinetics was evaluated by weight loss measurement. The results show that in red soil, the corrosion rate of X70 steel decreases with time, and follows the exponential decay law. General corrosion with non-uniform and localized pitting occurred on the steel surface.α-FeOOH was the dominate products during corrosion in whole buried periods, and the corrosion products exhibited well protective properties. The potentiodynamic polarization tests revealed that icorr decreased with time, indicating the improvement of corrosion resistance. The results of Electrochemical impendence spectroscopy (EIS) are consistent with potentiodynamic polarization tests.

  4. Field corrosion characterization of soil corrosion of X70 pipeline steel in a red clay soil

    Directory of Open Access Journals (Sweden)

    Shengrong Wang

    2015-06-01

    Full Text Available The corrosion behavior of X70 pipeline steel buried in red soil environment has been studied. The surface morphology and elemental distribution were determined by scanning electron microscopy (SEM,energy dispersive X-ray spectroscopy (EDS, and X-ray diffraction (XRD. The corrosion kinetics was evaluated by weight loss measurement. The results show that in red soil, the corrosion rate of X70 steel decreases with time, and follows the exponential decay law. General corrosion with non-uniform and localized pitting occurred on the steel surface. α-FeOOH was the dominate products during corrosion in whole buried periods, and the corrosion products exhibited well protective properties. The potentiodynamic polarization tests revealed that icorr decreased with time, indicating the improvement of corrosion resistance. The results of Electrochemical impendence spectroscopy (EIS are consistent with potentiodynamic polarization tests.

  5. Numerical strategies for corrosion management: spatial statistics and finite element simulation

    NARCIS (Netherlands)

    Lopez De La Cruz, J.M.

    2008-01-01

    The techniques presented in this thesis are focused to improve corrosion management by providing a better insight into the nature of corrosion. Spatial statistics and finite element simulations are applied to different corrosion patterns to study possible interaction among pits. In order to achieve

  6. Corrosion And Thermal Processing In Cold Gas Dynamic Spray Deposited Austenitic Stainless Steel Coatings

    Science.gov (United States)

    2016-06-01

    testing cell . Source: [56]. ............................................................................................................68  Figure 36...for galvanic corrosion [26]. This is shown schematically in Figure 3. 7 Figure 3. Schematic mechanism of pitting corrosion. Source: [29]. The...here is corrosion resistance. The chromium carbide precipitate can form a galvanic couple with the surrounding steel and the depletion of chromium in

  7. Nanostructure and Properties of Corrosion Resistance in C+Ti Multi-Ion-Implanted Steel

    Institute of Scientific and Technical Information of China (English)

    张通和; 吴瑜光; 刘安东; 张旭; 王晓妍

    2003-01-01

    The corrosion and pitting corrosion resistance of C+ Ti dual and C+Ti+C ternary implanted H13 steel were studied by using a multi-sweep cyclic voltammetry and a scanning electron microscope. The effects of phase formation on corrosion and pitting corrosion resistance were explored. The x-ray diffraction analysis shows that the nanometer-sized precipitate phases consist of compounds of Fe2 Ti, TiC, Fe2C and Fe3 C in dual implanted layer and even in ternary implanted layer. The passivation layer consists of these nanometer phases. It has been found that the corrosion and pitting corrosion resistance of dual and ternary implanted H13 steel are improved extremely. The corrosion resistance of ternary implanted layer is better than that of dual implantations and is enhanced with the increasing ion dose. When the ion dose of Ti is 6 × 1017/cm2 in the ternary implantation sample, the anodic peak current density is 95 times less than that of the H13 steel. The pitting corrosion potential of dual and ternary implantation samples is in the range from 55mV to 160mV which is much higher than that of the H13 steel. The phases against the corrosion and pitting corrosion are nanometer silkiness phases.

  8. An experimental study on cavitation erosion-corrosion performance of ANSI 1020 and ANSI 4135 steel

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Leqin; Qiu, Ning [Institute of Process Equipment, Zhejiang University, Hangzhou (China); Hellmann, Dieter-Heinz [KSB Aktiengesellschaft, Frankenthal (Germany); Zhu, Xiaowen [Zhejiang Keer Pump Stock Co., Ltd, Whenzhou (China)

    2016-02-15

    Cavitation erosion is quite complex, containing corrosion-erosion interaction effect. High temperature oxidization may be aroused after bubble collapse, accompanied by hot gas contacting with the pump component surface. The analysis of the erosion pits can be an effective way to know the mechanism of cavitation erosion. In present paper, the cavitation erosion resistance of carbon steel (ANSI 1020) and alloy steel (ANSI 4135) were tested in an ultrasonic vibration apparatus. By using energy dispersive X-ray spectroscope and three dimensional laser microscope, the chemical composition around erosion pits and the oxidation film structure were analyzed. By using metallographic microscope and scanning electronic microscope, the metallographic structure of specimens (e.g., carbon steel and alloy steel), the nano structured iron oxide and corresponding influence on specimen's anti-erosion performance were discussed. Based on the comparison between the different tests performed in distilled water and tap water respectively, results can be obtained that erosion rate of carbon steel and alloy steel varies with the component of water which had close correlation to the oxidation effect. Erosion rate of alloy steel 4135 was much lower in distilled water compared to tap water while the difference of carbon steel 1020 was not that large. The remarkable different responses of these two materials had close relationship with oxidation effect. The oxidation effect transferred the original structure of alloy steel surface which had high anti-erosion capability, into newly generated iron oxide structure, which was preferentially to be attacked. The pumping of slightly corrosive fluids frequently leads to erosion-corrosion damage on impellers, and corrosion can further amplify the erosion process.

  9. Stainless steel corrosion scale formed in reclaimed water: Characteristics, model for scale growth and metal element release.

    Science.gov (United States)

    Cui, Yong; Liu, Shuming; Smith, Kate; Hu, Hongying; Tang, Fusheng; Li, Yuhong; Yu, Kanghua

    2016-10-01

    Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiform chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HClO results in higher ferric content inside the scales. Cl(-) and SO4(2-) ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales. Copyright © 2016. Published by Elsevier B.V.

  10. Corrosion resistance of silane/silicate composite films on hot-dip galvanized steel%热镀锌钢表面硅烷/硅酸盐复合膜的耐蚀性能研究

    Institute of Scientific and Technical Information of China (English)

    吴海江; 卢锦堂

    2009-01-01

    To improve the corrosion resistance of silane films further, the silane/silicate composite films were prepared by immersion hot-dip galvanized (HDG) steel samples in silane solution firstly and then in sodium silicate solution. The corrosion resistance of the composite films were investigated by neutral salt spray (NSS)test, humid thermic test, salt water test and electrochemical impedance spectroscopy (EIS). The results revealed that the corrosion resistance of the composite films was significantly enhanced, which was superior to the single silane film, even better than some chromate passivation film. Furthermore, the low frequency inductive loop in EIS was disappeared and the low frequency impedance values for the composite films in 5% NaCl solution were firstly increased then decreased with the increasing of the immersion time, which demonstrated the self-healing activity of the composite films.%为了改善硅烷膜的耐蚀性,将硅烷化热镀锌钢板用硅酸钠溶液封闭后处理,获得了硅烷/硅酸盐复合膜.采用中性盐雾试验(NSS)、湿热试验、盐水全浸试验和电化学交流阻抗谱(EIS)评价了膜层的耐蚀性能.结果表明,与单一硅烷膜相比,复合膜的耐蚀性能明显提高,超过了常规铬酸盐钝化膜.尤其是在5%NaCl溶液中,复合膜的低频阻抗数值随浸泡时间的增加先增大后减小,表明其具有一定的"自修复"能力.

  11. General Corrosion and Localized Corrosion of Waste Package Outer Barrier

    Energy Technology Data Exchange (ETDEWEB)

    K.G. Mon

    2004-10-01

    The waste package design for the License Application is a double-wall waste package underneath a protective drip shield (BSC 2004 [DIRS 168489]; BSC 2004 [DIRS 169480]). The purpose and scope of this model report is to document models for general and localized corrosion of the waste package outer barrier (WPOB) to be used in evaluating waste package performance. The WPOB is constructed of Alloy 22 (UNS N06022), a highly corrosion-resistant nickel-based alloy. The inner vessel of the waste package is constructed of Stainless Steel Type 316 (UNS S31600). Before it fails, the Alloy 22 WPOB protects the Stainless Steel Type 316 inner vessel from exposure to the external environment and any significant degradation. The Stainless Steel Type 316 inner vessel provides structural stability to the thinner Alloy 22 WPOB. Although the waste package inner vessel would also provide some performance for waste containment and potentially decrease the rate of radionuclide transport after WPOB breach before it fails, the potential performance of the inner vessel is far less than that of the more corrosion-resistant Alloy 22 WPOB. For this reason, the corrosion performance of the waste package inner vessel is conservatively ignored in this report and the total system performance assessment for the license application (TSPA-LA). Treatment of seismic and igneous events and their consequences on waste package outer barrier performance are not specifically discussed in this report, although the general and localized corrosion models developed in this report are suitable for use in these scenarios. The localized corrosion processes considered in this report are pitting corrosion and crevice corrosion. Stress corrosion cracking is discussed in ''Stress Corrosion Cracking of the Drip Shield, the Waste Package Outer Barrier, and the Stainless Steel Structural Material'' (BSC 2004 [DIRS 169985]).

  12. 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.

  13. Effect of ascorbic acid on the pitting resistance of 316L stainless steel in synthetic tap water

    Science.gov (United States)

    Hong, Min-Sung; Kim, Seon-Hong; Im, Shin-Young; Kim, Jung-Gu

    2016-07-01

    This study examined the effect of L-ascorbic acid (A.A) concentration on the pitting corrosion properties of 316L stainless steel (316L STS) of heat exchanger in synthetic tap water containing 400 ppm of Cl- ion. The pitting corrosion of 316L STS can be effectively inhibited by the 10-4 M of A.A concentration. In this condition, the adsorption of A.A reinforced the passive film of steel by blocking the Cl- ions at the active site. However, the passive film was deteriorated and severe pitting corrosion occurred above the 10-4 M of A.A concentration. Above the 10-4 M of A.A concentration, A.A generates soluble chelate rather than absorbs on the steel surface and it causes passive film deterioration and severe pitting corrosion. The critical ratio, which is a critical ratio of surface coverage of aggressive to inhibitive ion necessary to initiate localized corrosion, calculated 2.93 up to the 10-4 M. It has approximately 2.93:1 ratio of the coverage of local Cl- ions to A.A. Above the critical ratio, the pitting corrosion will occur with degradation of the passive film. On the other hands, above the 10-4 M A.A concentration caused a negative effect because the heat energy for adsorption is increased.

  14. Real-time electronic monitoring of a pitted and leaking gas gathering pipeline

    Energy Technology Data Exchange (ETDEWEB)

    Asperger, R.G.; Hewitt, P.G.

    1986-08-01

    Hydrogen patch, flush electrical resistance, and flush linear polarization proves wre used with flush coupons to monitor corrosion rates in a pitted and leaking sour gas gathering line. Four inhibitors were evaluated in stopping the leaks. Inhibitor residuals and the amount and ratio of water and condensate in the lines were measured at five locations along the line. The best inhibitor reduced reduced the pit-leak frequency by over a factor of 10. Inhibitor usage rate was optimized using the hydrogen patch current as a measure of the instantaneous corrosion rate. Improper pigging was identified as a cause of corrosion transients. This problem is discussed in relation to the pigging of pipelines in stratified flow where moving fluids are the carriers for continuously injected corrosion inhibitors.

  15. Effect of heat treatments on 8090 AlLi alloy pitting susceptibility in sea water

    Energy Technology Data Exchange (ETDEWEB)

    Beccaria, A.M. [CNR, Genova (Italy). Istituto per la Corrosion Marina dei Metalli; Traverso, P. [CNR, Genova (Italy). Istituto per la Corrosion Marina dei Metalli

    1996-05-01

    The pitting susceptibility of 8090 Al-Li alloy in sea water, after different heat treatments, was investigated. Free corrosion and electrochemical tests were carried out at 25 C, in quiescent sea water at pH=8.2 and dissolved oxygen =6.5 ppm. The microstructure was examined by metallographic microscopy and by X-Ray microdiffractometry, while the corrosion layer was characterized by chemical methods and by Infrared and X-ray photoelectron spectroscopies. The following was observed: . aging treatments lead to a non homogeneous microstructure which increases the average corrosion rate as well as pitting susceptibility; . heat treatments do not affect the average passive film composition; . in all examined states, Al-Li alloy 8090 is subject to localized corrosion which takes place preferentially at the grain boundaries. (orig.)

  16. Effect of Trace Sn on Pitting Behaviors of High Voltage Anode Aluminum Foil

    Institute of Scientific and Technical Information of China (English)

    Jingbo SONG; Weimin MAO; Hong YANG; Huiping FENG

    2008-01-01

    The effect of trace Sn on the pitting morphology of high voltage anode aluminum foils was investigated. The distributions of microelement Sn, Fe, Si, Cu and Mg in the surface layer of aluminum foils with different Sn content were determined by using a secondary ion mass spectrometer. It was found that the micro-alloyed Sn is enriched at the external surface. The mechanism of pitting behavior of trace Sn on aluminum surface is similar with that of lead. Enrichment of Sn in the surface layer provides large numbers of sites for initiation of pitting corrosion, while pitting sites appeared relatively inhomogenously in the foils without Sn. Sn, as an eco-friendly microelement, can be applied to replace Pb in improving the homogenous pitting behaviors of high voltage aluminum foils, in which the volume fraction of cube texture is not reduced.

  17. 热镀锌钢板表面硅烷膜的制备工艺与耐蚀性能%Preparation and Corrosion Resistance of Silane Film on Hot-dip Galvanized Steel

    Institute of Scientific and Technical Information of China (English)

    吴海江; 卢锦堂

    2009-01-01

    采用正交试验结合中性盐雾试验和极化曲线测定等方法,研究了热镀锌钢板表面的硅烷膜在制备过程中的硅烷体积分数、水解溶剂中甲醇体积分数、水解时间、水解温度、溶液PH值、浸涂时间等因素对硅烷膜耐蚀性能的影响,并确定了最佳成膜工艺,讨论了硅烷膜作用机理.结果表明:最佳成膜工艺为硅烷体积分数7%、溶液pH值4、水解溶剂中甲醇体积分数10%、水解温度40℃、水解时间6 h、浸涂时间120 s,采用该工艺制备硅烷膜可明显推迟热镀锌钢板出现白锈的时间;硅烷膜同时也抑制了热镀锌钢板在腐蚀过程中阳极和阴极的反应,显著改善了热镀锌钢板的耐蚀性能.%A nontoxic silanized treatment process for hot-dip galvanized steel was investigated by the orthogonal experiment. The protection of silane films on galvanized steel surface was evaluated by neutral salt spray test and polarization test. The factors affecting the corrosion resistance of silane films were discussed, including concentration of silane solution, concentration of methanol, hydrolysis time, hydrolysis temperature, pH of silane solution and immersion time. The optimum technological parameters were obtained, and the mechanism was analyzed. The results show that the silane films had the optimum anti-corrosion properties under the conditions of concentration of the silane solution 7%, concentration of methanol in hydrolysis solvents 10%, hydrolysis time 6 h, hydrolysis temperature 40 ℃, pH of the silane solution 4 and immersion time 120 s acted as a physical barrier of galvanized steel and suppressed both cathodic and anodic reactions of corrosion simultaneously. The time of white rust occurence on galvanized coating was delayed. The silane films obtained excellent corrosion resistance under the optimum technological conditions.

  18. Pitting process visualization

    Directory of Open Access Journals (Sweden)

    Michal Černý

    2010-01-01

    Full Text Available The paper describes time-domain simulation of gear pitting damage using animation program. Key frames have been used to create illusion of motion. The animation uses experimental results of high-cycle fatigue of material. The fatigue damage occurs in the nominal creep area on the side of the gear tooth sample loaded with variable-positioned Hertz pressure. By applying the force, the pressure cumulates between two convex surfaces. This phenomenon results in material damage under of curved surfaces in contact. Moreover, further damage has been registered on the surface. This is due to exceeding the elastic-plastic state limit and development of „tabs“. The tabs serve as origin of surface micro cracks powered by shear stress and enclosed grease pressure as well. This deformation and extreme pressures of Pascal law contribute to elongation and growth of the surface micro crack. Non-homogenous parts of material volume support the initialization/development of the micro cracks as well. Resulting visualization of the tooth-side fatigue damage provides clear and easy-to-understand description of the damage development process right from the micro crack initialization to the final fragmentation due to pitting degradation.

  19. Corrosion mechanism of 13Cr stainless steel in completion fluid of high temperature and high concentration bromine salt

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yan [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083 (China); Xu, Lining, E-mail: xulining@ustb.edu.cn [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Minxu [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083 (China); Meng, Yao [Beijing Institute of Aeronautical Materials, Beijing 100095 (China); Zhu, Jinyang; Zhang, Lei [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-09-30

    Highlights: • The corrosion behavior of 13Cr steel exposed to bromine salt completion fluid containing high concentration bromine ions was investigated. • There are passive circles around pits on the 13Cr steel surface after 7 d of exposure. • Macroscopic galvanic corrosion formed between the passive halo and the pit. • The mechanism of pitting corrosion on 13Cr stainless steel exposed to heavy bromine brine was established. - Abstract: A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH{sup −} ligand generates and adsorbs in a certain scale because of abundant OH{sup −} on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs.

  20. PH and Electrochemical Responsive Materials for Corrosion Smart Coating Applications

    Science.gov (United States)

    Li, Wenyan; Calle, Luz M.

    2008-01-01

    Corrosion is a costly issue for military operations and civil industries. While most corrosion initiates from localized corrosion form, such as pitting, failure directly caused by localized corrosion is the most dangerous kind, because it is difficult to anticipate and prevent, occurs very suddenly and can be catastrophic. One way of preventing these failures is with a coating that can detect and heal localized corrosion. pH and other electrochemical changes are often associated with localized corrosion, so it is expected that materials that are pH or otherwise electrochemical responsive can be used to detect and control corrosion. This paper will review various pH and electrochemical responsive materials and their potential applications in corrosion smart coatings. Current research results in this field will also be reported.

  1. The effect of corrosion inhibitors on microbial communities associated with corrosion in a model flow cell system.

    Science.gov (United States)

    Duncan, Kathleen E; Perez-Ibarra, Beatriz Monica; Jenneman, Gary; Harris, Jennifer Busch; Webb, Robert; Sublette, Kerry

    2014-01-01

    A model flow cell system was designed to investigate pitting corrosion in pipelines associated with microbial communities. A microbial inoculum producing copious amounts of H₂S was enriched from an oil pipeline biofilm sample. Reservoirs containing a nutrient solution and the microbial inoculum were pumped continuously through six flow cells containing mild steel corrosion coupons. Two cells received corrosion inhibitor "A", two received corrosion inhibitor "B", and two ("untreated") received no additional chemicals. Coupons were removed after 1 month and analyzed for corrosion profiles and biofilm microbial communities. Coupons from replicate cells showed a high degree of similarity in pitting parameters and in microbial community profiles, as determined by 16S rRNA gene sequence libraries but differed with treatment regimen, suggesting that the corrosion inhibitors differentially affected microbial species. Viable microbial biomass values were more than 10-fold higher for coupons from flow cells treated with corrosion inhibitors than for coupons from untreated flow cells. The total number of pits >10 mils diameter and maximum pitting rate were significantly correlated with each other and the total number of pits with the estimated abundance of sequences classified as Desulfomicrobium. The maximum pitting rate was significantly correlated with the sum of the estimated abundance of Desulfomicrobium plus Clostridiales, and with the sum of the estimated abundance of Desulfomicrobium plus Betaproteobacteria. The lack of significant correlation with the estimated abundance of Deltaproteobacteria suggests not all Deltaproteobacteria species contribute equally to microbiologically influenced corrosion (MIC) and that it is not sufficient to target one bacterial group when monitoring for MIC.

  2. 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.

  3. Microclimates and Corrosion: A Mathematical Model of Corrosion for Gando AFB, Spain

    Science.gov (United States)

    1990-09-01

    certain points); pitting (highly localized corrosion resulting in deep penetration at only a few spots); parting (the selective attack of one or more... Exposicion Ambiental(1987-1988). Unpublished Report No. 15. INTA, Madrid, Spain, 1989. 16. Schlotzhauer, D. Sandra and Littell, C. Ramon. SAS System for...LIME: An Environmental Corrosion Severity Classification System: Final Report Part I. Sep 1978 - Dec 1979. Contract F33615-78-C-5224. East Lansing MI

  4. Corrosion-resistant coating development

    Energy Technology Data Exchange (ETDEWEB)

    Stinton, D.P.; Kupp, D.M.; Martin, R.L. [Oak Ridge National Lab., TN (United States)

    1997-12-01

    SiC-based heat exchangers have been identified as the prime candidate material for use as heat exchangers in advanced combined cycle power plants. Unfortunately, hot corrosion of the SiC-based materials created by alkali metal salts present in the combustion gases dictates the need for corrosion-resistant coatings. The well-documented corrosion resistance of CS-50 combined with its low (and tailorable) coefficient of thermal expansion and low modulus makes CS-50 an ideal candidate for this application. Coatings produced by gelcasting and traditional particulate processing have been evaluated.

  5. Identifying the influential factors in corrosive processes on the LP shaft of the Elverlingsen E4 turbogenerator set during unit shutdown procedures

    Energy Technology Data Exchange (ETDEWEB)

    Seipp, H.G.; Leidich, F.U. [ALSTOM Power Support GmbH, Mannheim (Germany); Freund, E. [Mark-E AG, Elverlingsen Power Plant (Germany)

    2003-07-01

    Overhauls repeatedly revealed cracks on the grooves of blade suspensions on LP turbine rotors in various turbo-generator sets. Some of these cracks caused costly repairs. Without exception, the starting points of the cracks were identified to be in areas affected by shallow pitting corrosion. In many cases, the same phenomena were found in units which underwent frequent hot and cold start-ups. In order to avoid corrosive attacks on the LP turbine during operational standstills, the shutdown procedures for the unit 4 in Elverlingsen were modified. (orig.) [German] An den Nuten der Schaufelaufhaengungen an ND-Turbinenlaeufern verschiedener Turbogruppen wurden bei Revisionen Risse gefunden, die teilweise aufwaendige Sanierungsmassnahmen zur Folge hatten. Die Rissausgaenge lagen ausnahmslos im Bereich von Muldenkorrosionsangriffen. Besonders haeufig traten diese Phaenomene bei Blockeinheiten mit haeufigen Warm- und Kaltstarts auf. Zur Vermeidung von Korrosionsangriffen an der Niederdruck-Turbine waehrend Betriebsstillstaenden wurde das Abfahren des Blockes 4 im Kraftwerk Elverlingsen modifiziert. (orig.)

  6. 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.

  7. Titanium corrosion in alkaline hydrogen peroxide environments

    Science.gov (United States)

    Been, Jantje

    1998-12-01

    , the plane close to a prismatic plane orientation appeared to be the most corrosion resistant plane. The plane close to a basal plane orientation suffered from extensive pitting and roughening of the surface.

  8. Pitted Rock Named Ender

    Science.gov (United States)

    1997-01-01

    This image was taken by the Sojourner rover's right front camera on Sol 33. The rock in the foreground, nicknamed 'Ender', is pitted and marked by a subtle horizontal texture. The bright material on the top of the rock is probably wind-deposited dust. The Pathfinder Lander is seen in the distance at right. The lander camera is the cylindrical object on top of the deployed mast.Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and managed the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  9. Scattering length density profile of Ni film under controlled corrosion: A study in neutron reflectometry

    Indian Academy of Sciences (India)

    Surendra Singh; A K Poswal; S K Ghosh; Saibal Basu

    2008-11-01

    We report the density depth profile of an as-deposited Ni film and density profile for the same film after controlled electrochemical corrosion by chloride ions, measured by unpolarized neutron reflectometry. The neutron reflectometry measurement of the film after corrosion shows density degradation along the thickness of the film. The density profile as a function of depth, maps the growth of pitting and void networks due to corrosion. The profile after corrosion shows an interesting peaking nature.

  10. Inhibition of aluminum corrosion using Opuntia extract

    Energy Technology Data Exchange (ETDEWEB)

    El-Etre, A.Y

    2003-11-01

    The inhibitive action of the mucilage extracted from the modified stems of prickly pears, toward acid corrosion of aluminum, is tested using weight loss, thermometry, hydrogen evolution and polarization techniques. It was found that the extract acts as a good corrosion inhibitor for aluminum corrosion in 2.0 M HCl solution. The inhibition action of the extract was discussed in view of Langmuir adsorption isotherm. It was found that the adsorption of the extract on aluminum surface is a spontaneous process. The inhibition efficiency (IE) increases as the extract concentration is increased. The effect of temperature on the IE was studied. It was found that the presence of extract increases the activation energy of the corrosion reaction. Moreover, the thermodynamic parameters of the adsorption process were calculated. It was found also that the Opuntia extract provides a good protection to aluminum against pitting corrosion in chloride ion containing solutions.

  11. Consideration on corrosion fatigue crack life assessment; Fushoku hiro kiretsu hassei jumyo hyoka ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Morita, K. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1996-10-01

    Discussions were given on corrosion fatigue crack life by using corrosion fatigue crack initiation test and analysis. The test used 13Cr-based stainless steel as a test material, and aquamarine at 60{degree}C as a corrosion environment. The fatigue test was performed under a tension loading condition with a stress ratio of 0.1 and an iterative velocity of 1.7 Hz by using a 10-tonf fatigue testing machine. In the corrosion fatigue crack initiation test, a pit has been generated on a boundary of an exposed part and a painted part for masking, hence direct observation was impossible on pit growth behavior. Therefore, an intrinsic crack model was introduced from pit dimensions as observed from a fracture face, and analysis was made on corrosion fatigue crack growth by using the linear fracture dynamics, wherein clarification was made on a phenomenon occurring after the crack growth passes the pit growth until the test piece is fractured. A proposal was made to define the time when fatigue crack initiates and grows from the bottom of a pit as a result of surpassing the growth of corrosion pit as the corrosion fatigue crack life. 4 refs., 7 figs., 1 tab.

  12. 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.

  13. Long Term Corrosion/Degradation Test Six Year Results

    Energy Technology Data Exchange (ETDEWEB)

    M. K. Adler Flitton; C. W. Bishop; M. E. Delwiche; T. S. Yoder

    2004-09-01

    the performance assessment for the SDA. The corrosion on the carbon steel, beryllium, and aluminum were more evident with a clear difference in corrosion performance between the 4-ft and 10-ft levels. Notable surface corrosion products were evident as well as numerous pit initiation sites. Since the corrosion of the beryllium and aluminum is characterized by pitting, the geometrical character of the corrosion becomes more significant than the general corrosion rate. Both pitting factor and weight loss data should be used together. For six-year exposure, the maximum carbon steel corrosion rate was 0.3643 MPY while the maximum beryllium corrosion rate was 0.3282 MPY and the maximum aluminum corrosion rate was 0.0030 MPY.

  14. An evaluation of microbial growth and corrosion of 316L SS in glycol/seawater mixtures

    Science.gov (United States)

    Lee, Jason S.; Ray, Richard I.; Lowe, Kristine L.; Jones-Meehan, Joanne; Little, Brenda J.

    2003-01-01

    Glycol/seawater mixtures containing > 50% glycol inhibit corrosion of 316L stainless steel and do not support bacterial growth. The results indicate bacteria are able to use low concentrations of glycol (10%) as a growth medium, but bacterial growth decreased with increasing glycol concentration. Pitting potential, determined by anodic polarization, was used to evaluate susceptibility of 316L SS to corrosion in seawater-contaminated glycol. Mixture containing a minimum concentration of 50% propylene glycol-based coolant inhibited pitting corrosion. A slightly higher minimum concentration (55%) was needed for corrosion protection in ethylene glycol mixtures.

  15. Corrosion of bio implants

    Indian Academy of Sciences (India)

    U Kamachi Mudali; T M Sridhar; Baldev Raj

    2003-06-01

    Chemical stability, mechanical behaviour and biocompatibility in body fluids and tissues are the basic requirements for successful application of implant materials in bone fractures and replacements. Corrosion is one of the major processes affecting the life and service of orthopaedic devices made of metals and alloys used as implants in the body. Among the metals and alloys known, stainless steels (SS), Co–Cr alloys and titanium and its alloys are the most widely used for the making of biodevices for extended life in human body. Incidences of failure of stainless steel implant devices reveal the occurrence of significant localised corroding viz., pitting and crevice corrosion. Titanium forms a stable TiO2 film which can release titanium particles under wear into the body environment. To reduce corrosion and achieve better biocompatibility, bulk alloying of stainless steels with titanium and nitrogen, surface alloying by ion implantation of stainless steels and titanium and its alloys, and surface modification of stainless steel with bioceramic coatings are considered potential methods for improving the performance of orthopaedic devices. This review discusses these issues in depth and examines emerging directions.

  16. 控冷工艺对热轧盘条氧化皮耐腐蚀性的影响%Influence of Control Cooling Technology on the Corrosion Resistance of Iron Scale on Hot-rolled Wire Rod

    Institute of Scientific and Technical Information of China (English)

    袁武华; 王峰

    2009-01-01

    为了提高热轧盘条的表面质量,采用热模拟实验研究了不同冷却温度、不同冷却速度对热轧盘条表面氧化皮性质的影响.用X射线衍射检测氧化皮的物象组成,用扫描电镜观察氧化皮的表面形貌、厚度、致密度,用加速失重腐蚀实验检测氧化皮的耐蚀性.研究结果表明:温度过高导致氧化皮厚并产生裂纹,温度过低氧化皮薄,起不到保护作用;快速冷却能形成致密氧化皮,且氧化皮中Fe2O3含量减少,Fe3O4和FeO比例增加,有利于提高氧化皮的性能,慢速冷却则氧化层厚.%In order to improve the surface quality of steel scale on wire rod, the influence of the cooling rate and the cooling temperature on the corrosion resistance of iron oxide scale on hot-rolled wire rod was investigated.The scale composition was analyzed primarily through XRD.The scale surface feature, the thickness and the tightness were observed through SEM.The anti-corrosive performance of steel scale was observed through accelerated corrosion tests.The results have indicated that the exorbitant temperature results in thick iron scale and crack, and the low temperature results in thin iron scale without protection value.The tight steel scale can be formed with rapid cooling, and the content of Fe2O3 in the iron scale decreases when the content ratio of Fe3O4 to FeO increases.This enhances the properties of the iron scale.The iron scale is thick with slow cooling.

  17. 转炉钢渣热态改性对镁质耐火材料的侵蚀行为%Corrosion behavior of hot modified BOF slag to magnesia based refractory crucible

    Institute of Scientific and Technical Information of China (English)

    代文彬; 李宇; 苍大强; 郭鹏

    2013-01-01

    以镁质坩埚为试验容器,配制碱度分别为1.2、1.5、1.7、1.9、2.2、2.4的改性钢渣并放置于坩埚中,以10℃·min-的速率升温至1 570℃并保温30 min加热熔化.研究了热态改性钢渣对镁质坩埚的侵蚀,并采用光学显微镜、SEM、EDS和XRD进一步分析了侵蚀行为.分析表明:改性钢渣对镁质耐火材料的侵蚀反应主要在熔渣-坩埚界面处进行,熔渣碱度≤1.5时耐火材料侵蚀加重;由于钢渣中铁离子渗透进方镁石晶体内,形成弥散分布的颗粒状富FeO固溶体和含FeO方镁石基质相,这两种物相受内部FeO、MgO质量比和钢渣中Al2O3含量的影响,选择性地同渣中不同化学组分进行反应而脱落溶解至钢渣中.%Six kinds of modified BOF slag with varied basicities (1. 2,1. 5,1.7,1. 9,2. 2,2.4,respectively) were prepared,put in six separate magnesia crucibles,heated to 1 570 ℃at 10℃· min-1 holding for 30 min. The corrosion of the hot modified slags to the magnesia crucible was analyzed with optical microscope ,SEM,EDS and XRD. Analysis shows that the corrosion reaction of magnesia crucible by the modified slags mainly occurs in the slag-crucible interface,and when the basicity of liquid slag is ≤1.5 the corrosion of crucible gets severe;Fe ions in liquid slag penetrate into the periclase crystals forming the dispersed granular FeO-rich solid solution and FeO-containing periclase matrix phase,and they selectively react with different components of liquid slag and dissolve in the slag affected by their mass ratio of FeO to MgO and the AI2O3 content in liquid slag.

  18. Redox conditions effect on flow accelerated corrosion: Influence of hydrazine and oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Bouvier, O. de [EDF, R and D Div., Moret sur Loing (France); Bouchacourt, M. [EDF, Engineering and Service Div., Villeurbanne (France); Fruzzetti, K. [EPRI, Science and Technology Div., Palo Alto, CA (United States)

    2002-07-01

    Flow accelerated corrosion (FAC) of carbon steels has been studied world-wide for more than twenty years and is now fairly well understood. The influence of several parameters like water chemistry (i.e. pH and oxygen content), temperature, hydrodynamic or mass transfer conditions (i.e. flow velocity, geometry, steam quality..) and steel composition on the corrosion kinetics has been demonstrated both theoretically and experimentally. However, the effect of a reducing environment and variable redox conditions have not yet been fully explored. It's well known that a reducing environment is effective in increasing the resistance of steam generator tubing to intergranular attack / stress corrosion cracking (IGA/SCC) and pitting. In that way, secondary water chemistry specifications have been modified from low hydrazine to high hydrazine chemistry in the steam-water circuit. Nevertheless, increasing hydrazine levels up to 200 {mu}g/kg could have a detrimental effect by potentially enhancing the FAC process. Moreover, in order to have a complete understanding of the possible impact of the water chemistry environment it is also important to consider the impact of redox conditions during shutdowns (cold and/or hot shutdowns) and start up periods when aerated water injections are made to maintain a constant water level in the Steam Generators from the auxiliary feedwater circuit. Therefore, a common EDF and EPRI R and D effort has been recently carried out to study the effects of hydrazine and oxygen on FAC. The results are presented as follows. (authors)

  19. Electrochemical Corrosion Testing of Neutron Absorber Materials

    Energy Technology Data Exchange (ETDEWEB)

    Tedd Lister; Ron Mizia; Arnold Erickson; Tammy Trowbridge

    2007-05-01

    This report summarizes the results of crevice-corrosion tests for six alloys in solutions representative of ionic compositions inside the Yucca Mountain waste package should a breech occur. The alloys in these tests are Neutronit A978a (ingot metallurgy, hot rolled), Neutrosorb Plus 304B4 Grade Ab (powder metallurgy, hot rolled), Neutrosorb Plus 304B5 Grade Ab (powder metallurgy, hot rolled), Neutrosorb Plus 304B6 Grade Ab (powder metallurgy, hot rolled), Ni-Cr-Mo-Gd alloy2 (ingot metallurgy, hot rolled), and Alloy 22 (ingot metallurgy, hot rolled).

  20. Corrosion mechanism of 13Cr stainless steel in completion fluid of high temperature and high concentration bromine salt

    Science.gov (United States)

    Liu, Yan; Xu, Lining; Lu, Minxu; Meng, Yao; Zhu, Jinyang; Zhang, Lei

    2014-09-01

    A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH- ligand generates and adsorbs in a certain scale because of abundant OH- on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs

  1. Influence of Trace Alloying Elements on Corrosive Resistance of Cast Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    DUAN Han-qiao; YAN Xiang; WEI Bo-kang; LIN Han-tong

    2005-01-01

    The influences of trace alloying elements niobium, vanadium and zirconium on the corrosive resistance of 18-8 type cast stainless steel have been studied in deta() orthogonal design experiments. The results show that zirconium is mainly in the form of compound inclusions, which is unfavorable to promote the corrosive resistance of the cast stainless steel. It can alleviate the disadvantageous influence of carbon addition on corrosive resistance when some elements such as vanadium and niobium exist in the steel, and niobium has a remarkable influence on the intergranular corrosive resistance but unobvious on the pitting corrosion, and vanadium has a slightly favorable influence on the corrosive resistance of the steel.

  2. Zinc Corrosion Resistance and Inactivation Process of Sink Roll in Hot Galvanization%热镀锌沉没辊的耐锌腐蚀失效过程

    Institute of Scientific and Technical Information of China (English)

    王晖; 张广伟; 孟晓霞; 段思华; 徐常恩; 关升

    2012-01-01

    采用超音速火焰喷涂技术在316L不锈钢基体上制备WC-12Co涂层,并测试其在430℃锌液中的耐腐蚀性,分析沉没辊的腐蚀机理以及失效过程.采用SEM、EDS和XRD分析了腐蚀前、后涂层表面显微结构、化学成分及其相组成的变化.结果表明,WC- 12Co粒子之间通过高速碰撞发生强烈的塑性变形而结合在一起,涂层内部致密性很好,喷涂过程中没发生明显氧化现象;涂层的显微硬度平均为1 215 HV0.2,结合强度达到85MPa;无涂层试样在腐蚀59 h后直径减少20%;经过10天的浸锌试验后,涂层开始产生均匀性腐蚀,涂层中的Co基体受液锌腐蚀生成Co5 Zn21化合物,涂层开始遭到破坏;经过15天浸锌试验后,部分锌液穿过涂层与基体中的Fe化合生成FeZn13(即锌渣),涂层局部开始脱落,涂层失效开始.%The WC-12Co coatings were sprayed by high velocity oxyfule spraying (HVOF) on 316L stainless steel. The corrosion resistance was tested at 430℃ and the inactivation process of the sink roll was studied. The changes of microstructure, chemical composition and phase constituent during the corrosion process were analyzed by SEM,EDS and XRD. The results show that the WC-12Co coating is deposited through intensive plastic deformation of the spray particles by high-speed impact, and no oxidation phenomena is discovered in the spray process. The average of microhardness and bond strength of the coating attained 1 215 HV0.2 and 85 MPa respectively. The diameter of non-coating samples decreased by 20 % after corrosion of 59 h. The coating started to corrode uniformity after 10 days. Co5 Zn21 compounds were generated when Co based metal was corroded by liquid Zinc and the coating was distroied. After 15 days, FeZn13 was generated with Fe in base material when part of liquid Zinc went through the coating. Part of the coating fell off and the failure began.

  3. Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel

    2000-01-01

    Microbially influenced corrosion (MIC) of carbon steel may occur in media with microbiological activity of especially sulphate-reducing bacteria, e.g. on pipelines buried in soil and on marine structures. MIC of carbon steel must be monitored on-line in order to provide an efficient protection...... corrosion and detects localised corrosion, but the sensitivity is not high enough for monitoring initiation of pitting and small attacks. Electrochemical techniques as LPR and EIS give distorted data and unreliable corrosion rates, when biofilm and corrosion products cover the steel surface. However, EIS...... and control the corrosion. A number of monitoring techniques is industrially used today, and the applicability and reliability of these for monitoring MIC is evaluated. Coupons and ER are recommended as necessary basic techniques even though localised corrosion rate cannot be measured. FSM measures general...

  4. Evaluation of oxygen corrosion in waterflood and disposal water systems

    Energy Technology Data Exchange (ETDEWEB)

    Conger, H.C.

    1967-01-01

    The case histories presented illustrate how specially polished pipe nipples have been used and examined in the field to evaluate the seriousness of an oxygen corrosion problem. The case histories also illustrate how these test pipe nipples have been used to evaluate actual, not relative, effectiveness of a chemical treatment program to control oxygen corrosion. Data are presented and discussed showing the relationship between corrosion rates of test pipe nipples and actual in-service equipment. The case histories show how corrosion rates based on pipe test nipple data were used to project equipment life under no chemical treatment vs. chemical treatment. A comparative study of corrosion rates between the use of pipe nipples and coupons as a means of measuring oxygen corrosion is discussed. A further comparative study is made between coupon corrosion rates based on weight loss and pit depth penetration.

  5. Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel

    2000-01-01

    and control the corrosion. A number of monitoring techniques is industrially used today, and the applicability and reliability of these for monitoring MIC is evaluated. Coupons and ER are recommended as necessary basic techniques even though localised corrosion rate cannot be measured. FSM measures general......Microbially influenced corrosion (MIC) of carbon steel may occur in media with microbiological activity of especially sulphate-reducing bacteria, e.g. on pipelines buried in soil and on marine structures. MIC of carbon steel must be monitored on-line in order to provide an efficient protection...... corrosion and detects localised corrosion, but the sensitivity is not high enough for monitoring initiation of pitting and small attacks. Electrochemical techniques as LPR and EIS give distorted data and unreliable corrosion rates, when biofilm and corrosion products cover the steel surface. However, EIS...

  6. Alloys For Flexible Hoses In A Corrosive Environment

    Science.gov (United States)

    Macdowell, Louis G., III; Ontiveros, Cordelia

    1992-01-01

    High-nickel alloy resists pitting corrosion. Report evaluates metal alloys for flexible hoses in corrosive environment. Tested to find alternatives to 304L stainless steel. Nineteen alloys selected for testing on basis of reputation for resistance to corrosion. Top five, in order of decreasing resistance to corrosion: Hastelloy(R) C-22, Inconel(R) 625, Hastelloy(R) C-276, Hastelloy(R) C-4, and Inco(R) alloy G-3. Of these, Hastelloy(R) C-22 found best for flexible-hose application.

  7. Corrosion protection

    Science.gov (United States)

    Brown, Donald W.; Wagh, Arun S.

    2003-05-27

    There has been invented a chemically bonded phosphate corrosion protection material and process for application of the corrosion protection material for corrosion prevention. A slurry of iron oxide and phosphoric acid is used to contact a warm surface of iron, steel or other metal to be treated. In the presence of ferrous ions from the iron, steel or other metal, the slurry reacts to form iron phosphates which form grains chemically bonded onto the surface of the steel.

  8. Corrosion behaviour of ion implanted aluminium alloy in 0.1 M NaCl electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Chu, J.W.; Evans, P.J. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia); Sood, D.K. [Royal Melbourne Inst. of Tech., VIC (Australia)

    1993-12-31

    Aluminum and its alloys are widely used in industry because of their light weight, high strength and good corrosion resistance which is due to the formation of a protective oxide layer. However, under saline conditions such as those encountered in marine environments, this group of metals are vulnerable to localised degradation in the form of pitting corrosion. This type of corrosion involves the adsorption of an anion, such as chlorine, at the oxide solution interface. Ion implantation of metal ions has been shown to improve the corrosion resistance of a variety of materials. This effect occurs : when the implanted species reduces anion adsorption thereby decreasing the corrosion rate. In this paper we report on the pitting behavior of Ti implanted 2011 Al alloy in dilute sodium chloride solution. The Ti implanted surfaces exhibited an increased pitting potential and a reduced oxygen uptake. 5 refs., 3 figs.

  9. Corrosion Engineering.

    Science.gov (United States)

    White, Charles V.

    A description is provided for a Corrosion and Corrosion Control course offered in the Continuing Engineering Education Program at the General Motors Institute (GMI). GMI is a small cooperative engineering school of approximately 2,000 students who alternate between six-week periods of academic study and six weeks of related work experience in…

  10. Corrosion sensor

    Science.gov (United States)

    Glass, Robert S.; Clarke, Jr., Willis L.; Ciarlo, Dino R.

    1994-01-01

    A corrosion sensor array incorporating individual elements for measuring various elements and ions, such as chloride, sulfide, copper, hydrogen (pH), etc. and elements for evaluating the instantaneous corrosion properties of structural materials. The exact combination and number of elements measured or monitored would depend upon the environmental conditions and materials used which are subject to corrosive effects. Such a corrosion monitoring system embedded in or mounted on a structure exposed to the environment would serve as an early warning system for the onset of severe corrosion problems for the structure, thus providing a safety factor as well as economic factors. The sensor array is accessed to an electronics/computational system, which provides a means for data collection and analysis.

  11. Effect of O{sub 2} on corrosion of 3Cr steel in high temperature and high pressure CO{sub 2}–O{sub 2} environment

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Xueqiang; Liu, Wei, E-mail: weiliu@ustb.edu.cn; Wu, Fei; Xu, Chuanchuan; Dou, Juanjuan; Lu, Minxu

    2015-02-28

    Highlights: • 3Cr steel suffered severe localized corrosion in CO{sub 2}–O{sub 2} environment. • Fe(OH){sub 3} in CO{sub 2}–O{sub 2} corrosion scale of 3Cr steel caused Cr nonuniform distribution. • A development mechanism of CO{sub 2}–O{sub 2} corrosion pits of 3Cr steel was proposed. - Abstract: The development of corrosion scale of 3Cr steel in an aqueous environment containing 95% CO{sub 2}–5% O{sub 2} was characterized and analyzed by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD) and in situ electrochemical impedance spectroscopy (EIS). The results show that the corrosion of 3Cr steel was promoted by dissolved oxygen. Fe(OH){sub 3} precipitation formed at local areas, leading to the nonuniform distribution of Cr element and pitting corrosion. With the increase of corrosion time, Cr-rich area formed at the bottom of pits, where the pitting corrosion process was inhibited. The importance of Fe(OH){sub 3} and Cr-rich area on the formation of corrosion pits and pits development was emphasized.

  12. 热镀锌钢表面铈转化膜的表征与腐蚀电化学行为%Characterization and electrochemical corrosion behavior of cerium conversion coating on hot-dip galvanized steel

    Institute of Scientific and Technical Information of China (English)

    吴海江; 卢锦堂

    2011-01-01

    The cerium conversion coatings were prepared on hot-dip galvanized (HDG) steel sheets treated in 20 g/L Ce(NO3)3·6H2O solution (pH = 4, 25 ℃). The corrosion electrochemical behavior of the cerium conversion coatings was compared with that of blank hot-dip galvanized sample in 5% NaCl solution using polarization curves and electrochemical impedance spectra (EIS). The morphology and composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the corrosion current density of the HDG decreases and the polarization resistance increases after cerium nitrate conversion treatment.While the cerium conversion coatings can markedly restrain the anodic and cathodic reaction during the zinc corrosion process, thereby its corrosion protective efficiency remarkably increases. It is also found that the low-frequency impedance initially increases and then decreases with the treatment time increasing, which demonstrates clearly that the resistance to the migration of electrolyte through the conversion coatings initially increases and subsequently decreases with the treatment time increasing. When the treatment time is prolonged from 30 min to 1 h, the maximal impedance of the conversion coating is up to 8-9 kΩ·cm2 and its corrosion resistance is optimal. The cerium conversion coating is apt to crack in the vicinity of zinc grain boundaries, and the dry riverbed morphology gradually forms with the treatment time increasing. The cerium conversion coating is composed of Ce, Zn and O elements, which mainly consists of CeO2,Ce(OH)4 (or CeO2·2H2O), ZnO and a small quantity of Ce2O3, Ce(OH)3 (or Ce2O3·2H2O).%将热镀锌钢在20 g/L Ce(NO3)·6H2O溶液(pH=4,25℃)中处理10s~24 h,获得铈转化膜试样.应用极化曲线和电化学交流阻抗谱(EIS)研究铈转化膜试样和空白热镀锌试样在5%NaCl溶液中的耐蚀性能.利用扫描电镜(SEM)和X射线光电子能谱(XPS)研

  13. Corrosion behaviour of non-ferrous metals in sea water

    Energy Technology Data Exchange (ETDEWEB)

    Birn, Jerzy; Skalski, Igor [Ship Design and Research Centre, Al. Rzeczypospolitej 8, 80-369 Gdansk (Poland)

    2004-07-01

    The most typical kinds of corrosion of brasses are selective corrosion (dezincification) and stress corrosion. Prevention against these kinds of corrosion lies in application of arsenic alloy addition and appropriate heat treatment removing internal stresses as well as in maintaining the arsenic and phosphorus contents on a proper level. The most typical corrosion of cupronickels is the local corrosion. Selective corrosion occurs less often and corrosion cracking caused by stress corrosion in sea water does not usually occur. Crevice corrosion is found especially in places of an heterogeneous oxidation of the surface under inorganic deposits or under bio-film. Common corrosive phenomena for brasses and cupronickels are the effects caused by sea water flow and most often the impingement attack. Alloy additions improve resistance to the action of intensive sea water flow but situation in this field requires further improvement, especially if the cheaper kinds of alloys are concerned. Contaminants of sea water such as ammonia and hydrogen sulphide are also the cause of common corrosion processes for all copper alloys. Corrosion of copper alloys may be caused also by sulphate reducing bacteria (SRB). Galvanic corrosion caused by a contact with titanium alloys e.g. in plate heat exchangers may cause corrosion of both kinds copper alloys. Bronzes belong to copper alloys of the highest corrosion resistance. Failures that sometimes occur are caused most often by the cavitation erosion, by an incorrect chemical composition of alloys or at last by their inadequate structure. The main problems of aluminium alloys service in sea water are following phenomena: local corrosion (pitting and crevice corrosion), galvanic corrosion, exfoliation and corrosion in the presence of OH- ions. The cause of local corrosion are caused by presence of passive film on the alloy's surface and presence of chlorides in sea water which are able to damage the passive film. Galvanic corrosion is

  14. A proper solution to study the etch pits on LiAlO 2 single crystal

    Science.gov (United States)

    Huang, Huichun; Chou, Mitch M. C.; Gan, Dershin; Shen, Pouyan

    2010-12-01

    Detailed structures of the etch pits on the (1 0 0), (0 1 0), and (0 0 1) surfaces of LiAlO 2 single crystals have been studied. The crystal was grown by the Czochralski-pulling technique. Hot water is found to be a good etching solution for LiAlO 2 crystal. On the (1 0 0) surface, many shallow rhomboidal etch pits with a deep rhombic pit at the center are revealed and can line up to form boundaries. These etch pits are categorized into two groups which are symmetric relative to the [0 1 0] direction and are separated by boundaries made up of dense etch pits. On the (0 0 1) surface, square pyramid-like etch pits are present. However, rectangle-like etch pits are found on the (0 1 0) surface, which may not be related to dislocations. The density and the distribution of dislocations are studied. A scheme of the domain structure is proposed to explain the observed shapes and distributions of etch pits.

  15. 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.

  16. Hot conditioning equipment conceptual design report

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, F.W., Westinghouse Hanford

    1996-08-06

    This report documents the conceptual design of the Hot Conditioning System Equipment. The Hot conditioning System will consist of two separate designs: the Hot Conditioning System Equipment; and the Hot Conditioning System Annex. The Hot Conditioning System Equipment Design includes the equipment such as ovens, vacuum pumps, inert gas delivery systems, etc.necessary to condition spent nuclear fuel currently in storage in the K Basins of the Hanford Site. The Hot Conditioning System Annex consists of the facility of house the Hot Conditioning System. The Hot Conditioning System will be housed in an annex to the Canister Storage Building. The Hot Conditioning System will consist of pits in the floor which contain ovens in which the spent nuclear will be conditioned prior to interim storage.

  17. On Corrosion of Ferrous in Typical Indian Soils-Part II Wrought Iron

    Directory of Open Access Journals (Sweden)

    Brajendra Nath Tripathi

    1965-07-01

    Full Text Available Corrosion of wrought iron in ten Indian soils, employing Schwerdtfeger's soil corrosion cell procedure has been studied. The corrosion of wrought iron n non-acidic solid proceeds through electrochemical mechanism. Usually the rate of corrosion is maximum at the beginning and with the development of the film of the common products, the rate gradually decreases with time until it becomes more or less constant . In most of the cases 'uneven' general or local corrosion with pittings is observed. The maximum penetration is directly proportional to the corrodibility. Soils having moisture equivalent in the range 25-30% are most corrosive. The corrosivity of soils increases with increase in the concentration of soluble electrolytes. Ferric oxide present in laterite soil functions as a cathodic depolariser and hence increase the corrosivity. In and acidic sol the corrosion mainly proceeds through the mechanism of direct chemical reaction . The results have also been analyzed and correlated with various factors.

  18. 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.)

  19. Experimental investigations on macro cell corrosion in chloride-contaminated concrete

    NARCIS (Netherlands)

    Gulikers, J.J.W.

    1996-01-01

    Chloride-induced reinforcement corrosion in concrete is characterised by the action of so-called macrocells. The associated localised form of corrosion results from the strong electrochemical interaction between the relatively small pitting sites acting as anodes and the large passive steel areas ac

  20. Experimental investigations on macro cell corrosion in chloride-contaminated concrete

    NARCIS (Netherlands)

    Gulikers, J.J.W.

    1996-01-01

    Chloride-induced reinforcement corrosion in concrete is characterised by the action of so-called macrocells. The associated localised form of corrosion results from the strong electrochemical interaction between the relatively small pitting sites acting as anodes and the large passive steel areas

  1. Effect of Microstructure on the Performance of Corrosion Resistant Alloys

    OpenAIRE

    Kishan Roodbari, Marzieh

    2015-01-01

    Corrosion by pitting in aluminum alloys is a very complex process that can be affected by various factors such as chemical composition and microstructure of the alloys. The electrochemistry and distribution of second phases populating the alloy are the main factors that significantly influence the corrosion of aluminum alloys. The purpose of the present work is to contribute to a deeper understanding of how the chemical composition and microstructure affect the ability of an al...

  2. Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel

    2000-01-01

    Abstract Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel Microbially influenced corrosion (MIC) of carbon steel may occur in media with microbiological activity of especially sulphate-reducing bacteria, e.g. on pipelines buried in soil and on marine structures. MIC...... of carbon steel must be monitored on-line in order to provide an efficient protection and control the corrosion. A number of monitoring techniques is industrially used today, and the applicability and reliability of these for monitoring MIC is evaluated. Coupons and ER are recommended as necessary basic...... techniques even though localised corrosion rate cannot be measured. FSM measures general corrosion and detects localised corrosion, but the sensitivity is not high enough for monitoring initiation of pitting and small attacks. Electrochemical techniques as LPR and EIS give distorted data and unreliable...

  3. 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.

  4. Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel

    2000-01-01

    of carbon steel must be monitored on-line in order to provide an efficient protection and control the corrosion. A number of monitoring techniques is industrially used today, and the applicability and reliability of these for monitoring MIC is evaluated. Coupons and ER are recommended as necessary basic......Abstract Monitoring Techniques for Microbially Influenced Corrosion of Carbon Steel Microbially influenced corrosion (MIC) of carbon steel may occur in media with microbiological activity of especially sulphate-reducing bacteria, e.g. on pipelines buried in soil and on marine structures. MIC...... techniques even though localised corrosion rate cannot be measured. FSM measures general corrosion and detects localised corrosion, but the sensitivity is not high enough for monitoring initiation of pitting and small attacks. Electrochemical techniques as LPR and EIS give distorted data and unreliable...

  5. 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.

  6. Ultrasonic scattering from a hemispherical pit theory and experimental measurement precision

    Science.gov (United States)

    Eason, Thomas J.; Bond, Leonard J.; Lozev, Mark G.

    2017-02-01

    The accuracy and precision of pulse-echo ultrasonic thickness measurement systems are influenced by systematic and environmental factors including the topographic profile of the back-wall surface. For the case of thickness measurement from the outside surface of a pipe, the back-wall surface can vary in roughness as a result of internal corrosion. A single corrosive pit can be geometrically represented by a hemisphere in a half-space to model the initiation point of rough surface corrosion, or to model isolated pitting degradation as is possible with naphthenic acid corrosion in oil refineries. The elastic wave scattering from a single hemispherical pit has been studied in the Non-Destructive Evaluation (NDE) community, as well as scattering from a hemispherical canyon in the seismology community for various incident and reflected wave angles, modes, and frequency ranges with both analytical and discretized numerical methods. This paper looks to first review recent scattering theory (developed in the seismology community) on a full frequency range analytical solution for a normal incident longitudinal wave at a normal reflection angle from a hemispherical canyon, and then extend this theory to NDE applications with the introduction of a new far-field scattering amplitude term. Next, a selection of new theoretical scattering amplitude solutions are presented along with semi-analytical simulation and experimental measurement results. Finally, a statistical methodology to determine thickness measurement accuracy and precision taking into consideration asymmetric measurement uncertainty is referenced.

  7. Preparation and Corrosion Resistance Evaluation of Cerium Salt/Silane Composite Coating on Hot-Dip Galvanized Steel%热镀锌钢铈盐/硅烷复合膜的制备及其耐蚀性能

    Institute of Scientific and Technical Information of China (English)

    吴海江; 徐国荣; 许剑光; 徐红梅; 吴玉蓉; 颜焕元

    2013-01-01

    热镀锌钢板上单一的铈盐、硅烷钝化膜有一些缺点,对提高其耐蚀性作用不大.为此,将热镀锌钢板先经铈盐溶液处理,再用乙烯基三甲氧基硅烷溶液浸渍,获得了铈盐/硅烷复合钝化膜.采用扫描电镜(SEM)、俄歇电子能谱(AES)、盐水全浸试验和电化学交流阻抗谱(EIS)研究了复合膜层的表面形貌、结构特性和耐蚀性能.结果表明:硅烷膜能较好地填充铈盐转化膜中的裂纹,铈盐/硅烷复合膜层连续、完整、致密,厚400~450 nm,与基体结合较好,复合膜中硅烷膜/铈盐转化膜/锌基体的化学成分呈连续的梯度变化;与热镀锌钢相比,单一铈盐转化膜、硅烷膜的交流阻抗值增加了1个多数量级,复合膜的则增加了约2个数量级,复合膜层的耐蚀性较单一膜层显著增强,且优于常规铬酸盐钝化膜.%Hot-dip galvanized steel was firstly treated in the solution of cerium nitrate and then immersed in vinyltrimethoxysilane solution to obtain composite coating consisting of cerium salt coating and silane coating. The morphology and microstructure of as - obtained composite coating were analyzed by scanning electron microscopy and Auger elec tron spectroscopy, and its corrosion resistance was evaluated based on immersion test in salt water and electrochemical imped ance spectroscopic analysis as well. Results showed that the mi- crocracks in the cerium conversion coating could be well filled up with the silane coating. As-obtained cerium salt/silane composite coating with a thickness of 400 ~ 450 nm was continuous, com plete and compact, and had good adhesion to the steel substrate as well as gradient chemical composition. In the meantime, the electrochemical impedance values of the cerium conversion coat ing and silane coating were increased by more than one order of magnitude as compared with that of hot-dip galvanized steel sub strate, and the electrochemical impedance value of the cerium salt

  8. Review of Artificial Neural Networks (ANN) applied to corrosion monitoring

    Science.gov (United States)

    Mabbutt, S.; Picton, P.; Shaw, P.; Black, S.

    2012-05-01

    The assessment of corrosion within an engineering system often forms an important aspect of condition monitoring but it is a parameter that is inherently difficult to measure and predict. The electrochemical nature of the corrosion process allows precise measurements to be made. Advances in instruments, techniques and software have resulted in devices that can gather data and perform various analysis routines that provide parameters to identify corrosion type and corrosion rate. Although corrosion rates are important they are only useful where general or uniform corrosion dominates. However, pitting, inter-granular corrosion and environmentally assisted cracking (stress corrosion) are examples of corrosion mechanisms that can be dangerous and virtually invisible to the naked eye. Electrochemical noise (EN) monitoring is a very useful technique for detecting these types of corrosion and it is the only non-invasive electrochemical corrosion monitoring technique commonly available. Modern instrumentation is extremely sensitive to changes in the system and new experimental configurations for gathering EN data have been proven. In this paper the identification of localised corrosion by different data analysis routines has been reviewed. In particular the application of Artificial Neural Network (ANN) analysis to corrosion data is of key interest. In most instances data needs to be used with conventional theory to obtain meaningful information and relies on expert interpretation. Recently work has been carried out using artificial neural networks to investigate various types of corrosion data in attempts to predict corrosion behaviour with some success. This work aims to extend this earlier work to identify reliable electrochemical indicators of localised corrosion onset and propagation stages.

  9. Hanford Double Shell Waste Tank Corrosion Studies - Final Report FY2015

    Energy Technology Data Exchange (ETDEWEB)

    Fuentes, R. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Wyrwas, R. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-05-01

    During FY15, SRNL performed corrosion testing that supported Washington River Protection Solutions (WRPS) with their double shell tank (DST) integrity program. The testing investigated six concerns including, 1) the possibility of corrosion of the exterior of the secondary tank wall; 2) the effect of ammonia on vapor space corrosion (VSC) above waste simulants; 3) the determination of the minimum required nitrite and hydroxide concentrations that prevent pitting in concentrated nitrate solutions (i.e., waste buffering); 4) the susceptibility to liquid air interface (LAI) corrosion at proposed stress corrosion cracking (SCC) inhibitor concentrations; 5) the susceptibility of carbon steel to pitting in dilute solutions that contain significant quantities of chloride and sulfate; and 6) the effect of different heats of A537 carbon steel on the corrosion response. For task 1, 2, and 4, the effect of heat treating and/ or welding of the materials was also investigated.

  10. High temperature corrosion in gasifiers

    Directory of Open Access Journals (Sweden)

    Bakker Wate

    2004-01-01

    Full Text Available Several commercial scale coal gasification combined cycle power plants have been built and successfully operated during the last 5-10 years. Supporting research on materials of construction has been carried out for the last 20 years by EPRI and others. Emphasis was on metallic alloys for heat exchangers and other components in contact with hot corrosive gases at high temperatures. In this paper major high temperature corrosion mechanisms, materials performance in presently operating gasifiers and future research needs will be discussed.

  11. Use of electrochemical tests for assessment of corrosion-erosion synergism in bare and TiN-coated stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Diana Maria; Congote, Juan Pablo; Cano, Jose Ricardo; Toro, Alejandro [Tribology and Surfaces Group - GTS, National University of Colombia, Cra 80 N 65-223, Medellin (Colombia); Tschiptschin, Andre Paulo [Metallurgical and Materials Engineering Department, University of Sao Paulo, Av. Prof. Mello Moraes 2463 / CEP 05508-900, Sao Paulo (Brazil)

    2004-07-01

    The mechanisms of degradation of TiN -coated stainless steels under static corrosion, liquid impingement and corrosion-erosion were studied as a function of the mean impact velocity and mean impingement angle. Micro-cutting, intergranular corrosion, pitting corrosion and spalling of the TiN layer were observed depending on the test conditions. The response of the coated surfaces changed from ductile to brittle behavior as a function of the mean impact velocity. Adherence between the substrate and the TiN coating, which was evaluated with the aid of electrochemical measurements, played a central role in corrosion-erosion resistance of the surfaces. Low adherence was related to the occurrence of an anodic peak in polarization curves obtained in 0.5 M H{sub 2}SO{sub 4} + 3.5% NaCl solution, either with solids - free solution (liquid impingement) or with addition of 30 wt-% quartz sand particles (corrosion-erosion). Synergism between uniform corrosion and erosive attack was evaluated by measuring the shift in the critical current density for all the materials tested. On the other hand, the pitting potential measured in dynamic corrosion and corrosion-erosion conditions was always higher than that obtained under static corrosion. However, the number of pits increased with the mean impact velocity. This indicates that agitation was beneficial to avoid the acidification and growing of the pit, although a higher amount of preferential locals for pit initiation were created with respect to the static tests. No effect of the mean impact angle was observed on the pitting potential. The electrochemical tests were also used to evaluate the effectiveness of the passivation process under the combined action of the corrosive fluid and impacting particles. In a general way, the increase in impact velocity led to an increase in the passive current density of all the materials tested. (authors)

  12. In vitro corrosion behaviour and metallic ion release of different prosthodontic alloys.

    Science.gov (United States)

    Gil, F J; Sánchez, L A; Espías, A; Planell, J A

    1999-12-01

    The corrosion resistance for six metallic alloys often used in clinical dentistry, was evaluated by measuring their polarisation resistance in an artificial saliva environment. The critical current density (icr), the passive current density (ip), the corrosion potential (Ecorr) and the critical pitting potential (Ecp), were studied. Metallic ion release from the different alloys was analysed in a saliva environment at 37 degrees C. The nickel-chromium alloy exhibited important corrosion and a high quantity of ions was released. The titanium presented a low value of ion release and a good corrosion resistance due to the passive film on the metal surface. The high gold content alloy provided the best corrosion resistance.

  13. 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.

  14. Numerical Simulation of Monitoring Corrosion in Reinforced Concrete Based on Ultrasonic Guided Waves

    OpenAIRE

    Zheng, Zhupeng; Lei, Ying; Xue, Xin

    2014-01-01

    Numerical simulation based on finite element method is conducted to predict the location of pitting corrosion in reinforced concrete. Simulation results show that it is feasible to predict corrosion monitoring based on ultrasonic guided wave in reinforced concrete, and wavelet analysis can be used for the extremely weak signal of guided waves due to energy leaking into concrete. The characteristic of time-frequency localization of wavelet transform is adopted in the corrosion monitoring of re...

  15. Hot Money, Hot Potato

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    International hot money flowing into Chinese capital markets has caught the attention of Chinese watchdogs The Chinese are not the only ones feasting on the thriving property and stock markets. Apparently, these markets are the targets of international h

  16. FY2005 AND FY2006 CORROSION SURVEILLANCE RESULTS FOR L BASIN

    Energy Technology Data Exchange (ETDEWEB)

    Vormelker, P; Cynthia Foreman, C

    2008-01-30

    This report documents the results of the L-Basin Corrosion Surveillance Program for the fiscal years 2005 and 2006. The water quality and basin conditions for the coupon immersion period are compared to the corrosion evaluation results from detailed metallurgical analysis of the coupons. Test coupons were removed from the basin on two occasions, March 29, 2005 and May 23, 2006, examined and photographed. Selected coupons were metallurgically characterized to evaluate the extent of general corrosion and pitting. Crystallographic and energy dispersive spectroscopy analysis were performed on a typical specimen, as-removed from the basin, to characterize the surface debris. Marked changes were noted in both the 2005 and 2006 specimens compared to previous years corrosion results. A new pitting incidence has occurred on the faces of the aluminum coupons compared to localized pitting at crevice regions only on specimens withdrawn in 2003 and 2004. The pitting incidence is attributed to sand filter fines that entered the basin on July 27, 2004 from an inadvertent backflush of the new sand filter. Pitting rate results show a trend of slowing down over time which is consistent with aluminum pit kinetics. Average pit growth rates were equal to or lower in all 2006 aluminum coupons than those removed in 2005. A trend line shows that pitting corrosion rates on Al1100, 6061, and 6063 coupons are slowing down since pit depth measurements were initiated in 2003. No impact to stored spent fuel is expected from the debris. The storage configuration of the majority of L-Basin spent fuel, in bundles, should provide a measure of isolation from debris settling in the basin.

  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. Experimental Stress Analysis at Railway Inspection Pit

    Directory of Open Access Journals (Sweden)

    Nicuşor Laurentiu Zaharia

    2008-10-01

    Full Text Available Railway inspection pits are used in railway halls. The purpose of inspection pits is to allow the working under the vehicle. Inspection pits can be found in locomotive depots, factories etc. The new design for a inspection pit in a railway hall involve tests in purpose of homologations the railway infrastructure. Before the homologation committee meeting, tests are made; after the test, a testing report is made which it will be part at homologation documents.

  19. Characterisation of Crevice and Pit Solution Chemistries Using Capillary Electrophoresis with Contactless Conductivity Detector

    Directory of Open Access Journals (Sweden)

    Robert J.K. Wood

    2013-09-01

    Full Text Available The ability to predict structural degradation in-service is often limited by a lack of understanding of the evolving chemical species occurring within a range of different microenvironments associated with corrosion sites. Capillary electrophoresis (CE is capable of analysing nanolitre solution volumes with widely disparate concentrations of ionic species, thereby producing accurate and reliable results for the analysis of the chemical compositions found within microenvironment corrosion solutions, such as those found at crevice and pit corrosion sites. In this study, CE with contactless conductivity detection (CCD has been used to characterize pitting and crevice corrosion solution chemistries for the first time. By using the capillary electrophoresis with contactless conductivity detection (CE-CCD system, direct and simultaneous detection of seven metal cations (Cu2+, Ni2+, Fe3+, Fe2+, Cr3+, Mn2+, and Al3+ and chloride anions was achieved with a buffer solution of 10 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium hydroxide at pH 4 using a pre-column complexation method. The detection limits obtained for the metal cations and chloride anions were 100 and 10 ppb, respectively. The CE-CCD methodology has been demonstrated to be a versatile technique capable of speciation and quantifying the ionic species generated within artificial pit (a pencil electrode and crevice corrosion geometries for carbon steels and nickel-aluminium bronze, thus allowing the evolution of the solution chemistry to be assessed with time and the identification of the key corrosion analyte targets for structural health monitoring.

  20. NIR detection of pits and pit fragments in fresh cherries (abstract)

    Science.gov (United States)

    The feasibility of using near infrared (NIR) diffuse reflectance spectroscopy for the detection of pits and pit fragments in cherries was demonstrated. For detection of whole pits, 300 cherries were obtained locally and pits were removed from half. NIR reflectance spectra were obtained in triplicate...

  1. Effects of acidity and alkalinity on corrosion behaviour of Al-Zn-Mg based anode alloy

    Science.gov (United States)

    Ma, Jingling; Wen, Jiuba; Li, Quanan; Zhang, Qin

    2013-03-01

    Effects of 1 M HCl, 0.6 M NaCl with different pH values and 4 M NaOH solutions on the corrosion behaviour of Al-5Zn-1Mg-0.02In-0.05Ti-0.5Mn (wt%) alloy have been investigated using measurements of self-corrosion, potentiodynamic polarization, cyclic polarization experiment combined with open circuit potential technique and scanning electron microscopy. The corrosion behaviour of the alloy was found to be dependant on the Cl-, OH- ions and pH value. In acidic or slightly neutral solutions, general and pitting corrosion occurred simultaneously. In contrast, exposure to alkaline solutions results in general corrosion which was traced back to the dissolution of the resistive oxidation film on the surface of the alloy. Experience revealed that the alloy was susceptible to pitting corrosion in all chloride solution. The alloy undergoes two types of localized corrosion process, leading to the formation of hemispherical and crystallographic pits. Polarization resistance measurements which are in good agreement with those of self-corrosion, show that the corrosion kinetic is minimized in slightly neutral solutions (pH = 7).

  2. Evaluation of hot corrosion resistance of Ni-base alloys using immersion test, coating test and embedding test; Shinseki shiken , tofu shiken , maibotsu shiken ni yoru Ni ki gokin no koon taishoku sei hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Zang, G.; Nishikata, A.; Tsuru, T. [Tokyo Inst. of Tech. (Japan)

    1997-07-20

    Coating test, immersion test and embedding test are usually employed as the methods for testing high temperature corrosion caused by molten salts. In this study, corrosion-resistant properties of twelve kinds of Ni-based alloys are evaluated systematically by immersion, coating and embedding tests using a sulfate, a chloride and a mixture thereof as the molten salts, and the differences of the results obtained by each testing method are examined. The main results of this study are described herein. The reproducibility of said tests is getting higher in an order of embedding test, coating test and immersion test. Especially an extremely high reproducibility is shown by the immersion test. In all corrosive ashes of sulfate, chloride and the mixture thereof, a good correlation is shown between the results of the immersion test and those of the coating test. The results of embedding test are correlated well with those of other tests in sulfate and sulfate/chloride mixture circumstance, while no such a correlation is indicated in chloride. In chloride corrosive ash and sulfate/chloride mixture corrosive ash, the corrosion amounts in coating and embedding tests are rather bigger than that in immersion test. In particular, a large amount of corrosion more than one digital is shown in the alloys with excellent corrosion-resistance. 33 refs., 11 figs., 5 tabs.

  3. Corrosion resistance and its mechanism of Ni-Cu-P coating and 316L stainless steel in hot hydrochloric acid solution%Ni-Cu-P镀层和316L不锈钢在热盐酸溶液中的耐蚀性及机制

    Institute of Scientific and Technical Information of China (English)

    薛亚军

    2013-01-01

    Effect of temperature and concentration on the corrosion behavior of Ni-Cu-P coating and 316L stainless steel was studied by mass loss method.The results show that the corrosion resistance of Ni-Cu-P coating is better than that of 316L stainless steel in hot hydrochloric acid solution.The effect of hydrochloric acid concentration on the corrosive rate of 316L stainless steel is greater than that of Ni-Cu-Pcoating.The corrosive rates of 316L stainless steel and Ni-Cu-P coating increase 2.7 and 0.6 times respectively while increasing hydrochloric acid concentration from 5% to 20%.For the Ni-Cu-P coating,the uniform corrosion occurs in the hydrochloric acid solution.However,the selective corrosion mechanism is found for 316L stainless steel,and the higher temperature and concentration of corrosion medium,the more serious selective corrosion.%采用质量损失法研究了温度和浓度对化学镀Ni-Cu-P镀层和316L不锈钢在盐酸溶液中的腐蚀行为.结果表明,在高温盐酸溶液中,Ni-Cu-P镀层的耐蚀性优于316L不锈钢,盐酸浓度对316L不锈钢腐蚀速率的影响大于Ni-Cu-P镀层,盐酸浓度由5%升高到20%,316L不锈钢和Ni-Cu-P镀层的腐蚀速率分别增大了2.7倍和0.6倍;在盐酸溶液中,Ni-Cu-P镀层发生均匀腐蚀,316L不锈钢发生选择性腐蚀,且温度和浓度越高,选择性腐蚀越严重.

  4. Corrosion in airframes

    OpenAIRE

    PETROVIC ZORAN C.

    2016-01-01

    The introductory chapter provides a brief reference to the issue of corrosion and corrosion damage to aircraft structures. Depending on the nature and dimensions of this non uniformity, three different categories of corrosion are defined: uniform, selective and localized corrosion. The following chapters present the forms of corrosion that can occur in three defined categories of corrosion. Conditions that cause certain types of corrosion in various corrosive environments are discussed. Examp...

  5. CORROSION IN AIRFRAMES

    OpenAIRE

    PETROVIC ZORAN C.

    2016-01-01

    The introductory chapter provides a brief reference to the issue of corrosion and corrosion damage to aircraft structures. Depending on the nature and dimensions of this non uniformity, three different categories of corrosion are defined: uniform, selective and localized corrosion. The following chapters present the forms of corrosion that can occur in three defined categories of corrosion. Conditions that cause certain types of corrosion in various corrosive environments are discussed. Examp...

  6. Localized corrosion of aluminum alloys for OTEC heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Dexter, S C

    1979-01-01

    The effects of dissolved oxygen, pH and temperature on the rate of initiation and growth of pitting and crevice corrosion of aluminum alloy 5052 and pure aluminum have been determined. Variations in pH and temperature rather than dissolved oxygen are shown to account for increased corrosion rates of 5000 series aluminum alloys that have been reported for deep ocean exposures. The impact of these results on the use of aluminum for OTEC heat exchanger tubing and on possible approaches to corrosion control are discussed.

  7. Corrosion and failure processes in high-level waste tanks

    Energy Technology Data Exchange (ETDEWEB)

    Mahidhara, R.K.; Elleman, T.S.; Murty, K.L. [North Carolina State Univ., Raleigh, NC (United States)

    1992-11-01

    A large amount of radioactive waste has been stored safely at the Savannah River and Hanford sites over the past 46 years. The aim of this report is to review the experimental corrosion studies at Savannah River and Hanford with the intention of identifying the types and rates of corrosion encountered and indicate how these data contribute to tank failure predictions. The compositions of the High-Level Wastes, mild steels used in the construction of the waste tanks and degradation-modes particularly stress corrosion cracking and pitting are discussed. Current concerns at the Hanford Site are highlighted.

  8. New Generation Energy Efficient Refractory Application in Soaking Pits of Bhilai Steel Plant, Sail

    Science.gov (United States)

    Roy, Indranil; Chintaiah, Perumetla; Bhattacharya, Ajoy Kr.; Garai, Swapan Kr.; Ray Choudhury, Pankaj Kr.; Tiwari, Laksman

    In Bhilai Steel Plant (BSP), soaking pits are used for heating ingots for successive rolling into blooms. Pits are operated at a temperature of around 1350°C. Mixed gas (Mixture of Blast Furnace gas & Coke Oven gas) of calorific value around 2040 kcal/Nm3 is used as fuel. The walls of soaking pits were lined with traditional 38% Al2O3 firebricks and top 500mm was cast with 70% Al2O3 low cement castable (LCC). This type of lining results in frequent damages due to hitting by ingots while being lifted from pit by overhead cranes thus affecting the availability of pit. Life of pits was 2 to 2.5 years in BSP with 3-4 cold repairs and 3-4 hot repairs. Energy loss through the wall is also quite high in this type of lining. To triumph over the limitations of the conventional lining, a lining design was developed for the walls which consist of special 70% Al2O3 LCC having high hot strength (HMOR) in combination with specially design flexible SS-304 anchors. Ceramic fiber blanket and insulation bricks were provided between castable and the metallic shell of the pit to minimize the heat loss. A heating schedule was developed and introduced based on available infrastructure at BSP for proper curing of modified LCC based lining. After introduction of modified lining, pit no. 14/2 is running for more than 2.5 years without any repair. To capitalize the success, two more pits i.e. 12/1 and 9/2 were converted to modified lining. These pits are also running satisfactorily for more than 1.5 years. The modification has resulted in higher availability with substantial increase in production. Shell temperature of the modified pits reduced to 90° - 140°C from 120° - 200°C of conventional pits. This shows reduction in heat loss through walls, resulting less fuel consumption and energy saving of about 18%.

  9. Structural Origins of Martian Pit Chains

    Science.gov (United States)

    Wyrick, D.; Ferrill, D. A.; Morris, A. P.; Colton, S. L.; Sims, D. W.

    2003-12-01

    Pit craters are circular to elliptical depressions found in alignments (chains), which in many cases coalesce into linear troughs, and are common on the surface of Mars. Pit craters lack an elevated rim, ejecta deposits, or lava flows that are associated with impact craters or calderas. It is generally agreed that these features are formed by collapse into a subsurface cavity. Hypotheses regarding the formation of pit crater chains require development of a substantial subsurface void to accommodate collapse of the overlying sediments. Suggested mechanisms of formation include: collapsed lava tubes, dike swarms, collapsed magma chamber, karst dissolution, fissuring beneath loose material, and dilational faulting. The research described here is intended to constrain current interpretations of pit crater chain formation by analyzing their distribution and morphology. The western hemisphere of Mars was systematically mapped using Mars Orbiter Camera (MOC) images to generate ArcView Geographic Information System (GIS) coverages. All visible pit crater chains were mapped, including their orientations and associations with other structures. We found that pit chains commonly occur in areas that show regional extension or local fissuring. There is a strong correlation between pit chains and fault-bounded grabens. Frequently, there are transitions along strike from (i) visible faulting to (ii) faults and pits to (iii) pits alone. We performed a detailed quantitative analysis of pit crater morphology using MOC narrow angle images, Thermal Emission Imaging System (THEMIS) visual images and Mars Orbiter Laser Altimeter (MOLA) data. This allowed us to interpret a pattern of pit chain evolution and calculate pit depth, slope, and volume. The information collected in the study was then compared with non-Martian examples of pit chains and physical analog models. We evaluated the various mechanisms for pit chain development based on the data collected and conclude that dilational

  10. Study on hot corrosion behavior of Yb{sub 2}Zr{sub 2}O{sub 7} ceramic against Na{sub 2}SO{sub 4} + V{sub 2}O{sub 5} molten salts at temperatures of 900-1200 C in air

    Energy Technology Data Exchange (ETDEWEB)

    Li, S.; Liu, Z.G.; Ouyang, J.H. [Institute for Advanced Ceramics, Department of Materials Science, Harbin Institute of Technology, No. 92 West Da-Zhi Street, Harbin 150001 (China)

    2012-04-15

    Yb{sub 2}Zr{sub 2}O{sub 7} ceramic powders synthesized by chemical-coprecipitation and calcination method were pressureless-sintered at 1700 C for 10 h in air to fabricate dense bulk materials. Hot corrosion studies were performed on Yb{sub 2}Zr{sub 2}O{sub 7} against Na{sub 2}SO{sub 4} and Na{sub 2}SO{sub 4} + V{sub 2}O{sub 5} (molar ratio = 1:1) molten salts in a temperature range of 900-1200 C for 8 h in air, respectively. Chemical reactions were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Yb{sub 2}Zr{sub 2}O{sub 7} ceramic was severely corroded by Na{sub 2}SO{sub 4} + V{sub 2}O{sub 5} molten salt, however, no chemical reaction was found between individual Na{sub 2}SO{sub 4} and Yb{sub 2}Zr{sub 2}O{sub 7}. Yb{sub 2}Zr{sub 2}O{sub 7} reacted with Na{sub 2}SO{sub 4} + V{sub 2}O{sub 5} molten salt to form YbVO{sub 4} and m-ZrO{sub 2}. The thickness of hot corrosion scales formed at different temperatures was investigated to evaluate hot corrosion behavior based on fluxing mechanism. The introduction of vanadium into sulfate led to subsequent formation of NaVO{sub 3}, which was acidic enough to dissolve Yb{sub 2}Zr{sub 2}O{sub 7} by acidic fluxing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Controlling internal corrosion of oil and gas pipelines : the corrosion inhibitor selection software (CISS) program

    Energy Technology Data Exchange (ETDEWEB)

    Doiron, A.; Papavinasam, S. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Materials Technology Laboratory

    2009-07-01

    The internal pitting corrosion of oil and gas pipelines can be effectively controlled through the addition of inhibitors. However, simulation of field operating conditions is necessary because the performance of corrosion inhibitors is influenced by several interacting parameters. This paper reviewed the Corrosion Inhibitor Selection Software (CISS) program. The materials transported in production pipelines are often multiphase, containing oil, aqueous (brine), and gas phases. The corrosion rate and inhibitor performance are influenced by composition, temperature, flow and pressure. Steel composition and structure also influence both the rate and type of corrosion. Improvements in corrosion test methodologies are aimed at simulating field corrosion conditions in the laboratory in a compressed time-scale. The parameters that influence the types of corrosion must be simulated in order for laboratory methodology to be relevant. The variables controlled should be quantifiable. There should also be a correlation between the influence of variables controlled in the laboratory and of the same variables in the field. The CISS program evaluates inhibitors in the following 4 steps: (1) pipeline operating conditions, (2) selection of laboratory methodology, (3) determination of operating conditions for the laboratory methodologies, and (4) selection of corrosion inhibitors. The 7 objectives of the CISS program are to optimize the strategies of inhibitor selection for pipeline applications; determine the hydrodynamic parameters of the pipe from field operating conditions; select appropriate laboratory methodologies for evaluating inhibitors; determine flow conditions for high-shear laboratory methodologies; develop a qualitative relationship between corrosion rates of non-shear laboratory methodologies and of pipelines; evaluate corrosion inhibitors based on results from different laboratory methodologies; and design cost-effective inhibitors for future applications. 47 refs

  12. EFFECTS OF CHEMISTRY AND OTHER VARIABLES ON CORROSION AND STRESS CORROSION CRACKING IN HANFORD DOUBLE SHELL TANKS

    Energy Technology Data Exchange (ETDEWEB)

    BROWN MH

    2008-11-13

    Laboratory testing was performed to develop a comprehensive understanding of the corrosivity of the tank wastes stored in Double-Shell Tanks using simulants primarily from Tanks 241-AP-105, 241-SY-103 and 241-AW-105. Additional tests were conducted using simulants of the waste stored in 241-AZ-102, 241-SY-101, 241-AN-107, and 241-AY-101. This test program placed particular emphasis on defining the range of tank waste chemistries that do not induce the onset of localized forms of corrosion, particularly pitting and stress corrosion cracking. This document summarizes the key findings of the research program.

  13. Corrosion assessment of dry fuel storage containers

    Energy Technology Data Exchange (ETDEWEB)

    Graves, C.E.

    1994-09-01

    The structural stability as a function of expected corrosion degradation of 75 dry fuel storage containers located in the 200 Area Low-Level Waste Burial Grounds was evaluated. These containers include 22 concrete burial containers, 13 55-gal (208-l) drums, and 40 Experimental Breeder Reactor II (EBR-II) transport/storage casks. All containers are buried beneath at least 48 in. of soil and a heavy plastic tarp with the exception of 35 of the EBR-II casks which are exposed to atmosphere. A literature review revealed that little general corrosion is expected and pitting corrosion of the carbon steel used as the exterior shell for all containers (with the exception of the concrete containers) will occur at a maximum rate of 3.5 mil/yr. Penetration from pitting of the exterior shell of the 208-l drums and EBR-II casks is calculated to occur after 18 and 71 years of burial, respectively. The internal construction beneath the shell would be expected to preclude containment breach, however, for the drums and casks. The estimates for structural failure of the external shells, large-scale shell deterioration due to corrosion, are considerably longer, 39 and 150 years respectively for the drums and casks. The concrete burial containers are expected to withstand a service life of 50 years.

  14. Investigation of corrosion of welded joints of austenitic and duplex stainless steels

    Science.gov (United States)

    Topolska, S.

    2016-08-01

    Investigation of corrosion resistance of materials is one of the most important tests that allow determining their functional properties. Among these tests the special group consist electrochemical investigations, which let to accelerate the course of the process. These investigations allow rapidly estimating corrosion processes occurring in metal elements under the influence of the analysed environment. In the paper are presented results of investigations of the resistance to pitting corrosion of the steel of next grades: austenitic 316L and duplex 2205. It was also analysed the corrosion resistance of welded joints of these grades of steel. The investigations were conducted in two different corrosion environments: in the neutral one (3.5 % sodium chloride) and in the aggressive one (0.1 M sulphuric acid VI). The obtained results indicate different resistance of analysed grades of steel and their welded joints in relation to the corrosion environment. The austenitic 316L steel characterizes by the higher resistance to the pitting corrosion in the aggressive environment then the duplex 2205 steel. In the paper are presented results of potentiodynamic tests. They showed that all the specimens are less resistant to pitting corrosion in the environment of sulphuric acid (VI) than in the sodium chloride one. The 2205 steel has higher corrosion resistance than the 316L stainless steel in 3.5% NaCl. On the other hand, in 0.1 M H2SO4, the 316L steel has a higher corrosion resistance than the 2205 one. The weld has a similar, very good resistance to pitting corrosion like both steels.

  15. Improvement of the mechanical properties and corrosion resistance of biodegradable β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy: the adding β-Ca3(PO4)2, hot extrusion and aging treatment.

    Science.gov (United States)

    Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Deng, Youwen; Dai, Han; Dai, Yilong; Xiong, Hanqing; Fang, Hongjie

    2017-05-01

    In this study, 10%β-Ca3(PO4)2/Mg-6%Zn (wt.%) composites with Mg-6%Zn alloy as control were prepared by powder metallurgy. After hot extrusion, the as-extruded composites were aged for 72h at 150°C. The effects of the adding β-Ca3(PO4)2, hot extrusion and aging treatment on their microstructure, mechanical properties and corrosion resistance were investigated. The XRD results identified α-Mg, MgZn phase and β-Ca3(PO4)2 phase in these composites. After hot extrusion, grains were significantly refined, and the larger-sized β-Ca3(PO4)2 particles and coarse MgZn phases were broken into linear-distributed β-Ca3(PO4)2 and MgZn phases along the extrusion direction. After aging treatment, the elements of Zn, Ca, P and O presented a more homogeneous distribution. The compressive strengths of the β-Ca3(PO4)2/Mg-Zn composites were approximately double those of natural bone, and their densities and elastic moduli matched those of natural bone. The immersion tests and electrochemical tests revealed that the adding β-Ca3(PO4)2, hot extrusion and aging treatment could promote the formation of protective corrosion product layer on the sample surface in Ringer's solution, which improved corrosion resistance of the β-Ca3(PO4)2/Mg-Zn composites. The XRD results indicated that the corrosion product layer contained Mg(OH)2, β-Ca3(PO4)2 and hydroxyapatite (HA). The cytotoxicity assessments showed the as-extruded β-Ca3(PO4)2/Mg-Zn composite aged for 72h was harmless to L-929 cells. These results suggested that the β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy were promising to be used for bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Launch Pad Coatings for Smart Corrosion Control

    Science.gov (United States)

    Calle, Luz M.; Hintze, Paul E.; Bucherl, Cori N.; Li, Wenyan; Buhrow, Jerry W.; Curran, Jerome P.; Whitten, Mary C.

    2010-01-01

    Corrosion is the degradation of a material as a result of its interaction with the environment. The environment at the KSC launch pads has been documented by ASM International (formerly American Society for Metals) as the most corrosive in the US. The 70 tons of highly corrosive hydrochloric acid that are generated by the solid rocket boosters during a launch exacerbate the corrosiveness of the environment at the pads. Numerous failures at the pads are caused by the pitting of stainless steels, rebar corrosion, and the degradation of concrete. Corrosion control of launch pad structures relies on the use of coatings selected from the qualified products list (QPL) of the NASA Standard 5008A for Protective Coating of Carbon Steel, Stainless Steel, and Aluminum on Launch Structures, Facilities, and Ground Support Equipment. This standard was developed to establish uniform engineering practices and methods and to ensure the inclusion of essential criteria in the coating of ground support equipment (GSE) and facilities used by or for NASA. This standard is applicable to GSE and facilities that support space vehicle or payload programs or projects and to critical facilities at all NASA locations worldwide. Environmental regulation changes have dramatically reduced the production, handling, use, and availability of conventional protective coatings for application to KSC launch structures and ground support equipment. Current attrition rate of qualified KSC coatings will drastically limit the number of commercial off the shelf (COTS) products available for the Constellation Program (CxP) ground operations (GO). CxP GO identified corrosion detection and control technologies as a critical, initial capability technology need for ground processing of Ares I and Ares V to meet Constellation Architecture Requirements Document (CARD) CxP 70000 operability requirements for reduced ground processing complexity, streamlined integrated testing, and operations phase affordability

  17. Stifling of Crevice Corrosion in Alloy 22

    Energy Technology Data Exchange (ETDEWEB)

    Mon, K G; Gordon, G M; Rebak, R B

    2005-06-08

    Artificially creviced Alloy 22 (N06022) specimens may be susceptible to crevice corrosion in presence of hot chloride containing solutions. The presence of oxyanions in the electrolyte, especially nitrate, may inhibit the nucleation and growth of crevice corrosion. Constant potential tests were performed using tightly creviced specimens of Alloy 22. It was found that crevice corrosion may initiate when a constant potential above the crevice repassivation potential is applied. It was found that as the crevice corrosion nucleated, the current initially increased but later decreased. The net measured current can be converted into penetration following a power law fit of the experimental data. The average power law coefficient ''n'' was found to be 0.439, suggesting that even under constant applied potential crevice corrosion penetration is diffusion controlled.

  18. STIFLING OF CREVICE CORROSION IN ALLOY 22

    Energy Technology Data Exchange (ETDEWEB)

    K.G. Mon; G.M. Gordon; R.B. Rebak

    2005-07-01

    Artificially creviced Alloy 22 (N06022) specimens may be susceptible to crevice corrosion in presence of hot chloride containing solutions. The presence of oxyanions in the electrolyte, especially nitrate, may inhibit the nucleation and growth of crevice corrosion. Constant potential tests were performed using tightly creviced specimens of Alloy 22. It was found that crevice corrosion may initiate when a constant potential above the crevice repassivation potential is applied. It was found that as the crevice corrosion nucleated, the current initially increased but later decreased. The net measured current can be converted into penetration following a power law fit of the experimental data. The average power law coefficient ''n'' was found to be 0.439, suggesting that even under constant applied potential, crevice corrosion penetration is diffusion controlled.

  19. 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.

  20. Passive Corrosion Behavior of Alloy 22

    Energy Technology Data Exchange (ETDEWEB)

    R.B. Rebak; J.H. Payer

    2006-01-20

    Alloy 22 (NO6022) 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 nano-meters 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.

  1. Pitting growth modelling in buried oil and gas pipelines using statistical techniques; Modelado del crecimiento de picaduras en tuberias enterradas que transportan hidrocarburos utilizando tecnicas estadisticas

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, J. C.; Caleyo, F.; Valorm, A.; Hallen, J. M.

    2011-07-01

    New deterministic and stochastic predictive models are proposed for external pitting corrosion in underground pipelines. The deterministic model takes into consideration the local chemical and physical properties of the soil as well as the pipeline coating to predict the time dependence of pitting depth and rate in a range of soils. This model, based on results from a field study, was used to conduct Monte Carlo simulations that established the probability distribution of pitting depth and growth rate in the studied soils and their evolution over the life of the pipeline. In the last stage of the study, an empirical Markov chain-based stochastic model was developed for predicting the evolution of pitting corrosion depth and rate distributions from the observed properties of the soil. (Author) 18 refs.

  2. A Conceptual Model for the Interaction between Carbon Content and Manganese Sulphide Inclusions in the Short-Term Seawater Corrosion of Low Carbon Steel

    Directory of Open Access Journals (Sweden)

    Robert E. Melchers

    2016-05-01

    Full Text Available The critical role of manganese sulphide (MnS inclusions for the initiation of the short-term growth of pitting or localized corrosion of low carbon steels has long been recognized. Classical results show that pitting probability and pitting severity increases with increased sulphide concentration for low carbon steels as a result of magnesium sulphides acting as local cathodes for initiating pitting corrosion. However, the iron carbides (cementite in steels can also act as local cathodes for initiation of pitting corrosion. Herein it is proposed that there is competition between pits for cathodic area and that this will determine the severity of pitting and general corrosion observed in extended exposures. Preliminary experimental data for immersion exposures of up to 56 days in natural seawater of three low carbon steels show, contrary to conventional wisdom, greater pit depths for the steels with lower S content. However, the pit depth results are consistent with lower C/S ratios. This is considered to support the concept of cathodic competition between C and S. It is proposed that this offers explanations for a number of other phenomena, including the thus far unexplained apparently higher reactivity of some MnS inclusions.

  3. Localized corrosion of carbon steels due to sulfate-reducing bacteria. Development of a specific sensor; Corrosion localisee des aciers au carbone induite par des bacteries sulfato-reductrices. Developpement d'un capteur specifique

    Energy Technology Data Exchange (ETDEWEB)

    Monfort Moros, N.

    2001-11-01

    This work concerns the microbiologically influenced corrosion of carbon steels in saline anaerobic media (3% of NaCl) containing sulfato-reducing bacteria (Desulfovibrio gabonensis, DSM 10636). In these media, extreme localised corrosion occurs by pitting under the bio-film covering the metallic substrate. A sensor with concentric electrodes was designed to initiate the phenomenon of bio-corrosion, recreating the favourable conditions for growth of a corrosion pit, and then measuring the corrosion current maintained by bacterial activity. The pit initiation was achieved through either of two methods. The electrochemical conditioning involved driving the potential difference between inner and outer electrodes to values corresponding to a galvanic corrosion that can be maintained by the bacterial metabolism. The mechanical process involved removal of a portion of the bio-film by scratching, yielding galvanic potential differences equivalent to that found by the conditioning technique. This protocol was found to be applicable to a bio-corrosion study on industrial site for the monitoring of the metallic structures deterioration (patent EN 00/06114, May 2000). Thereafter, a fundamental application uses the bio-corrosion sensor for Electrochemical Impedance Spectroscopy (EIS), Electrochemical Noise Analysis (ENA) and current density cartography by the means of micro-electrodes. Thus, the EIS technique reveals the importance of the FeS corrosion products for initiation of bio-corrosion start on carbon steel. In addition, depending on the method used to create a pit, the ENA gives rise to supplementary processes (gaseous release) disturbing the bio-corrosion detection. The beginning of a bio-corrosion process on a clean surface surrounded with bio-film was confirmed by the current density cartography. These different results establish the sensor with concentric electrodes as an indispensable tool for bio-corrosion studies, both in the laboratory and on industrial sites

  4. Microbiologically mediated reduction in the pitting of mild steel overlaid with plywood

    Energy Technology Data Exchange (ETDEWEB)

    Soracco, R J; Berger, L R; Berger, J A; Mayack, L A; Pope, D H; Wilde, E W

    1984-01-01

    Laboratory experiments were conducted to determine the role of microorganisms in the pitting of mild steel flooring, which had been overlaid with plywood. The experimental setups consisted of 4.8 mm (3/16 in.) mild steel plates covered with 12.7 mm (1/2 in.) thick pieces of plywood which were exposed to several different aqueous media supplemented with various combinations of a soil suspension and selected inorganic and organic compounds. Half of the replicate metal-wood-water setups were sterilized and aseptically maintained during incubation after which they were checked for the presence of viable microorganisms and pitting of the mild steel. Results of the first set of experiments showed that pitting of the mild steel specimens in many of these setups occurred after a reasonably short incubation period (3 to 6 months). However, the method used to exclude microorganisms by sterilizing the components separately was unsuccessful. In a second set of experiments, setups were sterilized by exposure to gamma irradiation after they had been assembled. The sterilized setups remained sterile after incubation while those which were not originally sterile still contained viable microorganisms. Pitting of the mild steel specimens was more severe when they were exposed to sterile conditions than when viable microorganisms were present. These experiments showed that while microorganisms are known to enhance corrosion processes in some circumstances, their presence can reduce corrosion in others.

  5. 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.

  6. Corrosion of LY12 aluminum alloy in sodium chloride solution

    Institute of Scientific and Technical Information of China (English)

    程英亮; 张昭; 曹发和; 李劲风; 张鉴清; 王建明; 曹楚南

    2003-01-01

    The corrosion behavior of LY12 alloy in sodium chloride solution and its electrochemical noise were reported. The development of the micro-pits on the alloy surface was monitored by scanning electron microscopy, scanning tunneling microscopy, and electrochemical noise method. All the measurements show that the corrosion of LY12 alloy can be divided into two stages: a very reactive initial stage and a relative constant stable stage. The initial stage is corresponded to the adsorption of Cl ions and its reaction with the oxide film and the dissolution of Mg containing particles. The stable stage is corresponded to the development of the micro-pits by the galvanic attack formed by Al-Fe-Cu-Mn containing particles and the matrix. The initial stage lasts about 2-3 h while the stable stage dominates the whole corrosion process.

  7. Pit formation on stainless steel surfaces pre-treated with biosurfactants produced by Pseudomonas fluorescens

    Energy Technology Data Exchange (ETDEWEB)

    Dagbert, Catherine [ECP-LGPM, Grande Voie des Vignes, 92295 Chatenay-Malabry (France)], E-mail: catherine.dagbert@ecp.fr; Meylheuc, Thierry; Bellon-Fontaine, Marie-Noelle [INRA, UMR 763 Bioadhesion et Hygiene des Materiaux, F-91300 Massy (France); AGROPARISTECH, UMR 763 Bioadhesion et Hygiene des Materiaux, F-91300 Massy (France)

    2008-12-01

    Today, it is widely established that the surface tension of water can be reduced by some microorganisms capable of synthesizing surface-active compounds called biosurfactants (BS). BS characteristics depend on the microorganism that produces them and therefore, on the microorganism culture conditions. Some studies on chemical surfactants have shown that the adsorption of surface-active compounds plays a major role in corrosion; indeed they are used as a good corrosion inhibition tool. The purpose of this study was first, to estimate the importance and behavior of the stainless steels passive film on the adsorption of BS, produced by the Gram negative bacteria Pseudomonas fluorescens, and secondly, to study the impact of these treatments on the pitting corrosion. In this paper, the galvanostatic polarization technique, used as accelerated method for determining the characteristic pit potentials on stainless steels, is examined. Pit growth, shape and cover formation were also observed. The surface topography of the corroded specimens was investigated using field emission scanning electron microscopy (FESEM)

  8. Corrosion fatigue of bladed disk attachments of low-pressure turbine

    Energy Technology Data Exchange (ETDEWEB)

    Asai, K. [Material Research Lab., Hitachi, Ltd., Hitachi (Japan); Sakurai, S.; Nomura, K. [Thermal Power and Hydroelectric Systems Div., Hitachi, Ltd., Hitachi (Japan); Saito, E.; Namura, K. [Power and Industrial Systems R and D Lab., Hitachi, Ltd., Hitachi (Japan)

    2004-07-01

    The mechanism of a disk cracking in a low-pressure steam turbine was investigated by finite-element and fracture mechanics analysis and, based on the results of the investigation, a life assessment method was derived. The disk cracking was found to be caused by growth of corrosion pits, superposition of multiple vibration modes, and an increase in the standard deviation of the natural frequency of grouped blades after long-term operation. Taking these findings into consideration, the authors then developed a life-assessment method for disk cracking composed of evaluations (1) maximum corrosion pit size at the current situation, (2) corrosion pit growth after a certain term, and (3) failure-occurrence ratio for the estimated corrosion pit depth. Maximum corrosion-pit size is evaluated by extreme value statistical analysis using the data obtained by replica inspection. The failure-occurrence ratio is evaluated by Monte Carlo simulation considering two uncertainties, namely, the standard deviation of the natural frequency of grouped blades and the stimulus ratio. The values of both uncertainties were determined by the inverse problem analysis of the disk cracking. In light of these results, the authors found that replacing conventional tenon-shroud grouped blades with continuous-cover blades is effective from the view point of vibratory behavior. (orig.)

  9. Unexpected corrosion of stainless steel in low chloride waters – microbial aspects

    DEFF Research Database (Denmark)

    Hilbert, Lisbeth Rischel; Carpén, Leena; Møller, Per

    2009-01-01

    Abstract Stainless steels EN 1.4301 and 1.4401/1.4404 are normally considered corrosion resistant in low chloride natural waters like drinking water. However, a number of corrosion failures have been observed in e.g. fire extinguisher systems and drinking water installations, where stagnant...... in drinking water qualities, due to the formation of a biofilm. In itself, this is not enough to initiate pitting in these water qualities, but combined with a geometrically or metallurgically vulnerable area, corrosion may accelerate. The mechanism is linked to the naturally occurring microbial activity...... conditions or periods of low water consumption have occurred prior to the failure. Typically the corrosion attacks appear within 2-3 years in weld nuggets, heat affected zones or in crevices like e.g. press fitting pipe connections. The failure mode is pitting and crevice corrosion leading to leaks and rust...

  10. Effect of prior corrosion state on the fatigue small cracking behaviour of 6151-T6 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li Xudong [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Naval Aeronautical Engineering Academy Qingdao Branch, Qingdao 266000 (China); Wang Xishu, E-mail: xshwang@tsinghua.edu.cn [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Ren Huaihui; Chen Yinlong [Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084 (China); Mu Zhitao [Naval Aeronautical Engineering Academy Qingdao Branch, Qingdao 266000 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Relationship of corrosion pit and fatigue crack is established based on SEM. Black-Right-Pointing-Pointer An equivalent relationship between accelerated and natural corrosion is build up. Black-Right-Pointing-Pointer Prior corrosion damage is crucial to the subsequent fatigue cracking behaviour. Black-Right-Pointing-Pointer The prior corrosion fatigue crack growth rate is expressed by the term of k{sigma}{sub max}{sup n}a. Black-Right-Pointing-Pointer Corrosion states such as SC15, are defined based on corrosion spectrum. - Abstract: The purpose of this paper was to estimate the reliable effect of prior corrosion state on fatigue micro crack initiation and early stage propagation behaviour of aluminum alloy based on scanning electron microscopy (SEM) in situ observation. Results indicated that multi-cracks initiation occurred almost at the corrosion pits and the early stage of fatigue micro crack propagation behaviour can be described by K{sub I}/K{sub II}-mixed mode. The importance of crack-face interaction via crack-face corrosion pits interlocking/bridging was emphasised in the mixed mode. The fatigue crack growth rate in the corrosion states can be empirically expressed by the term of k{sigma}{sub max}{sup n}a.

  11. Corrosion effects on friction factors

    Energy Technology Data Exchange (ETDEWEB)

    Magleby, H.L.; Shaffer, S.J.

    1996-03-01

    This paper presents the results of NRC-sponsored material specimen tests that were performed to determine if corrosion increases the friction factors of sliding surfaces of motor-operated gate valves, which could require higher forces to close and open safety-related valves when subjected to their design basis differential pressures. Friction tests were performed with uncorroded specimens and specimens subjected to accelerated corrosion. Preliminary tests at ambient conditions showed that corrosion increased the friction factors, indicating the need for additional tests duplicating valve operating parameters at hot conditions. The additional tests showed friction factors of corroded specimens were 0.1 to 0.2 higher than for uncorroded specimens, and that the friction factors of the corroded specimens were not very dependent on contact stress or corrosion film thickness. The measured values of friction factors for the three corrosion films tested (simulating three operating times) were in the range of 0.3 to 0.4. The friction factor for even the shortest simulated operating time was essentially the same as the others, indicating that the friction factors appear to reach a plateau and that the plateau is reached quickly.

  12. 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.

  13. Underground pipeline corrosion

    CERN Document Server

    Orazem, Mark

    2014-01-01

    Underground pipelines transporting liquid petroleum products and natural gas are critical components of civil infrastructure, making corrosion prevention an essential part of asset-protection strategy. Underground Pipeline Corrosion provides a basic understanding of the problems associated with corrosion detection and mitigation, and of the state of the art in corrosion prevention. The topics covered in part one include: basic principles for corrosion in underground pipelines, AC-induced corrosion of underground pipelines, significance of corrosion in onshore oil and gas pipelines, n

  14. Effect of Carbon Steel Composition and Microstructure on CO2 Corrosion

    Science.gov (United States)

    Akeer, Emad S.

    the protective FeCO 3 layer which was probably related to the local increase in shear stress and the changes in pressure caused by turbulence at the high flow rates. Although all steels suffered from pitting corrosion to different degrees, the FeCO3 layer formed on normalized steel was more protective than the one formed on quenched and tempered steel (Q&T). This can be attributed to microstructure, because the pearlite structures present in the normalized steel conferred superior FeCO3 adherence to the steel surface. On the other hand, X65II steel, which has metallurgical characteristics consistent with a normalized hot rolled material, suffered pitting corrosion, which initiated even before increasing wall shear stress. This type of localized corrosion was related to inclusions and phase distributions within the ferrite/pearlite microstructure. In a separate series of experiments, the formation mechanisms of the FeCO3 corrosion product layer were challenged for each steel at high wall shear stress (535Pa) and at 80°C, pH 6.6, and 1.5 bar pCO 2. It was observed that the FeCO3 corrosion product layers did not form at this high wall shear stress, even under conditions that were supersaturated with respect to FeCO3. This was related to mass transfer behavior, where the fast movement of species from and toward the steel surface contributed to removal of 5 generated ferrous ions and prevented the formation of an FeCO3 layer. High local shear stresses may have also mechanically interfered with formation of any FeCO3 layer on the steel surface. At high wall shear stress, the general corrosion rates of normalized steels (X52, A106GRB) are higher than for Q&T steels. This can be related to the amount of iron carbides in the steel. There was no localized corrosion observed at high wall shear stress since no FeCO3 formed on the steels.

  15. Corrosion of aluminium, stainless steels and AISI 680 nickel alloy in nitrogen-based fuels

    Energy Technology Data Exchange (ETDEWEB)

    Kap, I.; Starostin, M.; Shter, G.E.; Grader, G.S. [Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa (Israel)

    2012-07-15

    Nitrogen-based compounds can potentially be used as alternative non-carbon or low-carbon fuels. Nevertheless, the corrosion of construction materials at high temperatures and pressures in the presence of such fuel has not been reported yet. This work is focused on the corrosion of AISI Al 6061, 1005 carbon steel (CS), 304, 316L, 310 austenitic stainless steels (SS) and 680 nickel alloy in highly concentrated water solution of ammonium nitrate and urea (ANU). The corrosion at 50 C and ambient pressure and at 350 C and 20 bar was investigated to simulate storage and working conditions. Sodium chloride was added to the fuel (0-5 wt%) to simulate industrial fertilizers and accelerated corrosion environment. Heavy corrosion of CS was observed in ANU solution at 50 C, while Al 6061, 304 and 316L SS showed high resistance both to uniform and pitting corrosion in ANU containing 1% of sodium chloride. Addition of 5% sodium chloride caused pitting of Al 6061 but had no influence on the corrosion of SS. Tests in ANU at 350 C and 20 bar showed pitting on SS 304 and 316L and 680 nickel alloy. The highest corrosion resistance was found for SS 310 due to formation of stable oxide film on its surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel (X 5 CrNiCuNb 17 4 PH) in comparison to the soft martensitic stainless steel X 4 CrNiMo 16 5 1 ESR in chloride containing aqueous media. Pt. 1. Corrosion investigations and stress corrosion tests to optimize the heat treatment according to the stress corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt-Thomas, K.G.; Wunderlich, R.; Happle, T.

    1989-06-01

    The stress corrosion was investigated for all heat-treatments of the 17-4 PH in 22% NaCl(pH3) solution. The precipitation hardening steel was most resistant to stress corrosion in concentrated NaCl-solution after a three-stage heat-treatment. There was no improvement of corrosion fatigue resistance after metallurgical aftertreatment of soft martensitic steel compared to the untreated material. This is due to the instable passive behaviour of the material which led to crack initiation, especially during the 150/sup 0/C experiments, at chloride-induced places of pitting. The investigation of the electrochemical corrosion behaviour of both materials showed that the pH-value hardly influences corrosion resistance. An increase of the salt content leads to higher pitting induction. At temperatures of 80/sup 0/C in a saturated NaCl-solution the material showed no corrosion resistance. In potentiokinetic investigations, a direct transition from the active area to the pitting potential was observed. In accordance with both the corrosion fatigue and the stress corrosion cracking investigations, it was found that pitting at the martensite precipitator starts primarily around Cu-containing or oxidic inclusions. (orig./MM).

  17. 镓含量对纯铝的耐蚀性的影响%Studies on the Influence of Gallium Content on the Corrosion Resistance of Pure Aluminum

    Institute of Scientific and Technical Information of China (English)

    LIN Jin-ping; WANG Jun; SUN Bao-de

    2008-01-01

    The effect of small amount gallium (up to 0.06%) on the corrosion behavior of pure aluminum (99.99%,4N) in chloride solution was investigated using a potentiodynamic polarization technique.It has been found that the open circuit corrosion potential and the pitting potential shifted in the active (negative) direction with increasing gallium content,while corrosion rate and pitting occurrence factor for aluminum increased.The effect of gallium on the degradation of corrosion resistance is rather small while the gallium content is below 0.03mass%.The gallium content should be kept less than 0.03mass% in the pure aluminum.

  18. Liquid-Air Interface Corrosion Testing Simulating The Environment Of Hanford Double Shell Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Gray, J. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcia-Diaz, B. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Murphy, T. H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hicks, K. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-01-30

    Coupon tests on A537 carbon steel materials were conducted to evaluate the Liquid-Air Interface (LAI) corrosion susceptibility in a series of solutions designed to simulate conditions in the radioactive waste tanks located at the Hanford Nuclear Facility. The new stress corrosion cracking requirements and the impact of ammonia on LAI corrosion were the primary focus. The minimum R value (i.e., molar ratio of nitrite to nitrate) of 0.15 specified by the new stress corrosion cracking requirements was found to be insufficient to prevent pitting corrosion at the LAI. The pH of the test solutions was 10, which was actually less than the required pH 11 defined by the new requirements. These tests examined the effect of the variation of the pH due to hydroxide depletion at the liquid air interface. The pits from the current testing ranged from 0.001 to 0.008 inch in solutions with nitrate concentrations of 0.4 M and 2.0 M. The pitting and general attack that occurred progressed over the four-months. No significant pitting was observed, however, for a solution with a nitrate concentration of 4.5 M. The pitting depths observed in these partial immersion tests in unevaporated condensates ranged from 0.001 to 0.005 inch after 4 months. The deeper pits were in simulants with low R values. Simulants with R values of approximately 0.6 to 0.8 appeared to significantly reduce the degree of attack. Although, the ammonia did not completely eliminate attack at the LAI, the amount of corrosion in an extremely corrosive solution was significantly reduced. Only light general attack (< 1 mil) occurred on the coupon in the vicinity of the LAI. The concentration of ammonia (i.e., 50 ppm or 500 ppm) did not have a strong effect.

  19. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4

    Science.gov (United States)

    Jonnalagadda, Krishna Praveen; Mahade, Satyapal; Curry, Nicholas; Li, Xin-Hai; Markocsan, Nicolaie; Nylén, Per; Björklund, Stefan; Peng, Ru Lin

    2016-12-01

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  20. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4

    Science.gov (United States)

    Jonnalagadda, Krishna Praveen; Mahade, Satyapal; Curry, Nicholas; Li, Xin-Hai; Markocsan, Nicolaie; Nylén, Per; Björklund, Stefan; Peng, Ru Lin

    2017-01-01

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  1. 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

  2. [Corrosion of stainless steel 201, 304 and 316L in the simulated sewage pipes reactor].

    Science.gov (United States)

    Bao, Guo-Dong; Zuo, Jian-E; Wang, Ya-Jiao; Gan, Li-Li

    2014-08-01

    The corrosion behavior of stainless steel 201, 304 and 316L which would be used as sewer in-situ rehabilitation materials was studied in the simulated sewage pipes reactor. The corrosion potential and corrosion rate of these three materials were studied by potentiodynamic method on the 7th, 14th, 21st, 56th day under two different conditions which were full immersion condition or batch immersion condition with a 2-day cycle. The electrode process was studied by Electrochemical Impedance Spectroscopy (EIS) on the 56th day. The microstructure and composition of the corrosion pitting were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) on the 56th day. The results showed that 304 and 316L had much better corrosion resistance than 201 under both conditions. 304 and 316L had much smaller corrosion rate than 201 under both conditions. The corrosion resistance of all three kinds of stainless steel under the batch immersion condition was much better than those under the full immersion condition. The corrosion rate of all three kinds of stainless steel under the batch immersion condition was much smaller than those under the full immersion condition. Point pitting corrosion was formed on the surfaces of 304 and 316L. In comparison, a large area of corrosion was formed in the surface of 201.

  3. In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

    KAUST Repository

    Itty, Pierre-Adrien

    2014-06-01

    In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

  4. Limitations of using a thermal imager for snow pit temperatures

    Directory of Open Access Journals (Sweden)

    M. Schirmer

    2013-10-01

    Full Text Available Driven by temperature gradients, kinetic snow metamorphism is important for avalanche formation. Even when gradients appear to be insufficient for kinetic metamorphism, based on temperatures measured 10 cm apart, faceting close to a~crust can still be observed. Recent studies that visualized small scale (< 10 cm thermal structures in a profile of snow layers with an infrared (IR camera produced interesting results. The studies found melt-freeze crusts to be warmer or cooler than the surrounding snow depending on the large scale gradient direction. However, an important assumption within the studies was that a thermal photo of a freshly exposed snow pit was similar enough to the internal temperature of the snow. In this study, we tested this assumption by recording thermal videos during the exposure of the snow pit wall. In the first minute, the results showed increasing gradients with time, both at melt-freeze crusts and at artificial surface structures such as shovel scours. Cutting through a crust with a cutting blade or a shovel produced small concavities (holes even when the objective was to cut a planar surface. Our findings suggest there is a surface structure dependency of the thermal image, which is only observed at times with large temperature differences between air and snow. We were able to reproduce the hot-crust/cold-crust phenomenon and relate it entirely to surface structure in a temperature-controlled cold laboratory. Concave areas cooled or warmed slower compared with convex areas (bumps when applying temperature differences between snow and air. This can be explained by increased radiative transfer or convection by air at convex areas. Thermal videos suggest that such processes influence the snow temperature within seconds. Our findings show the limitations of the use of a thermal camera for measuring pit-wall temperatures, particularly in scenarios where large gradients exist between air and snow and the interaction of snow

  5. ADVANCED HOT GAS FILTER DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    Matthew R. June; John L. Hurley; Mark W. Johnson

    1999-04-01

    Iron aluminide hot gas filters have been developed using powder metallurgy techniques to form seamless cylinders. Three alloys were short-term corrosion tested in simulated IGCC atmospheres with temperatures between 925 F and 1200 F with hydrogen sulfide concentrations ranging from 783 ppm{sub v} to 78,300 ppm{sub v}. Long-term testing was conducted for 1500 hours at 925 F with 78,300 ppm{sub v}. The FAS and FAL alloys were found to be corrosion resistant in the simulated environments. The FAS alloy has been commercialized.

  6. Corrosion resistance of nickel and nickel alloys. (Latest citations from Information Services in Mechanical Engineering database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-02-01

    The bibliography contains citations concerning the corrosion resistance of nickel and nickel alloys used in electrical and structural materials and chemical processes. Topics include susceptibility of nickel to high temperature sulfidation, normal exposure to saline and other high chloride environments, pitting corrosion, and metal coatings. Special cases of corrosion of weld-filler metal combinations are also included. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  7. THE INFLUENCE OF NANOENGINEERED Cu DEFECTS ON ALUMINUM PITTING INITIATION

    Energy Technology Data Exchange (ETDEWEB)

    WALL,F.D.; SON,K.A.; MISSERT,N.A.; BARBOUR,J.C.; MARTINEZ,M.A.; ZAVIDIL,K.R.; SULLIVAN,J.P.; GOPELAND,R.G.; CIESLAK,W.R.; BUCHHEIT,R.G.; ISAACS,H.S.

    1999-11-01

    Nanoengineering technologies have been used to generate well defined arrays of pure Cu islands within an Al thin film matrix in order to examine the impact of noble particle defects on the initiation of metastable pitting. The Cu particles form local galvanic cells with the surrounding Al matrix and drive metastable corrosion. Electrical isolation of the Cu particles from the Al occurs due to selective Al dissolution and appears to correlate to cessation of metastable events. Distributions of parameters related to the electrochemical signature of an event suggests that size and spacing of particles do not impact the signatures of individual events. However, event frequency data indicate that the propensity for a structure to induce localized events is linked to Cu island diameter and separation.

  8. PERFORMACE OF MULTI-PROBE CORROSION MONITORING SYSTEMS AT THE HANFORD SITE

    Energy Technology Data Exchange (ETDEWEB)

    CAROTHERS KD; BOOMER KD; ANDA VS; DAHL MM; EDGEMON GL

    2010-01-14

    Between 2007 and 2009, several different multi-probe corrosion monitoring systems were designed and installed in high-level nuclear waste tanks at the U.S. Department of Energy's Hanford Site in WaShington State. The probe systems are being monitored to ensure waste tanks operate in regions that minimize localized corrosion (i.e., pitting) and stress corrosion cracking. The corrosion monitoring systems have been installed in wastes with different chemistry types. An ongoing effort during the same time period has generated non-radioactive simulants that are tested in the laboratory to establish baseline corrosion monitoring system performance and characterize data to allow interpretation of readings from the multiple corrosion monitoring systems. Data collection from these monitoring systems has reached the point where the results allow comparison with the laboratory testing. This paper presents analytical results from the corrosion monitoring system development program.

  9. 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.

  10. Microbially induced corrosion of carbon steel in deep groundwater environment

    Directory of Open Access Journals (Sweden)

    Pauliina eRajala

    2015-07-01

    Full Text Available The metallic low and intermediate level radioactive waste generally consists of carbon steel and stainless steels. The corrosion rate of carbon steel in deep groundwater is typically low, unless the water is very acidic or microbial activity in the environment is high. Therefore, the assessment of microbially induced corrosion of carbon steel in deep bedrock environment has become important for evaluating the safety of disposal of radioactive waste. Here we studied the corrosion inducing ability of indigenous microbial community from a deep bedrock aquifer. Carbon steel coupons were exposed to anoxic groundwater from repository site 100 m depth (Olkiluoto, Finland for periods of three and eight months. The experiments were conducted at both in situ temperature and room temperature to investigate the response of microbial population to elevated temperature. Our results demonstrate that microorganisms from the deep bedrock aquifer benefit from carbon steel introduced to the nutrient poor anoxic deep groundwater environment. In the groundwater incubated with carbon steel the planktonic microbial community was more diverse and 100-fold more abundant compared to the environment without carbon steel. The betaproteobacteria were the most dominant bacterial class in all samples where carbon steel was present, whereas in groundwater incubated without carbon steel the microbial community had clearly less diversity. Microorganisms induced pitting corrosion and were found to cluster inside the corrosion pits. Temperature had an effect on the species composition of microbial community and also affected the corrosion deposits layer formed on the surface of carbon steel.

  11. Corrosion behaviour of stainless steel in contact with wine and beer

    Directory of Open Access Journals (Sweden)

    V. Alar

    2016-07-01

    Full Text Available The effects of wine and beer on the corrosion behavior of AISI 304, AISI 316 and AIS 316Ti were investigated using the electrochemical and gravimetric methods. Physical and chemical parameters of wine and beer were determined before and after the immersion of the steel plates. The corrosion behavior of materials was evaluated using the conducting cyclic potentiodynamic polarization measurements for localized corrosion. The corrosion potential (Ecorr, and the pitting potential (Epit were determined through the application of the cyclic polarization method. Changes caused in the values of the roughness parameter Ra by immersing the samples into electrolytes were also studied.

  12. Effect of Rare Earths on Corrosion Resisting Properties of Carbon-Manganese Clean Steels

    Institute of Scientific and Technical Information of China (English)

    郭锋; 林勤; 孙学义

    2004-01-01

    Electrochemistry experiments were made on carbon-manganese clean steel with rare earths Ce and La respectively to observe corrosion parameters such as corrosion current icorr, and characteristic potential of pitting Eb. The results indicate that the rare earths have effect on corrosion resisting properties of carbon-manganese clean steel, and the optimum contents of La is about 0.011% (mass fraction) and Ce about 0.014% (mass fraction) respectively. The change of corrosion resistance is related to the action of rare earths on microstructure and effect on surface state of samples in the process of polarization.

  13. Research needs for corrosion control and prevention in energy conservation systems

    Energy Technology Data Exchange (ETDEWEB)

    Brooman, E.W.; Hurwitch, J.W.

    1985-06-01

    A group of 28 electrochemists, materials scientists and corrosion engineers was brought together to determine if the government could have a role as a focal point for corrosion R and D, discuss opportunities in fundamental research and solving corrosion problems, and develop a research agenda. Participants from government, industry and academia assembled into four technical discussion groups: localized corrosion, general corrosion, high temperature corrosion, and corrosion control and prevention. Research needs were identified, discussed, then assigned a figure of merit. Some 44 corrosion control and prevention topics were identified as having a high priority for consideration for funding. Another 35 topics were identified as having a medium priority for funding. When classified according to corrosion phenomenon, the areas which should receive the most attention are molten salt attack, crevice corrosion, stress-corrosion cracking, erosion-corrosion, pitting attack, intergranular attack and corrosion fatigue. When classified according to the sector or system involved, those which should receive the most attention are chemical processes, transportation, buildings and structures, electric power generation, and batteries and fuel cells.

  14. Corrosion of copper in alkaline chloride environments

    Energy Technology Data Exchange (ETDEWEB)

    King, F. [Integrity Corrosion Consulting Ltd., Calgary (Canada)

    2002-08-01

    The available literature information on the corrosion and electrochemical behaviour of copper in alkaline environments has been reviewed. The purpose of the review was to assess the impact of an alkaline plume from cementitious material on the corrosion behaviour of a copper canister in an SKB-3 type repository. The effect of the evolution of the environmental conditions within the repository have been considered, including the effects of temperature, redox conditions, pore-water salinity and pH. If the pore-water pH increases prior to the establishment of anoxic conditions, the canister surface will passivate as the pore-water pH exceeds a value of {approx} pH 9. Passivation will result from the formation of a duplex Cu{sub 2}O/Cu(OH){sub 2} film. The corrosion potential will be determined by the equilibrium potential for the Cu{sub 2}O/Cu(OH){sub 2} couple under oxic conditions, or by the Cu/Cu{sub 2}O redox couple under anoxic conditions (in the absence of sulphide). Pitting corrosion is only likely to occur early in the evolution of the repository environment, whilst the canister is still relatively cool (<40 deg C), whilst there is still O{sub 2} available to support localised corrosion, and prior to the increase in pore-water pH and salinity. The subsequent increase in canister surface temperature, pore-water pH and salinity, and decrease in O{sub 2} will make pit initiation less likely, although the canister will remain passive provided the pore-water pH is maintained above pH 9. The higher the pore-water pH, the more strongly the canister is passivated and the less likely the surface is to undergo localised attack. If the pore-water salinity increases prior to the increase in pH, there could be a period of active canister corrosion before passivation occurs.Under these circumstances, the corrosion potential will be a true mixed potential, determine by the relative kinetics of Cu dissolution as CuCl{sub 2} - and of the reduction of O{sub 2}. The development

  15. Corrosion behaviour of sintered Ti–Ni–Cu–Nb in 0.9% NaCl environment

    Directory of Open Access Journals (Sweden)

    Moipone Linda Lethabane

    2015-10-01

    Full Text Available The uniform and localized corrosion behaviour of sintered Ti–Ni containing niobium and copper additions were studied using potentiodynamic and cyclic polarization measurements in 0.9% sodium chloride. Results indicated that copper and niobium addition did not have significant effects on the uniform corrosion characteristics, but significantly improved the pitting corrosion resistance. Both copper and niobium additions significantly increased the re-passivation potentials, while copper was observed to reduce the pitting hysteresis loop area. Alloys containing 15% copper and 2% niobium additions depicted the most improved pitting corrosion resistance, and increased the re-passivation value from −315.60 mV to a high re-passivation potential of 840.68 mV.

  16. Hot Corrosion Behavior of Bare, Cr3C2-(NiCr) and Cr3C2-(NiCr) + 0.2wt.%Zr Coated SuperNi 718 at 900 °C

    Science.gov (United States)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-01-01

    Corrosion in incinerators, power plants, and chemical industries are frequently encountered due to the presence of salts containing sodium, sulphur, and chlorine. To obviate this problem, bare and coated alloys were tested under environments simulating the conditions present inside incinerators and power plants. 0.2 wt.% zirconium powder was incorporated in the Cr3C2-(NiCr) coating powder. The original powder and Zr containing powder was sprayed on Superni 718 alloy by D-gun technique. The bare and coated alloys were tested under Na2SO4 + K2SO4 + NaCl + KCl and Na2SO4 + NaCl environment. The corrosion rate of specimens was monitored using weight change measurements. Characterization of the corrosion products has been done using FE-SEM/EDS and XRD techniques. Bare and coated alloys showed very good corrosion resistance under given molten salt environments. Addition of 0.2wt.%Zr in Cr3C2-25%(NiCr) coating further greatly reduced the oxidation rate as well as improved the adherence of oxide scale to the coating surface during the time of corrosion.

  17. Corrosion Testing Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Corrosion Testing Facility is part of the Army Corrosion Office (ACO). It is a fully functional atmospheric exposure site, called the Corrosion Instrumented Test...

  18. Effects of aluminum nanocrystals on the corrosion resistance of aluminum-based metallic glasses

    Science.gov (United States)

    Lucente, Ashley Marie

    Aluminum-based metallic glasses possess some remarkable attributes that make them appealing for corrosion prevention applications. For example, Al-based glasses are resistant to pitting corrosion and can function as a corrosion barrier film, a sacrificial anode, and provide active corrosion inhibition by releasing alloying elements as inhibiting ions. While the amorphous structure makes these functions possible by allowing a high alloying element content to be achieved in solid solution, it is also a potential weakness because the amorphous structure is metastable. Partial crystallization occurs over time as nanometer-scale, solute-depleted f.c.c. Al precipitates ("nanocrystals") nucleate and grow within a remaining amorphous matrix. There was once some concern that these nanocrystals may serve as pit initiation sites and degrade the good pitting resistance of an amorphous alloy. Contrary to early predictions, this work shows that several partially nanocrystalline Al-based alloys are as corrosion resistant as fully amorphous alloys of the same bulk composition. This thesis provides an in-depth investigation of several mechanisms that can explain the good corrosion resistance of partially nanocrystalline glasses. The corrosion resistance of the amorphous and partially nanocrystalline glasses was first characterized by examining chloride induced pitting. The results of these experiments guided diagnostic studies of chloride-induced metastable pitting and stable pit growth, alkaline dissolution and passivation behavior, and surface characterization using SEM, TEM, and AFM, all at a sensitivity level tailored to detect nm-scale corrosion processes. These techniques together served as diagnostics to help determine the mechanism by which the corrosion resistance of a partially nanocrystalline Al-based glass may be similar or superior to that of its fully amorphous precursor. The overall conclusion of this dissertation is that Al-based glassy alloys with solute

  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. 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.

  1. Corrosion performance of structural alloys.

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.

    1999-07-15

    Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.

  2. 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.

  3. Corrosion effects of runway de-icing chemicals on aircraft alloys and coatings

    Energy Technology Data Exchange (ETDEWEB)

    Huttunen-Saarivirta, E., E-mail: elina.huttunen-saarivirta@tut.fi [Department of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere (Finland); Kuokkala, V.-T.; Kokkonen, J. [Department of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere (Finland); Paajanen, H. [Finnish Air Force Materiel Command, Plans Division, Support Systems Section, P.O. Box 210, FI-33101 Tampere (Finland)

    2011-03-15

    Research highlights: {yields} Corrosion effects of urea and four new runway de-icing chemicals on Al alloy 2024, Mg alloy RZ5 and cadmium-plated and subsequently chromate-treated steel 4340 were examined by three types of corrosion tests. {yields} Corrosion effects of urea on Al alloy 2024 were more pronounced than those of the new de-icing chemicals, with pitting corrosion being evident in urea in all tests. {yields} The rate of corrosion in Mg alloy RZ5 was often higher in new de-icing chemicals than in urea, although the form of corrosion was the same in most cases, i.e., general corrosion. {yields} Corrosion effects of the five runway de-icing chemicals on cadmium-plated and subsequently chromate-treated steel 4340 were slightly different in all three tests, but some loss of the coating layers was detected in all cases. - Abstract: Corrosion effects of five runway de-icing chemicals on aluminium alloy 2024, magnesium alloy RZ5 and cadmium-plated and subsequently chromate-treated steel 4340 were investigated by cyclic polarisation measurements, open circuit potential monitoring and cyclic chemical exposure tests. The runway de-icing chemicals included in the study contained urea, which has a long history as a runway de-icing chemical, and four new commercial de-icing chemicals, which were based on betaine and potassium formate. Corrosion effects of urea on aluminium alloy 2024 were more pronounced than those of the new de-icing chemicals. In urea, the breakdown potential, indicating the onset of pitting, was clearly distinguishable in the cyclic polarisation curve and pitting corrosion was detected on the specimen surface after all three types of tests. Weight losses during the chemical exposure tests were also higher for urea than for the other four chemicals, where pitting corrosion was only occasionally detected. The opposite was true in the case of magnesium alloy RZ5: although the alloy experienced general corrosion in each de-icing chemical included in the

  4. Corrosion behaviour of polished and sandblasted titanium alloys in PBS solution.

    Science.gov (United States)

    Burnat, Barbara; Walkowiak-Przybyło, Magdalena; Błaszczyk, Tadeusz; Klimek, Leszek

    2013-01-01

    In this work, we performed comparative studies of the effect of surface preparation of Ti6Al4V and Ti6Al7Nb biomedical alloys and the influence of endothelial cells on their corrosion behaviour in PBS (Phosphate Buffered Saline). Two different methods of surface modification were applied - polishing and sandblasting. The polished Ti6Al7Nb alloy was found to have the best resistance against general corrosion in PBS. It was characterized by the lowest corrosion rate, the widest passive range and the lowest reactivity. Both alloys prepared by sandblasting exhibited worse corrosion properties in comparison to the polished ones. This can be associated with a greater development of their surface and the presence of Al2O3 grains which caused an increase of corrosion potential but might also influence the weakening of the passive layer. Results of potentiodynamic anodic polarization indicated that more resistant to pitting corrosion was Ti6Al7Nb alloy regardless of the method of surface preparation. In those cases, anodic polarization caused only an increase of passive layer, while in the case of sandblasted Ti6Al4V alloy it caused a pitting corrosion. The results obtained allowed us to conclude that the niobium-titanium alloys had higher corrosion resistance than titanium alloys with vanadium. Moreover, it was stated that endothelial cells improved the corrosion resistance of all the titanium alloys examined.

  5. 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.

  6. 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.

  7. Localized corrosion behaviour in simulated human body fluids of commercial Ni-Ti orthodontic wires.

    Science.gov (United States)

    Rondelli, G; Vicentini, B

    1999-04-01

    The corrosion performances in simulated human body fluids of commercial equiatomic Ni-Ti orthodontic wires having various shape and size and produced by different manufacturers were evaluated; for comparison purposes wires made of stainless steel and of cobalt-based alloy were also examined. Potentiodynamic tests in artificial saliva at 40 degrees C indicated a sufficient pitting resistance for the Ni-Ti wires, similar to that of cobalt-based alloy wire; the stainless steel wire, instead, exhibited low pitting potential. Potentiodynamic tests at 40 degrees C in isotonic saline solution (0.9% NaCl) showed, for Ni-Ti and stainless steel wires, pitting potential values in the range approximately 200-400 mV and approximately 350 mV versus SCE, respectively: consequently, according to literature data (Hoar TP, Mears DC. Proc Roy Soc A 1996;294:486-510), these materials should be considered potentially susceptible to pitting; only the cobalt-based alloy should be immune from pitting. The localized corrosion potentials determined in the same environment by the ASTM F746 test (approximately 0-200 mV and 130 mV versus SCE for Ni-Ti and stainless steel, respectively) pointed out that for these materials an even higher risk of localized corrosion. Slight differences in localized corrosion behaviour among the various Ni-Ti wires were detected.

  8. Floating Lid Constructions for Pit Water Storage

    DEFF Research Database (Denmark)

    Heller, Alfred

    1997-01-01

    Seasonal storage is necessary if renewable heat sources are to be applied on a large scale. Pit water storage seems to be a cheaper alternative to steel tank storage. The lid price is the largest component of a pit water store with a cost share of about 60% of the total storage cost. Due to the l...

  9. Speed, Acceleration, Chameleons and Cherry Pit Projectiles

    Science.gov (United States)

    Planinsic, Gorazd; Likar, Andrej

    2012-01-01

    The paper describes the mechanics of cherry pit projectiles and ends with showing the similarity between cherry pit launching and chameleon tongue projecting mechanisms. The whole story is written as an investigation, following steps that resemble those typically taken by scientists and can therefore serve as an illustration of scientific…

  10. Hot microswimmers

    Science.gov (United States)

    Kroy, Klaus; Chakraborty, Dipanjan; Cichos, Frank

    2016-11-01

    Hot microswimmers are self-propelled Brownian particles that exploit local heating for their directed self-thermophoretic motion. We provide a pedagogical overview of the key physical mechanisms underlying this promising new technology. It covers the hydrodynamics of swimming, thermophoresis and -osmosis, hot Brownian motion, force-free steering, and dedicated experimental and simulation tools to analyze hot Brownian swimmers.

  11. Arne - Exploring the Mare Tranquillitatis Pit

    Science.gov (United States)

    Robinson, M. S.; Thangavelautham, J.; Wagner, R.; Hernandez, V. A.; Finch, J.

    2014-12-01

    Lunar mare "pits" are key science and exploration targets. The first three pits were discovered within Selene observations [1,2] and were proposed to represent collapses into lava tubes. Subsequent LROC images revealed 5 new mare pits and showed that the Mare Tranquillitatis pit (MTP; 8.335°N, 33.222°E) opens into a sublunarean void at least 20-meters in extent [3,4]. A key remaining task is determining pit subsurface extents, and thus fully understanding their exploration and scientific value. We propose a simple and cost effective reconnaissance of the MTP using a small lander (IEEE ICRA [6] Strawser et al. (2014) J. Hydrogen Energy. [7] Dubowsky et al. (2007) Proc. CLAWAR.

  12. Vapor Space Corrosion Testing Simulating The Environment Of Hanford Double Shell Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Gray, J. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcia-Diaz, B. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Murphy, T. H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hicks, K. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-01-30

    As part of an integrated program to better understand corrosion in the high level waste tanks, Hanford has been investigating corrosion at the liquid/air interface (LAI) and at higher areas in the tank vapor space. This current research evaluated localized corrosion in the vapor space over Hanford double shell tank simulants to assess the impact of ammonia and new minimum nitrite concentration limits, which are part of the broader corrosion chemistry limits. The findings from this study showed that the presence of ammonia gas (550 ppm) in the vapor space is sufficient to reduce corrosion over the short-term (i.e. four months) for a Hanford waste chemistry (SY102 High Nitrate). These findings are in agreement with previous studies at both Hanford and SRS which showed ammonia gas in the vapor space to be inhibitive. The presence of ammonia in electrochemical test solution, however, was insufficient to inhibit against pitting corrosion. The effect of the ammonia appears to be a function of the waste chemistry and may have more significant effects in waste with low nitrite concentrations. Since high levels of ammonia were found beneficial in previous studies, additional testing is recommended to assess the necessary minimum concentration for protection of carbon steel. The new minimum R value of 0.15 was found to be insufficient to prevent pitting corrosion in the vapor space. The pitting that occurred, however, did not progress over the four-month test. Pits appeared to stop growing, which would indicate that pitting might not progress through wall.

  13. NV - Assessment of wildlife hazards associated with mine pit lakes

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Several open pit mines in Nevada lower groundwater to mine ore below the water table. After mining, the pits partially fill with groundwater to form pit lakes. Water...

  14. Effects of chloride ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    Hui-yan Li; Chao-fang Dong; Kui Xiao; Xiao-gang Li; Ping Zhong

    2016-01-01

    The effects of Cl− ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength marten-sitic stainless steel (UHSMSS) were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl− ion concentration was found to exist (approximately 0.1wt%), above which pitting occurred. The pitting potential decreased with increasing Cl− ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting cor-rosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polariza-tion potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.

  15. Effects of chloride ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

    Science.gov (United States)

    Li, Hui-yan; Dong, Chao-fang; Xiao, Kui; Li, Xiao-gang; Zhong, Ping

    2016-11-01

    The effects of Cl- ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel (UHSMSS) were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl- ion concentration was found to exist (approximately 0.1wt%), above which pitting occurred. The pitting potential decreased with increasing Cl- ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting corrosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polarization potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.

  16. Aircraft Corrosion

    Science.gov (United States)

    1981-08-01

    allowed to dry. The area is then checked for the golden brown color which is produced by the chemical conversion material. If the work area requires...Materials, pp. 258-3074 1968. 41. W. IH. Ailor, "Seven-year exposure at Point leyes , California," "Corrosion in Natural Environments, ASTM STP 558," American... Color Units 3 Turbidity Units 0.7 pH Units 7.6 Temperature OF 76 Sp. Conductivity MMhos 425 B.O.D. (5 days at 206C) 0.2 SjV i;~-- 1201 A .9 8 ~ 8 kl

  17. Is Playing in the Pit Really the Pits?: Pain, Strength, Music Performance Anxiety, and Workplace Satisfaction in Professional Musicians in Stage, Pit, and Combined Stage/Pit Orchestras.

    Science.gov (United States)

    Kenny, Dianna T; Driscoll, Tim; Ackermann, Bronwen J

    2016-03-01

    Typically, Australian orchestral musicians perform on stage, in an orchestra pit, or in a combination of both workplaces. This study explored a range of physical and mental health indicators in musicians who played in these different orchestra types to ascertain whether orchestra environment was a risk factor affecting musician wellbeing. Participants comprised 380 full-time orchestral musicians from the eight major state orchestras in Australia comprised of two dedicated pit orchestras, three stage-only symphonic orchestras, and three mixed stage/pit orchestras. Participants completed a physical assessment and a range of self-report measures assessing performance-related musculoskeletal disorders (PRMD), physical characteristics including strength and perceived exertion, and psychological health, including music performance anxiety (MPA), workplace satisfaction, and bullying. Physical characteristics and performance-related musculoskeletal profiles were similar for most factors on the detailed survey completed by orchestra members. The exceptions were that pit musicians demonstrated greater shoulder and elbow strength, while mixed-workload orchestra musicians had greater flexibility Significantly more exertion was reported by pit musicians when rehearsing and performing. Stage/pit musicians reported less physical exertion when performing in the pit compared with performing on stage. Severity of MPA was significantly greater in pit musicians than mixed orchestra musicians. Pit musicians also reported more frequent bullying and lower job satisfaction compared with stage musicians. There were few differences in the objective physical measures between musicians in the different orchestra types. However, pit musicians appear more psychologically vulnerable and less satisfied with their work than musicians from the other two orchestra types. The physical and psychological characteristics of musicians who perform in different orchestra types have not been adequately

  18. Surface treatment and corrosion behaviour of austenitic stainless steel biomaterial

    Science.gov (United States)

    Oravcová, M.; Palček, P.; Zatkalíková, V.; Tański, T.; Król, M.

    2017-02-01

    In this article results from corrosion behaviour of austenitic stainless steel AISI 316L after different surface treatments are published. “As received” surface and surface after grinding resulted in lower resistance to pitting corrosion in physiological solution than electrochemically polished in H3PO4+H2SO4+H2O. Electropolishing also improved the surface roughness in comparison with the “as received” surface. Deposition of Al2O3 nanometric ALD coating improves the corrosion resistance of stainless steel in chloride-containing environment by shifting the breakdown potential toward more positive values. This oxide coating not only improves the corrosion resistance but it also affects the wettability of the surface, resulting in hydrophobic surface.

  19. 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.

  20. The Application of Foundation Pit Monitoring Technology to the Excavation

    OpenAIRE

    Qiu Jin; Li Fei

    2015-01-01

    The foundation pit monitoring plays an important role in the foundation pit supporting projects especially in those deep foundation pit projects. Through the whole monitoring of the foundation pit construction from the excavation to the backfill, we can learn about the forcing and deforming process of the foundation pit supporting system, and grasp the impact of external condition changes on the foundation pit. This paper takes a project in Jinan as an example to establish a specific monitori...

  1. ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DURING CORROSION PROCESS OF 8090 Al-Li ALLOY IN EXCO SOLUTION

    Institute of Scientific and Technical Information of China (English)

    J.F. Li; Z.Q. Zheng; C.Y. Tan; S.C. Li; Z. Zhang; J.Q. Zhang

    2004-01-01

    The corrosion behavior and electrochemical impedance spectroscopy ( EIS) features of 8090 Al-Li alloys in EXCO solution were investigated, and the EIS was simulated using an equivalent circuit. At the beginning of immersion in EXCO solution, the EIS is comprised by a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency, and the inductive component decreases and disappears with immersion time. Once exfoliation or severe pitting corrosion is produced, two capacitivearcs appear in the EIS. These two capacitive arcs are originated from the two parts of the corroded alloy surface, the original flat alloy surface and the new inter-face exposed to the aggressive EXCO solution due to the exfoliation or pitting corrosion.Some corrosion development features of 8090 Al-Li alloys in EXCO solution can be obtained through simulated EIS information.

  2. The corrosion inhibition of iron and aluminum by various naturally occurring biological molecules

    Energy Technology Data Exchange (ETDEWEB)

    McCafferty, E.; Hansen, D.C. [Naval Research Lab., Washington, DC (United States)

    1995-12-31

    Biological polymers that exhibit a strong affinity for metal surfaces are increasingly becoming the focus of research toward the development of environmentally friendly corrosion inhibitors. This paper deals with the use of various naturally occurring organic molecules as corrosion inhibitors for iron or aluminum. Among the organic molecules considered are catecholate and hydroxamate siderophores isolated from bacteria, the adhesive protein from the blue mussel Mytilus edulis L, and caffeic acid and chlorogenic acid. FTIR analysis, anodic polarization curves, and AC impedance measurements were used to determine the adsorption and effectiveness of the various organic molecules as corrosion inhibitors. Parabactin, a catecholate siderophore, was effective in inhibiting both the corrosion of iron in hydrochloric acid and the pitting of aluminum in 0.1 M sodium chloride. The adhesive protein from the blue mussel was also effective in inhibiting the pitting of aluminum.

  3. The corrosion of depleted uranium in terrestrial and marine environments.

    Science.gov (United States)

    Toque, C; Milodowski, A E; Baker, A C

    2014-02-01

    Depleted Uranium alloyed with titanium is used in armour penetrating munitions that have been fired in a number of conflict zones and testing ranges including the UK ranges at Kirkcudbright and Eskmeals. The study presented here evaluates the corrosion of DU alloy cylinders in soil on these two UK ranges and in the adjacent marine environment of the Solway Firth. The estimated mean initial corrosion rates and times for complete corrosion range from 0.13 to 1.9 g cm(-2) y(-1) and 2.5-48 years respectively depending on the particular physical and geochemical environment. The marine environment at the experimental site was very turbulent. This may have caused the scouring of corrosion products and given rise to a different geochemical environment from that which could be easily duplicated in laboratory experiments. The rate of mass loss was found to vary through time in one soil environment and this is hypothesised to be due to pitting increasing the surface area, followed by a build up of corrosion products inhibiting further corrosion. This indicates that early time measurements of mass loss or corrosion rate may be poor indicators of late time corrosion behaviour, potentially giving rise to incorrect estimates of time to complete corrosion. The DU alloy placed in apparently the same geochemical environment, for the same period of time, can experience very different amounts of corrosion and mass loss, indicating that even small variations in the corrosion environment can have a significant effect. These effects are more significant than other experimental errors and variations in initial surface area.

  4. Pitting Mechanism for Aluminum Electrolytic Capacitor High Voltage Foil%铝电解电容器高压电子箔点蚀机理的研究

    Institute of Scientific and Technical Information of China (English)

    王志申; 何业东; 孙志华; 刘明; 张晓云; 陆峰

    2012-01-01

    采用极化曲线和场发射扫描电镜等方法,研究了铝电解电容器高压电子箔在高温强酸性溶液中的点蚀机理.结果表明:在开路状态下铝光箔在硫酸盐酸发孔溶液中可以产生点蚀,测到自腐蚀电位就是点蚀电位;形成隧道孔后,阳极极化曲线出现点蚀电位,且点蚀过电位与隧道孔长度之间存在线性关系.根据点蚀的微电池模型及其在阳极极化下微电池的腐蚀极化图,提出产生上述现象的原因是阳极极化时带孔铝箔的表面由阴极向阳极转变,其转变的临界点即所测到的点蚀电位.%Pitting mechanism for aluminum electrolytic capacitor high voltage foil in strong acidic solution was investigated by means of polarization curve and scanning electron microscopy(SEM). The results indicate that pitting can generate on the surface of Al foil under open circuit, and its corrosion potential measured is pitting potential. Pitting potential appears on the polarization curves of Al foil with tunnel pits, and there is linear relationship between the pitting over-potential and the tunnel length. According to micro-cell model of pitting and the corrosion polarization diagrams of micro-cell, it is thought that the surface of Al foil with tunnel pits transforms from cathode to anode during anodic polarization, and the critical point of the transformation is the measured pitting potential.

  5. Study of Microbiologically Induced Corrosion Action on Al-6Mg-Zr and Al-6Mg-Zr-Sc

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria (SRB) solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It was found that the oxide film was more compact owing to the addition of Sc resulting in the open circuit potential shifting by about 100mV positively. On the other hand, it was seen that the pitting sensitivity of Al-6Mg-Zr-Sc alloy in SRB solution decreased and its microbiologically influenced corrosion resistance was improved. Pitting corrosion occurring on the surface of the two alloys under the comprehensive action of the metabolism of SRB was observed by SEM. It was obtained by EDS that the corrosion degree increased with time and corrosion was furthered by deposition of the product.

  6. 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.

  7. 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.

  8. Influence of welding speed on corrosion behaviour of friction stir welded AA5086 aluminium alloy

    Institute of Scientific and Technical Information of China (English)

    Kamran Amini; Farhad Gharavi

    2016-01-01

    The plates of AA5086 aluminium alloy were joined together by friction stir welding at a fixed rotation speed of 1000 r/min various welding speeds ranging from 63 to 100 mm/min. Corrosion behavior of the parent alloy (PA), the heat affected zone (HAZ), and the weld nugget zone (WNZ) of the joints were studied in 3.5% (mass fraction) aerated aqueous NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion susceptibility of the weldments increases when the welding speed increases to 63 and 100 mm/min. However, the value of corrosion rate in the weldments is lower than that in the PA. Additionally, the corrosion current density increases with increasing the welding speed in the HAZ and the WNZ. On the contrary, the corrosion potential in the WNZ appears more positive than in the HAZ with decreasing the welding speed. The WNZ exhibits higher resistance compared to the HAZ and the PA as the welding speed decreases. The results obtained from the EIS measurements suggest that the weld regions have higher corrosion resistance than the parent alloy. With increasing the welding speed, the distribution and extent of the corroded areas in the WNZ region are lower than those of the HAZ region. In the HAZ region, in addition to the pits in the corroded area, some cracks can be seen around the corroded areas, which confirms that intergranular corrosion is formed in this area. The alkaline localized corrosion and the pitting corrosion are the main corrosion mechanisms in the corroded areas within the weld regions. Crystallographic pits are observed within the weld regions.

  9. 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)

  10. EVIDENCE OF CORROSIVE GAS FORMED BY RADIOLYSIS OF CHLORIDE SALTS IN PLUTONIUM-BEARING MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, K.; Louthan, M.

    2010-02-01

    Corrosion and pitting have been observed in headspace regions of stainless steel containers enclosing plutonium oxide/salt mixtures. These observations are consistent with the formation of a corrosive gas, probably HCl, and transport of that gas to the headspace regions of sealed containers. The NH{sub 4}Cl films found on the walls of the sealed containers is also indicative of the presence of HCl gas. Radiolysis of hydrated alkaline earth salts is the probable source of HCl.

  11. The Effect of General Corrosion on the Guided Wave Inspection of the Pipeline

    OpenAIRE

    Zhang Jin Heng; Li Chang; Yang Yang

    2016-01-01

    The guided wave method can inspect pipelines very quickly and widely. For instance, it can inspect the overall pipelines by digging several detection pits or removing part of coating material to set the array ring. However, it will make the guided wave attenuate more seriously and make the signals hard to identify when setting the array ring on the general corrosion. In this study, the wave propagation will be discussed when the general corrosion is under the array ring and the severe localiz...

  12. Corrosion of the copper canister in the repository environment

    Energy Technology Data Exchange (ETDEWEB)

    Hermansson, H.P.; Eriksson, Sture [Studsvik Material AB, Nykoeping (Sweden)

    1999-12-01

    The present report accounts for studies on copper corrosion performed at Studsvik Material AB during 1997-1999 on commission by SKI. The work has been focused on localised corrosion and electrochemistry of copper in the repository environment. The current theory of localised copper corrosion is not consistent with recent practical experiences. It is therefore desired to complete and develop the theory based on knowledge about the repository environment and evaluations of previous as well as recent experimental and field results. The work has therefore comprised a thorough compilation and up-date of literature on copper corrosion and on the repository environment. A selection of a 'working environment', defining the chemical parameters and their ranges of variation has been made and is used as a fundament for the experimental part of the work. Experiments have then been performed on the long-range electrochemical behaviour of copper in selected environments simulating the repository. Another part of the work has been to further develop knowledge about the thermodynamic limits for corrosion in the repository environment. Some of the thermodynamic work is integrated here. Especially thermodynamics for the system Cu-Cl-H-O up to 150 deg C and high chloride concentrations are outlined. However, there is also a rough overview of the whole system Cu-Fe-Cl-S-C-H-O as a fundament for the discussion. Data are normally accounted as Pourbaix diagrams. Some of the conclusions are that general corrosion on copper will probably not be of significant importance in the repository as far as transportation rates are low. However, if such rates were high, general corrosion could be disastrous, as there is no passivation of copper in the highly saline environment. The claim on knowledge of different kinds of localised corrosion and pitting is high, as pitting damages can shorten the lifetime of a canister dramatically. Normal pitting can happen in oxidising environment, but

  13. 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.

  14. Microbial corrosion of aluminum alloy.

    Science.gov (United States)

    Yang, S S; Chen, C Y; Wei, C B; Lin, Y T

    1996-11-01

    Several microbes were isolated from the contaminated fuel-oil in Taiwan and the microbial corrosion of aluminum alloy A356-T6 was tested by MIL-STD-810E test method. Penicillium sp. AM-F5 and Cladosporium resinac ATCC 22712 had significant adsorption and pitting on the surface of aluminum alloy, Pseudomonas acruginosa AM-B5 had weak adsorption and some precipitation in the bottom, and Candida sp. AM-Y1 had the less adsorption and few cavities formation on the surface. pH of the aqueous phase decreased 0.3 to 0.7 unit for 4 months of incubation. The corrosion of aluminum alloy was very significant in the cultures of Penicillium sp. AM-F2, Penicillium sp. AM-F5 and C. resinac ATCC 22712. The major metabolites in the aqueous phase with the inoculation of C. resinac were citric acid and oxalic acid, while succinic acid and fumaric acid were the minors.

  15. Boiler and steam generator corrosion: Fossil fuel power plants. (Latest citations from the NTIS bibliographic database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-01

    The bibliography contains citations concerning corrosion effects, mechanisms, detection, and inhibition in fossil fuel fired boilers. Fluidized bed combustors and coal gasification are included in the applications. The citations examine hot corrosion, thermal mechanical degradation, and intergranular oxidation corrosion studies performed on the water side and hot gas side of heat exchanger tubes and support structures. Coatings and treatment of material to inhibit corrosion are discussed. Corrosion affecting nuclear powered steam generators is examined in a separate bibliography. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  16. 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.

  17. Corrosion resistance of premodeled wires made of stainless steel used for heart electrotherapy leaders

    Science.gov (United States)

    Przondziono, J.; Walke, W.; Młynarski, R.; Szatka, W.

    2012-05-01

    The purpose of the study is to evaluate resistance to electrochemical corrosion of wire made of X10CrNi18-8 stainless steel designed for use in cardiology treatment. The influence of strain formed in the premodeling process and methods of wire surface preparation to corrosive resistance in artificial plasma solution were analysed. Wire corrosion tests were carried out in the solution of artificial plasma. Resistance to electrochemical corrosion was evaluated on the ground of recorded curves of anodic polarization by means of potentiodynamic method. Potentiodynamic tests carried out enabled to determine how the resistance to pitting corrosion of wire changes, depending on strain formed in the premodeling process as well as on the method of wire surface preparation. For evaluation of phenomena occurring on the surface of tested steel, electrochemical impedance spectroscopy (EIS) was applied. Deterioration of corrosive properties of wire along with the increase in the formed strain hardening was observed.

  18. Inhibition of the Cu65/Zn35 brass corrosion by natural extract of Camellia sinensis

    Energy Technology Data Exchange (ETDEWEB)

    Ramde, Tambi, E-mail: t_ramde@univ-ouaga.bf [Equipe Chimie Physique et Electrochimie, Laboratoire de Chimie Moléculaire et des Matériaux, Université de Ouagadougou, 03 BP 7021 Ouagadougou 03 (Burkina Faso); Department of Industrial Engineering, University of Trento, via Sommarive 9, 38123 Trento (Italy); Rossi, Stefano; Zanella, Caterina [Department of Industrial Engineering, University of Trento, via Sommarive 9, 38123 Trento (Italy)

    2014-07-01

    In this work, the corrosion inhibition of brass was studied using natural plant extract, Camellia sinensis, in 0.1 M Na2SO4 solutions with pH 7 and pH 4. Electrochemical techniques (potentiodynamic polarization, electrochemical impedance spectroscopy) and scanning electron microscopy (SEM) were applied to study the brass corrosion behavior in presence and absence of the extract. The results indicated that the extract is a very effective corrosion inhibitor for brass corrosion process in both the acidic and neutral media by virtue of adsorption. The inhibition effect increases by time as demonstrated by the EIS monitoring for 120 h. In the blank solution the corrosion process leads to the formation of a dark oxide patina at pH 7 and induces localized corrosion morphology at pH 4. The extract presence can avoid both the dark patina and the pits formation.

  19. Effect of Colouring Process on Pitting Susceptibility of Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    S.S.Mahmoud; M.M.Ahmed

    2008-01-01

    Colouring of the austenitic stainless steel alloy (20.45% Cr, 8.57% Ni) was carried out in NaNO3-KNO3 eutectic melt without and with additions of Na2O2, NaCl and their mixtures at different temperatures ranging from 400-600℃, under open-circuit and galvanostatic anodic polarization conditions. The produced colours greatly depend on the thickness of oxide films, which in turn depends on the composition of the molten bath and its temperature. The more attractive, bright, adherent and uniform coloured oxide films can be obtained at 400, 450 and 500℃ in molten nitrate bath containing NaCl and Na2O2 mixtures. The pitting corrosion susceptibility of the coloured oxide films was tested in FeCl3 and NaCl as corrosive media. The obtained results indicate that the pitting corrosion susceptibility of the coloured oxide films greatly depends on the previous operating conditions of the colouring process of the stainless steel specimens such as the composition of molten bath, temperature and technique of colouring process.

  20. Application of two-phase flow modeling as a basis for scheduling corrosion maintenance activities in wet sour gas pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, D. [NeoCorr Engineering Ltd., Calgary, Alberta (Canada); Bich, N.N. [Shell Canada Ltd., Calgary, Alberta (Canada)

    1997-08-01

    Pipeline failures attributed to internal corrosion in the oil and gas producing industry have not been decreasing despite the many corrosion mitigation, monitoring and inspection programs implemented. This paper describes how preliminary investigations for evaluating the susceptibility of internal corrosion for wet sour gas pipelines have been based on integrating the latest knowledge in fluid flow and sour gas corrosion mechanisms. It is anticipated future efforts to correlate the onset of slug flow regime with historical corrosion and inspection data may lead to development of an improved criteria for predicting the onset of corrosive water traps and for triggering appropriate maintenance activities. This paper provides details of two corrosion failure Case Studies where application of flow modeling has improved the understanding of the operating hazards that contributed to the formation of a corrosive environment leading to high-rate initiation and growth of localized pitting corrosion. Preliminary analysis indicates slug flow pattern, and long water residence time of water within stagnant traps increases the likelihood of pitting corrosion.