Feb 29, 2012 ... Stainless-Steel Tubing . ...... Protective Coating of Carbon Steel, Stainless Steel, ... Tubing, Steel, Corrosion Resistant, Types 304 and ...... stainless steels are susceptible to pitting corrosion and crevice corrosion in a marine ...

...false Operation and maintenance of corrosion protection. 280.31 Section...31 Operation and maintenance of corrosion protection. All owners and operators of steel UST systems with corrosion protection must comply with the...

Sep 5, 1995 ... This effect resulted in decreased galvanic activity of the zinc particles for ... SCE.9 Below this potential, the corrosion of the steel is reduced. Coating B does ..... polymers as corrosion protective coatings for stainless steel.

In this paper, a corrosion resistance of stainless steel was investigated by the electrochemical measurement and the immersion test to apply them to the most corrosive part of steel structures at the water line area in the arctic ocean. Consequently, it was clarified that the crevice corrosion and the corrosion at welds covered with an oxide film on the stainless steel occurred irrespective of low temperatures near the freezing point. The stainless steel also caused considerable galvanic corrosion to carbon steel, especially at the part adjacent to the weld metal. It was shown that both the crevice corrosion on stainless steel and the galvanic corrosion on carbon steel can be prevented to occur by applying cathodic protection to the dissimilar metal joints. A pretective potential of {minus} 0.78V was required for the galvanic pair of stainless steel and carbon steel. Thus, it was concluded that a combination of stainless steel and cathodic protection was an effective countermeasure. 16 refs., 10 figs.

Volatile corrosion inhibiting (VCI) papers are a popular choice for protecting metallic corrosion. Accelerated corrosion tests were conducted to compare the effectiveness parts from of papers formulated for multimetal protection to those formulated for the protection of ferrous metals only. The tests were conducted using SAE C1010 steel panels. Chlorides and sulfur dioxide were used to accelerate the corrosion rate. The results indicate that in highly corrosive conditions, the multimetal papers provide better protection to carbon steel than the papers formulated for ferrous metals only.

NASA began corrosion studies at the Kennedy Space Center (KSC) in 1966 during the .... The evaluation of protective coatings for carbon steel, stainless steel, and .... This effect resulted in decreased galvanic activity of the zinc particles for ...

Initial and steady-state corrosion rates were determined for carbon steel, low-alloy steel, series 300 stainless steels and Ni-Cr-Fe Alloy 600 at two stations in the Northwestern Atlantic Ocean. Corrosion specimens were deployed by submersibles at depths of 3000 and 3700 meters for up to three years. The experimental conditions were flowing, semistagnant, and stagnant seawater as well as complete burial in deep-ocean sediments. Mean steady-state corrosion rates for carbon and low-alloy steels ranged from 0.02 to 2.7 mils/year in the various seawater environments. Steady-state corrosion rates in the sediments were more variable and resulted in the highest observed rates of 6.40/year for carbon steel and 6.42 mils/year for HY-80 low alloy steel. Galvanic corrosion of carbon steel in contact with stainless steel resulted in significant accelerated corrosion of the carbon steel only in the flowing seawater and sediment environments. Corrosion rates for the corrosion-resistant alloys, including the stainless steels and Alloy 600, were extremely low averaging 0.0001 mil/year for the longer exposures. Some localized pitting and underdeposit corrosion were observed on a few specimens. The presence of carbon steel in direct contact with stainless steel protected the stainless steel from localized corrosion. This research provided insight into the nature of corrosion on the deep-ocean floor. 7 figures, 6 tables.

Basic research has been made on utilization of super stainless steel as a material for condensers in thermal power plants. This steel contains more Cr or Mo than the conventional sea water resistant steel, and is superior in local corrosion resistance. The tested super stainless steels are ferrite-based steel (29 Cr-4 Mo-2 Ni steel) and austenite-based steel (20 Cr-18 Ni-6Mo-0.2 Ni steel). Sea water immersion test on joints of a super stainless steel tube and a stainless steel tube plates revealed that the tube plates require cathodic protection to prevent corrosion. A SUS316L stainless steel can be used as the tube plate when cathodic protection is used. Verification has been made on the super stainless steel for its corrosion resistance against contaminated sea water and ammonium. A long-term corrosion resistance test has made clear the levels of deposits, state of tube corrosion (no corrosion was recognized), and corrosion resistance of joints between the tube and the tube plate (SUS316L stainless steel can be used as the tube plate with cathodic protection). No damages have been found on the super stainless steel in the tests for erosion resistance, deposit attack resistance, and sand erosion resistance. 9 figs., 10 tabs.

The present project was dedicated to the corrosion information system 'CORIS' with the purpose of elaborating a knowledge-based system for the selection of protection measures against atmospheric corrosion. The range of knowledge of the system is the corrosion system unalloyed or low alloy steel/atmosphere and its purpose is the selection of protection measures for unalloyed and low-alloy steel structures exposed to the atmosphere. (orig./MM)

Prevention of crevice corrosion was studied for STS 304 stainless steel using a Mg-alloy galvanic anode in solutions with various specific resistivity. The crevice corrosion and corrosion protection characteristics of the steel was investigated by the electrochemical polarization and galvanic corrosion tests. Experimental results show that the crevice corrosion of STS 304 stainless steel does not occur in solutions of high specific resistivity, but it occurs in solutions of low specific resistivity like in solutions with resistivities of 30, 60 and 115 {Omega} {center_dot} m. With decreasing specific resistivity of the solution, the electrode potential of STS 304 stainless steel in the crevice is lowered. The potential of STS 304 stainless steel in the crevice after coupling is cathodically polarized more by decreasing specific resistivity indicating that the crevice corrosion of STS 304 stainless steel is prevented by the Mg-alloy galvanic anode

Migrating corrosion inhibitors (MCI) were developed to protect steel rebar from corrosion in concrete. They were designed to be incorporated as an admixture during concrete batching or used for surface impregnation of existing concrete structures. Two investigations are summarized. One studied the effectiveness of MCIs as a corrosion inhibitor for steel rebar when used as an admixture in fresh concrete mix. The other is a long-term study of MCI concrete impregnation that chronicles corrosion rates of rebar in concrete specimens. Based on data from each study, it was concluded that migrating corrosion inhibitors are compatible with concrete and effectively delay the onset of corrosion.

Underground steel pipes with optimal corrosion protection promote reliable operations and preserve the value of operating resources for utilities companies. Approximately 32000 km - nearly once around the world - that is the total length of the gas distribution network administered and serviced by WinKKS, the management system for documentation and analysis of corrosion protection data - a decisive tool for condition-oriented maintenance.

The corrosion rate of structural steels in the adverse marine and offshore environments affects the economic interest of offshore structures since the loss of steel may have significant impact on structural safety and performance. With more emphasis to maintain existing structures in service for longer time and hence to defer replacement costs, there is increasing interest in predicting corrosion rate at a given location for a given period of exposure once the protection coating or cathodic protection is lost. The immersion depth, salinity, steel composition and water pollution will be taken into account. Various corrosion allowances are prescribed for structural members by different standards. There are no studies to determine the appropriate corrosion allowance for steel structures in marine environment in Malaysia. The objectives of the research are to determine the nature and rate of corrosion in mm/year for steel structures in marine environment. It also tries to identify whether the corrosion rate is affected by differences in the chemical composition of the steels, and microalgae. Two sets of corrosion coupons of Type 3 Steel consisting of mild steel were fabricated and immersed in seawater using steel frames. The corrosion rate of the coupon in mm/ per year is estimated based on the material weight loss with time in service. The results are compared with recommendations of the code.

Abstract in english Passive films formed in bicarbonate solutions on carbon steel, chromium steel and high speed steel have been characterized by XPS. The passive films formed on chromium and high speed steels showed superior protective properties than those formed on carbon steel. It was confirmed by XPS that the steel composition influences the passive film composition. Chromium oxide and hydroxide, as well as molybdenum and tungsten oxides and hydroxides are present in the passive film of (more) chromium steel and high speed steel, respectively, besides iron oxide and hydroxide. The more complex composition of the oxide film on high speed steel explains its electrochemical behaviour and highest corrosion resistance.

Long-term corrosion protection of steel towers of offshore wind turbines is a great challenge for the wind power industry. The contribution explains the causes of damage and the various attempts to prevent it. (orig.)

The galvanic corrosion of commercially pure titanium coupled with 18.8 stainless steel was studied in various kinds of corrosive media. In reducing acids, although the corrosion potential of titanium itself was in the active range and less noble than that of stainless steel, it was shifted into the passive range by coupling with stainless steel. Thus titainium was anodically protected and its corrosion rate decreased remarkably, whereas the corrosion rate of stainless steel remained unchanged. For instance, titanium and stainless- steel couples were perfectly resistant in 10% hydrochloric acid, 10% sulfuric acid, and 10% oxalic acid solutions at room temperature, in which uncoupled titanium was corroded. This phenomenon of anodic protection was also observed in boiling 1% hydrochloric acid, 1% sulfuric acid, and 0.5% oxalic acid solutions. In oxidizing acids, such as nitric acid, the galvanic corrosion was negligible because the potentials of titanium and stainless steel were in their own passive ranges, and that of the couple was also in the passive range of both metals. In the case of boiling 99% acetic acid, no galvanic corrosion was observed, either. In neutral chloride solutions, such as 3% sodium chloride solution, the potential of couple fluctuated and the direction of galvanic current changed irregularly because of the instability of protective film on stainless steel. However, the galvanic current was always less than 1 mu A/cm/sup 2/, so that the galvanic corrosion was also negligible. (auth)

Galvanic corrosion on the least nobel material can be a serious problem when two dissimilar materials are coupled together in a seawater piping system. Typical examples of such couples are carbon steel or copper nickel alloys coupled to stainless steel or titanium. Mathematical modeling and field experience show that the use of an insulating spool piece may efficiently reduce the galvanic corrosion when the attack has the character of general corrosion, but less efficiently when the attack is more localized. In the latter case the use of internal cathodic protection is a more effective protection against galvanic corrosion than the spool piece.

The authors assess the protective properties of three inhibitors based on pyridines and aminonitriles in the corrosion protection of natural gas field production equipment against the effects of hydrogen sulfide solutions of different pH. The tests were made on 65G steel wire. The resistance of the steel to corrosion and crack propagation as well as hydrogen embrittlement is given for each of the inhibitors.

At the 6th Corrosion Meeting in Frankfurt, selected experts described the state of knowledge of the materials and corrosion protection systems of flue gas purification systems in powerstations, waste incinerators and sludge combustion plants, including the steel chimneys after combustion plants. The author's work in this Meeting Handbook is divided into basic information on the materials and corrosion protection systems used and the representation of practical experience from the last ten years, with consequences for the future. (orig./HP)

Corrosion of steel by alternating current was investigated as far back as the early 1900`s. These early studies and others in the 1950--60`s indicated that AC corrosion of steel was only a fraction of an equivalent amount of direct current (i.e., less than 1% of a like amount of DC) and in addition was controlled to negligible levels with cathodic protection applied to industry standards. In 1986 however, an investigation into a corrosion failure on a high pressure gas pipeline in Germany indicated that the sole cause of the failure was AC corrosion. This corrosion failure on an otherwise well protected pipeline resulted in several laboratory and field studies which indicated, that above a certain minimum AC current density, standard levels of cathodic protection will not control AC corrosion and AC mitigation is required to prevent further corrosion. Several other corrosion anomalies were discovered at coating holidays during the follow-up investigations in Germany. The authors have investigated several corrosion occurrences on pipelines in Ontario during the last 2--3 years which appear to be caused by AC corrosion. This presentation traces the literature record on AC electrolysis from the past to the present and discusses the key parameters which determine the likelihood of corrosion attack. Several case histories of suspected AC corrosion will be discussed and guidelines on how to assess whether or not a pipeline is susceptible to AC corrosion will be offered.

A variety of coatings based on electrosynthesized polypyrrole were deposited on zinc coated steel in presence or absence of ultrasound, and studied in terms of corrosion protection. Cr III and Cr VI commercial passivation were used as references. Depth profiling showed a homogeneous deposit for Cr III, while SEM imaging revealed good surface homogeneity for Cr VI layers. These chromium-based passivations ensured good protection against corrosion. Polypyrrole (PPy) was also electrochemically deposited on zinc coated steel with and without high frequency ultrasound irradiation in aqueous sodium tartrate-molybdate solution. Such PPy coatings act as a physical barrier against corrosive species. PPy electrosynthesized in silent conditions exhibits similar properties to Cr VI passivation with respect to corrosion protection. Ultrasound leads to more compact and more homogeneous surface structures for PPy, as well as to more homogeneous distribution of doping molybdate anions within the film. Far better corrosion protection is exhibited for such sonicated films. PMID:22516111

The corrosion of metals represents a terrible waste of both natural resources and money, the failure of some stainless steel resulting from pitting corrosion is some times considered a technological problem, consequently, much effort has been expended in attempting to understand and overcome the corrosion therefore, many stainless steel/ environment combinations have been studied. The use of heterocyclic compounds as inhibitors is one of the most practical methods for protection against corrosion in acidic media. In continuation of our work on development of macrocyclic compounds as corrosion inhibitors we report in our study the corrosion inhibiting behaviour of organic compound Methoxy-2-Allyl-4 Phenol (MAP) containing coordinating and conjugation groups, at three forms (natural, polymerized and chemically treated) on the corrosion of stainless steel in phosphoric acid. This study focused on the comparison for corrosion inhibition proprieties of these different applications using potentiodynamic polarization, electrochemical impedance spectroscopy and SEM. The specimen was evaluated to determine change in his corrosion potential and resistance polarization; These MAP products have exhibited corrosion inhibition by maintaining a high resistance polarization (low corrosion rate) in each application. These results reveal that this compound is efficient inhibitor in all forms; the most inhibition efficiency is obtained with polymerized form. To further evaluate the test data, the steel surfaces were analyzed using scanning electron microscopy, SEM observations of surface treated concrete confirmed presence of inhibitor on the steel surfaces. (authors)

The authors present results of their investigation of the influence of hydrogen sulfide on crack growth in the corrosion fatigue of 32Kh3NMFA steel in a 3 percent NaCl solution and of the protective properties of the title inhibitor as well as its influence on the role of hydrogen embrittlement in corrosion fatigue crack propagation.

In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

The corrosion performance of two types of weldable martensitic stainless steel seamless pipe for pipeline application is investigated. 11Cr steel pipe developed for sweet environment gives better resistance to CO{sub 2} corrosion than the 13Cr martensitic stainless steel for OCTG. 12Cr steel pipe developed for light sour environment shows good SSC resistance in a mild sour environment and superior CO{sub 2} corrosion resistance at high temperature and high CO{sub 2} partial pressure condition. The suitable condition for the 11Cr steel pipe and the 12Cr steel pipe in sweet environment, and the critical pH and H{sub 2}S partial pressure for the 12Cr steel pipe welded joint in sour environment are clarified. Both welded joints have superior resistance to hydrogen embrittlement under the cathodic protection condition in sea water.

This work dealt with the evaluation of galvanic corrosion rate in a corrosion cell having annular gap of 0.5 mm between carbon steel 1018 and alloy 600 as a function of temperature and boron concentration. Temperature and boron concentration were ranged from 110 to 300 .deg. C and 2000{approx}10000 ppm, respectively. After the operating temperature of the corrosion cell where the electrolyte was injected was attained at setting temperature, galvanic coupling was made and at the same time galvanic current was measured. The galvanic corrosion rate decreased with time, which was described by corrosion product such as protective film as well as boric acid deposit formed on the carbon steel with time. From the galvanic current obtained as a function of temperature and boron concentration, it was found that the galvanic corrosion rate decreased with temperature while the corrosion rate increased with boron concentration. The experimental results obtained from galvanic corrosion measurement were explained by adhesive property of corrosion product such as protective film, boric acid deposit formed on the carbon steel wall and dehydration of boric acid to be slightly soluble boric acid phase. Moreover the galvanic corrosion rate calculated using initial galvanic coupling current instead of steady state coupling current was remarked, which could give us relatively closer galvanic corrosion rate to real pressurized water reactor

For corrosion protection of 55% Al-Zn-coated steel, a dense polypyrrole (PPy) film is electrochemically formed on 55% Al-Zn-coated steel in an acidic tartrate solution under constant current control. The film potentially consists of an inner layer of aluminium and/or zinc oxide and an outer PPy layer doped with tartrate anions. The PPy layer can maintain passivation of 55% Al-Zn-coated steel in a 3.5wt.% NaCl aqueous solution and protected the steel for several hours. The doping of molybdate anions into the PPy-tartrate film greatly improved the film's protective properties.

This short paper seeks to provide a summary of the main knowledge about the general corrosion of carbon steels in high temperature water. In pure water or slightly alkaline deaerated water, steels develop a protective coating of magnetite in a double layer (Potter and Mann oxide) or a single layer (Bloom oxide). The morphology of the oxide layer and the kinetics of corrosion depend on the test parameters controlling the solubility of iron. The parameters exercising the greatest influence are partial hydrogen pressure and mass transfer: hydrogen favours the solubilization of the magnetite; the entrainment of the dissolved iron prevents a redeposition of magnetite on the surface of the steel. Cubic or parabolic in static conditions, the kinetics of corrosion tends to be linear in dynamic conditions. In dynamic operation, corrosion is at least one order of magnitude lower in water with a pH of 10 than in pure water with a pH of 7. The activation energy of corrosion is 130 kJ/mol (31 kcal/mol). This results in the doubling of corrosion at around 300 deg C for a temperature increase of 15 deg C. Present in small quantities (100-200 ppb), oxygen decreases general corrosion but increases the risk of pitting corrosion - even for a low chloride content - and stress corrosion cracking or corrosion-fatigue. The steel composition has probably an influence on the kinetics of corrosion in dynamic conditions; further work would be required to clarify the effect of some residual elements. (author). 31 refs., 9 figs., 2 tabs.

Galvanic action between zinc and steel is an important property that contributes to the high corrosion resistance of zinc-coated steels. Quantitative knowledge of the galvanic throwing power (i.e., the area of the steel surface that is not covered with zinc but is galvanically protected by the coating in the surrounding area) is of practical importance to the effective application of zinc-coated steel products. The present investigation reported results of a study of the galvanic protection distance determined for the steel/zinc galvanic couple under various laboratory and field conditions.

Elastomer coatings (rubber) are industrially used to protect phosphoric acid storage tanks against corrosion. Rubber constitutes a barrier against the penetration of H3PO4 to metallic surface. Coatings damage induces both acid infiltration and steel corrosion. In this concept, acoustic emission (AE) monitoring technique could be used for the detection of coatings damage as well as for steel corrosion under the coating. In the present work AE was coupled to electrochemical measurements (EM) for rubber damage evaluation and steel corrosion on three types of steels (XC48, E20 and A60) at room temperature in concentrated phosphoric acid (30% P2O5) contaminated by Cl-, F-, SO42-. Electrochemical behaviour of steels was studied and characterized by potentiodynamic curves and polarization resista...

The preoxidation and corrosion tests were carried out on the steels and test alloys of the types AISI 310 and 309 as well as on the alloy 800 H. Test results show that the layers which were purposefully applied to the steels of the type AISI 310 protect t...

Researchers are developing polymer-based coating systems to reduce scaling and corrosion of air-cooled condensers that use a geothermal fluid spray for heat transfer augmentation. These coating systems act as barriers to corrosion to protect aluminum fins and steel tubing; they are formulated to resist the strong attachment of scale. Field tests have been done to determine the corrosion and scaling issues related to brine spraying and a promising organometallic polymer has been evaluated in salt spray tests.

With regard to steel structures in wavy sea areas, tests and discussions were given on sand erosion, corrosion protection effect of cathodic protection, and behavior of electric potential in steel materials. Site tests were carried out at a breaker zone pier in the Namisaki Marine Research Facilities in Ibaraki Prefecture, where water depth is about -5 m and current flow rate ranges from 0 to 50 cm/s. Depth to the sea bottom changes by 3 to 4 m annually due to effects of waves. In the tests, test pieces were attached to a steel pipe shaft, and upon completion of the tests, corrosion rate and corrosion preventive rate were measured. Continuous measurements were carried out on electric potential of the steel pipe shaft. The result of the tests may be summarized as follows: the corrosion rate near the sea bottom ranged from 0.3 to 0.4 mm a year, which is greater than in corrosion in ordinary sea water; the corrosion rate of a test piece attached with a sheath was 0.03 to 0.05 mm a year, showing the influence of sand erosion; the corrosion preventive rate for test pieces applied with cathodic protection was 98 to 99%, proving good corrosion prevention against sand erosion. 6 refs., 8 figs., 1 tab.

Cathodic corrosion protection should ensure safe operation of underground steel pipelines and should contribute to maintaining the value of this plant. It is therefore extremely important to keep these devices in constantly faultless and optimum operation. Therefore the effectiveness of the cathodic protection of pipelines must be monitored. The DVGW Work Sheet GW 10 determines the guidelines for the setting to work and monitoring of cathodic corrosion protection of storage containers and steel pipelines installed underground. This is a report on experience with this Work Sheet at Thuega AG. (orig.).

Active cathodic corrosion prevention has proven its worth as a protective provision against corrosion damage to underground steel piping systems. The protection achieved is checked and documented by means of regular measurements of potential along the pipe. Since manual evaluation of the data obtained is both time-consuming and susceptible to error, there was a need for development of a system for automatic data adquisition and processing. This article reports the results of this project. (orig.).

Steel producers use various organic and inorganic coatings to protect cold-rolled steel (CRS) sheets from corrosion during shipment and storage. It is well known that CRS sheets can be protected from corrosion by galvanizing, phosphating, chromating, topcoating with organic, or their combinations. The chromate rinsing is particularly effective for preventing white rusting of galvanized steel. But there is an increasing interest in a replacement for the chromating process because of environmental and health concerns. The objective of the present work is to develop a chrome-free conversion coating for steel sheets. Various carboxylic acids and their salts have been studied for coating phosphated electrogalvanized (EG) steel sheets, including 10-undecenoic acid (UA), oleic acid (OA), and other fatty acids such as stearic acid (SA) and palmitic acid (PA). When they were used alone, or subsequently coated with resin, they could produce a highly hydrophobic surface and improve the corrosion resistance. Thiols such as 1-octadecanethiol (ODT) can form a self-assembled monolayer on metal substrates. This close-packed monolayer could provide an excellent corrosion resistance for EG steel sheets. It was capable of withstanding 50˜60 hours of salt spray test (SST) although its thickness was only a few nanometers. The EG steel itself usually started rusting only after 2˜4 hours of salt spray. In another coating system, thiols were mixed with a conventional resin to improve the corrosion resistance of EG steel. This new technique gave 100˜120 hours of corrosion resistance. When the resin was applied directly on EG steel surface, its corrosion resistance was less than 72 hours. It was shown that further optimization of this technique increased the corrosion resistance to 200 hours and more in the standard SST.

Corrosion tests were carried out on austenitic AISI 316L and 1.4970 steels and on MANET steel up to 2000 h of exposure to flowing (up to 2 m/s) Pb/Bi. The concentration of oxygen in the liquid alloy was controlled at 10{sup -6} wt%. Specimens consisted of tube and rod sections in original state and after alloying of Al into the surface. After 2000 h of exposure at 420 and 550 deg. C the specimen surfaces were covered with an intact oxide layer which provided a good protection against corrosion attack of the liquid Pb/Bi alloy. After the same time corrosion attack at 600 deg. C was severe at the original AISI 316L steel specimens. The alloyed specimens containing FeAl on the surface of the alloyed layer still maintained an intact oxide layer with good corrosion protection up to 600 deg. C.

Flue gas desulfurization systems (FGDs) are operated in severely corrosive environments that cause sulfuric acid dew-point corrosion. The corrosion behavior of low-alloy steels was tested using electrochemical techniques (electrochemical impedance spectroscopy, potentiodynamic tests, potentiostatic tests), and the corrosion products were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical results showed that alloying W with small amounts of Sb, Cu, and Co improves the corrosion resistance of steels. The results of surface analyses showed that the surface of the steels alloyed with W consisted of W oxides and higher amounts of Sb and Cu oxides. This suggests that the addition of W promotes the formation of a protective WO3 film, in addition to ...

The corrosion products formed on carbon and weathering steels exposed in marine, industrial and rural environments in the United States for 16 years have been investigated using Moessbauer spectroscopy, Raman spectrometry and chemical analysis. Moessbauer spectroscopy was used to measure the fraction of each oxide in the corrosion coatings and micro-Raman spectrometry was used to locate and map the oxides to 2 {mu}m spatial resolution. Moessbauer spectroscopy identified the corrosion products in the weathering steels as 75% goethite, 20% lepidocrocite and 5% maghemite. Raman analysis showed that the corrosion products generally formed as alternating layers containing different oxides. For the weathering steels the protective inner-layer closest to the steel substrate consisted of nano-sized goethite ranging in size from 5-30 nm and having a mean particle size of about 12 nm. The outer-layer close to the coating surface, consisted of lepidocrocite and goethite with the former oxide being most abundant. Electron probe micro-analysis measured significant chromium in the goethite close to the steel substrate. Comparison of the goethite in the corrosion products was made with synthetic chromium substituted goethite with nearly identical microstructural characteristics being recorded. It is concluded that chromium inclusions in the goethite are important for formation of a nano-phase oxide layer which may help protect the weathering steel from further corrosion.

The effects of galvanic coupling between D6AC steel, 6061-T6 aluminum, Inconel 718, and graphite-epoxy composite material (G/E) in 3.5% NaCl were studied. Measurements of corrosion potentials, galvanic currents and corrosion rates of the bare metals using weight-loss methods served to establish the need for corrosion protection in cases where D6AC steel and 6061-T6 aluminum are galvanically coupled to G/E in salt water while Inconel 718 was shown to be compatible with G/E. Six tests were made to study corrosion protective methods for eliminating galvanic corrosion in the cases of D6AC steel and 6061-T6 aluminum coupled to G/E. These results indicate that, when the G/E is completely coated with paint or a paint/polyurethane resin combination, satisfactory protection of the D6AC steel is achieved with either a coat of zinc-rich primer or a primer/topcoat combination. Likewise, satisfactory corrosion protection of the aluminum is achieved by coating it with an epoxy coating system.

The melt-crystallized poly(phenyl) ether ether ketone (PEEK) polymer was overlaid on crystalline zinc phosphate (Zn [center dot] Ph) conversion coating-deposited and nondeposited cold-rolled steels at 400 C in air or in N[sub 2] environments. The ability of these coatings systems to protect the steel against corrosion was evaluated from the rate of cathodic delamination of the coating layer from the steel. Because the cathodic reaction, H[sub 2]O + 1/20[sub 2] + 2e[sup [minus

The corrosion rate of tubular grade L-80 carbon steel under downhole conditions of a northern oil field of Kuwait was investigated. This was done using the injection seawater, formation water and a 50:50 mixture of both waters in the presence of commercially available corrosion inhibitor, scale inhibitor, and biocide products separately and in combination with each other. The main objective of this study was to investigate the effect of the corrosion inhibitor and its interaction with the scale inhibitor and the biocide, as seen in the corrosion rate of L80 carbon steel. This was done using the manufacturers' recommended dosage levels of the corrosion inhibitor, scale inhibitor and biocide. The corrosion rates were measured by linear polarization. Tests were conducted using the rotating cylinder electrode method with rotational speeds of 1000 and 2000 rpm at 80 deg. C. The seawater results indicated that the corrosion-scale inhibitor and biocide-scale inhibitor combinations provided the best protection at both rotation speeds. In formation water, the effects of rotation speed were more apparent with higher corrosion rates of L-80 carbon steel accompanying higher shear forces. In the 50: 50 mix waters and the formation water, the corrosion-scale inhibitors-biocide combination provided the best protection at both rotational speeds under downhole conditions of a northern oil field of Kuwait. (authors)

NiCr coatings were deposited on some boiler tube steels by High Velocity Oxy Fuel spraying process using LPG as fuel gas. Hot corrosion behaviour of uncoated as well as HVOF sprayed specimens was studied in an environment of Na2SO4–60%V2O5 at 900°C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion. SEM/EDAX, XRD and EPMA techniques were used to analyse the corrosion products. The NiCr coating found to be very effective in decreasing the corrosion rate of the uncoated steels. The NiCr coated samples showed no cracking or spalling of oxide scale during hot corrosion. The formation of protective oxide scale as observed may be contributing to the development of hot corrosion resistance in the coatings studied, which mainly consists of oxides of NiO, NiCr2O4 and Cr2O3.   

A novel method for coating surface polishing has been applied for a systematic study of the localized individual coating regions of the Al–Si coated steel. Polarization, EPMA and corrosion potential measurements have been applied for determination the ability of each region for protection of underlying steel. The susceptibility of the Si rich region, interface region and Fe-rich region to pitting corrosion decreases in the following order: Si-rich region>Fe-rich region>interface region. The elemental distribution of Si and Fe plays an important role in the corrosion behavior of coating film and influences its susceptibility to pitting process.   

...Administration [A-428-815, A-580-816] Corrosion-Resistant Carbon Steel Flat Products...the antidumping duty (AD) orders on corrosion-resistant carbon steel flat products...Reviews of the Antidumping Duty Orders on Corrosion-Resistant Carbon Steel Flat...

...731-TA-616 and 618 (Third Review)] Corrosion-Resistant Carbon Steel Flat Products...revocation of the countervailing duty order on corrosion-resistant carbon steel flat products...Korea and the antidumping duty orders on corrosion- resistant carbon steel flat...

...731-TA-616 and 618 (Third Review)] Corrosion-Resistant Carbon Steel Flat Products...revocation of the countervailing duty order on corrosion-resistant carbon steel flat products...Korea and the antidumping duty orders on corrosion- resistant carbon steel flat...

...constructed of stainless steel or other equally corrosion resistant metal and in such manner...constructed of stainless steel or other equally corrosion resistant metal. This equipment...constructed of stainless steel or other equally corrosion resistant metal. This equipment...

After several years of research in laboratory, the ability to detect active corrosion by Acoustic Emission technique has been successfully proved. The benefit of using this technology has been recognised by chemical and petrochemical industry to detect stress corrosion cracking and pitting of stainless steel alloy. The purpose of this paper is to present an extension of this technique to coated low alloy carbon steel. In this case, the mechanism of corrosion is well-known uniform corrosion but the damage appears in restricted area where the passive protection is no more efficient. The goal is to make a diagnosis on the propagation of the localised corrosion or to verify the integrity of the corrosion protective layer on components during in service conditions. This need arises from un-predicted failures of industrial equipment due to fast propagation of corrosion damage, after the destruction of coating. This paper presents several situations where CORPAC technology has been applied, not only to detect and locate damage from corrosion, but also to validate repairs and evaluate the efficiency of corrosion protection. (authors)

The geologic sequestration of CO{sub 2} is a proposed method to limit greenhouse gas emissions and has been the subject of many studies in the last decade. Wellbore systems achieve isolation of the storage reservoir through a combination of steel (generally carbon steel) and Portland cement. CO{sub 2} leakage along the steel-cement interface has the potential to accelerate corrosion. We conduct experiments to assess the corrosion risk at cement-steel interface under in situ wellbore conditions. Wellbore interfaces were simulated by assemblies constructed of J55 mild steel and Portland class G (Epoxy was used in this study to separate) cement and corrosion was investigated in supercritical CO{sub 2} saturated brines, (NaCl = 1 wt%) at T = 50 C, pCO{sub 2} = 1200 psi with interface gap size = 100 {micro}m and {infinity} (open surface). The experiments were carried out in a high-pressure, 1.8 L autoclave. The corrosion kinetics were measured employing electrochemical techniques including linear polarization resistance and electrochemical impedance spectroscopy techniques. The corrosion scales were analyzed using secondary electron microscopy, back scattering electron microscopy, energy dispersive spectroscopy and x-ray diffraction. Corrosion rates decreased as time with or without interface gap. In this case corrosion rates are controlled by scale protectivity through the interface gap. Scaled steel corrosion rates were two orders of magnitude less compared with fresh steel. The corrosion scale is pseudo crystalline at the open interface. Well-crystallized scale was observed at interface gap sizes 100 {micro}m. All corrosion scales were composed of iron carbonates.

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 corrosion rates, when biofilm and corrosion products cover the steel surface. However, EIS might be used for detection of MIC. EN is a suitable technique to characterise the type of corrosion attack, but is unsuitable for corrosion rate estimation. The concentric electrodes galvanic probe arrangement initiates localised corrosion on the anode and seems applicable to evaluate the risk of MIC. Hydrogen permeation measurements are very useful to monitor hydrogen induced cracking accelerated by MIC.

The results of laboratory and comparative industrial research study of sucker rods made of the 20N2M and 15NZM brand steels are presented. The rods were developed at the Ochersk machine building factory for opeation in a corrosive environment. Based on the analysis conducted, it is determined that sucker rods made of the 15N3M brand steel are somewhat more applicable to highly corrosive operational environments as compared to the 20N2M steel. An analysis of the basis for this reasoning is presented and it stems from conclusion concerning the construction of the columns sring and their equipping with protective couplings.

Steel is one of the most versatile materials known to mankind. It is used in a variety of applications. In many of these applications, it is exposed to the atmosphere, leading to rust formation, which weakens structures made using steel. Hence, protection is important. The popular methods to prevent corrosion are painting, galvanizing, electroplating etc. The widely used Chrome etching process is very effective in corrosion inhibition as well as in hardening the steel. But, Chromium and its compounds are highly placed among the toxic chemicals listed under pollution prevention initiatives of the EPA. Hence, it was decided to find alternatives to this process.

Reinforced concrete structures such as bridges, parking decks, and balconies are designed to have a service life of over 50 years. All too often, however, many structures fall short of this goal, requiring expensive repairs and protection work earlier than anticipated. The corrosion of reinforced steel within the concrete infrastructure is a major cause for this premature deterioration. Such corrosion is a particularly dangerous problem for the facilities at NASA s Kennedy Space Center. Located near the Atlantic Ocean in Florida, Kennedy is based in one of the most corrosive-prone areas in the world. In order to protect its launch support structures, highways, pipelines, and other steel-reinforced concrete structures, Kennedy engineers developed the Galvanic Liquid Applied Coating System. The system utilizes an inorganic coating material that slows or stops the corrosion of reinforced steel members inside concrete structures. Early tests determined that the coating meets the criteria of the National Association of Corrosion Engineers for complete protection of steel rebar embedded in concrete. Testing is being continued at the Kennedy's Materials Science Beach Corrosion Test Site.

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.

The influence of 16 different geothermally related environments on a number of potentially useful steels was examined for both general and localized corrosion and at ambient and 150/sup 0/C. Variation in chloride concentration of 1 to 20% generally demonstrated only minor aggressiveness in acidified solutions. In general, the presence of H/sub 2/S raised the corrosion rate. However, very low concentrations (10 ppM) indicated higher rates than in saturated brines. This is rationalized on the basis of the inability to develop a semi-protective film at the low H/sub 2/S concentration. The corrosion rate for the Cr-Mo steel was unexpectedly high at ambient, but improved substantially at 150/sup 0/C. The Ni-Cu-Nb steel consistently demonstrated excellent resistance in all environments, except the 10 ppM H/sub 2/S at ambient. At 150/sup 0/C there were no exceptions to its superior performance. Maximum pit depth studies, analyzed statistically, indicated that the Ni-Cu-Nb alloy was the most resistant to localized attack. A clean (low inclusions) Mn-C and a clean vacuum melted steel ranked well. A comparison of two almost identical Mn-C steels one clean and one dirty clearly indicated the deleterious influence of inclusions on the tendency for localized corrosion. The profiling of a protected section of a creviced or pitted sample helped to delineate the nebulous line of demarcation between general and localized corrosion in these low alloy steels.

Thermal sprayed aluminium (TSA) coatings are widely used for the protection of steels from aqueous corrosion, including offshore structures and components that are exposed to seawater immersion, tidal and splash zone environments. In this paper, the influence of deposition parameters of aluminium coating on its corrosion properties was studied. For different application parameters of TSA coatings, the thickness, the microstructure and corrosion properties were determined. Determination of thickness was performed according to EN ISO 2064:2000 relating to the definition and determination of the thickness of metallic and other inorganic layers. Microstructure was determined using a Olympus GX50 optical microscope. The corrosion properties of the coatings were compared using an accelerated electrochemical corrosion test method. Electrochemical studies were carried out in accordance with the requirements of ASTM standard G 102 - 89. The TSA coating performance was quantified in terms of its corrosion potential and the corrosion rate, which was estimated from Tafel polarisation resistance measurements.

...atmospheric corrosion, vandalism...Operating conditions of the pipeline...Potential natural forces inherent...spills due to corrosion, gouges...pipeline's coating & corrosion condition, and steel...butane, Natural Gas...

...Corrosion-Resistant Carbon Steel Flat 8/1/09-7...1/09-7/31/10 Steel Nails, A-570-909...31/10 Sulfanilic Acid, A-570-815...Corrosion-Resistant Carbon Steel Flat Products, C- 1...Stainless Steel Sheet and...

Austenitic stainless steels type 304L, 316L and 310Nb are largely used as structural materials for equipments handling nitric acid media in reprocessing plants. In almost all nitric media, these materials, protected by a chromium(III) oxide rich layer, remain in their passive state. However, in some particular nitric media, their corrosion potential may be shifted towards their transpassive domain. In this domain, they can suffer intergranular corrosion, even though they are not sensitized owing to their very low carbon content. The corrosion potential of the steel depends greatly on the cathodic reaction involved in the oxido-reduction process between the elements Fe, Cr, Ni of the steel and the oxidizing species of the medium. Three cases of an increase in the corrosion potential can be ...

Abstract in english The atmospheric corrosion behaviour of galvanised steel sheets and steel/55%Al-Zn system with or without different paint schemes was analysed. The samples were exposed to the atmosphere in the experimental station of CIDEPINT. Periodically, all specimens were visually inspected and sampling was made to evaluate the general behaviour of the protective system. Normalised physicochemical and EIS tests were performed on each specimen. The corrosion products were characterised (more) by SEM. The data included in the present work concern to the first step of exposure (800 days). The foreseen whole period of testing is 7 years. From the present results may be concluded that: 1) on the analysed industrial environment, the bare sheets of steel/55%Al-Zn system have suffered less damage than the bare galvanised ones, 2) chloride and sulphide are present in the corrosion products denoting the aggressiveness of environment, and 3) in general, all duplex systems have shown a fairly good protective behaviour.

Introduced to utilities in the late 1960's, weathering steel' appeared to offer a way to reduce structure weight and maintenance of lattice towers through the application of bare, high strength steel that had natural corrosion resistance. Weathering steel found wide application in lattice and tubular transmission structures. Through its service life, however, the weathering steel showed evidence of continuing corrosion rather than the expected protection from corrosion. A consortium of utilities was formed to investigate the impact on structure reliability of the continuing corrosion of the steel beyond initial expectations. Through the completion of field surveys and laboratory tests, projected lifetime corrosion rates, structural integrity and potential sealer/penetrant systems were evaluated. The investigation has shown that existing lattice and tubular structures fabricated from weathering steel will provide continued reliable service with minimal maintenance programs. Weathering Steel remains practical for new lattice and tubular structures provided steps are taken during the design process to minimize the retention and collection of moisture between and around metal contact surfaces and during the operation of the line to minimize vegetation encroachment around structures.

Electrochemical potentiodynamic polarization studies were conducted for a variety of ferrous and nonferrous metals in methylphosphonic difluoride. Studies were also made of the effects of organic inhibitors on the corrosion rates of 1,020 steel, type 316L, and type 304 stainless steel, and magnesium in methylphosphonic difluoride. Chemical weapons in the US include binary munitions in which two components are kept in separate compartments until activation. These munitions must be stockpiled for long periods of time (up to 30 years) and then must operate reliably when the need arises. The principal cause of failure will be corrosion of the storage container by the highly corrosive methylphosphonic difluoride (DF). The objectives of this study were to: investigate the kinetics and mechanisms of corrosion of Al 6061-T6 and candidate metal alloys in DF; establish effective corrosion inhibitors; and ultimately incorporate or immobilize inhibitors into coatings that provide protection above the liquid line.

Structural materials development is a key issue for the realization of advanced lead cooled nuclear systems. One specific challenge for fuel claddings and heat exchanger tubes is the so called fretting corrosion by flow induced vibrations. To address this matter, the ferritic-martensitic steel T91 and the austenitic steel 1.4970 were submitted to fretting corrosion test in liquid lead. Preliminary indications concerning the role of temperature and time/number of cycles in the fretting corrosion process, were achieved performing fretting corrosion tests at 450/500degreeC and for 150/600h (5.4x106/2.16x107cycles). The interaction between fretting (mechanical wear) and corrosion processes (oxidation/dissolution) in liquid lead was also investigated. The experiments revealed that protective ox...

The oxidation of nitrided and nitrocarburised steel provides useful protection against wear and corrosion, and is consequently used in industries. For some time now, solid electrolyte sensors have been used to improve the adjustment and control of treatment conditions. Investigations have been carried out to study the relationship between the treatment parameters, the structure of the nitrided layer, and the corrosion behaviour of the treated surfaces. (orig.)

Corrosion and abrasive wear are two important aspects to be considered in numerous engineering applications. Looking at steels, high-chromium high-carbon tool steels are proper and cost-efficient materials. They can either be put into service as bulk materials or used as comparatively thin coatings to protect lower alloyed construction or heat treatable steels from wear and corrosion. In this study, two different corrosion resistant tool steels were used for the production of coatings and bulk material. They were processed by thermal spraying and super solidus liquid phase sintering as both processes can generally be applied to produce coatings on low alloyed substrates. Thermally sprayed (high velocity oxygen fuel) coatings were investigated in the as-processed state, which is the most co...

The corrosion resistance of any metallic material depends on the environment to which it is exposed. DMR-1700 steel is a material for structural applications that has been recently developed at Defence Metallurgical Research Laboratory by changing the chemistry of alloying elements. Therefore, a detailed understanding of its corrosion characteristics under different environmental conditions is essential. In the present paper, we report the results of a systematic corrosion study that was carried out on the new steel to determine the effect of the environment on the protective nature of the oxide scale that forms on its surface under different environmental conditions. Furthermore, the oxide scale as well as the resistance to pitting and crevice corrosion were studied in various environments. The surface morphologies of the corroded steels were observed under a scanning electron microscope (SEM) to determine the nature of the corrosion. On the basis of studies by different techniques, DMR-1700 steel is recommended for the manufacture of components used in various systems in conjunction with the application of an appropriate protective coating to improve its resistivity to corrosion.

The corrosion property of carbon steel was evaluated using an autoclave under CO(2)-saturated water phase and water-saturated CO(2) phase with impurities (O(2) and SO(2)) at 80 bar CO(2) and 50 °C to simulate the condition of CO(2) transmission pipeline in the carbon capture and storage (CCS) applications. The results showed that the corrosion rate of carbon steel in CO(2)-saturated water was very high and it increased with adding O(2) in the system due to the inhibition effect of O(2) on the formation of protective FeCO(3). It is noteworthy that corrosion took place in the water-saturated CO(2) phase under supercritical condition when no free water is present. The addition of O(2) increased the corrosion rates of carbon steel in water-saturated CO(2) phase. The addition of 0.8 bar SO(2) (1%) in the gas phase dramatically increased the corrosion rate of carbon steel from 0.38 to 5.6 mm/y. This then increased to more than 7 mm/y with addition of both O(2) and SO(2). SO(2) can promote the formation of iron sulfite hydrate (FeSO(3)·3H(2)O) on the steel surface which is less protective than iron carbonate (FeCO(3)), and it is further oxidized to become FeSO(4) and FeOOH when O(2) is present with SO(2) in the CO(2)-rich phase. The corrosion rates of 13Cr steel were very low compared with carbon steel in CO(2)-saturated water environments with O(2), whereas it was as high as carbon steel in a water-saturated CO(2) phase with O(2) and SO(2). PMID:21049923

In the manufacture of sulphuric acid more stringent environmental standards and operation economics have forced the industry to improve product utilization, energy efficiency and reliability. A key to improving both the thermal efficiency and reliability is the use and/or development of more corrosion resistance materials including stainless steels, especially in the parts of the plant that handle the condensed acid. Application of more corrosion resistant material requires a better understanding of the corrosion mechanism involved in concentrated H2SO4-H2O (>90 wt.%) solutions. While corrosion kinetics of carbon steel, the traditional material of construction, are relatively well understood, this is much less true in the case of the cyclic active-passive corrosion of stainless steels. Models proposed to explain the cyclic active-passive corrosion involve a periodic formation of either a protective metal sulphate film or an insoluble sulphur layer. To better understand the reactivity and/or passivity of stainless steel in concentrated H2SO4-H2O solutions a study employing immersion and electrochemical techniques, including rotating electrodes, was conducted in order to clarify the following: (1) The state of stainless steel passivity. (2) The conditions in which passivity is stable. (3) The role played by the major alloying elements in establishing and maintaining the passive state. The study involved evaluating the corrosion behaviour of stainless steels S30403 and S43000 along with iron, chromium and nickel in 93.5 wt.% H2SO4 at temperatures between 25--80°C. Major discoveries of the study include: (1) A content of 17--18 wt.% chromium is sufficient to anodically passivate S43000 as the potential is made more noble. Passivity is not stable and requires anodic polarization. (2) Alloyed nickel plays an active role in improving the corrosion resistance of stainless steel. A content of 8 wt.% nickel is sufficient promote a periodic passivation of the base Fe-(17--18)wt.% Cr stainless steel under open-circuit conditions which reduces the corrosion rate by at least an order of magnitude. (3) The electrolysis of concentrated H2SO4-H 2O solutions involves a potential-dependent reduction of H2SO 4 molecules to sulphur-containing species with an oxidation state lower than six (6). The various reduction products have a significant effect on the stainless steel corrosion resistance. (4) Successful modelling of the corrosion of nickel has been accomplished by using a galvanic interaction between a noncontinuous nickel sulphide (NiS) deposit, formed in situ, and the uncovered nickel metal. (5) Successful modelling of the active-passive corrosion of S30403 has been accomplished using a galvanic interaction between NiS(Ni) and S43000.

Provisions of the Clean Air Act Amendments of 1990 will further restrict the use of high solvent-content paints beginning in 1996, requiring the U.S. Army Corps of Engineers to replace some of the coatings now used to protect steel from corrosion in atmos...

Passivation films on both the aluminum and titanium surfaces ... proved inherently resistant to attack by all of the extreme service aircraft ... Coatings are also required to protect acoustic honeycomb sandwich parts .... in figure 2, using Ti-6A1-4V titanium bolts and silver-plated A286 corrosion-resistant steel nuts. Centered ...

ZrO2 coatings for corrosion protection were deposited on 304 stainless steel by sol-gel method using zirconium propoxide as precursor and densified in air and in oxygen-free (argon or nitrogen) atmospheres. XRD and IR data of the films were practically independent of the atmosphere used in the densi...

Corrosion protection performance of a completely soluble polyaniline-dodecylbenzenesulfonic acid salt (PANI-DBSA) on C45 steel has been studied with electrochemical impedance and potentiodynamic measurements. Chloroform is the most suitable solvent to process the pristine PANI-DBSA because of neglig...

In this study, preparation and electrochemical corrosion protection studies of a series of polyimide-Clay nanocomposite (PCN) materials were first presented. Subsequently, the as-prepared PCN materials were characterized by FTIR, XRD and TEM studies. In-situ monitoring for redox behavior of as-prepared PCN materials was identified by UV-visible and CV studies. It should be noted that PCN coating was found to reveal advanced corrosion protection effect on cold-rolled steel (CRS) electrode as compared to that of neat non-electroactive polyimide coating based on series of electrochemical corrosion measurements in 5 wt% NaCl electrolyte. Enhancement of corrosion protection of PCN coatings on CRS electrode may be interpreted by following two possible reasons: (1) redox catalytic capabilities (i...

CORIS is an integrated computerized information system for corrosion and corrosion protection. It is made of databases covering corrosion, materials specification, physical properties of the corrosion media, the corrosion literature and two expert systems (a) materials behavior in a sulfuric acid environment and (b) pitting corrosion behavior of stainless steels in chloride media. A user-friendly interface enables the use of the system without any specific computer knowledge. The modular development of the system enables the link of different software packages under the same graphic user interface. The user`s own knowledge and data can be implemented into the system. Thus CORIS is an open system which handles data delivered by the developers and data input by the users. The system includes about 350 pure substances with 10,000 mixtures and 1,800 materials.

Background: The problems with water wall corrosion have been accelerating over the last years. There are a number of reasons for this. Originally mild steels were successfully used in power plant water walls. The magnetite layer that forms at the fire side of the tubes when the boiler is taken into operation protected from corrosion attack. The fuels at that time (oil, coal, gas) were not able to break down the magnetite by corrosion. In addition, there were no restrictions for pollutions and for the combustion itself that could contribute to corrosion attack. The usage of fossil fuels has decreased substantially over the last 25 years, not least by environmental reasons. As a replacement a number of different kinds of bio mass fuels are used. These are typically more or less corrosive and the magnetite layers are attacked. The corrosion is often supported by reducing conditions as a result of the restrictions of the NO{sub x}-pollution. Also the waste fuelled boilers have huge corrosion problems. This has been the case for the last 25 years but nowadays the number of such plants is so much higher and the service data have been turned up. Corrosion protection of the water wall tubes started to be successful in the beginning of the seventies by the introduction of the composite tube. Such tubes are fabricated by mild steel or a low alloy core and corrosion resistant austenite steel or nickel base as an about 2 mm thick corrosion protective coating. Weld cladding of the water wall tubes was introduced in the 1980's as a significantly cheaper alternative to the composite tubes. Thermal spraying and refractory protection are other methods. These corrosion protection methods have not always been effective. For example, depending on incorrect materials selection, incorrect performance and incorrect method selection for the current corrosion or erosion attack. Therefore, there is a need for increased knowledge of which protection method and material that will work economically for a given situation. In the first phase of the present project a literature survey concerning water wall corrosion protection methods was carried out [1]. Advantages, disadvantages and possibilities by the use of refractories, composite tubes, thermal spraying, hybrid coatings and weld cladding were investigated. An experience survey of problems with and protection of, water wall corrosion in Swedish plants was conducted as well. In an experimental part of the project six different weld clad materials were tested in water walls of five different boilers, representing different types of operation and fuel data. The test materials consisted of some conventional and newly developed weld clads for high temperature corrosion. These trials gave many interesting results but the exposure time was only one year of operation. A second phase of the project has now been carried out. In this study the test materials has been service exposed for another year. In addition, the literature and the experience surveys have been updated. Literature survey: There are some recent developments of water wall corrosion protection methods. One way is to flame spray relatively thick layers onto water wall sections. Then these sections were heat treated by induction heating such as the spray layers sintered see Figure 0.1 below. The sinter material consisted of 15 % Cr, 4,3 % Si, 3.1 % B and 2,5% Mo which gave very high hardness, HV 815. Three years service exposure of test panels gave no significant corrosion at all whereas carbon steel tubes exposed at the same time corroded 1.5 mm. In addition, the output of the boiler increased as a result of flame spray + sintering method. The reason is that refractory, with lower heat transfer properties, otherwise should be the solution for the water wall corrosion

...Administration [C-580-818] Certain Corrosion-Resistant Carbon Steel Flat Products...countervailing duty order on certain corrosion-resistant carbon steel flat products...either clad, plated, or coated with corrosion-resistant metals such as zinc,...

as stress corrosion. The tensioner was fabricated from. 18 Ni maraging steel of Rockwell .... cell, cervice or galvanic corrosion. ... ment often cause stress corrosion cracking. Sensitized austenitic stainless steel crack at room temperature ...

The weathering steel is a low alloy steel added by a little amount of Cu, Cr, Ni, P and so forth and it was developed by the US Steel Corporation in 1930s. A distinctive feature of this steel is as follows, namely though it has an approximately same mechanical properties as the plain steel, when it is left exposed as an uncovered state in the atmosphere, a dense protective coating called the `stabilizing rust` is naturally formed on the surface, so that a corrosion propagation thereafter is restrained. There are 2 kinds of the steel of this type. Namely, one is no phosphorous type which does not contain the phosphorous and is used for the welding structures, and the other is the phosphorous containing type which is more excellent in an atmosphere corrosion resistance and is used for the sheet such as the roof and wall. The weathering steel can not always be used in any atmospheric environments. It is necessary to pay attention using especially under the conditions of the coast zone and the places where the wetting occurs all the time. In this paper, as one of the corrosion measurement technologies to evaluate a rust stability of the weathering steel quantitatively, a principle of the electrochemical alternating current impedance is explained, and then an application example for a development of the nondestructive quantitative diagnosis method for a rust stability of the weathering steel by adopting this technology is interpreted. 6 refs., 11 figs.

Pieces of 304L stainless steel, alumina-coated by plasma spraying, were placed during one week at about 1170K in the furnace of the Waste-to-Energy plant of Limoges, France. The resistance against corrosion was only slightly improved compared to non-coated alloy. The origin of this unsatisfactory result lies in the cracking of the coating that occurred when the pieces were introduced in the furnace, due to the great difference in the Coefficient of Thermal Expansion (CTE) of alumina and 304L steel. However, the plasma-sprayed alumina coatings themselves appear as impervious enough to provide an efficient protection of this alloy against the very corrosive atmosphere of the incinerator.

A pre-treatment system consisting of a nanostructured titania interlayer loaded with an inhibitor and a hybrid silicate film deposited on the TiO2 layer is shown to provide protection against active corrosion of mild steel. A nanostructured TiO2 interlayer was prepared on the mild steel surface via controllable hydrolysis of titanium alkoxide. To further improve this pre-treatment, the hybrid silicate film was synthesized from tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane precursors. The morphology and structure of the titania interlayer and hybrid silicate film were characterized with atomic force microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. The corrosion performance of the coatings was examined using electrochemical techniq...

Since its invention by M. U. Schoop in the beginning of the 20th century, thermal spray has been used for corrosion protection applications in naval, on-shore, submerged and atmospheric environments. Thermally sprayed coatings of zinc, zinc alloys, aluminum and aluminum alloys are currently the most popular materials used for active corrosion protection of steel and concrete, which can be applied using either of the widely known thermal spray processes of combustion wire or electric arc wire. In the oil and gas exploration and production industry, corrosion protection applications using these technologies have evolved since the early sixties. Thermal spray technology has successfully been used to protect steel-based materials from corrosion in many different fields of application like platforms and pipelines. The most used material in the oil and gas industry is TSA (Thermally Sprayed Aluminum) coating. TSA coatings, with a lifetime of 25 to 30 years, require no maintenance except for cosmetic reasons when painted. The surface temperature of a TSA can go as high as 480 deg C. Although TS (Thermal Spray) is an older process, the number of applications and the number of m{sup 2} it is applied to is still increasing resulting from its maintenance-free and reliable active corrosion-protection features. (author)

Corrosion protection of stainless steel (13% Cr) coated with poly(ortho-ethoxyaniline) (POEA) has been investigated. The layers of POEA were synthesised from sulphuric and phosphoric acid solutions by means of cyclic voltammetry. The protecting properties of the layers in supporting electrolytes were investigated by monitoring the open circuit potential (Eoc) vs. time, and by electrochemical impedance spectroscopy (EIS). It was found that polymer layers provide corrosion protection, i.e. they help to stabilise the potential of the metal in the passive potential region. The protective properties of POEA layers have shown to be superior to polyaniline (PANI) layers, which is explained by a denser morphology of POEA. The behaviour of POEA obtained on stainless steel, examined by EIS, is diffe...

Since water knows different ways to penetrate into insulation systems, insulated metal surfaces are often attacked by corrosion. In order to avoid such damage, it is essential that water is prevented, as far as possible, from entering into the material. Adequate structural measures and vapour barriers are described in the 'AGI-Arbeitsblaetter'. In the case of high corrosion attack, the anticorrosive - suitably coatings or wrappings - should be applied directly on the metal surface. A long-term protection of chromium nickel steels against pitting and stress corrosion cracking can be successfully achieved by applying aluminium foils. (orig.).

The evolution of atmospheric corrosion of MnCuP weathering steel in a simulated coastal-industrial atmosphere was investigated by weight gain, SEM, XRD, and electrochemical measurements. The results indicate that the corrosion kinetics divides into two stages with a higher corrosion rate in the first stage and a lower rate in the second stage. The increased amount of @a-FeOOH indicates an improved resistance of the rust. The rust enhances initially and then stabilizes the cathodic process, but the anodic process tends to be inhibited. The EIS results indicate that the protective ability of the rust layer can be evaluated by the charge transfer resistance.

This article discusses methods for corrosion protection of mine shaft construction elements used in the Voroshilovgradugol' coal mines. Chemical properties of mine water in the Voroshilovgradugol' mines are investigated: pH level ranges from 6.8 to 8.6, the mineral content in water ranges from 1500 to 2400 mg/dm/SUP/3. The mean corrosion rate of steel elements in mine shafts ranges from 0.2 to 0.3 mm/years. Methods of corrosion protection by paints are evaluated. The following paints are described: the EhF-094 ground paint, and the KhS-759, KhV.774 and EhF-1219 paints. The following aspects are discussed: painting, drying, number of paint layers, methods for testing paint protection quality, layer thickness, paint composition, types of hardeners. Protective influence of paints is evaluated.

The review of materials and protective coatings for constructions working in aggressive chemical conditions have been done. The new trends and solutions have been performed. Manufacturing and properties of Si-B protective coatings in comparison with other corrosion resistant materials have been described. It has been shown the better anticorrosive properties of elaborated Si-B coatings manufactured in the diffusion powder process than specified for stainless steels dedicated for working in chemical aggressive conditions. (author). 2 tabs.

Corrosion tests of CrN-coated steels were conducted in liquid lead-bismuth (Pb-Bi) at 450°C and 550°C for 3000 h to investigate the applicability of CrN coating to a liquid Pb-Bi environment. CrN coatings on F82H (Fe-8Cr-2W-0.3V-0.04Ta-0.1C) and 316SS exhibited good compatibility in liquid Pb-Bi during corrosion test at 450°C. The CrN coating layer suffered heavy damage such as cracking and spalling, and showed no effectiveness as a protective layer in corrosion test at 550°C. Nickel and chromium in 316SS dissolved into Pb-Bi through the damaged coating layer at 550°C. It is considered that stresses caused by the difference of thermal expansion coefficients between CrN and steels led to cracking and spalling of the CrN coating through corrosion attack by liquid Pb-Bi at 550°C.   

Corrosion tests were carried out in recycle apparatures to prepare cooling-water treatment. The corrosion behaviour of unalloyed steel St 38b-2 in dependence on m-value of water was tested. The corrosion-inhibiting effect of sodium polyphosphate, zinc sulfate, 1-hydroxy-1,1-diphosphonic acid (HEDP) and the trisodium salt of HEDP and polyacrylate and their combinations in water with m-value 1.0-1.5 mmole per litre was tested in comparison with unalloyed steel. The corrosion rate increases strongly below a m-value of 2.2 mmol per litre. Sodium polyphosphate, sodium polyphosphate/zinc sulfate and zinc sulfate-polyacrylate show good protection features in water with m-value 1.0-1.5 mmole per litre. The trisodium salt of HEDP has an insufficient effect. (orig.).

Corrosion protection and monitoring are important factors in the design and management of pipelines. This paper discusses methods for predicting corrosion rates and variation of corrosion along a pipeline and how this can influence the strategy for material selection and planned operation of the line. Corrosion monitoring as a tool in corrosion protection programs should be considered in this perspective. The non-intrusive FSM (Field Signature Method) technology for internal corrosion monitoring may influence the material selection and planned corrosion protection for a pipeline. This paper discusses how a well-designed corrosion monitoring system can make the low cost material option of carbon steel/inhibitors more attractive from an operational and safety point of view. This FSM technology is also discussed as to how the FSM technology can be used for optimization of the pipeline`s inspection program, contributing to a more cost-effective operation and an extended life of the pipeline. The FSM technology is briefly presented, with examples of applications and field data.

...Certain Corrosion-Resistant Carbon Steel Flat Products from the Republic of Korea...antidumping order on corrosion-resistant carbon steel flat products (CORE) from the Republic...respondents) of the subject merchandise: Dongbu Steel Co., Ltd., (Dongbu), Dongkuk...

This research addresses the problem of localised corrosion of stainless steel PEMFC bipolar plates. The susceptibility to pitting and crevice corrosion of austenitic AISI 304 stainless steel has been investigated both by post-mortem microscopic analysis of the end-plates of a laboratory single-cell and by studies of electrochemically corroded stainless steels, in the presence of specially-designed crevice-formers simulating the operating conditions of a PEMFC. This work is based on optical and scanning-electron microscopies as well as potentiostatic and potentiodynamic measurements. The crevice-formers we considered were: Teflon, graphite and AISI 304. The samples, coupled to the crevice-formers have been tested in aqueous solutions containing Cl{sup -}, SO{sub 4}{sup 2-} and F{sup -}. From the E-log i plot, the values of corrosion, pitting, crevice and protection potential have been obtained and perfect and imperfect passivity conditions have been identified. (author)

The corrosion behaviour of nitrogen-implanted (with and without Ti-coating) 4145 steel was investigated using the potentiodynamic technique in a 0.5M sodium acetate/acetic acid buffer (pH 5.0) solution. Nitrogen ions (N+2) were implanted at 100 keV with doses ranging from 1 × 1016 to 3 × 1017 ions cm-2. Parameters such as polarization resistance, anodic and cathodic Tafel slopes along with corrosion rates were evaluated. The best results were obtained with a dose of 3× 1017 ions cm-2. Surface morphology studied by scanning electron microscopy revealed fewer pits in Ti-coated 4145 steel. Moreover, it also suggested an increase in Ep = Epass - Epit compared to uncoated steel, thus protecting the surface from active corrosion. EDXA analysis was also carried out to study the constituents and possible mechanism of pitting.

The inhibition effects of 2-amino-5-mercapto-1,3,4-thiadiazole (2A5MT) and 2-mercaptothiazoline (2MT) on mild steel corrosion in 1.0M H2SO4 were studied with potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy techniques. It was shown that both 2A5MT and 2MT act as good corrosion inhibitors for mild steel protection. The high inhibition efficiencies were attributed to the simple blocking effect by adsorption of inhibitor molecules on the steel surface. The effects of the presence of extra NH2 group and N atom in 2A5MT on the ability to act as corrosion inhibitors were investigated by theoretical calculations.

Long-term performance of CO2 storage reservoirs will require that wells (injection, monitoring, and pre-existing) continue to provide isolation of the buoyant CO2 plume. Short-term leakage concerns are driven by the quality of the well completions, particularly placement of Portland cement. However, operational and CO2-injection induced stresses in the reservoir may introduce small defects in the well isolation system, allowing migration of small quantities of CO2 and brine. Evidence for such leaks has been observed in a CO2-enhanced oil recovery well (Carey et al. 2007) and in a natural CO2 reservoir (Crow et al. 2010). The key question in long-term performance is whether these leaks will grow as wellbore materials degrade or whether carbonate precipitation reactions will self-heal the defects. In this study, we focus on the interface between steel casing and Portland cement. In a properly completed well, Portland cement provides a protective, alkaline environment for carbon steel that precludes the possibility of external corrosion. The protective cement can be damaged either by the formation of small gaps at the interface, known as microannuli, or by the carbonation of cement which eliminates cement alkalinity. To investigate these issues, we conducted experiments on cement-steel composites at conditions ranging from atmospheric to high-pressure to determine the susceptibility of steel to corrosion in the presence of well-bonded cement, carbonated cement, and cement separated from the steel by varying gap distances. The presence of cement greatly reduces corrosion rates of steel because an iron carbonate scale forms rapidly and provides a mass-transfer barrier. Similarly, a small gap at the cement-steel interface provides a mass-transfer barrier. Our results show that scale formation provides a more significant barrier to corrosion and that even small gaps (corrosion rates are initially very low until CO2 penetrates to the steel-cement interface. Corrosion rates then rise as the passivating oxide layer on steel is destroyed but then fall again as a carbonate scale forms. The degree of protection is enhanced with thicker cement. With time, this carbonate scale develops to the extent that it provides almost as much protection as in the unaltered cement-steel system. Carey, J.W. et al. (2007) International Journal of Greenhouse Gas Control, Vol. 1, pp. 75-85. Crow, W, Carey, J.W., et al. (2010)International Journal of Greenhouse Gas Control, Vol. 4, pp. 186-197.

At the Institute for Corrosion Protection (Institut fur Korrosionsschutz) in Dresden, the CaCl2 test was developed to test high-alloyed CrNiMo steels and NiCrMo alloys and was applied for pitting and crevice corrosion resistance tests of those materials and their weldments. This test was carried out as a potentiostatic test at 0.2VSCE in a solution of 4.5 mol/l CaCl2 with an initial pH value of 3.2. Investigations on the influence of filler material, heat treatment and varying heat inputs per unit length of the welds confirm the applicability of the test. With reference to the results from a round-robin test carried out by a study group of the GfKORR working committee Corrosion Protection of Iron and Steel (Korrosionsschutz von Eisen und Stahl) on material grade 2.4605 (alloy 59) and its w...

Reusable launch vehicles located by the ocean are subject to harsh seacoast environments before launch and immersion after splashdown at sea and towback to the refurbishment facility. High strength aluminum and non-corrosion resistant steel alloys are prone to general corrosion and pitting due to galvanic couples and protective coating damage. Additional protection of structural materials with thermally sprayed pure aluminum coatings was evaluated for plasma, arc spray and high velocity oxy-fuel (HVOF) processes. Comparisons are made for corrosion rates of various coated aluminum alloy and steel substrates when exposed to ASTM B-117 neutral salt fog testing and also to beach exposure tests performed at Kennedy Space Center, Florida. Recent development work involved the use of high deposition rate thermal arc-spray equipment. The use of an inverter power supply reduced powdering and enhanced operator visibility. Deposition rates of 45.36--68.04 kilograms/hour are obtainable using 4.76--6.35 millimeter diameter wire electrodes.

Onshore gas transmission lines are conjointly protected against external corrosion by cathodic protection (CP) and organic coatings. If both protection systems are simultaneously faulty, the pipe may be subjected to local loss of protection criteria. Consequently, the development of a corrosion due to the ground intrinsic corrosiveness may occur. To guarantee an optimal and safe use of its 31000 km buried gas transmission network, Gaz de France regularly inspects its pipelines. When indications of metal damage are suspected, excavations are realized to carry out a finer diagnosis and, if necessary, to repair. Whenever, corrosions are encountered, although it occurs very scarcely, it is necessary to evaluate its degree of gravity: activity, mechanism, and kinetics. Among corrosion defects, it is indeed essential to differentiate those active, from those older inactive at the time of excavation, since those last ones may possibly have been annihilated, by a PC reinforcement for instance. Eventually, the identification of the corrosion mechanism and its associated rate will provide an assessment of the risks encountered by other sections of the pipeline similar to that excavated. This study investigates to what extent the degree of gravity (activity, kinetics) of a corrosion can be determined by the characterization and identification of its associated corrosion products. Moreover, it will attempt to relate it to the close environment features as well as to the operating conditions of the pipe. The preliminary results presented in this paper consist in a laboratory study of the time evolution of corrosion products formed on the surface of ordinary low carbon steel samples. The specimens have been previously subjected to various polarization conditions in various aqueous media. The selected solutions are characteristic of ground waters. The main parameters considered for the definition of the media were its initial chemical composition, pH and dissolved gas composition. The corrosion products were characterized by Raman spectroscopy, SEM and X-rays diffraction. In-situ tests with the Raman spectrometer were carried out to monitor the corrosion products evolution with time. (authors)

Uniform Corrosion · Galvanic Corrosion · Concentration Cell Corrosion · Pitting Corrosion ... Metals corrode because we use them in environments where they are chemically unstable. ... Her husband is wearing stainless steel eyeglasses.

Steel in concrete is protected against corrosion by the high pH value of the concrete. The passivity can however be broken if chloride ions penetrate into the concrete. It is presumed that a certain amount of chloride is needed to activate the steel. This value is called the threshold level. Even though many attempts have been performed no reliable value has been found. One of the reasons for this is probably that the threshold value is influenced by the humidity of the concrete. At very high humidity the transport of oxygen to the steel surface is slow and at low humidity the electrical resistance increases. The aim of this investigation has been to determine at what humidity the corrosion rate reaches its highest value. With this as a background new tests can be performed to predict the chloride threshold value. The results indicate that it most probably do exist a threshold value for each concrete quality. At chloride contents above the threshold value the steel looses its passivity. If severe corrosion takes place or not is however strongly dependent on the humidity of the concrete. In a close interval around 95 % relative humidity the steel is attacked by pitting corrosion when the threshold value is exceeded. At lower and higher humidity the passivity is incomplete and the corrosion rate in most cases marginal. Future investigations concerning chloride threshold values is recommended to be performed at a relative humidity of 95 % and by using reference samples according to proposed procedure.

...procedure used to apply the wear and corrosion protective surface coating to attach...incorrect procedure to apply the wear and corrosion protective surface coating was used...procedure used to apply the wear and corrosion protective surface coating to...

The duplex stainless steels are characterized by two phase structures composed of a mixture of austenite and ferrite phases. They offer high toughness, good weldability, satisfactory corrosion protection, excellent stress corrosion cracking resistance and high strength. Because of these characteristics, these steels have been widely used in various applications such as oil, gas, and chemical industries. Duplex stainless steels generally have suffered embrittlement when exposed at elevated temperature, i.e. above 300 C. To avoid this embrittlement, conventional duplex stainless steels are subject to solution treatment followed by water quenching in the final stage of production or fabrication, which limits the size of products. Kim et al. have recently reported that embrittlement can be greatly reduced by the partial or full replacement of Mo by W in 22Cr-base duplex stainless steels. For the processing of duplex stainless steel, fusion welding is a major fabrication method for corrosion resistant applications. Therefore the welding behavior of these materials has to be fully defined. The purpose of this study is to investigate the effect of Mo substitution by W on the impact property of simulated heat affected zones in 22Cr duplex stainless steels. Structural transformation associated with Mo substitution by W in HAZ has been also investigated on W-containing alloys and conventional 3% Mo duplex stainless steel.

9-12 % Cr steels are of high interest for the application as heat-exchanger tubes in power generation stations. Indeed they possess a high thermal conductivity and favourable mechanical properties at temperatures up to 650 deg. C. However, even though conventional ferritic-martensitic 9-12 % Cr steels are from a mechanical point of view designed for service temperatures up to 650 deg. C, their use at such high temperatures is rather limited in corrosive environments. One solution could consist in protecting these steels by suitable corrosion resistant coatings. Pack cementation is one of the easiest and cheapest coating processes for high temperature applications. Yet, for ferritic-martensitic steels, the coating temperature can lie at 650 deg. C maximum. Above this limit, the decomposition of the martensite is accelerated, and the mechanical properties of the material would be deteriorated. The present work consisted in coating the 9 % Cr steel P91 and the 12 % Cr steel HCM12A without modifying their microstructure. Therefore, the coating process was either carried out at 650 deg. C or combined with the heat treatment of the ferritic-martensitic steel. Due to the low coating temperature, aluminide coatings were developed first. Later, a two step Cr+Al coating was obtained. The corrosion resistance of the developed coatings was tested at 650 deg. C for 1000 h in a simulated coal firing atmosphere composed of: 14 % CO{sub 2}, 10 % H{sub 2}O, 1 % O{sub 2}, 0.1 % SO{sub 2}, 0.01 % HCl (bal. N{sub 2}). The corrosion behaviour of the coated samples showed a better resistance than the bare materials. Furthermore, the comparison was extended to aluminide coatings obtained by Fluidized Bed Chemical Vapour Deposition (FBCVD) on 9-12 % Cr steels. Eventually, the corrosion resistance was compared with bare and coated austenitic steels as well as the nickel-based alloy IN 617. (authors)

The application of anti-corrosion, abrasion-resistant coatings on low cost substrate materials such as mild steel offers an attractive alternative to the use of expensive alloys which are required for some components of fossil energy conversion systems. Chemical vapour depostion (CVD) is a means of producing a number of refractory coatings, such as titanium diboride, which may provide the necessary protection from the hostile environments generated by fossil energy conversion. The experimental conditions required to form titanium diboride coatings on coupons of carbon steel sheet were investigated in Phase 1 of this project. In Phase 2 cylindrically-shaped specimens of steel were coated with TiB/sub 2/. Sublayers of electrodeposited nickel and titanium carbide as well as controlled slow cooling were required to prevent flaking of the coating. Tests being conducted on these specimens indicate that TiB/sub 2/ coatings applied by CVD provide good protection against corrosion by sulphurous gases at 800/sup 0/C. 8 figs., 3 tabs.

Corrosion inhibition of stainless steel due to a sulfate-reducing bacteria (SRB) biofilm in seawater was studied. By atomic force microscopy, a layer of fish-scale-like biofilm was found to form as stainless steel coupons were exposed to the culture media with SRB, and this biofilm grew more and more compact. As a result, coupons' surface under the biofilm turned irregular less slowly than that exposed to the sterilized culture media. Then, physicoelectric characteristics of the electrode/biofilm/solution interface were investigated by electrochemical impedance spectroscopy (EIS), and the coverage of the biofilm as well as the relative irregularity of coupons' surface was also recorded by EIS spectra. Finally, anodic cyclic polarization results further demonstrated the protective property of the biofilm. Therefore, in estimation of SRB-implicated corrosion of stainless steel, not only the detrimental SRB metabolites but also the protective SRB biofilm as well should be taken into account.

An Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass with a diameter of 5 mm was prepared with the copper-mold-casting method. The corrosion resistance of this amorphous steel in sulfuric-acid solutions was determined by electrochemical measurements. The passive film formed on the surface of the alloy after immersion in the 0.5-mol/l H2SO4 solution for 1 week was analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical measurements show that the corrosion resistance of the amorphous steel in the 1 mol/l-H2SO4 solution is superior to a stainless steel (SUS 321), and is almost the same as Ti6Al4V, which shows that the amorphous steel has an excellent corrosion resistance in sulfuric-acid solutions. As the concentration of the sulfuric-acid solutions increases from 0.5 mol/l to 4 mol/l, the corrosion resistance of the amorphous steel decreases. The XPS result reveals that a bilayer structure of protective film formed on the surface of the amorphous steel in a H2SO4 solution. The compositions of the inner part of the film are MoO2, Cr2O3, CoO, and FeO, and those of the outer film are MoO3, Cr(OH)3, Co(OH)2, and Fe(OH)3.

The corrosion behaviors of zinc-rich coating with various zinc contents, ranging from 0 to 60 volume percent, in thin organic coatings (below 5mm) were characterized by electrochemical impedance spectroscopy (EIS), free corrosion potential (Ecorr) measurement and cycle corrosion test (CCT). It was verified that both coatings with 60 volume percent of zinc powder and without zinc powder showed good corrosion resistance mainly due to the cathodic protection and barrier effect, respectively. On the other hand, coatings with an intermediate concentration (10-40vol.%) of zinc powder was not successful in protecting a steel substrate efficiently. To improve anticorrosion property of zinc-rich coating, the surface modification of zinc particle was carried out with derivatives of phosphoric and ph...

Thick titanium nitride coatings, which have high hardness, were obtained by gas tunnel type plasma reactive spraying. In this study, the corrosion behavior of the thick TiN coatings was investigated using the electrochemical polarization measurement in 1 M hydrochloric (HCl) solution at room temperature of 295 K. The polarization curve of stainless steel (SUS304) was also measured in order to clarify the effect of corrosion resistance of TiN coatings on the substrates as protective layer. The results showed that the TiN coating could protect the substrate surface from corrosion. It also revealed that the corrosion resistance of TiN coatings was improved as the thickness of TiN coatings was increased.

The work-over of oil and gas wells is generally not caused by uniform corrosion, but by localized corrosion such as pitting and/or flow induced localized corrosion (FILC), very often also called erosion corrosion. Therefore, to decide on appropriate mitigation methods the understanding of the mechanisms of localized corrosion is indispensable. One mechanism which still needs considerable research is the mechanism of FILC, specifically the initiation of FILC. For the first time fracture mechanical properties of scales from wet corrosion were considered with respect to the initiation steps of flow induced localized corrosion of steel under conditions of scale forming corrosion processes. Fracture mechanical data for iron carbonate scales from carbon dioxide corrosion, assessed by first principle considerations, were compared with their own experimental data in a failure mode diagram which correlates the tendency of scale spalling with scale thickness related critical strains. Inhibitors influence the fracture mechanical properties of corrosion product scales by reducing their thickness, porosity and intrinsic growth stresses. The destruction and spalling of iron carbonate scales is primarily the effect of intrinsic stresses. Extrinsic stresses like wall shear stresses in flowing media are generally too small to contribute much to the local destruction of scales. FILC is initiated at sites of local spalling if critical flow intensities prevent re-formation of protective scales.

The corrosion of reinforcing steel embedded in concrete causes cracks and delamination in the concrete. The application of impressed current cathodic protection utilizing electrically conductive polymer concrete to distribute the current across concrete bridge deck surfaces is gradually becoming a standard practice in the highway industry. In order to protect the bridge substructures, a sprayable electrically conductive polymer concrete coating is being developed. This thin coating has a very low resistivity and can distribute the cathodic protection current across the concrete surfaces that are to be protected.

The corrosion behavior of ceria/titania coated 304 stainless steel (304 SS) was studied by anodic polarization measurements in 0.05 N NaCl. Coatings were prepared by sol-gel methods, were approximately 0.5 {micro}m thick and bonded well to the substrate. The as-received stainless steel suffers sensitization at the coating cure temperature of 900 C and a 500 mV decrease in pitting potential results. When the coating is present, however, despite sensitization of the substrate, the pitting potential is about the same as for the as-received stainless steel. The latter result indicates that the coating does protect the underlying metal from pitting corrosion. Following polarization, coated samples show significantly fewer pits than as-received stainless steel and resist crevice attack.

The electrochemical behaviour in sulphuric acid of two austenitic stainless steels (AISI 304 L and AISI 321) modified by sulphur ion implantation has been studied. Surface analysis of oxygen and sulphur by LEEIXS and XRFS were performed before and after polarization on unimplanted and on implanted samples. I/E curves with implanted steels reveal an important corrosion peak (..cap alpha.. peak) recovering widely the active peak of unimplanted samples. For high implanted doses, another peak (..beta.. peak) appears in the passive range. High doses implanted steels polarized in the range of the ..cap alpha.. peak exhibit a sulphur enriched black surface layer. SEM examination of this layer shows it is constituted by flakes rolling up themselves. The formation of a superficial non-protective sulphide layer and the internal stresses of this layer explain the corrosion enhancement of sulphur implanted materials. After dissolution of this layer the behaviour of unimplanted steels is found again.

Deposition of hard coatings may influence the mechanical properties of the bulk material and its corrosion resistance. In this work we study the hardness of the coated and the back side of 100Cr6 steel plates. Electrochemical corrosion tests were performed in O{sub 2}-saturated acetate buffer of pH 5.6 at 25degC. Chromium nitride and titanium nitride coatings prepared by different physical vapour deposition processes, such as arc, thermionic arc evaporation, magnetron sputtering and ion-beam-assisted deposition (IBAD) were compared. The results show that, for sufficient corrosion protection, chromium nitride layers have to be thicker than 500 nm. An increased nitrogen partial pressure in the evaporation chamber of the IBAD process improves the corrosion resistance significantly. The hardness of the substrates was reduced in the case of thermoionic arc evaporation only, indicating a deposition temperature of more than 250degC. For this process, however, we obtained the best corrosion results. (orig.).

We have investigated the characteristics of cyclic crack resistance of medium- and high-strength wheel steels and their ability to form a protective film on a newly formed surface in distilled water and 3.5% NaCl aqueous solution. We have established that the negative influence of these corrosive environments on the cyclic crack resistance of both steels is insignificant and manifests itself most of all at the beginning of the medium-amplitude region of the cyclic crack resistance (fatigue-crack growth rate) diagrams, which is more noticeable for medium-strength steel.

Purpose - Organic coatings remain the most widely used way of protecting steel structures from corrosion. Traditional anticorrosive paints contain lead or hexavalent chromium compounds as active pigments. The use of these classical chromates is nowadays restricted by increasing environmental awareness and stringent national and international regulations. An alternative is the use of ion-exchangeable pigments. The purpose of this paper is to show that cation-exchanged zeolites can be considered as a safe and efficient alternative to traditional hazardous pigments in protecting steel surfaces. Design/methodology/approach - The new pigments were characterised using different analytical and spectro-photometric techniques. Characterisation of these pigments using X-ray diffraction and scanning ...

The primary corrosion mitigation of the external surface of high pressure steel gas pipelines is protective coatings with secondary protection usually by cathodic protection. Adhesion and resistance to cathodic disbondment of the coating is critical for its integrity and grit blasting is an important process in achieving this adhesion. The effect of surface roughness, from grit blasting, on the intergranular stress corrosion cracking resistance of X70 gas pipelines was investigated using slow strain rate testing in carbonate/bicarbonate solution at 75degreeC. The effect of orientation of test pieces with respect to the axial direction of pipes was also investigated.Time to failure ratios decreased with increasing surface roughness indicating reduced stress corrosion cracking resistance. Th...

Emphasis was directed toward evaluating the usefulness of a polyethersulfone (PES)-dissolved N-methyl pyrrolidone (NMP) solvent precursor as a low-temperature film-forming anti-corrosion coating for carbon steel in simulated geothermal environments at brine temperatures up to 300 C. A {approx} 75 {micro}m thick PES coating performed well in protecting the steel against corrosion in brine at 200 C. However, at {>=} 250 C, the PES underwent severe hydrothermal oxidation that caused the cleavage of sulfone- and ether-linkages, and the opening of phenyl rings. These, in turn, led to sulfone {yields} benzosulfonic acid and ether {yields} benzophenol-type oxidation derivative transformations, and the formation of carbonyl-attached open rings, thereby resulting in the incorporation of the functional groups, hydroxyl and carbonyl, into the coating. The presence of these functional groups raised concerns about the diminutions in water-shedding and water-repellent properties that are important properties of the anti-corrosion coatings; such changes were reflected in an enhancement of the magnitude of susceptibility of the coatings surfaces to moisture. Consequently, the disintegration of the PES structure by hydrothermal oxidation was detrimental to the maximum efficacy of the coating in protecting the steel against corrosion, allowing the corrosive electrolytes to infiltrate easily through it.

This dictionary contains about 13.500 entries in each part of the following fields: Basic principles of corrosion (metals and their properties - electromotive series - passivity - lattice defects - corrodents - concepts of corrosion); Types of corrosion (corrosion of metals and non-metals - electrochemical corrosion - chemical corrosion - liquid-metal corrosion); Corrosion control (protection by influencing the state of a corroding system); Protection by coatings; Corrosion testing (field, plant, and laboratory testing - long-term and short-term tests). (orig./HP).

The work addresses the influence of cementation and electrodeposition of copper coatings on the corrosion resistance of AISI 304 stainless steel immersed in 30 wt.% H2SO4 at temperatures of 25 and 50 °C. Corrosion process was evaluated by gravimetric tests, DC measurements and electrochemical impedance spectroscopy (EIS). The specimen surfaces were analysed by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The corrosion performance of AISI 304 stainless steel in sulphuric acid solution was greatly improved by copper coatings. The amount of copper deposited by the cementation process was sufficient to protect the stainless steel of corrosion. A greater amount of copper obtained by electrodeposition treatments does not supply further improvement in the corrosion behaviour. The improved corrosion resistance is related to copper dissolution at the initial stages of immersion tests and the presence of Cu2+ in the solution, which makes the medium more oxidizing, increasing the stability of the passive layer. In addition, the presence of copper at the surface reduces the overpotential of cathodic reaction, enabling the transition from an active region to the passive one.

The compatibility of selected metals representative of those commonly used in dispensing systems was evaluated in an aggressive E20 formulation (CE20a) and in synthetic gasoline (Reference Fuel C) in identical testing to facilitate comparison of results. The testing was performed at modestly elevated temperature (nominally 60 C) and with constant fluid flow in an effort to accelerate potential interactions in the screening test. Based on weight change, the general corrosion of all individual coupons exposed in the vapor phase above Reference Fuel C and CE20a as well as all coupons immersed in Reference Fuel C was essentially nil (<0.3 {micro}m/y), with no evidence of localized corrosion such as pitting/crevice corrosion or selective leaching at any location. Modest discoloration was observed on the copper-based alloys (cartridge brass and phosphor bronze), but the associated corrosion films were quite thin and apparently protective. For coupons immersed in CE20a, four different materials exhibited net weight loss over the entire course of the experiment: cartridge brass, phosphor bronze, galvanized steel, and terne-plated steel. None of these exhibited substantial incompatibility with the test fluid, with the largest general corrosion rate calculated from coupon weight loss to be approximately 4 {micro}m/y for the cartridge brass specimens. Selective leaching of zinc (from brass) and tin (from bronze) was observed, as well as the presence of sulfide surface films rich in these elements, suggesting the importance of the role of sulfuric acid in the CE20a formulation. Analysis of weight loss data for the slightly corroded metals indicated that the corrosivity of the test environment decreased with exposure time for brass and bronze and increased for galvanized and terne-plated steel. Other materials immersed in CE20a - type 1020 mild steel, type 1100 aluminum, type 201 nickel, and type 304 stainless steel - each appeared essentially immune to corrosion at the test conditions.

The losses caused by the effect of the corrosion are of the order of 2-3,5% of the GDP of the developed countries or developing only in direct costs, losses in structures or products. This figure doubles by the indirect costs, losses of productivity or demands for delays. Beside the possible losses of human lives, any intent leaded to the decrease of the corrosion in rusty metals is a commendable objective from the point of view of the protection of the environment. Building industry employing reinforced concrete is able to project some structural elements (pillars, wrought, beam, etc.) in principle free of corrosion, assuring during many years the useful life of the work in service. However, the reinforced concrete would be' a perfect solution if the indefinite permanency of the passive state of the steel could be guaranteed. Indeed, although the steel is protected against corrosion due to basic pH which provides the cement, the severe action of saline media or the effect of CO2 can diminish this protection conditions beginning the corrosion in steel elements. Type-p doped conducting polymers, as polypyrrole, are firm candidates to protect carbon steel providing galvanic protection by stabilising the passive layer of Fe oxides initially grown. Doping the polymeric matrix with polioxometalates, concretely phosphotungstate PW12O403-, is a very interesting hypothesis due to their oxidising effect, improving the anodic protection by the hybrid material electrosynthesised on carbon steel substrate. First in the present work, a new method was developed by cyclic voltammetry in LiClO4 + acetonitrile medium in order to diminish the unavoidable oxidation of carbon steel when the electrosyntesis of the hybrid material polypyrrole/PW12O403- is carrying out. The beginning potential of polypyrrole polymerisation is about 0.8 V (vs. Ag/AgCl), a positive potential where oxidation of Fe substrate is high, not allowing the electrodeposition of the hybrid material. On the other hand, this pretreatment should guarantee appropriate conditions in order to obtain a coating with high adhesion on carbon steel. Once studied the better parameters for the synthesis of the hybrid material by cyclic voltammetry, hybrid material is morphological, chemical and electrochemical characterised by the following techniques: Cyclic Voltammetry, Scanning Electron Microscopy, Energy Dispersive X Ray, X Ray Photoelectron Spectroscopy and Electrochemical Impedance Spectroscopy. The hybrid material polypyrrole/PW 12O403-. chemical structure presents Fe oxides and hydroxide within the polypyrrole polycationic matrix. Hybrid material polypyrrol/PW12O403- diminishes the corrosion of carbon steel in NaOH and Porland cement filtering solutions. These cement solutions simulate the pore fluid conditions existing in cured mortar or concrete elements. Fe ion concentration data were determinated in corrosion tests. Voltammetric response of polymeric coatings was evaluated by cyclic voltammetry. Finally, the protection provided by hybrid material polypyrrole/PW 12O403, in oxidised and reduced state, was evaluated on carbon steel electrodes embedded in Portland cement mortars immersed in seawater and submitted to an accelerated carbonation process for 265 days. Polymeric material covered carbon steel electrodes in reduced state suffer a Fe gravimetric loss 15 times lower than the ones of bare electrodes against chlorides attack, due to the effect of physical barrier. Hybrid material covered electrodes in oxidised state after being submitted to a carbonation process suffer a Fe gravimetric loss 2.5 times lower than the ones of bare electrodes, due to galvanic protection provided by hybrid material polypyrrole/PW 12O403- on carbon steel.

Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

The book discusses the following subjects: 1. Causes and types of corrosion; 2. corrosion protection measures; 3. protective materials; 4. selection of protective materials; 5. testing of protective materials. (MM)

Materials selection for pipe and fittings used to convey corrosive fluids has often been a challenge. Traditionally, exotic Corrosion Resistant Alloys (CRA) have been used in corrosive environments despite their high cost. Plastic lined carbon steel piping offers a cost effective alternative to the use of CRAs by eliminating corrosion, significantly reducing the use of toxic chemicals and the heavy metal usually present in CRAs. Thermoplastic Liners offer the combination of corrosion resistance and mechanical strength, which are unachievable with singular materials. Under pressure conditions, the liner is fully supported by the metalwork, while under vacuum conditions, the liner must be thick enough along with venting system to withstand the collapsing forces created by the negative pressure. Plastic liners have been used successfully to line and protect metallic pipelines for many years and have become an indispensable requirement of the oil and gas industry particularly with water injection and hydrocarbon services. In the case of internally corroded pipes, the use of thermoplastic liners for rehabilitation is an option to extend the lifetime of companies' assets, reduce maintenance cost and increase intervals between T and Is. For new construction, plastic liners in carbon steel pipes can compete technically and economically with pipelines of CRA materials and other corrosion inhibition systems. This paper describes various design features, installations of thermoplastic liners in comparison to other corrosion inhibition methods. (author)

High temperature corrosion limits the operation of equipment used in the Power Generation Industry. Some of the more destructive corrosive attack occurs on the surfaces of heat exchangers, boilers, and turbines where the alloys are subjected to large temperature gradients that cause a high heat flux through the accumulated ash, the corrosion product, and the alloy. Most current and past corrosion research has, however, been conducted under isothermal conditions. Research on the thermal-gradient-affected corrosion of various metals and alloys is currently being studied at the Albany Research Center’s SECERF (Severe Environment Corrosion and Erosion Research Facility) laboratory. The purpose of this research is to verify theoretical models of heat flux effects on corrosion and to quantify the differences between isothermal and thermal gradient corrosion effects. The effect of a temperature gradient and the resulting heat flux on corrosion of alloys with protective oxide scales is being examined by studying point defect diffusion and corrosion rates. Fick’s first law of diffusion was expanded, using irreversible thermodynamics, to include a heat flux term – a Soret effect. Oxide growth rates are being measured for the high temperature corrosion of cobalt at a metal surface temperature of 900ºC. Corrosion rates are also being determined for the high temperature corrosion of carbon steel boiler tubes in a simulated waste combustion environment consisting of O2, CO2, N2, and water vapor. Tests are being conducted both isothermally and in the presence of a temperature gradient to verify the effects of a heat flux and to compare to isothermal oxidation.

Plasma-enhanced chemical vapor deposition (PECVD) has been used to grow corrosion-resistive, semiconducting thin films of the graphite-like polymer polyperinaphthalene (PPN) from 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA). Unlike thermal chemical vapor deposition of PPN from PTCDA, where thin film growth is catalyzed by a transition metal substrate, PPN films have been grown by PECVD for the first time on non-catalytic substrates: indium tin oxide (ITO)-coated glass, aluminum and silicon. Films with the same morphology and molecular characteristics have also been grown on steel substrates, where iron functions as a growth catalyst. Potentiodynamic corrosion measurements in pH 5 water show that PPN films on steel provide an effective corrosion protection layer.Plasma deposition pa...

A pre-treatment system consisting of a nanostructured titania interlayer loaded with an inhibitor and a hybrid silicate film deposited on the TiO{sub 2} layer is shown to provide protection against active corrosion of mild steel. A nanostructured TiO{sub 2} interlayer was prepared on the mild steel surface via controllable hydrolysis of titanium alkoxide. To further improve this pre-treatment, the hybrid silicate film was synthesized from tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane precursors. The morphology and structure of the titania interlayer and hybrid silicate film were characterized with atomic force microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. The corrosion performance of the coatings was examined using electrochemical techniques, including potentiodynamic scanning and electrochemical impedance spectroscopy. The TiO{sub 2} nanostructure calcinated/inhibitor/hybrid silicate system shows enhanced corrosion performance, as confirmed by impedance and polarization measurements.

...baseplate. The stake material must resist corrosion and deterioration when exposed to soil and... (v) Metallic components shall be either corrosion resistant or protected against corrosion and must not produce galvanic corrosion...

The inhibitive action of some thiadiazole derivatives, namely 2,5-bis(2-thienyl)-1,3,4-thiadiazole (2-TTH) and 2,5-bis(3-thienyl)-1,3,4-thiadiazole (3-TTH) against the corrosion of mild steel in 0.5 M H2SO4 solution has been investigated using weight loss measurements, Tafel polarisation and electrochemical impedance spectroscopy (EIS) techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution. The protection efficiency increased with increasing inhibitors concentration and the ability of the molecule to adsorb on the steel surface was dependent on the position of the sulphur atom on the thienyl substituent. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. Potentiodynamic polarisation studies clearly showed that 2-TTH and 3-TTH acted as mixed inhibitors. Adsorption of these inhibitors on steel surface obeyed to Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal sulphuric solution by n-TTH is due to the formation of a chemisorbed film on the steel surface. Molecular modelling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies.

...prevent releases due to structural failure, corrosion, or spills and overfills for as long...contains product must be protected from corrosion, in accordance with a code of practice...protection systems are designed by a corrosion expert; (iii) Impressed...

In this study, we analyzed the application of photovoltaic solar energy as a source of cathodic protection in metallic structures foundations on transmission lines towers. As preliminary studies concerning the need for cathodic protection of the structure, we have measured the resistivity of the soil, the pH and the natural corrosion potential. After the verification of the need for protection against corrosion, the cathodic protection system (CPS) was designed calculating the current to be injected, the PV system and a monitoring system. For analyzing the efficacy of the CPS, a comparison was made between the measurements done in two towers very close to each other, one with a CPS and the other acting as a witness. By comparing the loss in masses of the carbon steel coupons installed arou...

Titanium anodes coated with precious metal oxide are successfully used in cathodic protection since decades. The main focus in Germany is on protection of pipelines, steel in concrete for parking garages and hot water boilers. Due to positive long term experience bridges, tunnels and offshore applications are protected with Titanium anodes all over Europe. Even though there is long term experience and Titanium anodes are frequently in use the question on Titanium corrosion, breakdown voltage, etc. is raised repeatedly, this article offers the answers on these questions. (orig.)

The effect of hydrogen sulfide, hydrogen cyanide, polysulfide and hydrogen thiocyanate on the corrosion behaviour of high-alloy steels and a nickel base alloy in solutions containing ammonium carbonate is studied by using electrochemical methods. The essential mechanisms influencing the value of corrosion attack are shown by schematic diagrams. Low H{sub 2}S concentrations will increase the corrosion rate, high concentrations will decrease it by forming a protective sulfide layer. Polysulfide stabilizes the free corrosion potential in the passive region of the materials at the redox potential because of the cathodic current of sulfur reduction. HCN on the one hand increases the corrosion rate of active specimens in solutions containing H{sub 2}S by removing the protective sulfide layer, on the other hand it inhibits the corrosion in solutions containing HSCN. Even in solutions containing H{sub 2}S are inhibiting effects and instable passivity possible at specimens covered with an oxydic layer. The value of corrosion attack in solutions containing HSCN will be increased by CO{sub 2} and depends on the nickel content of the materials. (orig.).

For the purpose of revealing new areas of applying the investigated protection properties of alkylimidazolines (AIA), produced on the basis of synthetic fatty acid fractions C/sub 7/--C/sub 10/, C/sub 10/--C/sub 16/, C/sub 17/--C/sub 20/, C/sub 21/--C/sub 25/, aliphatic acids and polyethylenepropylamines (foam azolines, (FAZ) 7 to 9, 10 to 16; 17 to 20, 21 to 25 and M21 to 25). The protection properties were judged according to the corrosion of plates made of steel 45, protected films of 5% solutions of these compounds in AS-6 oil, according to the results of the tests in thermal moisture chamber G-4, sea water, salt fog chamber. Water removal and high speed actions were evaluated. It was shown that FAZ increase the diameter of the water displacement of pure oil AS-6 with 15 to 20 up to 75 millimeters, however their water displacement capacity is somewhat worse than in AIA. The FAZ protect steel from corrosion, with which the FAZ 21 to 25 and M21 to 25 surpass the AIA with the tested ones in the thermal moisture chamber, and the FAZ 17 to 20 have better protection properties in the sea water chamber. The oil solutions of FAZ 17 to 20, 21 to 25, M21 to 25 protect steel more effectively from corrosion in a salt fog in comparison to the pure oils AS-6. They completely displace such a strong electrolyte as HBr. M21 to 25 can be recommended as inhibitors of corrosion in oils.

Different laser energy densities were utilized to treat AISI 304 stainless steel via Nd:YAG pulsed laser surface melting (LSM). The surface composition and microstructure of the stainless steel were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). In particular, the corrosion behaviors of the stainless steel surface without and with LSM were evaluated by the electrochemical polarization measurement in 3.5wt.% NaCl aqueous solution at room temperature. The results showed that the stainless steel surface without LSM suffered severe localized pitting under the testing conditions. A thin surface oxide protective layer was produced on the stainless steel surface with LSM, which considerably improved the corr...

In this paper the passive oxide film modification of an AISI 304L stainless steel by a surface treatment carried out with an atmospheric-pressure plasma jet (APPJ) generated by air was analysed. In addition, the influence of the surface modification on the corrosion properties of this steel was estimated. The passive surface film of stainless steel was examined by X-ray photoelectron spectroscopy (XPS) and by Secondary Ions Mass Spectrometry (SIMS) depth profiling before and after the plasma treatment. Potentiodynamic anodic polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to investigate the effects of the surface plasma treatments on the corrosion protection properties of the plasma treated samples. The plasma treatments allowed the formation ...

Stainless steel is quite attractive as bipolar plate material for polymer electrolyte fuel cells (PEFCs). Passive film on stainless steel protects the bulk of it from corrosion. However, passive film is composed of mixed metal oxides and causes a decrease in the interfacial contact resistance (ICR) between the bipolar plate and gas diffusion layer. Low ICR and high corrosion resistance are both required. In order to impart low ICR to stainless steel (SUS304), carbon-coating was prepared by using plasma-assisted chemical vapor deposition. Carbon-coated SUS304 was characterized by Raman spectroscopy and atomic force microscopy. Anodic polarization behavior under PEFC operating conditions (H{sub 2}SO{sub 4} solution bubbled with H{sub 2} (anode)/O{sub 2} (cathode) containing 2 ppm HF at 80 C) was examined. Based on the results of the ICR evaluated before and after anodic polarization, the potential for using carbon-coated SUS304 as bipolar plate material for PEFC was discussed. (author)

Alloys for design and construction of structural components needed to contain process streams and provide internal structures in advanced heat recovery and hot gas cleanup systems were examined. Emphasis was placed on high-strength, corrosion-resistant alloys for service at temperatures above 1000 {degrees}F (540{degrees}C). Data were collected that related to fabrication, joining, corrosion protection, and failure criteria. Alloys systems include modified type 310 and 20Cr-25Ni-Nb steels and sulfidation-resistance alloys HR120 and HR160. Types of testing include creep, stress-rupture, creep crack growth, fatigue, and post-exposure short-time tensile. Because of the interest in relatively inexpensive alloys for high temperature service, a modified type 310 stainless steel was developed with a target strength of twice that for standard type 310 stainless steel.

Electrochemical impedance spectroscopy (EIS) is used to derive an expression for predicting the service life of organic coating in a C4-type environment (industrial and costal areas with moderate salinity) as defined in ISO 12944 standard for paints and varnishes?corrosion protection of steel structures by protective paint systems. Three coating systems with a record of 2, 5, and 10?years of durability were selected for the study. The selection was also based on proven composition and dry film thickness (DFT) of the coatings as per ISO 12944. Electrochemical impedance measurements of the paint-coated panels were carried out by exposing the coated mild steel panels without scribe in different corrosive environments such as immersion in NaCl solution, neutral salt spray, etc. Neutral salt sp...

Experiments for the pipeline steel has been carried out in a multiphase flow loop system at high temperature and high pressure. The study provides an example of the increased corrosion rate under multiphase flow condition due to the presence of small amounts of H{sub 2}S. Under these operating conditions, iron sulphide film interferes with the formation of iron carbonate scale, which is less protective. The simultaneous presence of CO{sub 2} and H{sub 2}S in produced fluids can make a very aggressive environment, which may lead to severe corrosion for the mild steel. CO{sub 2} and H{sub 2}S have been shown to produce competing films at temperature between 30 and 120 deg. C and it was observed that FeS is more protective than FeCO{sub 3} at 90 deg. C. The phases formed on the surface analyzed by SEM and XRD. (authors)

It is essential for materials used at high-temperatures in corrosive atmosphere to maintain their specific properties, such as good creep resistance, long fatigue life and sufficient high-temperature corrosion resistance. Usually, the corrosion resistance results from the formation of a protective scale with very low porosity, good adherence, high mechanical and thermodynamic stability and slow growth rate. Standard engineering materials in power generation technology are low-Cr steels. However, steels with higher Cr content, e.g., austenitic steels, or Ni-base alloys are used for components applied to more severe service conditions, e.g., more aggressive atmospheres and higher temperatures. Three categories of alloys were investigated in this study. These materials were oxidised in laboratory air at temperatures of 550 C in the case of low-alloy steels, 750 C in the case of an austenitic steel (TP347) and up to 1000 C in the case of the Ni-base superalloys Inconel 625 Si and Inconel 718. Emphasis was put on the role of grain size on the internal and external oxidation processes. For this purpose various grain sizes were established by means of recrystallization heat treatment. In the case of low-Cr steels, thermogravimetric measurements revealed a substantially higher mass gain for steels with smaller grain sizes. This observation was attributed to the role of alloy grain boundaries as short-circuit diffusion paths for inward oxygen transport. For the austenitic steel, the situation is the other way round. The scale formed on specimens with smaller grain size consists mainly of Cr{sub 2}O{sub 3} with some FeCr{sub 2}O{sub 4} at localized sites, while for specimens with larger grain size a non-protective Fe oxide scale is formed. This finding supports the idea that substrate grain boundaries accelerate the chromium supply to the oxide/alloy phase interface. Finally, in the Ni-base superalloys deep intergranular oxidation attack was observed, taking place preferentially along random high-angle grain boundaries. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Electrochemical frequency modulation (EFM), a nondestructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is applied here to investigate the inhibition performance of tyrosine (Tyr) toward corrosion of low chromium alloy steel in 0.50?M HCl. Measurements were conducted under various experimental conditions in the range of temperature (20?60??C). Results obtained from EFM were compared with other traditional corrosion monitoring techniques, namely Tafel extrapolation, impedance, and weight loss. Polarization measurements showed that Tyr acted as a mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protected the m...

Several hard, corrosion-resistant and neutron-absorbing iron-based amorphous alloys have now been developed that can be applied as thermal spray coatings. These new alloys include relatively high concentrations of Cr, Mo, and W for enhanced corrosion resistance, and substantial B to enable both glass formation and neutron absorption. The corrosion resistances of these novel alloys have been compared to that of several austenitic alloys in a broad range of synthetic brines, with and without nitrate inhibitor, at elevated temperature. Linear polarization and electrochemical impedance spectroscopy have been used for in situ measurement of corrosion rates for prolonged periods of time, while scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) have been used for ex situ characterization of samples at the end of tests. The application of these new coatings for the protection of spent nuclear fuel storage systems, equipment in nuclear service, steel-reinforced concrete will be discussed.

Erosion-corrosion is a mechanical wear of material, which occurs when high velocity steam hits a surface. Erosion-corrosion has been a traditional problem for steam turbines. Steam turbines operating with saturated steam in nuclear application or in non-reheat applications are most exposed to this wear of material. Erosion- corrosion of carbon steel turbine casing, piping, preheaters, moisture separators, reheaters, valves etc is limiting the lifetime of a powerplant if nothing is undertaken to prevent further wear. This paper describes the ALSTOM Power wide experience in preventing plant equipment against erosion-corrosion. Based on 25-years experience ALSTOM has developed the metal-spray coating method in order to ensure long time protection. Recent inspections of coated surfaces have confirmed the long-lasting feature of the ALSTOM method. (orig.)