Showing papers in "Corrosion in 1986"
TL;DR: In this article, a review of localized corrosion is presented by a consideration of the four steps involved in localized corrosion: adsorption of the reactive anion on the oxide covered aluminum; chemical reaction of the adsorbed anion with the aluminum ion in the aluminum oxide lattice or the precipitated aluminum hydroxide; thinning of the oxide by dissolution; and direct attack of the exposed metal by the anion, perhaps assisted by anodic potential.
Abstract: Localized corrosion, which usually appears as pitting, crevice corrosion (CC), or certain aspects of stress corrosion cracking (SCC), is a multi-step process. This review is organized by a consideration of the four steps involved in localized corrosion: (1) adsorption of the reactive anion on the oxide covered aluminum; (2) chemical reaction of the adsorbed anion with the aluminum ion in the aluminum oxide lattice or the precipitated aluminum hydroxide; (3) thinning of the oxide by dissolution; and (4) direct attack of the exposed metal by the anion, perhaps assisted by an anodic potential. The experimental work reported in the literature is evaluated within this framework.
279 citations
TL;DR: In this paper, it was found that the ratio of magnetite to hematite in the surface oxide film appears to increase with increasing water vapor pressure, ascending temperature, and extending oxidation time.
Abstract: Laser Raman spectroscopy (LRS) has been applied for the detection and characterization of thin corrosion films formed on iron in air at a temperature range from 100 to 150 C. In situ ellipsometric measurements have also been conducted for quantitative estimations of the film growth kinetics. It is found that (1) the oxidation of iron in dry air leads to the formation of a surface oxide film composed primarily of magnetite and (2) the water vapor in air accelerates the formation of hematite. The ratio of magnetite to hematite in the surface oxide film appears to increase with (1) increasing water vapor pressure, (2) ascending temperature, and (3) extending oxidation time.
144 citations
Abstract: The passive region of stainless steels (SSs), as defined by the low current regime between the active-passive transition and the pitting potential or the transpassive potential, is discuss...
143 citations
TL;DR: In this article, the basicity-dependent solubilities for NiO, Co3O4, Al2O3, Fe oxides, SiO2, and Cr 2O3 in fused Na2SO4 at 1200 K were investigated.
Abstract: Metals and alloys may experience accelerated oxidation when their surfaces are coated by a thin film of fused salt in an oxidizing gas. This mode of attack is called hot corrosion, and the most usual or dominant salt involved is sodium sulfate because of its high thermodynamic stability. The corrosive oxyanion fused salts exhibit an acid-base chemistry and are usually ionically conducting electrolytes, so that the corrosion attack must exhibit an electrochemical mechanism with certain characteristics analogous to aqueous atmospheric corrosion. Hot corrosion may involve fluxing of the protective oxides as either acidic or basic solutes in the fused salt. The thermodynamic phase stability can be described by high-temperature Pourbaix-type diagrams, and these can be used to interpret the basicity-dependent solubilities. Measured solubilities for NiO, Co3O4, Al2O3, Fe oxides, SiO2, and Cr2O3 in fused Na2SO4 at 1200 K exhibit remarkable agreement with the expected behavior and permit the calculation o...
140 citations
TL;DR: In this article, the corrosion of carbon steel in CO2-saturated environments that typically represent producing well waters encountered in natural gas reserves was investigated. But the results of the experiments were limited.
Abstract: Experimental results and analyses are reported on the corrosion of carbon steel in CO2-saturated environments that typically represent producing well waters encountered in natural gas rese...
140 citations
TL;DR: In this article, the effectiveness of 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) as a corrosion inhibitor was investigated by measuring corrosion weight losses and polarization curves of SS 41 steel in 0.3% NaCl.
Abstract: The effectiveness of 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) as a corrosion inhibitor was investigated by measuring corrosion weight losses and polarization curves of SS 41 steel in 0.3% NaCl. In concentrations lower than 50 ppm of HEDP, the corrosion of SS 41 steel was inhibited in accordance with the Langmuir adsorption isotherm of HEDP on the steel. The adsorption was believed to be a chemical adsorption resulting from the value of adsorption heat. In concentrations greater than 50 ppm of HEDP, the iron complex of HEDP developed, and the inhibition effect was decreased. Instead, it caused rust to be removed from the steel surface. The mutual inhibition effect by adding both HEDP and the Zn2+ ion in 0.3% NaCl solution was progressively more increased. It was shown that HEDP does not easily decompose.
128 citations
TL;DR: In this paper, the composition and structure of products formed in industrial and marine environments were identified, and the effects of time, side exposed, and surface chromate treatment were described.
Abstract: Because the atmospheric corrosion products that form on the surface of Al, Zn, and AlZn hot-dip coatings on sheet steel are difficult to characterize, they have not been extensively studied in the past. In this study, the composition and structure of products formed in industrial and marine environments were identified, and the effects of time, side exposed, and surface chromate treatment were described. Amorphous aluminum sulfate hydrate is the most abundant corrosion product on Al and AlZn coatings in both environments; it is well formed after only three years of exposure and is changed little after nine years. Al hydroxides were also present on aluminum-containing coatings exposed to the marine atmosphere, but not on those in the industrial atmosphere. The groundward side of the AlZn-coated panel exposed 250 m from the Atlantic Ocean had roughly as much AlZn sulfate hydrate as the skyward side of a panel exposed 25 m from the ocean. This finding discounts sea spray as the source of sulfur and ...
100 citations
TL;DR: This article reviewed work performed in the author's laboratory on the roles that corrosion products play in corrosion and materials degradation processes, focusing on the role of corrosion products in the degradation process of materials.
Abstract: This paper reviews work performed in the author's laboratory on the roles that corrosion products play in corrosion and materials degradation processes. Subject areas include the following...
73 citations
TL;DR: In this article, it is shown that voltages and currents are produced when conducting solutions are made to flow through a water treatment device that uses magnetic fields, and the magnitude of this voltage is found to vary with the solution flow rate in accordance with well-known laws of physics governing the motion of charged particles under the influence of a magnetic field.
Abstract: It is experimentally shown that voltages and currents are produced when conducting solutions are made to flow through a water treatment device that uses magnetic fields. The magnitude of this voltage is found to vary with the solution flow rate in accordance with well-known laws of physics governing the motion of charged particles under the influence of a magnetic field. Current vs flow rate plots and surface pH measurements yield results that are in accord with the presence of enhanced corrosion of the metal housing of the device. It is postulated that the current generated magnetohydrodynamically produces a precipitation initiator that favors the precipitation of scaling salts in the bulk of the solution rather than on the walls of the plumbing.
68 citations
TL;DR: In this article, anodic polarization data on numerous samples fabricated in both metal-semiconductor (MS) and metal-insulator-misconductor (MIS) configurations have demonstrated the protective nature of the built-in active electronic barrier.
Abstract: Aluminum surfaces exhibit significantly improved corrosion protection when coated with suitable semiconductor/insulator thin films. These coatings, generally realized in metal-semiconductor (MS) or metal-insulator-semiconductor (MIS) structural configurations, lead to an interfacial electric field that acts as an effective built-in electronic barrier. This active barrier significantly impedes electron transfer from the aluminum surface to foreign species that cause oxidation by accepting the electrons. Anodic polarization data on numerous samples fabricated in both MS [e.g., Al-indium tin oxide (ITO)] and MIS (e.g., Al-SiO2-ITO) configurations have demonstrated the protective nature of the built-in active electronic barrier. The electronic barrier heights have been shown to increase with (1) the presence of a thin (20- to 100-A) SiO2 layer at the metal/semiconductor interface and (2) the energy gap of ITO, which depends on the indium content. A comparison of these results with data obtained on pl...
67 citations
TL;DR: In this article, the erosion-corrosion of vertical 38mm diameter pipes carrying aerated slurry (20 vol% − 30 + 50 mesh silica sand) in 3.13% NaCl solution at 2 to 6 m/s was measured by weight loss measurements over periods of 100 h. The absolute values of the wear rate were sufficiently close to those measured by electrochemical methods and those calculated from a mass transfer correlation determined for this system, Sh=0.031,Re0.83,Sc0.33 to conclude that the dominant mode of metal loss is corrosion
Abstract: The erosion-corrosion of vertical 38-mm diameter pipes carrying aerated slurry (20 vol% − 30 + 50 mesh silica sand) in 3.13% NaCl solution at 2 to 6 m/s has been measured by weight loss measurements over periods of 100 h. Electrochemical methods have been applied to clarify the mechanism of the process and to determine the corrosion component of the metal. Total wear rates in the range of 6 to 25 mm/y were related to the slurry velocity (v) by wear rate=const vn The value of n was in agreement with oxygen mass transfer controlled corrosion being the dominant mode of metal loss, with n ≈ 1. The absolute values of the wear rate were sufficiently close to those measured by electrochemical methods and those calculated from a mass transfer correlation determined for this system, Sh=0.031 Re0.83 Sc0.33 to conclude that the dominant mode of metal loss is corrosion. The role of erosive action in the erosion-corrosion process is to prevent the formation of a complete rust film that normally stifles corros...
TL;DR: In this article, a growth of the nonsulfate-reducing marine bacterium Vibrio natriegens increased the corrosion current density (CD) of AISI 304 stainless steel (SS) coupons when grown in a marine medium.
Abstract: Growth of the nonsulfate-reducing marine bacterium Vibrio natriegens increased the corrosion current density (CD) of AISI 304 stainless steel (SS) coupons when grown in a marine medium. The corrosion rate, estimated as the corrosion CD (Icorr), calculated from the Tafel constants and polarization resistance, increased from 230 to 2900 nA/cm2 during a 6-day incubation period with V. natriegens. Just before the rapid increase in the corrosion CD, bacterial cells were seen by epifluorescent microscopy after acridine orange staining to colonize the SS surface. On the third day of exposure to seawater, the rapid increase in the corrosion CD correlated with the appearance of extracellular material from the colonizing bacteria, as observed by (1) epifluorescent microscopy, (2) scanning electron microscopy (SEM), and (3) nondestructive analysis of lyophilized biofilms by Fourier transform-infrared spectroscopy (FT-IR) using diffuse reflectance. The extracellular products from the colonizing bacteria corr...
TL;DR: In this paper, the isothermal and thermocyclic oxidation behavior of various advanced single-crystal and directionally solidified superalloys in flowing air at a temperature of 2000 F (1093 C) has been studied.
Abstract: The isothermal and thermocyclic oxidation behavior of various advanced single-crystal and directionally solidified superalloys in flowing air at a temperature of 2000 F (1093 C) has been studied. The experimental methods included thermogravimetric measurements of oxidation rates and examination of the reacted specimens by x-ray diffraction (XRD), optical metallography, and scanning electron microscopy (SEM). The oxidation mechanisms of the alloys are discussed.
TL;DR: In this paper, the authors presented a study of corrosion and stress corrosion cracking of Alloy 600, and the primary purpose of this work is to relate the corrosion susceptibility of the alloy after var...
Abstract: This paper presents a study of corrosion and stress corrosion cracking (SCC) of Alloy 600. The primary purpose of this work is to relate the corrosion susceptibility of the alloy after var...
TL;DR: In this paper, the authors used infrared absorption analysis and scanning electron microscopy (SEM) to identify different types of rust on unpainted weathering steel bridge spans from seven Louisiana bridges and from three other states.
Abstract: Rust samples from unpainted weathering steel bridge spans from seven Louisiana bridges and from three other states were subjected to various types of analysis to determine the mechanism of rusting on the weathering steels. The rust is generally in the form of coarse flakes in the coastal area, sheets in areas in which water retention and chloride contents are high, and powdery and fine grained in the middle and northern regions of the state. Layered sheet samples exhibit γ·Fe2O3·H2O at the air contact surface and magnetite (Fe3O4) at the metal contact surface. In addition to these forms of rust, α-FeOOH and δ-FeOOH have been found in the intermediate layers and in flakes, identified primarily through infrared absorption analysis and scanning electron microscopy (SEM). It is theorized from general findings that the γ form of rust forms from an amorphous bulk and is converted to the α- and δ-FeOOH forms, which are electrochemically reduced to magnetite in chloride-containing solutions. In addition ...
TL;DR: In this article, a rapidly proliferating obligate thermophilic bacterium with an optimum temperature range of 60 to 70 C was isolated from a failed nickel 201 brazed joint.
Abstract: A rapidly proliferating obligate thermophilic bacterium with an optimum temperature range of 60 to 70 C was isolated from a failed nickel 201 brazed joint. Corrosion experiments have demonstrated that the isolate is responsible for the (1) in situ production of acidic metabolites and (2) creation of differential aeration cells, resulting in a significant corrosion current.
TL;DR: In this article, the authors investigated the dissolution-repassivation behavior of AISI 304 stainless steel (SS) in 42% MgCl2 at 143 C using a straining electrode technique at different potentials.
Abstract: Dissolution-repassivation behavior of AISI 304 stainless steel (SS) in 42% MgCl2 at 143 C was investigated using a straining electrode technique at different potentials. Dissolution curren...
TL;DR: In this article, high-chromium cast iron and high-carbon steel grinding balls were subjected to jet slurry impingement in an electrochemically instrumented apparatus, and a synergistic effect was found between corrosion and wear.
Abstract: Samples of high-chromium cast iron and high-carbon steel grinding balls were subjected to jet slurry impingement in an electrochemically instrumented apparatus. The jet velocity was 6.6 m/s. Quartz and chalcopyrite slurries containing 15% solids were used at pH values ranging from 5 to 11. Pure wear rates were obtained by cathodic protection, while pure corrosion rates were obtained by the polarization resistance technique. A synergistic effect was found between corrosion and wear.
TL;DR: In this paper, a powder metallurgy (P/M) SiC whiskers (SiCw)/Al Aluminum Association (AA) 7091 aluminum composite material was performed.
Abstract: Corrosion studies of a powder metallurgy (P/M) SiC whiskers (SiCw)/Al Aluminum Association (AA) 7091 aluminum composite material were performed. The plate material, which was heat treated to the T-6 and T-7 tempers by conventional methods, exhibited preferential corrosion of the surface layers up to 2-mm thick. The regions of corrosion susceptibility were determined to result from improper processing and thermal treatments. Cold-worked regions resulting from extrusion were not completely removed by the conventional solution treatment and thus appeared as more corrosion susceptible. Large void volume fraction and excessive segregation of SiCw was also noted. Electrochemical, microscopic, and analytical techniques were used in these investigations. Attempts were made to remove the cold-worked regions and study the resultant corrosion properties. A comparative analysis of these results is discussed.
TL;DR: In this article, the authors investigated the corrosion properties of two different types of galvanizing layers, namely, a bright galvanizing layer with a pure zinc surface and a gray galvanizing surface with iron-zinc compounds in the surface was obtained on a silicon-containing steel.
Abstract: Corrosion properties in concrete of two different types of galvanizing layers were investigated. A bright galvanizing layer with a pure zinc surface was obtained on a silicon-free steel, and a gray galvanizing layer with iron-zinc compounds in the surface was obtained on a silicon-containing steel. Compared to the bright zinc, a higher reactivity of the gray zinc was found with respect to hydrogen evolution as well as the anodic dissolution rate. The high reactivity of the gray galvanizing layer means that it is impossible to prevent bubble formation during concreting by passivation with chromate. The corrosion potential of the gray galvanizing layer can attain the same level as that found for black steel, which promotes the risk of pitting in chloride-containing concrete. Contact with black steel was found to accelerate the corrosion of both bright and gray galvanizing.
TL;DR: The electrochemical impact of three bacterial isolates on three metal substrata has been quantified using this apparatus and three proposed mechanisms for MIC have been evaluated.
Abstract: The apparatus described in this paper, consisting of a two-compartment cell in which the compartments are biologically isolated and electrolytically continuous, is ideally suited for the study of microbiologically induced corrosion (MIC). The electrochemical impact of three bacterial isolates on three metal substrata has been quantified using this apparatus. In addition, three proposed mechanisms for MIC have been evaluated.
TL;DR: In this paper, a graphite fiber/magnesium composite was studied in dilute chloride solutions by immersion, scanning electron microscopy (SEM), and electrochemical techniques, and it was concluded that galvanic interaction plays an important role in the aqueous corrosion of graphite fibers.
Abstract: The corrosion behavior of a graphite fiber/magnesium composite has been studied in dilute chloride solutions by immersion, scanning electron microscopy (SEM), and electrochemical techniques. The composite consisted of graphite fibers coated with magnesium Alloy AZ91C hot pressed between thin foils of Alloy AZ31B. Within five days of immersion in 0.001 N NaCl, severe localized corrosion developed at the edges of the material where exposed graphite fibers existed. The reaction was accompanied by visible hydrogen evolution over the entire surface, and the attack was through the foil covering into the underlying matrix material. Electrochemical measurements in chloride solution of borated boric acid (pH 8.4, 1000 ppm Cl−) revealed significant galvanic currents between the magnesium foil and graphite fibers. These currents increased as the surface area ratio of graphite to magnesium increased. From this work, it is concluded that galvanic interaction plays an important role in the aqueous corrosion of...
TL;DR: In this paper, a finite difference model describing the diffusion of carbon in high-temperature alloys and its chemical reaction with the alloy components that lead to carbide precipitation was presented.
Abstract: A finite difference model describing the diffusion of carbon in high-temperature alloys and its chemical reaction with the alloy components that lead to carbide precipitation was set up pr...
TL;DR: In this paper, surface composition changes that occur during the dissolution and passivation of a single-crystal Ni50Fe50 (100) alloy were investigated by electron spectroscopy for chemical analysis.
Abstract: Surface composition changes that occur during the dissolution and passivation of a single-crystal Ni50Fe50 (100) alloy were investigated by electron spectroscopy for chemical analysis (ESC...
TL;DR: The double-loop electrochemical potentiokinetic reactivation (EPR) method was used to evaluate the intergranular corrosion (IGC) susceptibility of a duplex stainless steel (SS).
Abstract: The double-loop electrochemical potentiokinetic reactivation (EPR) method was used to evaluate the intergranular corrosion (IGC) susceptibility of a duplex stainless steel (SS). The purpose of the examination was to assess the influence of simulated weld cooling rates on microstructure and the subsequent IGC susceptibility. Those specimens that were rapidly cooled through a 1200 to 815 C (2200 to 1500 F) temperature range were found to exhibit the highest degree of susceptibility to intergranular attack (IGA) relative to those cooled more slowly through this region. Specimens cooled more slowly exhibited various degrees of improvement in the resistance to susceptibility. A good correlation was obtained between a modified oxalic acid test, similar to that described by ASTM Practice A262-A, and the electrochemical double-loop technique. The use of both of these procedures for IGC susceptibility examination is well documented for the case of 300 Series SS, but heretofore has not been described for t...
TL;DR: In this article, the instantaneous rates of the corrosion of Ni, Fe, and their alloys were measured in molten alkali chlorides, carbonates, and sulfates at 973 K by the electrochemical polarization resistance method.
Abstract: Instantaneous rates of the corrosion of Ni, Fe, and their alloys were measured in molten alkali chlorides, carbonates, and sulfates at 973 K by the electrochemical polarization resistance method. The stability of the oxide films formed on the surfaces was evaluated from steady-state anodic polarization curves. The polarization resistances varied proportionally to the corrosion currents measured by weight loss in all of the melts and obeyed the Stern-Geary equation. From the polarization resistance measurements, it was found that alloying with Cr increased the corrosion resistances of Ni and Fe in all of the melts and especially in molten sulfates. Alloying with Mo increased the corrosion resistance in molten chlorides, but decreased that in molten carbonates and sulfates. These results correspond well with those obtained from anodic polarization curves. It is concluded that the polarization resistance method is useful for assessing the corrosion resistance of alloys in molten salts.
TL;DR: In this paper, the long-term potentiostatic and potentiodynamic data were used to predict the behavior of actual two and three metal couples, and the predictions had a level of accuracy equal, or superior to, the conventional galvanic corrosion prediction techniques using galvanic rate tables or corrosion potential differences.
Abstract: Long-term potentiostatic polarization curves of up to 120 days duration were developed for the following materials in seawater: 90:30 copper:nickel (C70600), Monel 400 (N04400), Inconel 625 (N06625), Navy M-bronze (C92200), nickel-aluminum bronze (C95800), HY-80 steel, titanium 50 (R50400), 70:30 copper:nickel (C71500) and anode grade zinc (MIL-STD 18001). In addition, shcrt-term potentiodynamic polarization curves were developed at four scan rates and two pre-exposure levels for all materials. The scan rates used ranged from 0.5 to 100 V/h, and preexposure times were 1 h and 120 days. Long-term potentiostatic and potentiodynamic data were used to predict the behavior of actual two and three metal couples. The predictions had a level of accuracy equal, or superior to, the conventional galvanic corrosion prediction techniques using galvanic corrosion rate tables or corrosion potential differences.