Showing papers in "Corrosion in 1987"
TL;DR: In this paper, the current transients resulting from metastabie pitting events on stainless steel at potentials below the pitting potential are studied, and the kinetic factors hindering the replacement of a passive film by a salt film are discussed.
Abstract: Current transients resulting from metastabie pitting events on stainless steel at potentials below the pitting potential are studied. Metastable pits are covered during growth and exhibit a constant current density. Rupture of the cover during metastable growth leads to repassivation of the pit. If a salt film precipitates on the pit surface before the cover ruptures, pit growth is stabilized. The kinetic factors hindering the replacement of a passive film by a salt film are discussed.
396 citations
TL;DR: In this paper, the degradation of ferrous alloys by hydrogen is discussed, discussing the often conflicting results of experiments on the effects of hydrogen on the plastic properties of iron and steels.
Abstract: Despite the great technological importance of hydrogen embrittlement in many metals and alloys, and the many investigations thereby motivated, no firm consensus exists on the mechanism in any one case. This review concentrates on the degradation of ferrous alloys by hydrogen, discussing the often conflicting results of experiments on the effects of hydrogen on the plastic properties of iron and steels. The decohesion model and the localized slip model, both depending on the electronic disturbance at the adjoining metal atoms caused by hydrogen, and the experiments supporting one or the other point of view, are critically discussed. The versatility of hydrogen, which is capable of producing diverse effects, challenges the experimentalist to elucidate which characteristic of hydrogen predominates in a given set of circumstances.
210 citations
TL;DR: One of the major causes of magnesium corrosion is the presence of iron as an impurity in commercial alloys, and Alloying the material with manganese may reduce the corrosion rate to acceptable levels.
Abstract: One of the major causes of magnesium corrosion is the presence of iron as an impurity in commercial alloys. Alloying the material with manganese may reduce the corrosion rate to acceptable...
126 citations
TL;DR: In this article, it was shown that the crack velocity-strain rate relationship in the presence of multiple cracked specimens can be computed by considering the number of cracks, in which case it is possible to calculate (involving electrochemical data) the crack velocities.
Abstract: One of the problems in relation to predicting the rates of defect growth in structures displaying stress corrosion cracking (SCC) is that knowledge relating to realistic stress corrosion crack velocities is very limited. In monotonic slow strain rate tests (SSRTs) taken to total failure at usual strain rates and in tests on precracked specimens at stress intensity factors in excess of KISCC, stress corrosion crack velocities may be appreciably higher than are likely to occur in service, except in the very late stages of crack growth before a service failure. These differences probably develop partly because of differences in the effective crack tip strain rate, and consideration is given to various expressions for calculating the latter from the applied strain rate. For multiple cracked specimens, as in SSRTs, the importance of considering the number of cracks is demonstrated, in which case it is possible to calculate (involving electrochemical data) the crack velocity-strain rate relationships i...
105 citations
84 citations
TL;DR: In this paper, the intergranular stress corrosion cracking (IGSCC) of Alloy 600 steam generator tubing in primary water environments can require lengthy exposure times, even at high temperatures.
Abstract: Laboratory testing to produce intergranular stress corrosion cracking (IGSCC) of Alloy 600 steam generator tubing in primary water environments can require lengthy exposure times, even at ...
76 citations
TL;DR: Slow strain rate tests (SSRTs) on differently shaped tensile specimens machined from two heats of Alloy 600 tubing were conducted at 350 C in deaerated aqueous solutions containing small a....
Abstract: Slow strain rate tests (SSRTs) on differently shaped tensile specimens machined from two heats of Alloy 600 tubing were conducted at 350 C in deaerated aqueous solutions containing small a...
71 citations
TL;DR: In this article, the defects were located using a scanning vibrating probe electrode which measured the distribution of current density (CD) above the surface of the coated steel and enabled polarization measurements of specific areas of the surface to be made.
Abstract: Defects in ion vapor-deposited aluminum coatings on steel exposed to a 0.3 M H3BO4 solution adjusted to pH 8 were detected in situ. The nonaggressive borate solution was chosen to prevent any significant damage to the coating during defect location. The defects were located using a scanning vibrating probe electrode which measured the distribution of current density (CD) above the surface of the coated steel. The vibrating electrode technique enabled polarization measurements of specific areas of the surface to be made. The polarization measurements of the defect sites showed that they were not a result of exposed steel but were caused by the presence of inclusions.
55 citations
TL;DR: In this article, slow strain rate tests were conducted to study the effect of electrode potential on the intergranular stress corrosion cracking (IGSCC) of Alloy 600 in deaerated 0.01 M H3BO3 + 0.0...
Abstract: Slow strain rate tests (SSRTs) were conducted to study the effect of electrode potential on the intergranular stress corrosion cracking (IGSCC) of Alloy 600 in deaerated 0.01 M H3BO3 + 0.0...
53 citations
51 citations
TL;DR: In this article, Nitrogen has been shown to exert a beneficial influence on localized corrosion resistance of austenitic stainless steels, and the corrosion resistance and corrosion modes are quite different in N and non-N duplex SSs.
Abstract: Nitrogen (N) has been shown to exert a beneficial influence on localized corrosion resistance of austenitic stainless steels. With duplex stainless steels (SSs), N plays a dual role of controlling the austenite to ferrite ratio and increasing corrosion resistance. In addition, on rapid cooling from high temperatures, N can form deleterious precipitates in the ferrite reducing corrosion resistance. The corrosion resistance and corrosion modes are quite different in N and non-N duplex SSs. These differences are illustrated for a 25%Cr duplex SS.
TL;DR: In this paper, cylindrical steel specimens were polarized to −0.900 V (SCE) in natural seawater at 24 and 3 C with rotation speeds of 0 and 0.83 Hz.
Abstract: Experiments have been performed where cylindrical 1018 steel specimens were polarized to −0.900 V (SCE) in natural seawater at 24 and 3 C with rotation speeds of 0 and 0.83 Hz. The nature ...
TL;DR: In this article, it was shown that overhead electrical power transmission conductors, constructed from aluminium wires centrally reinforced by galvanized steel strands, have been found, in a few isolated instances, to suffe...
Abstract: Overhead electrical power transmission conductors, constructed from aluminium wires centrally reinforced by galvanized steel strands, have been found, in a few isolated instances, to suffe...
TL;DR: In this article, an investigation of the electrochemical noise generation during the stress corrosion cracking (SCC) of alpha-brass was conducted in Mattsson solution (ammoniacal copper sulfate solution) o...
Abstract: An investigation of the electrochemical noise generation during the stress corrosion cracking (SCC) of alpha-brass was conducted in Mattsson solution (ammoniacal copper sulfate solution) o...
TL;DR: In this article, the acidic and basic solubilities of the potential thermal barrier oxide components CeO2, HfO2 and Y2O3 were measured as a function of solvent basicity for fused Na2SO4-30 mol% NaVO3 at 9...
Abstract: The acidic and basic solubilities of the potential thermal barrier oxide components CeO2, HfO2, and Y2O3 were measured as a function of solvent basicity for fused Na2SO4-30 mol% NaVO3 at 9...
TL;DR: In this article, a systematic analytical electron microscopy (AEM) study was conducted on a series of AISI 304 stainless steels to determine the mechanisms by which N affects Cr carbide precipitation and the associated Cr depletion at grain boundaries.
Abstract: A systematic analytical electron microscopy (AEM) study was conducted on a series of AISI 304 stainless steels (SSs) to determine the mechanisms by which N affects Cr carbide precipitation and the associated Cr depletion at grain boundaries. Electrochemical potentiokinetic reactivation (EPR) tests conducted on the steels indicate that N additions up to 0.16 wt% retard sensitization, but above 0.16 wt%, they promote it. The microstructural investigation revealed that an increasing N content consistently caused the bulk diffusion coefficient of Cr in austenite to decrease and the grain boundary Cr concentration to increase. The increase in the degree of sensitization (EPR tests) for Cr contents above 0.16 wt% was found to result from Cr carbides precipitating discontinuously, which resulted in grain boundary migration and, hence, wider Cr-depleted zones.
TL;DR: The influence of prior cold work on the degree of sensitization of AISI 304 stainless steel has been studied for a wide range of cold work (up to 55%) by using a modified version of the conventional Strauss test as well as by using the more recently developed electrochemical potentiokinetic reactivation technique (EPR).
Abstract: The influence of prior cold work on the degree of sensitization of AISI 304 stainless steel (SS) has been studied for a wide range of cold work (up to 55%) by using a modified version of the conventional Strauss test as well as by using the more recently developed electrochemical potentiokinetic reactivation technique (EPR). It has been found that with up to approximately 20% of prior cold work, the degree of sensitization (DOS) increases with increasing cold work. However, for prior deformation levels exceeding 35%, a reverse trend has been noticed. It has also been observed that, irrespective of the degree of cold working (0 to 55%), the electrochemical technique can yield a reliable estimation of the degree of sensitization only when the integrated charge (Q) values are considered.
TL;DR: The actual time required to build up a passivating layer of siderite crystals on the steel surface is a function of the solution pH and the ability of the corrosion scale particles to adhere to the steel surfaces as discussed by the authors.
Abstract: The initial high corrosion rates of low-alloy carbon steel in CO2/brine mixtures are mitigated by the subsequent generation of loosely adherent iron carbide surface films, iron carbonate surface films, and, in the case of unbuffered waters, by a significant increase in pH caused by the loss of acid to the corrosion process forming these films. The actual time required to build up a passivating layer of siderite crystals on the steel surface is a function of the solution pH, via siderite solubility product considerations, and the ability of the corrosion scale particles to adhere to the steel surface.
TL;DR: In this article, the effect on corrosion of composition and microstructure in a series of FeCr-10%Ni alloys with increasing chromium content has been investigated in reducing acids.
Abstract: The effect on corrosion of composition and microstructure in a series of FeCr-10%Ni alloys with increasing chromium content has been investigated in reducing acids. In the range of 25 to 3...
TL;DR: In this article, the authors analyzed the reactivation currents of stainless steel scratched at constant potential in sulfuric acid and sulfate solutions in terms of model equations derived for different rates of film removal and reformation.
Abstract: Repassivation currents measured for stainless steel (SS) scratched at constant potential in sulfuric acid and sulfate solutions are analyzed in terms of model equations derived for different rates of film removal and reformation. For times longer than the duration of scratching, the current decrease can be described by the normal log I-log t relationship, but for shorter times, more complex equations apply. An equation in the form I=A0+A1 log (y/y+1), where y is the ratio between the time elapsed after scratching and the duration of scratching, is sufficiently accurate in most cases.
TL;DR: In this article, the authors used accelerated electrochemical techniques to study the corrosion of carbon steel in laboratory-simulated aqueous environments representing typical produced waters from natural gas production wells.
Abstract: Accelerated electrochemical techniques were used to study the corrosion of carbon steel in laboratory-simulated aqueous environments representing typical produced waters from natural gas production wells. Specifically, the separate and conjoint effects of the various ionic species in the electrolyte, and the influences of dissolved methane and propane on corrosion of the steel were investigated. Tests were performed at temperatures and pressures up to 95 C and 700 kPa, respectively. Some kinetic parameters were evaluated from both anodic and cathodic polarization measurements. The results showed that the reduction of H2O and HCO3− ions is important in explaining the cathodic polarization characteristics. The partial reactions occurring in the system were defined and explained, in part, from theoretical reconstruction of the experimental polarization curves.
TL;DR: In this article, the rate of copper corrosion by ferric ions (∼7 mM) in 0.5 M deaerated sulfuric acid in the presence and absence of benzotriazole (BTAH) has been studied.
Abstract: The rate of copper corrosion by ferric ions (∼7 mM) in 0.5 M deaerated sulfuric acid in the presence and absence of benzotriazole (BTAH) has been studied. The rotating disk electrode (RDE) has been used in weight loss experiments. In the range of BTAH concentrations between 0 and 3.0×10−4 M, the Levich equation is obeyed; i.e., the process is still controlled by transport of ferric ions to the electrode surface. Total inhibition of the corrosion process is observed when the BTAH concentration equals 5.0×10−3 M. The protective film follows a Langmuir adsorption isotherm, with an adsorption constant of 8.8×103 M−1. The chemical nature of the passivating film formed on the copper surface in this medium has been studied by in situ and ex situ fluorescence and Raman spectroscopies and the surface film characterized as a polymeric [Cu(I)BTA] complex.
TL;DR: In this paper, the corrosion behavior of AISI 316 stainless steel in formic and acetic acids was investigated by measuring the corrosion weight loss, the polarization curve, the impedance at the steel/solution interface, and the variation of natural electrode potential (NEP) with time.
Abstract: The corrosion behavior of AISI 316 stainless steel (SS) in formic and acetic acids was investigated by measuring the corrosion weight loss, the polarization curve, the impedance at the steel/solution interface, and the variation of natural electrode potential (NEP) with time. It was found that the corrosion rate of AISI 316 SS in formic and acetic acids was markedly dependent on the concentration of the acid and temperature. The corrosion rate in aqueous solution of these acids was larger than in nonaqueous solution, and the corrosion behavior in nonaqueous solution was quite different from that in aqueous solution. It was believed that Cr and Mo mainly contribute to the corrosion resistance of AISI 316 SS in aqueous solution, while Ni contributes slightly. In nonaqueous solution of formic acid, Cr mainly contributes to corrosion resistance, and Mo and Fe contribute slightly; in nonaqueous solution of acetic acid, Cr mainly contributes to corrosion resistance, while Mo contributes slightly. To ob...
TL;DR: In this article, the corrosion of Grade 12 titanium, a possible canister material for the storage of high-level nuclear wastes, has been studied in brine solution under γ radiation (Ce137, 1.5×105 rad/h), in which a variety of radiolytic species that may change the redox reactions involved in corrosion processes is known to be produced.
Abstract: The corrosion of Grade 12 titanium, a possible canister material for the storage of high-level nuclear wastes, has been studied in brine solution under γ radiation (Ce137, 1.5×105 rad/h), in which a variety of radiolytic species that may change the redox reactions involved in corrosion processes is known to be produced. It was found that radiolysis of the brine solution permits additional partial cathodic reactions and shifts the open circuit potential (OCP) of the alloy in the noble direction. Furthermore, it was found that the changes in the oxide responsible for decreased hydrogen absorption by Grade 12 Ti under γ radiation are caused by the radiolysis products of the brine solution and not by the direct effect of radiation on the metal or oxide. γ radiation also increases the pitting potential of the alloy in 1 M KBr solution at 25 C. Among the radiolytic products, hydrogen peroxide plays an important role in determining the corrosion conditions in the irradiated brine solution: (1) it provid...
TL;DR: Tungsten reference electrodes (TREs) were prepared by dipping tungsten wires into buffered solutions as discussed by the authors, and the use of these electrodes for voltammetric and potentiometric measurements was compared to that of SCEs.
Abstract: Tungsten reference electrodes (TREs) were prepared by dipping tungsten wires into buffered solutions. The use of these electrodes for voltammetric and potentiometric measurements was compared to that of silver-silver chloride, silver-silver nitrate, and saturated calomel electrodes (SCEs). Comparative studies were conducted at 5, 27, and 65 C in HCl-H2SO4, NaOH, TM-01-77, and buffered solutions for a period exceeding six months. The salt bridges of the tungsten electrodes were less likely to clog than those of the other reference electrodes. The potentials of the tungsten electrodes were slightly less reproducible than those of the silver-silver chloride electrodes (SSCEs), but more reproducible than those of the other reference electrodes. If necessary, the filling solution of the tungsten electrode can be varied to match the pH value of the test solution.
TL;DR: In this article, the pitting corrosion of zirconium in chloride solution under potentiostatic conditions was investigated and both stable and unstable pitting were observed, and it was observed that although the pit nucleation potential decreases (becomes more active) with an increase in chloride ion concentration, it does not follow a linear relationship with log [Cl−] in NaCl as well as in HCl solutions.
Abstract: Investigations were conducted on the pitting corrosion of zirconium in chloride solution under potentiostatic conditions. Both stable and unstable pitting were observed. Unstable pitting indicated by anodic current oscillations resulting from repetitive new pit nucleation and repassivation were all ultimately repassivated with time below the stable pit nucleation potential. Only stable pitting was considered in this study. It was observed that although the pit nucleation potential decreases (becomes more active) with an increase in chloride ion concentration, it does not follow a linear relationship with log [Cl−] in NaCl as well as in HCl solutions. The pit nucleation potential was not affected up to a certain pH value, but it shifted thereafter in the noble direction with a further increase in pH and, finally, no pitting corrosion was observed, depending on the bulk chloride ion concentration. An increase in temperature shifts the pit nucleation potential in the noble direction. The activation ...
TL;DR: In this article, the microstructural causes of intergranular corrosion in the nickel base weld metals designated as Alloy 182 and Alloy 82 were investigated and it was found that Alloy 182 corroded significantly more than Alloy 82 after various thermal aging treatments.
Abstract: This paper reports a study of the microstructural causes of intergranular corrosion (IGC) in the nickel base weld metals designated as Alloy 182 and Alloy 82. Both unwelded electrode material and welds made from various production heats of the electrodes were examined. In all cases, it was found that Alloy 182 corroded significantly more than Alloy 82 after various thermal aging treatments. This difference could be attributed to the fact that the precipitation of chromium-rich carbides along the grain boundaries caused more chromium depletion in Alloy 182 than in Alloy 82. The greater amount of chromium depletion in Alloy 182 resulted from the fact that it contains more carbon and iron and less chromium in its matrix than Alloy 82. Welds of Alloy 82 could be made susceptible to IGC if they picked up carbon during the welding process.
TL;DR: In this article, the pitting corrosion of nickel covered with films potentiostatically formed at various potentials for 3.6 ks in borate and phosphate solutions of pH 8.42 and pH 11.50 was investigated in 0.5 kmol/m3 NaCl solution.
Abstract: The pitting corrosion of nickel covered with films potentiostatically formed at various potentials for 3.6 ks in borate and phosphate solutions of pH 8.42 and pH 11.50 was investigated in 0.5 kmol/m3 NaCl solution at a constant potential of 0.395 V (SHE) higher than a critical pitting potential of 0.295 V in the same solution. The time, τ, obtained from the logarithmic plots for pitting current (ip) or amount of electric charge passed (Qp) vs time curves was found to be the transition time from pit nucleation to pit growth. The τ value was a linear function of potential in the passive region and showed a rapid increase at potential in the secondary passive region, irrespective of anion species and solution pH in which a film was formed. From the linear relationship between r and total film thickness in the passive region, it was proposed that a passive film formed in the solutions consists of two layers: an outer layer of Ni(QH)2 and an inner layer of NiO. Thereby, the pit nucleation was assumed ...
TL;DR: In this article, anodes operate in a reducing atmosphere, whereas cathodes operate under strongly oxidizing conditions, in difficult electrolytic environments. Electrochemical corrosion can limit the capacity of fuel cell anodes.
Abstract: Fuel cell anodes operate in a reducing atmosphere, whereas cathodes operate under strongly oxidizing conditions, in difficult electrolytic environments. Electrochemical corrosion can limit...
TL;DR: In this paper, the dissolution of copper was investigated in an alkaline aqueous solution at pH 12 (0.01 M NaOH) containing up to 1 M NaCl at 25 C. During cyclic voltammetry measurements, the first and second anodic peaks correspond to Cu I and Cu II oxide formation.
Abstract: The dissolution of copper has been investigated in an alkaline aqueous solution at pH 12 (0.01 M NaOH) containing up to 1 M NaCl at 25 C. During cyclic voltammetry measurements, the first and second anodic peaks correspond to Cu I and Cu II oxide formation, and the reduction processes of those oxides remained slightly affected by the presence of Cl− ions. With NaCl in solution, a large increase of the anodic dissolution current is observed, and, for the cathodic reaction, a third reduction peak appears on the voltammograms. The large increase of the current results from the localized attack of the surface by Cl− ions. The third cathodic peak corresponds to the reduction of CuCl (nantokite) accumulated on the electrode. The presence of CuCl suggests that the copper oxides/solution interface becomes acidic during the dissolution. The morphology of the accumulated CuCl and the presence of holes in it suggest that the corrosion product is non-protective. As flakes of CuCl detach from the surface to f...