Showing papers on "Corrosion published in 1979"

The Electrochemical Behavior of Alkali and Alkaline Earth Metals in Nonaqueous Battery Systems—The Solid Electrolyte Interphase Model

Abstract: It is suggested that in practical nonaqueous battery systems the alkali and alkaline earth metals are always covered by a surface layer which is instantly formed by the reaction of the metal with the electrolyte. This layer, which acts as an interphase between the metal and the solution, has the properties of a solid electrolyte. The corrosion rate of the metal, the mechanism of the deposition‐dissolution process, the kinetic parameters, the quality of the metal deposit, and the half‐cell potential depend on the character of the solid electrolyte interphase (SEI).

Corrosion of Stainless Steels

Abstract: With good pricing, high strength, as well as corrosion resistance, stainless steel is a widely used and popular choice for many applications as a rust resistant material, however many types of corrosion attack stainless steel, such as pitting and crevice corrosion, intergranular corrosion, stress-corrosion cracking, hydrogen embrittlement, general corrosion, and attack by high-temperature gases. This article reviews the corrosion mechanisms of stainless steel to understand the corrosion behavior of stainless steel which is important for the design of any application. Moreover, this article will provide a platform for selecting the suitable type of stainless steel for any application with high corrosion resistance.

Physical model for steel corrosion in concrete sea structures­ theory

Abstract: A physical-mathematical model is developed for concrete exposed to sea water. The model describes: (1)Diffusion of oxygen, chloride ions, and pore water through the concrete cover of reinforcement; (2)ferrous hydroxide near steel surface; (3)the depassivation of steel due to critical chloride ion concentration; (4)the cathodic and anodic electric potentials depending on oxygen and ferrous hydroxide concentrations according to Nernst equation; (5)the polarization of electrodes due to changes in concentration of oxygen and ferrous hydroxide; (6)the flow of electric current through the electrolyte in pores of concrete; (7)the mass sinks or sources of oxygen, ferrous hydroxide, and hydrated red rust electrodes, based on Faraday law; and (8)the rust production rate, based on reaction kinetics. To enable calculations, numerical values of all coefficients are indicated. The theory is completed by formulating the problem as an initial-boundary value problem.

Corrosion micromorphology of noble metal alloys and depletion gilding

Abstract: Noble metal alloys commonly undergo selective dissolution during anodic corrosion whereby the less noble component is dissolved preferentially. This is particularly interesting, as it leads to a depletion of the less noble species not only at the surface of the metal but also at an appreciable depth within it, implying that a mass transport of atoms is occurring either through the bulk of the crystal lattice or across the surface to support the continuing dissolution. Experiments in which the micromorphology of silver–gold alloys is observed during such corrosive treatment have shown that surface diffusion of gold plays an important part in this process. As surface silver atoms are dissolved the residual gold atoms reform into gold-rich islands so that fresh silver atoms are continuously exposed to the environment layer by layer. These observations will be described in detail elsewhere1. Here the mechanism of surface re-arrangement is considered, which leads to the accumulation of gold-rich surface regions, and throws a new light on the ancient craft of depletion gilding.

PHYSICAL MODEL FOR STEEL CORROSION IN CONCRETE SEA STRUCTURES­ ApPLICATION

Abstract: The theoretical physical model developed in a companion paper, is applied to a simplified calculation of corrosion rates and times to corrosion cracking of concrete cover. Setting up approximate estimates of effective resistance of the corrosion cell, and treating oxygen and chloride ion transport through concrete cover as quisi-stationary and one-dimensional, the corrosion problem is reduced to ordinary differential equations in time. For determining the extents of cathodic and anodic areas and the thickness of the rusting layer, a new principle stating that the actual corrosion current is maximum is postulated. Various steady-state corrosion processes are then analyzed, and after developing approximate formulas for the time of steel depassivation due to chloride ions and for cover cracking due to volume expansion of rust, a number of illustrative numerical examples are given. Diffusivities for chloride ions and oxygen are shown to be usually the controlling factors.

In vitro corrosion testing of titanium surgical implant alloys: an approach to understanding titanium release from implants.

Abstract: The excellent corrosion resistance of titanium and its alloys to physiological chloride solutions is well documented. Occasionally, however, titanium compounds have been found in tissue adjacent to titanium implants. These findings were reported to be unrelated to wear processes, suggesting that either the metal or its passive film was dissolving. The unpredictability of these findings further suggests that preimplantation surface treatments and/or variations in the physiological environment may be factors. To determine a mechanism by which titanium can be released from an implant a study was initiated which employed electrochemical techniques, Auger electron spectroscopy (AES), and replica transmission electron microscopy (RTEM). Specifically, the purpose was to characterize the passive film on titanium and Ti-6Al-4V, and to determine if there is dissolution of the film or metal in a static unstressed state. Passive film behavior of commercially pure titanium, Ti-6Al-4V and nitrided Ti-6Al-4V was studied by anodic polarization and pulse potentiostatic capacitance techniques in Ringer's solution at 37°C with and without physiological additions of several amino acids. Solution Po2, pH, and specimen surface finish were varied to include all probable in vivo conditions. In all tests, potentiostatic anodic polarization of each material yielded potential-current density curves which showed passivity over the entire experimental range. This range greatly exceeded the oxygen-reduction reversible electrode potential. No breakdown potentials were observed. The passive current density was not significantly affected by varying the experimental parameters. AES as well as charge and capacitance measurements showed that the electrochemical reaction which occurred was growth of the passive film. The data indicated that the effective electrochemical area of each specimen was less than its geometrical area, and was dependent on both pH and surface finish. The findings of this study showed that, under static conditions, titanium and Ti-6Al-4V should withstand exposure to physiological chloride solutions at body temperature indefinitely. Furthermore, the findings are consistent with a model of the implant surface inwhich the naturla air oxide that initially forms on an abraded implant surface is comprised of microscopic oxide needles. It is proposed that (i) the needless canbe broken off or dissolved in vivo, providing the source of the titanium sometimes found in tissue adjacent to an implant, and (ii) use of certain pretreatments may remove the needles prior to surgery, resulting in the more common case in which titanium is nto found in the tissue.

Electrochromism in Anodic Iridium Oxide Films II . pH Effects on Corrosion Stability and the Mechanism of Coloration and Bleaching

Abstract: The oxidation state of iridium ions in an oxide film, grown electrochemically on an Ir metal reflector electrode, can be rapidly and reversibly modulated according to the electrochromic redox reactionBy suitable choice of electrolyte composition and potential limits, the coloration and bleaching processes can be effected without causing oxide film growth or dissolution, or electrolyte decomposition. Color‐bleach (c‐b) cycles exhibit reflectance contrast changes, , and charging times, τ, suitable for electrooptic display devices, e.g., for a film 320 nm thick, at and . Long term corrosion stability is obtainable in mildly acidic sulfate electrolytes, e.g., at pH 3.5. Sulfate electrolytes are also apparently unique in preventing degradation of c‐b response times owing to changes in film structure. East write‐erase times are made possible by the highly porous and hydrated nature of the oxide film and the ready availability of the protons required for bleaching from an 'internal' source—free molecules in the electrolyte contained within the film pores and/or bound or OH groups on the oxide surface. The kinetics and mechanism of the electrochromic reaction in anodic iridium oxide films are discussed with particular reference to the requirement for preserving electroneutrality within the bulk oxide. Recent claims that this redox reaction can occur without exchange of protons with the electrolyte are shown not to be substantiated. Attractive features of the electrochromic iridium oxide system for display devices include: (i) broad spectral absorption; (ii) good contrast ratio; (iii) fast response; (iv) good corrosion stability; (v) good open‐circuit memory in the presence of water and dissolved ; (vi) suitable threshold and switching voltage levels; and (vii) the ability to grow and reform the oxide layer in situ in the electrooptic display cell. The charge (~20 mC cm−2) and energy (~30 mJ cm−2) required for coloration and bleaching are similar to those required for other electrochromic oxide systems, e.g., the tungsten bronzes.

Low cost bipolar current collector-separator for electrochemical cells

Abstract: A bipolar current collector-separator for electrochemical cells consists of a molded aggregate of electro-conductive graphite and a thermoplastic fluoropolymer combined in a weight ratio of 2.5:1 to 16:1. The bulk resistivity of such a molded bipolar current collector-separator is less than 4×10 -3 ohm inches (Ω in.). It has excellent corrosion resistance to a variety of feedstocks such as brine, aqueous HCl, etc. and to various electrolysis products such as caustic, chlorine, hydrogen, etc. In one alternative form the anodic side of a current collector-separator for a water electrolyzer is covered by a thin layer of a passivated metallic foil thus protecting the graphite current collector against attack by oxygen.

The Corrosion of Copper, Tin, and Their Alloys

Abstract: Part one discusses the corrosion of copper and its alloys, including atmospheric corrosion, oxidation, corrosion by other gases, aqueous and nonaqueous corrosion, stress-corrosion cracking, erosion, radiation, underground corrosion and purposeful corrosion. Part two treats the corrosion of tin and its alloys including atmospheric corrosion, gaseous corrosion, aqueous and non-aqueous corrosion, tinplate and the electrochemistry of the Sn -- Fe couple deterioration by phase change and Sn-whisker formation. Chemical and electrical polishing techniques for copper are described. Quantitative data are emphasized for engineering applications. Numerous ref. -- AATA

Corrosion of glass

Abstract: The compositional and structural changes on surfaces that affect the durability of soda-limesilica glasses are discussed. The book begins with a general review of corrosion and weathering phenomena in glass which is followed by a review of the applicable surface analytical techniques (scanning electron microscopy, energy dispersive x-ray analysis, Auger electron spectroscopy, electron microbeam probe, and infrared reflection spectroscopy) used to study these phenomena. There is in-depth consideration of corrosion of glass by aqueous solutions, weathering, and the effects of manufacturing methods on glass durability. -- AATA

A Finite Difference Numerical Analysis of Galvanic Corrosion for Semi‐Infinite Linear Coplanar Electrodes

Abstract: A finite difference numerical analysis technique has been used to evaluate the distribution of the electrode potential within the electrolyte above a galvanic corrosion couple with linear, semi‐infinite, coplanar electrodes. Corrosion reactions are assumed to be under activation control with logarithmic polarization behavior. The analysis accommodates any combination of electrochemical polarization parameters, corrosion current densities, solution conductivity, electrode dimensions, and depth of corrosion solution as variable parameters. Further, the analysis has been adapted to include the influence of an externally impressed polarization. The accuracy of the analysis procedure has been established by comparison with experimental results obtained from a model zinc‐copper galvanic corrosion couple. The effects of various parameters on the electrode potential distribution at the surface of the corrosion couple have been examined and their significance discussed.

On the Mechanism of Pitting of Aluminum

Abstract: : The Engell-Stolica potentiostatic method has been used for the kinetic study of the mechanism of pitting initiation of Al 1199. A statistical treatment of induction time has been developed in order to get meaningful data. Pitting initiation has been found to be potential-independent and the linear increase in the induction time for pitting with the increase of the potential applied in the passive range is due to the growth of the oxide film layer on the Al surface. The value of the critical potential obtained by extrapolation of the induction time vs potential plot to a zero induction time correlates with the value given in the literature. The trend toward a decrease in the kinetic order of the pitting reaction with an increase in the pH value of the aggressive solution has been confirmed. The independency of the kinetic order on the electrode potential of the solution indicates that the pitting initiation is controlled by a chemical process with the formation of an intermediate complex and therefore is consistent with the 'complex ion theory' of corrosion. (Author)

Sulfide Induced Corrosion of Copper Nickel Alloys

Abstract: The susceptibility of Cu-Ni alloys to accelerated corrosion in sea water containing low sulfide concentrations has been investigated. Test alloys included wrought 90/10 Cu-Ni, 70/30 Cu-Ni ...

The Corrosion of Cu-Ni Alloys 706 and 715 in Flowing Sea Water. II – Effect of Dissolved Sulfide

Abstract: The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in sulfide polluted flowing sea water has been studied as a function of sulfide concentration. The experimental techniques used include small amplitude cyclic voltammetry, AC impedance measurements, large amplitude cyclic voltammetry, and extensive surface examination by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction, and Auger electron spectrometry (AES). It is shown that the presence of sulfide induces a loss in passivity of the alloy surface due to the formation of cuprous sulfide as the principal corrosion product. Furthermore, accelerated corrosion of these materials in sulfide polluted sea water appears to arise from a shift in the corrosion potential to sufficiently active values that hydrogen evolution becomes a viable cathodic process.

Process for producing elevated temperature corrosion resistant metal articles

Abstract: A process for providing coatings on metal articles whereby the articles will be resistant to corrosion at elevated temperatures. The process involves the application of an overlay on an article surface, the overlay comprising a ductile metal of a composition normally resistant to corrosion at elevated temperatures. An outer layer of aluminide or metal which is resistant to corrosion at elevated temperatures but which is subject to embrittlement at such temperatures is applied to complete the coating. Porosity in the coating is then eliminated and a high integrity corrosion resistant coating not subject to cracking is obtained by heating the article in a gaseous atmosphere to elevated temperature and simultaneously applying isostatic pressure to the article.

The Cyclic Corrosion of the Lead‐Acid Battery Positive

Abstract: Simulated deep discharge cycling of a lead‐acid battery positive, using a linear potential sweep technique, was performed on pure and antimonial lead electrodes in sulfuric acid electrolyte with and without phosphoric acid additive. Discharge capacity, depth of corrosion, corrosion product morphology, adhesion between the substrate and corrosion product, and distribution of antimony, phosphorus, and sulfur in the corrosion product layer were monitored. Results indicated that the cyclic corrosion process occurring at the lead/lead dioxide electrode interface was controlled by the corrosion product layer consisting of an inner layer dominated by and an overlapping outer layer dominated by . Presence of antimony in the alloy was noted to improve the adhesion between the grid substrate and the inner layer, integrity of the inner layer, and interparticle bonding of lead dioxide particles. Phosphoric acid additive in electrolyte was noted to alter the structure of corrosion product layer resulting in improved adhesion between the grid and the inner layer and between the inner and outer layer.

Corrosion Behaviour of Cast Nickel Aluminium Bronze in Sea Water

Abstract: Corrosion trials have been carried out using cast nickel aluminium bronze alloy in the as cast, heat treated and welded states, and the specimens examined using optical and electron optical techniques. It has been shown that selective phase corrosion can occur near the heat affected zone of welded cast nickel aluminium bronze which is due to the attack of the a phase adjacent to the continuous lamellar K phase. Heat treatment of this alloy considerably reduces its susceptibility to corrosion due to both stress relief and structural changes caused by the thermal treatment.

The oxidation resistance of fine-grained sputter-deposited 304 stainless steel

Abstract: The air oxidation of free standing 0.1 cm thick sputter-deposited and wrought 304 stainless steel specimens was studied and the long term oxidation weight gains of the sputterdeposited material were much less than weight gains for the wrought material at 800, 900, and 1000°C. The amount of scaling was also much less on the sputtered material and a thin, adherent oxide formed. The oxide on the sputtered material was more uniform in composition and was higher in chromium and manganese compared to oxide on wrought stainless and eventually formed MnCr2O4 after long periods of exposure. No stratified oxide layers, as typically observed in wrought stainless steel, formed on the fine-grained sputtered material. The improved scaling resistance of the sputter-deposited steel was attributed to a combination of grain boundary enhancement of chromium diffusion, reduced stresses in the oxide and mechanical keying of the oxide to closely spaced grain boundaries. The stability of grain size for the sputtered material (grain size ≤ 6 μm) also contributed to the better oxide adherence.

Carbide coating process by use of molten borax bath in Japan

Abstract: Pore-free and smooth surface carbide layers can be formed on metals and carbon immersed in a molten borax bath above 1073 K. The carbide layers, consisting of VC, NbC, TiC, or Cr7C3, are formed by the reaction between the carbon atoms in the substrate and the carbide forming element atoms dissolved into the fused borax from additive powders such as ironvanadium, ironniobium, iron-titanium, ironchromium, and chromium. Core hardening of steel substrates can be simultaneous or by reaustenitizing after carbide coating. Carbide coated steels show excellent resistance to wear, seizure, corrosion and oxidation. The carbide layers are adherent to the substrate and do not exfoliate in severe service as in cold forming. The process effectively improves performance of dies, tools, machine parts, and is applied in various fields of Japanese industries.

Pitting corrosion for retaining acrylic resin facings.

Abstract: 1. Pitting corrosion provides undercuts suitable for retaining a resin facing. 2. Using a cathode with a proper shape, pits were uniformly distributed on the surface of a metal casting. The size of pits varies, depending on the time of pitting treatment. 3. The retentive pits were excellent in both retentive strength and marginal sealing when compared with spherical powder and beads.