Showing papers on "Corrosion published in 1975"
TL;DR: In this article, the relation between the corrosion rate of steel in carbonic acid and the CO2 partial pressure was determined by means of weight loss and polarization resistance measurements, and the effect of temperature on the corrosion process can be analyzed in terms of an activation energy for the overall corrosion process.
Abstract: The relation between the corrosion rate of steel in carbonic acid and the CO2 partial pressure was determined by means of weight loss and polarization resistance measurements. This relation is compared with that expected for completely dissociated acids, and appears to be significantly different. A theoretical analysis of this effect shows that it can be quantitatively explained if the direct reduction of undissociated carbonic acid is the rate-determining step in the cathodic process. Both anodic and cathodic processes have been further studied by means of potentiodynamic polarization curves. The effect of temperature on the corrosion rate can be analyzed in terms of an activation energy for the overall corrosion process.
404 citations
TL;DR: In this article, the results of stress corrosion tests with aluminum alloys that have been obtained to date with fracture mechanics techniques are reviewed. But the present and limited status of theoretical understanding of the stress corrosion cracking is outlined.
Abstract: Stress corrosion cracking of aluminum alloys is reviewed. An extensive failure analysis shows how many service failures occurred in the aerospace industry over a ten year period and what kind of alloys and stresses led to initiation and propagation of stress corrosion cracks which caused these service failures. The paper contains most of the results of stress corrosion tests with aluminum alloys that have been obtained to date with fracture mechanics techniques. Stress corrosion crack growth rate measurements are compared with the results from smooth specimen testing and it is shown that the correlation between the different test results is very satisfactory. The present and limited status of theoretical understanding of stress corrosion cracking is outlined. A major part of the paper is devoted to the results of the latest alloy development. High strength aluminum alloys of dramatically increased stress corrosion resistance are available now. In the near future, stress corrosion resistant alloys of even higher strength might become available. What is still lacking is a detailed understanding of the mechanisms by which stress corrosion cracks initiate and propagate.
308 citations
TL;DR: In this article, it is shown that seawater contains concentrations of Cl− far in excess of this figure, and since penetration by these ions to the reinforcing bars in concrete takes place within a small fraction of the service life of a marine concrete structure, corrosion might be expected to be a frequent problem.
Abstract: RECENT developments in concrete offshore structures have drawn attention to a disturbing ignorance of the mechanism by which steel corrosion is prevented when it is embedded in dense concrete1. The traditional view has been that the metal remains passivated owing to the high pH (∼ 12.5) of the pore solution in concrete. It is, however, well known that relatively small concentrations of Cl− destroy the corrosion inhibitive properties of non-buffered alkalis and ∼ 700 p.p.m. of Cl− will depassivate steel in limewater at pH 12.5 (ref. 2). Since seawater contains concentrations of Cl− far in excess of this figure, and since penetration by these ions to the reinforcing bars in concrete takes place within a small fraction of the service life of a marine concrete structure3, corrosion might be expected to be a frequent problem. In practice, however, there are many examples of reinforced concrete structures which have remained durable in seawater for 30 yr and more. Such corrosion problems as have been reported are, in the majority of cases, associated only with areas immediately above the level of high tide, where the concrete is not maintained in a saturated condition.
241 citations
TL;DR: In this article, the importance of diffusion under potentiostatic dissolution conditions with wire electrodes contained in inert supports was investigated for nickel and stainless steel specimens in concentrated chloride solutions, and the effect of changing the concentration or activity gradient of the dissolving metal cations within the artificial cavity was studied by alternating the composition of the bulk solution.
Abstract: The importance of diffusion was investigated under potentiostatic dissolution conditions with wire electrodes contained in inert supports. The artificial cavities created simulated localized corrosion conditions. Current-time behavior at voltages in excess of the critical pitting potential (>0.5V (SCE)) was examined for nickel and stainless steel specimens in concentrated chloride solutions. The effect of changing the concentration or activity gradient of the dissolving metal cations within the artificial cavity was studied by alternating the composition of the bulk solution. Solutions of FeCl/sub 2/, NiCl/sub 2/, CrCl/sub 3/, LiCl, NaCl, MgCl/sub 2/, and CeCl/sub 3/ ranging from 0.5 to 10M were used. Mass transfer models were developed for the observed transient and quasi steady-state periods of dissolution. (auth)
134 citations
TL;DR: In this article, the structure and chemistry of the iron sulphides are collated and a review of the mechanisms of corrosion of ferrous metals by the iron sulfides and soluble sulphide, including corrosion by the sulphate-reducing bacteria is discussed.
Abstract: Data on the structure and chemistry of the iron sulphides are collated. Corrosion of ferrous metals by the iron sulphides and soluble sulphide, including corrosion by the sulphate-reducing bacteria, is reviewed. Corrosion mechanisms are discussed.
113 citations
TL;DR: In this paper, the chemical composition of passive films formed on chromium steels with 4-30% Cr at 25 and 70°C in oxygenated water for different times was analyzed.
96 citations
TL;DR: In this paper, an analysis of metallurgical and electrochemical events at the tip of a propagating stress corrosion crack is presented, where the condition for crack propagation is that the creep strain-rate prevents repassivation for a period of time during which it is hypothesized that a change, Q mln, passes which initiates a further increment of crack growth.
93 citations
90 citations
TL;DR: In vitro corrosion of fresh amalgam resulted in the buildup of similar products as in vivo, and the corrosion products in an old amalgam were probably a mixture of tin-oxide and tin oxychloride.
Abstract: Corrosion products of amalgam produced in Ringer's solution were compared with products formed in vivo using scanning electron microscopy, X-ray microanalysis, and Potentiostatic anodic polarization. The corrosion products in an old amalgam were probably a mixture of tin-oxide and tin oxychloride. In vitro corrosion of fresh amalgam resulted in the buildup of similar products.
89 citations
TL;DR: In this article, a capacitance probe was used to detect the deflection occurring during ion implantation of thin specimens of annealed steel, which is related to the introduction of a surface compressive stress.
Abstract: Recent work on ion−implanted metals has demonstrated the existence of substantial changes in friction and wear properties brought about by ion implantation. The effects have been attributed to corrosion inhibition, metallurgical transformation, or mechanical surface hardening. In the work to be presented, a capacitance probe apparatus is described which has been used to detect the deflection occurring during ion implantation of thin specimens of annealed steel. The deflection is related to the introduction of a surface compressive stress. 100−keV argon ion implantation is found to produce surface stresses of several thousand lbs/in.2 which reach a maximum at a dose approximately 5.0×1016 ions−cm−2. Light ions, such as nitrogen, which form chemically stable compounds within the steel, generate similar stresses within the surface such that a macroscopic deflection of the specimen can be observed. In this case very high doses are required to maximize the stress (∠1017 ions−cm−2). The results are interpreted with reference to damage mechanisms and nitride formation, and are discussed in relation to the mechanical property changes previously reported.
TL;DR: In this article, a review of French data showed a reversal of the usual sensitizing effect in the case of intergranular stress corrosion cracking in high temperature, deaerated water.
Abstract: Intergranular stress corrosion cracking (SCC) of Inconel 600 is of concern to the nuclear power industry. Heat exchangers in commercial nuclear systems have shown SCC in only a fraction of a percent of the tubes in high temperature water, but laboratory SCC of Ni-containing alloys have been demonstrated by several research groups. This review revolves around French data, which show a reversal of the usual sensitizing effect in the case of SCC in high temperature, deaerated water. There is no cracking reported in material first heated so as to precipitate carbides at the grain boundaries, whereas high temperature annealed conditions lead to intergranular SCC in the same laboratory experiments. Electrochemically, SCC and also grain boundary corrosion are related to the potential level of a given test; however, it is not yet understood how the different grain boundary zones in Inconel 600 corrode (with and without applied stress) so that the mechanism of cracking remains speculative. Cr-depletion is...
TL;DR: The measured tensile and fatigue strengths of wrought and heat-treated cobalt chromium-molybdenum-carbon alloys such as HS21 were found to be more than twice those of as cast alloys of the same composition.
Abstract: The measured tensile and fatigue strengths of wrought and heat-treated cobalt chromium-molybdenum-carbon alloys such as HS21 were found to be more than twice those of as cast alloys of the same composition. The resistance of wrought HS21 to crevice corrosion at metal-Teflon contacts in isotonic salt solution at 37 degrees C was found to be considerably greater than that of cast HS21, wrought HS25, wrought MP35, or 316L stainless steel which are currently used for surgical implants. The increased crevice corrosion resistance and mechanical strength of wrought HS21 as compared to as cast HS21 was attributed to greater chemical and structural homogeneity as well as to finer grain size and distribution of secondary phases. Fabrication of shaped implants from wrought HS21 is possible by techniques currently used for the fabrication of industrial parts from other wrought cobalt-chromium base alloys.
01 Jan 1975
TL;DR: In this paper, a review of high-temperature chemical metallurgy is presented concerning the kinetics and thermodynamics of metal-slag-gas reactions, high temperature oxidation and corrosion processes, electrochemical sensors in metal--slag--gas environment, and electrometallurgical processes and systems.
Abstract: Papers are presented concerning high-temperature chemical metallurgy. The four sections of the book are general aspects of kinetics and thermodynamics of metal--slag--gas reactions, high temperature oxidation and corrosion processes, electrochemical sensors in metal--slag--gas environment, and electrometallurgical processes and systems. Separate abstracts for some papers were prepared. (FS)
TL;DR: An electrochemical model for the weathering of massive sulphide deposits that have undergone conditions similar to those affecting the Kambalda nickel deposits is presented in this article, where the effect on the model of physical perturbations such as rising and falling water table, faulting, etc.
Patent•
31 Dec 1975
TL;DR: In this article, the authors describe a set of coatings for the protection of nickel and cobalt superalloy articles at elevated temperatures, which is due to the formation of an alumina layer on the surface of the coating which serves to reduce oxidation/corrosion.
Abstract: Coatings are described which are particularly suited for the protection of nickel and cobalt superalloy articles at elevated temperatures. The protective nature of the coatings is due to the formation of an alumina layer on the surface of the coating which serves to reduce oxidation/corrosion. The coatings contain aluminum, chromium, yttrium (or other oxygen active elements) and a metal chosen from the group consisting of nickel, cobalt and iron or mixtures thereof. The coatings further contain a controlled percentage of silicon which serves to greatly improve the protection afforded by the alumina film to the surface of the coating.
TL;DR: An unusual combination of wear and corrosion resistance has been developed in cobalt and nickel base alloys known as Tribaloy ∗∗ intermetallic materials as discussed by the authors, which can resist wear under poor or unlubricated conditions from cryogenic temperatures to about 1000°C.
TL;DR: In this article, a mixture of carbon and lithium fluoride dispersed on a molecular scale was prepared at a temperature of 100°C by corrosion of polytetrafluoroethylene using lithium amalgam.
Journal Article•
TL;DR: In this article, the authors used an equipotential contour map to evaluate the corrosion activity of steel in concrete and found that after repair of concrete delaminations, the percentage of corrosive potentials decreased by about 50 percent.
Abstract: When the corrosive half-cell potentials on a bridge deck exceed about 10 percent or when corrosion-caused delamination exceeds about 1 percent of the deck area, a chloride analysis generally would not be required because the chloride content is already too great. For the average depth of reinforcing steel, the quantity of chloride apparently needed to cause corrosion was statistically related to the maximum amount at the 95 percent confidence limits of 1.0 lb/ cu yd (0.59 kg/ cu m). The accuracy of chloride determinations was about equal whether the concrete was drilled or cored. Although the half-cell potential of -0.35 volts CSE is indicative of active corrosion, an equipotential contour map is the most reliable means for evaluating the corrosion activity of steel in concrete. After repair of concrete delaminations, the percentage of corrosive potentials decreased by about 50 percent. Repairing concrete delaminations does not prevent or necessarily control corrosion at other locations.
TL;DR: In this article, the authors quantify the effect of depth of cover and two other variables, concrete slump and reinforcement bar size, on the tendency to produce the subsidence cracks over the reinforcement that lead to corrosion of the reinforcement in concrete bridge decks.
Abstract: The research reported here was undertaken to quantify the effect of depth of cover and two other variables, concrete slump and reinforcement bar size, on the tendency to produce the subsidence cracks over the reinforcement that lead to corrosion of the reinforcement in concrete bridge decks. A photoelastic study was also undertaken to determine the magnitudes of the tensile stresses above the reinforcement as a function of depth of cover. Finally, a corrosion study was carried out to verify that subsidence cracking over the reinforcement leads to corrosion of the reinforcement in the presence of deicing salts. The conclusions from this study were: depth of cover significantly affects subsidence cracking, corrosion potentials are significantly higher for cracked concrete, and tensile stresses over reinforcing bars due to body stresses in fresh concrete increase sharply with decreasing cover.
TL;DR: In this paper, a comparison of the results of intergranuiar (IG) corrosion testing by the standard method (ASTM A 262, Practice E) and by an electrochemical reactivation method is presented.
Abstract: A comparison is presented of the results of intergranuiar (IG) corrosion testing by the standard method (ASTM A 262, Practice E) and by an electrochemical reactivation method. Five Cr-Ni and Cr-Ni-Mo steels containing 0.025 to 0.09% C were tested. Discrepancies between the classical and the electrochemical test are accounted for by the fact that the reactivation method detects both continuous and local chromium-depleted areas in the steel structure, whereas the classical test reveals only continuous depletion zones leading to IG corrosion.
TL;DR: From analysis of the electrochemical reactions it was found that the passivity of gamma2 is due to the formation of stannous and/or stannic oxide (hydroxide) and that the corrosion failure of dental amalgam occurs through the dissolution of this passive oxide in gamma2 at potentials of minus 250 mV Vs. SCE with theformation of tine oxychloride.
Abstract: The electrochemical behaviour of the component phases of dental amalgam, viz. Ag3Sn(gamma),Ag2Hg3(gamma1), Sn7-8Hg(gamma2),Cu3Sn, Cu6Sn5 and a composite of gamma1 + gamma2 phases were evaluated in saline solution by standard anodic polarization techniques. Using multi-electrode theory a theoretical polarization diagram was constructed from the composite phases and compared with an anodic polarization profile attained from conventional dental amalgam. A strong agreement was obtained. From analysis of the electrochemical reactions it was found that the passivity of gamma2 is due to the formation of stannous and/or stannic oxide (hydroxide) and that the corrosion failure of dental amalgam occurs through the dissolution of this passive oxide in gamma2 at potentials of minus 250 mV Vs. SCE with the formation of tine oxychloride. The corrosion behaviour of Cu6Sn5 is similar to that of gamma2 phase and its presence impairs the corrosion resistance of dental amalgam. If the copper containing phase is Cu3Sn, it will be passive in Ringer's solution, possibly as a result of Tamman's "multiple rule of eight".
TL;DR: In this article, the free enthalpy of GR II has been evaluated to 1,020,400 ± 4,600 calories/mole, and the probable area of stability of the GR II in the tensionpH equilibria diagram for iron has been established.
TL;DR: The fracture modes, metallurgical and environmental influences, and suggested mechanisms of aqueous stress corrosion cracking in titanium alloys are reviewed in this paper, but the task of assembling a complete quantitative model is formidable.
Abstract: The fracture modes, metallurgical and environmental influences, and suggested mechanisms of aqueous stress corrosion cracking in titanium alloys are reviewed. Many observations can be rationalised, but the task of assembling a complete quantitative model is formidable.
TL;DR: In this article, the hot corrosion behavior of various nickel and cobalt-base alloys has been studied using the coating test, in which alloy samples were coated with approx. 1 mg/cm 2 Na 2 SO 4 and oxidized in slowly flowing oxygen at 1 atm. pressure.
TL;DR: The use of dissimilar metals would permit selection of the alloy of appropriate mechanical properties for each part of an implant and would allow improved corrosion resistance that certain alloys can convey to other alloys with which they are in contact.
Abstract: Previously, the use of dissimilar metals for the construction of surgical implants has been strongly discouraged because the combination of metals was likely to provoke more rapid corrosion of one metal. With the passive alloys that are in present and future application, however, a reconsideration of the use of dissimilar metals is required. Presently available electrochemical tests allow accurate prediction of safe and unsafe combinations of metals. The use of dissimilar metals would permit selection of the alloy of appropriate mechanical properties for each part of an implant and would allow improved corrosion resistance that certain alloys can convey to other alloys with which they are in contact.
TL;DR: In this paper, low-rate (∼ 0.5 mV/sec) cathodic linear sweep voltammetry (LSV) experiments were conducted on preanodized antimonial and nonantimonial lead.
Abstract: Low‐rate (∼ 0.5 mV/sec) cathodic linear sweep voltammetry (LSV) experiments were conducted on preanodized antimonial and nonantimonial lead. The sweeps were supplemented by current‐time traces obtained during the short term (≤ 1 hr) anodic treatment above the reversible potential in electrolytes. Despite complications from additional substrate corrosion during the sweeps, semiquantitative observations were possible and the cathodic discharge could be resolved into components. A major finding was that antimony in the lead retards the formation of in the preliminary anodic treatment. Implications from the results with regard to the behavior of the Pb‐acid battery positive plate are briefly discussed.
TL;DR: In this paper, the corrosion of copper in oxygenated sulfuric acid solutions was studied by means of weight-loss and polarization curves, and an explanation of this phenomena was proposed on the basis of chemical attack by dissolved oxygen on the Cu+ ions which are intermediates in the electrochemical copper oxidation scheme.
Abstract: The corrosion of copper in oxygenated sulfuric acid solutions was studied by means of weight‐loss and polarization curves. At a given potential, the rate of copper dissolution is greater in the presence than in the absence of oxygen reduction, which is contrary to the conventional theory of mixed potentials. An explanation of this phenomena is proposed on the basis of chemical attack by dissolved oxygen on the Cu+ ions which are intermediates in the electrochemical copper oxidation scheme. The model is further verified by results of varying the solution agitation rate, acid strength, and oxygen partial pressure.
Patent•
10 Mar 1975TL;DR: In this article, the superalloy body is coated by physical vapor deposition with a composition consisting essentially of 50-80% by weight of cobalt and 20-50% of chromium, and the body may then be coated with an overlayer of aluminum and heat treated to cause interdiffusion of aluminum into the undercoating and thereby enhance the hot corrosion and oxidation resistance of the super alloy body.
Abstract: A protective coating is provided for nickel-base and cobalt-base superalloys which is highly resistant to corrosion and oxidation in a fused Na2 SO4 environment at elevated temperatures. The superalloy body is coated by physical vapor deposition with a composition consisting essentially of 50-80% by weight of cobalt and 20-50% by weight of chromium. Optionally, the body may then be coated with an overlayer of aluminum and heat treated to cause interdiffusion of aluminum into the undercoating and thereby enhance the hot corrosion and oxidation resistance of the superalloy body.