Crevice Corrosion Of Stainless Steels Research Articles

The Role of Inclusions on Initiation of Crevice Corrosion of Stainless Steel: II . Theoretical Studies

A mathematical model for the initiation of crevice corrosion on 304 stainless steel in was developed. The central concept is that thiosulfate ions, formed by dissolution of inclusions and trapped within the crevice, act in concert with chloride ions to cause passivity breakdown when their concentrations exceed critical values. The model includes consideration of migration and diffusion of the supporting electrolyte, as well as ions produced by dissolution of metal and inclusions. Experimental data reported separately in Part I were compared with theoretical predictions for the critical geometry at which initiation occurred, and for the degree of cathodic protection required to prevent crevice corrosion. A simplified model was developed to predict conditions under which breakdown would be expected to occur for various cases of crevice geometry, potential at the edge of the crevice, and inclusion density.

ChemInform Abstract: Role of Inclusions on Initiation of Crevice Corrosion of Stainless Steel. Part 1. Experimental Studies.

AbstractThe initiation of crevice corrosion on 304 stainless steel in neutral NaCl solution is suggested to be caused by a concerted depassivation effect of Cl‐ and S2O32‐ ions, the latter being produced by electrochemical dissolution of MnS inclusions.

The Role of Inclusions on Initiation of Crevice Corrosion of Stainless Steel: I . Experimental Studies

Electrochemical dissolution of in deaerated was found to produce thiosulfate ions. In addition, the presence of both chloride and thiosulfate ions above critical levels of concentration was found to cause rapid depassivation of 304 stainless steel in well‐stirred deaerated solutions. Therefore, the hypothesis was explored that initiation of crevice corrosion in this system is caused by entrapped thiosulfate ions produced by electrochemical dissolution of inclusions. The hypothesis differs from the view that breakdown is caused by acidification owing to Cr dissolution and hydrolysis. An artificial crevice cell, constructed from two optically flat surfaces, was used to measure the initiation time under controlled variation of crevice gap, applied potential, and sulfide inclusion density. It was found that crevice corrosion did not initiate for sufficiently large crevice gaps, negative (cathodic) applied potentials, and low inclusion densities. In Part II of this series of papers, data are compared to predictions based on a mathematical model of the proposed “thiosulfate entrapment” mechanism.

表面改質によるステンレス鋼のすきま腐食防止技術

表面改質によるステンレス鋼のすきま腐食防止技術

ステンレス鋼のすきま腐食とその試験法

Structural materials having metal-metal or metal-nonmetal crevice parts were corroded locally within crevices in solutions containing chloride ions. Recent work and developments concerning methods for evaluating crevice corrosion of stainless steels and for providing protection against it are described.

Ion exchange resin fibres for potential measurement in crevice corrosion studies

Fibres of cation and anion exchange resins, regenerated in the Na + and Cl − forms respectively, have been used to monitor corrosion potentials during crevice corrosion of stainless steels. The resin fibre probe has a relatively high electrical resistance but has the significant advantage that it can be produced flush with the crevice wall, thus avoiding the entrainment of additional electrolyte.

3% NaCl水溶液中におけるステンレス鋼の金属/金属-すきま再不動態化電位に及ぼす合金元素の影響

3% NaCl水溶液中におけるステンレス鋼の金属/金属-すきま再不動態化電位に及ぼす合金元素の影響

Crevice corrosion and microthrowing power

The two concepts of crevice corrosion and electrolytic microthrowing power seem to have been connected very seldom, in spite of the fact that, on a closer look, microthrowing power would be expected to be a decisive factor in crevice corrosion of stainless steels. Whereas the electrolyte resistance is the predominating factor for the macrothrowing power, i.e. an even current distribution on macro-scale electrodes, the microthrowing power, i.e. an even current distribution on small-scale electrodes, like crevices, is governed by the product, |κ·dη/d i| of the electrolyte conductivity κ and of the slope dη/d i of the polarization curve. In the passive stage, preceding initiation of crevice corrosion dη/d i is exceptionally high, whereas κ is quite high in the concentrated and acid crevice solution formed in the propagation stage. Calculations are presented for the distribution of current and electrode potential on the crevice walls and of total crevice current and ohmic potential drop from the bottom to the mouth of a thin ( h = 0.01 cm) and deep ( L = 10 cm) metal/metal crevice of type 316 stainless steel in the preinitiation, initiation and propagation stages of crevice corrosion. The calculations are mainly based on equations derived by Wagner (Plating, 48(1961) 997) for the microthrowing power in the electodeposition of metals into thin and deep crevices on cathodes. As a basis for the calculations, we have determined the passive current density, i p, which has been found to be about two powers of ten lower than has commonly been assumed. The results of the calculations agree well with existing experimental data on current and potential distribution in crevices. The importance of differentiating between creviced anodes under potentiostatic control and naturally working crevice corrosion cells is emphasized.

Effect of Thiosulfate on Crevice Corrosion of Stainless Steels

Abstract Crevice corrosion studies were conducted on AISI 304, AISI 316L, and UHB 904L stainless steels using Teflon/metal crevices exposed to aqueous solutions of 1M NaCl and 1M NaCl + 0.01 M Na2S...

Compositional Changes of Anolyte on Electrolyzing Stainless Steel in High Temperature Chloride Media

In connection with crevice corrosion of stainless steel in high temperature water, Type 304 stainless steel was anodically electrolyzed in solution at temperatures up to 250°C with determination of compositional changes of the anolyte. Components of the steel dissolved as Fe2+, Cr3+, and Ni2+ and lowered the pH of the anolyte by hydrolysis of the dissolved ions. pH measured at room temperature decreased with increasing amounts of charge. During electrolysis at temperatures above 150°C, lower pH values and much more precipitates were obtained, and at 200° and 250°C hard films, which were mainly composed of and scarcely dissolved in hot , were formed on the specimens. In the electrolysis at 250°C, lower pH values were obtained in concentrated Cl− solutions. These pH changes of the anolyte were well described with the experimental results of hydrolysis of Cr3+ solutions. At 200° and 250°C, local corrosion of the steel in the anolyte occurred.

Intergranular attack during crevice corrosion of stainless steels

The crevice corrosion resistance of AISI type 316 stainless steel was investigated as a function of carbide precipitation and grain size in 0.5 M NaCl solution using a potentiodynamic technique and a specially designed crevice assembly. It has been found that if there is chromium depletion along the grain boundaries (for sensitized material) or if there is a large grain boundary area per unit volume (for fine grained material), the intergranular attack takes place in the crevice due to the presence of more active areas along the grain boundaries.

ステンレス鋼のすきま腐食再不動態化電位に及ぼす表面処理の影響

ステンレス鋼のすきま腐食再不動態化電位に及ぼす表面処理の影響

Role of sulphide inclusions in pitting and crevice corrosion of stainless steels

AbstractThe role of sulphide inclusions in the pitting and crevice corrosion of stainless steels is reviewed. It is noted that manganese sulphides, particularly those containing a central oxide core, are the most favourable sites for pit initiation. Replacing the manganese in the sulphide by chromium renders pit initiation more difficult. However, as the severity of the environment increases, pitting occurs at the less active inclusions. It is concluded that changing the composition of sulphides can give a useful, if somewhat limited, improvement in pitting resistance and in crevice-corrosion resistance. Further studies are needed to define the mechanism by which molybdenum, or molybdenum and nitrogen in combination, improve pitting and crevice -corrosion resistance in the presence of sulphide inclusions.

Role of sulphide inclusions in pitting and crevice corrosion of stainless steels

Role of sulphide inclusions in pitting and crevice corrosion of stainless steels

Role of sulphide inclusions in pitting and crevice corrosion of stainless steels

Role of sulphide inclusions in pitting and crevice corrosion of stainless steels

高温純水中におけるステンレス鋼の隙間腐食に及ぼすCr, Moの影響

高温純水中におけるステンレス鋼の隙間腐食に及ぼすCr, Moの影響

Crevice Corrosion of Stainless Steels in Sea Water: Correlation of Field Data with Laboratory Ferric Chloride Tests

Abstract Two year sea water immersion tests were carried out at four North American sites on a wide range of austenitic stainless steels. Some of these steels were found to be completely free from crevice corrosion at all exposure sites. Immersion of the alloys in FeCl3 in the laboratory provided a more severe test of their crevice corrosion resistance, which could be used to make conservative predictions of their performance in sea water.

The role of molybdenum in the crevice corrosion of stainless steels

The paper starts with a literature review of Mo as an alloying element in stainless steels, with particular reference to crevice corrosion. Relevant aspects of the chemistry and electrochemistry of Mo are also summarized and used to discuss the possible role of soluble Mo species in corrosion inhibition. The need to examine solutions of low-valent Mo is indicated. Experiments are reported on stainless steels in the active range of corrosion potentials and the influence of soluble Mo III and Mo IV. No inhibitive effects are found; but inhibition is produced by films of insoluble Mo IV oxide deposited on stainless steels. Such films can be produced by reduction of Mo VI solutions, but not by oxidation of Mo III. It is concluded that, in the corrosion of alloys, Mo probably passes directly from the metal into the protective film, and that soluble Mo compounds play no part in this process.

ステンレス鋼のすきま腐食

ステンレス鋼のすきま腐食

Crevice corrosion of stainless steels in sodium chloride solution

Nucleation of crevice corrosion of five stainless steels in NaCl solution has been studied using potentiokinetic and galvanostatic methods. It is inferred that a well reproducible critical potential for crevice corrosion nucleation exists. This potential depends on the type of steel and is more negative than the critical potential for pit nucleation. The difference between the potential for crevice corrosion and that for pitting is higher for more resistant steels than for less resistant ones. A mechanism explaining the crevice corrosion in chloride solutions is proposed.