bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative, Rapid Determination of Steel Surface Treatment Coverage
Authors: HEKAL I. M. , KORPI G. K.
Published: February 2013

An experimental technique quickly determines the integrity of surface treatments on steel. These treatments include tinplate, electrochemically produced chromium-chromium oxide and chromium phosphate type coatings, and any other film forming treatments. A quantitative relationship between rate of iron dissolution and surface treatment coverage is established. Continuous measurements of the rate of iron dissolution from a definite sample area also show the ability of some commercial surface treatments to prevent corrosion. Important experimental variables were temperature, rate of agitation, and corrodent solution composition.
A Capacitance-Resistance Study of Polybutadiene Coatings on Steel
Authors: TOUHSAENT ROBERT E. , LEIDHEISER HENRY
Published: February 2013

The capacitance and resistance of polybutadiene coatings on steel were determined as a function of time of exposure to air-saturated 3% sodium chloride solution. The results were interpreted in terms of a model in which the solution rapidly penetrates capillaries or defects in the coating followed by solution of water throughout the coating. The model predicted the resistance and the change in resistance of the coating with time. Generalized corrosion of the steel coincided with a departure from linear behavior of the capacitance-time curve and a coating resistance of 50,000 to 100,000 ohms for the 5 cm2 sample area.
Electrochemical Potentials of High Purity Metals in Sea Water
Authors: GROOVER R. E. , SMITH J. A. , LENNOX T. J.
Published: February 2013

The electrochemical potentials of high purity metals were determined in quiescent sea water. The data are presented as histograms and as potential-time graphs. The electrochemical potential of many of the metals never reached a steady state value, so it is impractical to assign a specific potential value to these metals. A galvanic series is included based on a subjective ranking of the histograms. Two of the metals, bismuth and tin, had relatively stable potentials in sea water, but at present they do not appear to offer any advantage over the Ag/AgCl reference electrode. The comparatively negative potential of the high purity aluminum may be of interest because of the possibility that a high potential galvanic anode with the weight advantage of aluminum could be developed.
Effect of Some Phosphoroorganic Compounds on the Corrosion Rate of Various Metals in Acid Solutions
Authors: DUS B. , SZKLARSKA-SMIALOWSKA Z.
Published: February 2013

Corrosion rate, polarization curves and double layer capacity measurements of Fe, Ni, Pb, and Zn in acid solutions in the presence of several seleno and thio-phosphoroorganic compounds were performed. It was found that the effectiveness of the given compound as a corrosion inhibitor depends on three main factors: (1) structure of the inhibitor molecule, (2) sign of the electric charge of the metal surface, and the (3) anodic or cathodic process determining the dissolution rate of the metal in an open circuit condition. Since the two last factors were different for the metals considered, the inhibitor efficiency of the given compound changed from one metal to another.
Dissolution of Ti-6Al-4V at Cathodic Potentials in 5N HCl
Authors: OWEN E. L. , MAY R. C. , BECK F. H. , FONTANA M. G.
Published: February 2013

Localized dissolution, which was observed on polished surfaces of Ti-6Al-4V during exposure to 5N HCl at cathodic potentials, is explained on the basis of the uneven growth of a surface hydride layer. The possible relation of this behavior to the initiation of stress corrosion cracks is also discussed.
An Electrochemical Study of Heteropoly Molybdates as Cooling Water Corrosion Inhibitors
Authors: WEISSTUCH A. , SCHELL C E.
Published: February 2013

The utility of heteropoly molybdate compounds as cooling water corrosion inhibitors for mild steel was investigated by various electrochemical techniques. It was shown that high concentrations of heteropoly molybdates are required to passivate mild steel electrodes. The breakdown of passivity was studied as a function of inhibitor volume and concentration of aggressive anions. Various approaches for the economic utilization of heteropoly molybdates are described, including high level pretreatment-low level maintenance level regimes and formulation with polyphosphates and zinc.
Electrochemical Aspects of Stress Corrosion of Steels in Alkaline Solutions
Authors: BIGNOLD G. J.
Published: February 2013

The existing theories of initiation and propagation of stress corrosion cracking (SCC) are examined with particular reference to their applicability to steels in caustic solutions. The electrochemical theory which considers cracking to be due to local active dissolution at the crack tip, and passivation of the walls, is developed into a model which explains the observed potential dependence of cracking rate and aspect ratio, and the existence of an anodic potential above which cracking ceases. The current distribution during stress corrosion at the rest potential is calculated, and it is shown that the cathodic current, unlike the anodic current, is not highly localized. The efficacy of anodic and cathodic polarization of a stress corrosion specimen is also examined, and it is shown that anodic control can be effective at the crack tip, whereas cathodic control only exists near the mouth of the crack.
Chemistry of Grain Boundaries and Its Relation to Intergranular Corrosion of Austenitic Stainless Steel
Authors: JOSHI A. , STEIN D. F.
Published: February 2013

The basis of intergranular corrosion in austenitic stainless steels is examined by relating the grain boundary composition to the corrosion properties. The technique of Auger electron spectroscopy has been used to obtain the chemistry of intergranular fracture surfaces. It was found that the chromium depleted zones exist and that the depletion theory was valid for tests in weakly oxidizing solutions. In highly oxidizing solutions, however, the impurity segregation and not chromium depletion best explains the deterioration of corrosion properties. Impurity elements such as sulfur, silicon, nitrogen, and phosphorous were observed in the various steels examined. An attempt is made to explain the observed corrosion properties on the basis of chromium depletion and solute segregation theories combined with an electrochemical mechanism.
Potentiostatic Polarization of Inconel X-750
Authors: TROUT B. L. , DANIELS R. D.
Published: February 2013

The anodic polarization characteristics of Inconel X-750 Alloy in two heat treated conditions, (1) solution treated and (2) solution treated and aged, were examined for sensitivity to temperature and to chloride ion concentration. The effects of microstructure and environment on the anodic passivation behavior of this alloy are correlated and discussed.
The Role of Hydrogen in the Mechanism of Stress Corrosion Cracking of Austenitic Stainless Steels in Hot Chloride Media
Authors: WILDE B. E. , KIM C D.
Published: February 2013

Previous studies on high strength martensitic stainless steels in sodium chloride solution have attributed crack growth to (1) hydrogen embrittlement at highly cathodic applied potentials, and (2) active path dissolution (to the exclusion of hydrogen embrittlement) at open circuit and anodic applied potentials. A recent re-evaluation of cracking in this system, however, has shown that crack growth at any applied potential can be adequately explained on the basis of a hydrogen embrittlement process. In view of this recent clarification, the question arises whether hydrogen is involved in the cracking of austenitic stainless alloys where this possibility had been previously excluded on a basis similar to that applied to high strength steels. To this end, electrochemical studies have been conducted on AISI Type 304 stainless steel in lithium chloride. The data indicate that although hydrogen is evolved under conditions of corrosion at the free corrosion potential, none is absorbed into the steel during cracking. When hydrogen absorption was promoted by the use of sodium arsenite as a poison, a marked increase in time to failure was observed, contrary to what would be expected if absorbed hydrogen was contributing to crack growth. To help clarify the kinetics of the surface reactions proceeding during cracking, the influence of applied current on time to failure in boiling lithium chloride is described. On the basis of the data obtained, it is concluded that hydrogen embrittlement plays little or no role in the crack propagation process, which is believed to proceed by a strain assisted anodic dissolution mechanism.
Investigation of Stress Corrosion Cracking Susceptibility of Fe-Ni-Cr Alloys in Nuclear Reactor Water Environments
Authors: CLARKE W. L. , GORDON G. M.
Published: February 2013

Nonstabilized 300 series stainless steels stressed over yield are susceptible to intergranular stress corrosion cracking (SCC) when exposed in the heavily sensitized condition to 288 C (550 F), high purity water containing dissolved oxygen. The effects of stress, oxygen levels, and significant metallurgical parameters on intergranular SCC of AISI Type 304 are being evaluated. Several promising intergranular SCC resistant alternate alloys have been identified through preliminary investigations, e.g., austeno-ferritic duplex and stabilized austenitic stainless steels.
Action of Carbon in Stress Corrosion Cracking of Mild Steel in Nitrate Solutions
Authors: FLIS J.
Published: February 2013

The effect of total carbon content on susceptibility of iron to stress corrosion cracking (SCC), on the depth of intergranular corrosion without stresses, anodic polarization curves, and the general corrosion rate was examined on decarburized Armco iron and its ferritic or martensitic alloys with carbon up to 1.4% in 5N NH4NO3 and 5N Ca(NO3)2, pH 5.0, at 75 and 100 C (167 and 212 F). The susceptibility to SCC and intergranular corrosion increased with the carbon content increasing up to about 0.009% or above, and it diminished with further increase in the carbon content. Carbon decreased the ability of iron to passivate (depassivating action), but it also promoted deposition of magnetite and enhanced its protective properties (impeding action). It is suggested that the observed effect of carbon on SCC and intergranular corrosion results from the predominance of the depassivating action at low carbon contents, and the predominance of the impeding action at higher carbon contents.
Vapor Pressure of Liquid Sodium Sulfate from 954 to 1204 C
Authors: FRYXELL R. E. , TRYTHALL C A. , PERKINS R. J.
Published: February 2013

The vapor pressure of liquid sodium sulfate in the range 954 to 1204 C (1750 to 2200 F) has been measured by the transpiration method in air. The results are much lower than those extrapolated into this temperature range from previously published results but are believed considerably more reliable on the basis of excellent conformance to Trouton's rule. The results are expressed by the equation:
Fractographic Interpretation of Subcritical Cracking in a High Strength Titanium Alloy (IMI 550)
Authors: WANHILL R.J. H.
Published: February 2013

A detailed fractographic study of subcritical crack growth in 3.5% aqueous NaCl and liquid mercury was made for IMI 550 (Ti-4AI-4Mo-2Sn-0.5Si) in an (α + β) heat treated condition. The work of Cox and Ajtchison, which showed that river markings are at high angles to genuine cleavage planes, is confirmed. Mechanisms for formation of the river markings are postulated, and a distinction is made between the cleavage topographies in salt water and mercury. Support is also found for the mechanism of liquid metal embrittlement postulated by Hancock and Ives. The overall appearance of the subcritical fracture surfaces provides an explanation for the low KISCC (salt water) customarily found for IMI 550.
Stress Corrosion Cracking of Iron and Nickel Base Alloys in Sulfate Solutions at 289 C
Authors: VERMILYEA DAVID A.
Published: February 2013

Stress corrosion cracking (SCC) of iron and nickel base alloys in aqueous solutions at 289 C (552 F) has been studied using a straining electrode apparatus. Cracking susceptibility decreases in the order sensitized stainless steel, cold worked stainless steel containing martensite, sensitized Inconel 600, annealed stainless steel, and annealed or cold worked Inconel 600 and alloy AL 326. High cracking susceptibility usually occurs when conditions result in the development of thick reaction products. Acid conditions and chromium depletion favor thick reaction products and enhance susceptibility.
Stress Corrosion Cracking of Sensitized Stainless Steel in Oxygenated High Temperature Water
Authors: BERRY WARREN E. , WHITE EARL L. , BOYD WALTER K.
Published: February 2013

The stress corrosion cracking (SCC) behavior of sensitized Type 304 stainless steel has been studied in 288 C (550 F) primary water as a function of oxygen and fluoride contents of the water, stress level, prestrain, heat treatment, and surface preparation (tarnish film, surface ground, or pickled). Susceptibility to intergranular cracking increased with increasing oxygen content in the water, increasing stress levels, or with tarnished or pickled surfaces. The other variables had little or no effect. Sensitized wrought Types 309 and 316 stainless steels were also susceptible to intergranular SCC, while sensitized Types 304L, 308L, and 347 stainless steels and Incoloy Alloy 800 and Inconel Alloy 600 did not crack under the most severe test conditions (3Sm stress loading in 288 C water containing 100 ppm oxygen).
A Hydrodynamic Analog of Polarization Processes
Authors: REINOEHL J. E.
Published: February 2013

Electrochemical currents, voltages, potentials, and polarization processes are described in terms of water currents, waterfalls heights, geographical elevations, and erosion processes, respectively.
Some Effects of ClO4− Ions on the Stability of Anodic Films Formed on Mild Steel
Authors: HOARE JAMES P. , MAO KAO- WEN
Published: February 2013

Steady state polarization curves were obtained on mild steel wires along with film stripping and mass balance measurements in mixed solutions of Na2SO4, NaClO3, and NaClO4. It was found that the anodic film on steel in Na2SO4 is electronically conducting with the transpassive current being consumed in O2 evolution. When NaClO4 was added to the Na2SO4 solution, the transpassive region was lowered by about 500 mV, the presence of a surface film was undetected, and the current was consumed in metal dissolution. The film on steel in NaClO3 was a uniform porous layer with less conductivity than that in Na2SO4. When NaClO4 was added to the NaClO3 solution, the anodic film was not dissolved as readily in the transpassive region and uneven metal removal was observed on the steel samples. The results were interpreted in terms of the dissolution of anodic films in the transpassive region by an ion exchange process between the oxide ions of the film and the anions adsorbed from solutions on the film.
Stress Corrosion Cracking of Aged U-4.5 Wt% Nb
Authors: MACKI JAMES M. , KOCHEN ROBERTL.
Published: February 2013

The stress corrosion cracking (SCC) behavior of the U-4.5 wt% Nb alloy aged 80 hours at 260 C (500 F) has been investigated. Smooth four point bend SCC tests and smooth static tensile SCC tests were used. The results of this study show that aged U-4.5 wt% Nb alloy is susceptible to SCC when stressed and exposed to water containing oxygen and chloride ions. The stress corrosion cracks which nucleate in the aqueous chloride environments proceed by an intergranular SCC fracture mode. No failures were observed in dry air containing less than 200 ppm moisture or in 100% relative humidity air. The surface tensile stress required for SCC is less than 20,000 psi in oxygen saturated water containing 50 ppm chloride ions.
Development of Ferritic Stainless Steels for Use in Desalination Plants
Authors: PESSALL N. , NURMINEN J. I.
Published: February 2013

This paper describes a research program aimed at optimizing the composition, heat treatment, and structure of ferritic stainless steels for use as condenser tube material in desalination plants. The results of corrosion tests carried out in a desalination plant are reported and discussed in relation to laboratory tests performed on the same alloy compositions. The corrosion measurements are used to outline general methods for maximizing the resistance of ferritic stainless steels to pitting and crevice crack attack in hot saline environments.
Corrosion Testing of Weldments
Authors: HENTHORNE MICHAEL
Published: February 2013

Weldments sometimes corrode preferentially in the weld metal itself or in the heat affected areas of the parent metal. The localized nature of the attack limits the usefulness of standard weight loss corrosion tests. Techniques for overcoming this limitation are discussed. The influence of specimen geometry and surface finish are dealt with as well as a variety of destructive and nondestructive methods for evaluating a corroded weldment. The advantages and limitations of the various ASTM intergranular tests for austenitic stainless, ferritic stainless, and nickel base alloys are reviewed. Guidelines for evaluating weldment corrosion are given, although it is recognized that there is no single best procedure for all situations. The use of sensitization treatments to simulate welding is discussed.
Analysis of the Influence of Hydrogen on Pitting Corrosion and Stress Corrosion of Austenitic Stainless Steel in Chloride Environment
Authors: SEYS A. A. , BRABERS M. J. , VAN HAUTE A. A.
Published: February 2013

In a study on the mechanism of pitting corrosion, a gas evolution in the pit has been observed. This gas has been gaschromatographically identified as hydrogen. The explanation of the evolution of hydrogen by the acidification of the pit electrolyte and the potential drop across the pit have been experimentally proved. By means of vacuum extraction experiments, the diffusion and dissolution of hydrogen in the metal has been shown. Experiments have been carried out to determine the effects of the dissolved hydrogen on the austenitic stainless steel. Replica techniques show that the hydrogen embrittles the metal around the pit. X-ray diffraction lines demonstrate that hydrogen causes phase transformations in the austenitic stainless steel. In the case of pitting corrosion, such transformations have not yet been confirmed. It is suggested that dissolved hydrogen can create new initiation places for pitting corrosion and in this way is responsible for the secondary pit initiation. The most important effect of hydrogen is connected with the internal stresses set up in the metal. There is no hydrogen development during the pitting corrosion of pure nickel. This leads to the conclusion that hydrogen is not of primary importance in the pitting corrosion process. A comparison is made between the pitting and the stress corrosion process. The electrochemical processes occurring in both localized corrosion forms are analogous. The hydrogen is responsible for the cracking in the stress corrosion process. Stress corrosion cracking is represented as a specific case of pitting corrosion.
Development of Pitting Resistant Fe-Cr-Mo Alloys
Authors: STREICHER MICHAEL A.
Published: February 2013

Because of the resistance of iron-chromium stainless steels to chloride stress corrosion, this alloy system was used as a base for developing superior resistance to various forms of corrosion by means of alloying with molybdenum, nickel, and the six metals of the platinum group. The effects of these alloying elements were evaluated by accelerated laboratory tests for pitting, intergranular, general, and stress corrosion. The optimum ductility and resistance to pitting, intergranular, and stress corrosion were found for an alloy of Fe-28% Cr-4% Mo with carbon not exceeding 0.010% and nitrogen below 0.020% (C+N <0.025%). This alloy resists pitting and crevice corrosion in 10% FeCl3-6H2O at 50 C (122 F) with six crevices on the specimen surfaces, and it resists all intergranular attack on a welded specimen in the boiling ferric sulfate-50% H2SO4 test. Addition of 2% Ni to this alloy extends its general corrosion resistance in oxidizing and organic acids to boiling 10% H2SO4 and 1% HCI, in which it is also self-repassivating. The nickel addition makes the alloy subject to stress corrosion cracking (SCC) in the boiling 45% MgCl2 test, but not in the NaCl wick test, which more nearly simulates plant exposures and cracks 18Cr-8Ni stainless steel. Additions of small -amounts of any of the six platinum metals, e.g., 0.020% Ru, also make the 28Cr-4Mo alloy passive in boiling 10% H2SO4. But only ruthenium, iridium, and osmium do this without impairing pitting resistance in halide solutions. For self-repassivation, 0.50% Ru is required, and this amount makes the alloy subject to stress corrosion in the boiling 45% MgCl2 test, but not in the wick test.
Some Errors in Linear Polarization Measurements and Their Correction
Authors: MANSFELD FLORIAN
Published: February 2013

The errors due to the use of the approximation Icorr′ = B′ΔI, where B′ depends on anodic and cathodic Tafel slopes, in commercial corrosion current meters is shown to be due to the nonlinearity of the current-potential curve in the vicinity of the corrosion potential. These errors are calculated for various combinations of Tafel slopes. It is proposed to use the relationship Icorr = κΔI, where κ depends on Tafel slopes, sign, and magnitude of polarization. The values of κ are tabulated for various combinations of Tafel slopes and polarization of +10 and −10 mV. The proposed procedure leads to correct values of corrosion currents independent of the degree of nonlinearity of the polarization curve.
Corrosion Product Characterization of a Nickel-Sodium Sulfate-Air System after Exposure to Temperatures Near 1000 C
Authors: REISING RICHARD F. , KRAUSE DOUGLAS P.
Published: February 2013

Gas turbine engines are susceptible to high temperature corrosion which is enhanced by marine atmospheres. This high temperature corrosion is also known as sulfidation because it is believed that the formation of metal sulfides from sulfur containing substances is essential. An understanding of the corrosion mechanisms involved is necessary in seeking methods of eliminating the problem, and the initial step in formulating mechanisms is to identify the chemical reactions involved. Corrosion product characterization is essential for this identification. Characterization of the corrosion products from the nickel-sodium sulfate-air system at temperatures near 1000 C (1832 F) suggests that the sodium sulfate acts as a flux rather than as a chemical reactant. Some of the techniques used to characterize the corrosion products are discussed.
Evaluation of Corrosion Rates from Polarization Measurements
Authors: LeROY RODNEY L.
Published: February 2013

Polarization measurements within 5 to 20 mV of the corrosion potential offer a powerful method for determining corrosion rates. In this paper, known methods for evaluating the corrosion current from polarization data are critically examined. It is noted that calculated currents are generally in error when the anodic and cathodic Tafel slopes are precisely known, due to non-linearity of the polarization curve. A new result is derived, which allows the corrosion current to be calculated without error if the Tafel slopes are known. Diagrams are presented which show the sensitivity of calculated corrosion rates to errors in estimation of the Tafel constants.
Effect of Plating Conditions on Performance of Porous Cadmium Deposit
Authors: ALTURA DAN , MANSFELD FLORIAN
Published: February 2013

Porous cadmium plating of high-strength steel was evaluated in terms of corrosion behavior, hydrogen embrittlement of the steel due to plating, and the relationship of these parameters to the microstructure of the electrodeposit. Emphasis was placed on investigating this system under conditions which can be encountered in industrial plating. High plating current density and low cadmium concentration of the plating bath result in severe hydrogen embrittlement. The rate of cadmium dissolution, when Cd plated steel was galvanically coupled to Al 2024, is found to increase linearly with increasing plating current density and is also affected by variation of the cadmium concentration of the plating bath. Additions of Na2CO3 tend to decrease cadmium dissolution rate, while FeSO4 additions have no apparent effect on either corrosion behavior of the Cd coating or hydrogen embrittlement of the steel. Scanning electron photomicrographs indicate that the plate structure is crystalline, containing numerous microscopic pores, some of which penetrate to the surface of the steel substrate. These pores are thought to facilitate the escape (during subsequent baking) of hydrogen trapped within the plate.
Effect of Plating Current Density on Properties of Titanium-Cadmium Deposit
Authors: ALTURA DAN , MANSFELD FLORIAN
Published: February 2013

Titanium-cadmium plating was evaluated at various plating current densities which may be encountered in industrial practice. Both high and low current densities resulted in increased hydrogen embrittlement tendency over the optimal plating condition. Deleting the current strike had no noticeable effect on embrittlement behavior. Salt spray testing indicated that gross corrosion behavior was independent of plating current density. The corrosion behavior of cadmium-plated steel coupled to aluminum alloys was both a function of plating current density and the type of aluminum alloy used. Plate microstructure was a strong function of plating current density.
Oxidation of Electrodeposited Nickel—1.6 Wt% Alumina
Authors: NWOKO V. O. , SHREIR L. L.
Published: February 2013

Oxidation of electrodeposited nickel containing 1.6 wt% alumina particles dispersed in it has been studied in the temperature range 800 to 975 C. Metallographic examination of specimens oxidized for 24 hours or more at 900 C and above revealed a two-layer scale; an outer columnar grey layer and an inner fine-grained layer. Although strongly adherent scales were formed, a comparative investigation with electrodeposited nickel at only 900 C indicated a slightly higher rate constant for Ni-Al2O3.
Potentials of Selected Metal Alloys in Sea Water at Elevated Temperatures
Authors: SMITH CARROLL A. , COMPTON KENNETH G.
Published: February 2013

Sixteen metal alloys were studied in aerated sea water at temperatures up to 200 C (392 F), and five of these were further studied in deaerated sea water in the same temperature range. Galvanic series are reported for temperatures of 30, 100, 160, and 200 C (86, 212, 320, and 392 F) in an autoclave, and for a trough at ambient conditions. The general effect of increased temperature in both aerated and deaerated sea water was to increase the electronegativity of most metals, and to reduce the spread between the median potential values. At 200 C, the metals merged into two groupings: aluminum and zinc being the most active, other metals were appreciably less negative. In contrast to other metals, zinc and carbon steel showed a tendency toward nobility at higher temperatures. Very small differences were found between the galvanic potentials of most metals in deaerated sea water as compared with these metals in aerated sea water. Titanium appeared to be the exception, being more active in deaerated sea water above 120 C (248 F).
Review of the Stress Corrosion Cracking of Inconel 600
Authors: VAN ROOYEN D.
Published: February 2013

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 sufficient to explain only some cases of intergranular corrosion. Grain boundary segregation seems to be of equal or greater importance in high temperature water, especially when the attack involves SCC. Grain boundaries may become cleaned when segregated elements dissolve in chromium carbide precipitates. Physically, precipitates at grain boundaries could possibly influence the manner in which the metal undergoes strain. Hydrogen as a cause of SCC has not been ruled out. The relationship between surface films formed and SCC of Alloy 600 in high temperature aqueous environments requires more work.
Investigation of the Mechanism of Stress Corrosion Cracking in High Strength Steels
Authors: MARICHEV Y. A. , ROSENFELD I. L.
Published: February 2013

An analysis is given of the modern outlook on the mechanism of cracking in high strength steel in the case of stress corrosion cracking (SCC). It is shown that numerous experimental data cannot be interpreted in terms of hydrogen embrittlement when it is considered as the only mechanism of crack growth. A phenomenon is described of multiple effects of cathodic polarization on the rate of crack growth in cracking of high strength steels. A new mechanism of SCC is suggested, whose main feature is found in that it not only allows for, but is in fact based upon the possibility of SCC of high strength steels by several mechanisms: local anodic dissolution, hydrogen embrittlement, and adsorption strength reduction. The mechanism entails alternation of rate-limiting processes, depending on various metallurgical and electrochemical factors, and on crack growth rate, which affect the kinetics of formation of barrier layers at the crack tip. A definition of critical growth rate is introduced, which is then investigated as function of a number of factors.
Factors Affecting Stress Corrosion Resistance of the Ti-8Mo-8V-2Fe-3AI Metastable Beta Titanium Alloy
Authors: CHAIT R. , LUM P.
Published: February 2013

The stress corrosion resistance of the metastable beta alloy Ti-8Mo-8V-2Fe-3AI extruded and heat treated to high strength levels is examined. Salt water KISCC data are presented for both solution treated and aged (STA) condition and the direct age (DA) conditions. It is shown that the better stress corrosion resistance is exhibited by the DA material. Further improvements in the stress corrosion resistance of DA material are realized with forged product that has undergone a large amount of reduction. Fractographs and micrographs are presented to support the above observations.
Acoustic Emission Method for Monitoring Corrosion Reactions
Authors: RETTIG T. W. , FELSEN M. J.
Published: February 2013

There is a continuing need for new test techniques to follow corrosion reaction processes and to predict long-term materials performance in aggressive environments. Additionally, there is a growing awareness of the importance of applying non-destructive inspection to determine the presence of corrosion in non-visible areas of equipment and structures. The possibilities of utilizing acoustic emission for a broad range of applications in the study of these problems were explored. Proprietary methods were developed to follow corrosion reactions and to monitor corrosion of simulated and actual structures. These experiments point out the applicability of acoustic emission as a sensitive new tool for corrosion research and non-destructive testing (NDT) in corrosion prone structures and equipment.
Molybdates as Corrosion Inhibitors in the Presence of Chlorides
Authors: LIZLOVS E. A.
Published: February 2013

The effect of the molybdate ion (MoO4=) concentration on the corrosion inhibition of 1010 steel was investigated in aerated chloride/sulfate-containing solutions. The chloride content was 304 ppm Cl−, and the sulfate was 352 ppm SO4=. Weight loss measurements and electrochemical methods were employed for the investigation. The pH was controlled at 8.7. Weight loss measurements indicated that about 165 ppm of molybdate reduced the corrosion rate below 10 mg·dm−2/day at room temperature. At 160 F (71 C), about 50 ppm of molybdate reduced the corrosion rate to 4 to 5 mg·dm−2/day. The potentiodynamic polarization studies and the examination of corrosion potential and immersion time relationship disclosed that the molybdate ion acts as a passivating agent in the presence of oxygen. Passivity was also obtained under potentiodynamic polarization conditions in a nitrogenated solution. No passivation was obtained in the absence of the molybdate ion. For spontaneous passivation, both molybdate and oxygen (oxidizing agent) were needed. Corrosion rates in a passive state according to the polarization curve should be nil.
Fracture of Tarnish Films on α-Brass
Authors: PROCTER R. P. M. , ISLAM M.
Published: February 2013

A study of the fracture of tarnish films on a 70/30 brass in pH 7.2 Mattsson's solution reveals that the film fractures transgranularly. Stressed metal specimens in the same solution crack intergranularly. The results are in disagreement with the reputed tarnish film rupture mechanism.
Environmental Factors in Stress Corrosion Cracking and Anodic Polarization of Zirconium in Methanol-HCl Solutions
Authors: PALIT G. C. , ELAYAPERUMAL K.
Published: February 2013

The effects of the environmental factors, aqueous HCl, anhydrous HCl, and water, on stress corrosion cracking (SCC) and anodic polarization of annealed zirconium in methanol-HCl solutions have been studied and the corresponding correlations are brought out. The occurrence of minimum time to failure by SCC, corresponding to maximum susceptibility, at a concentration of 0.4 Vol% aqueous HCl has been shown to be due to the coexistence of active and passive states. The activating and passivating species are Cl− ion and water, respectively.
Effect of Ultrasonic Waves on the Pitting Potentials of 18-8 Stainless Steel in Sodium Chloride Solution
Authors: NAKAYAMA T. , SASA K.
Published: February 2013

Critical pitting potential and protection potentials were measured potentiodynamically in 0.1N NaCl solution vibrated by a 200 kHz ultrasonic wave. The critical pitting potential was more noble in this environment than in a hydrostatic solution. This fact was confirmed potentiostatically. In hydrostatic solution, the protection potential seems to decrease with the increase of the level of pit propagation. When the electrodes are radiated by ultrasonic wave, the protection potential can be defined as 120 mV (SCE) and is independent of the degree of pit propagation.
Pitting of High Purity Zinc and Pitting Potential Significance
Authors: ALVAREZ M. G. , GALVELE J. R.
Published: February 2013

The passivity breakdown of high purity zinc in aqueous solutions containing different aggressive anions (Cl−, I−, SO4=, and NO3−) was studied. A critical evaluation of different methods for measuring the breakdown potential was made. Reproducible passivity breakdown potential measurements were given only by those methods producing mechanical disruption of the passive film. The passivity breakdown potential of high purity zinc was found to be independent of the nature of the anions tested, except for nitrates, and very close to the equilibrium potential of the reaction Zn = Zn2+ + 2e. The passivity breakdown potential in all the cases studied was found to be equal to the corrosion potential of zinc in the acid solution formed inside the pits. It is concluded that the pitting potential is the minimum potential at which an acidified solution can be produced and maintained in contact with the dissolving metal.
Corrosion Products of Iron Dissolution—Dependence on Anions in Solution
Authors: ALEXANDER BEVERLY J. , FOLEY R. T.
Published: February 2013

This paper deals with the identification of certain species produced during the corrosion of iron in oxygen-containing and oxygen-free solutions. Iron was allowed to corrode in acid solutions of constant pH of NaBr, NaCl, Nal, NaNO3, Na2HPO4, Na2SO4, and NaClO4. These reactions were conducted in (1) air-saturated solutions, (2) solutions purged with N2, and (3) a closed argon-purged system. The reactions were carried out in a special optical cell in an Hitachi EPS-3T spectrophotometer and measurements were made over the ultra-violet and visible regions. The results obtained in the air-saturated solutions indicated that although many of the spectra exhibited common features the spectra were unique for each individual solution. Thus the species arising in the dissolution process were dependent on the anion in solution.
Strain Enhanced Corrosion in the Iron-Caustic System
Authors: DIEGLE RONALD B. , VERMILYEA DAVID A.
Published: February 2013

Straining electrode experiments were performed to investigate the nature of strain enhanced corrosion of iron in caustic electrolyte. The strain enhanced corrosion rate was generally linearly dependent on applied strain rate, and its potential dependence paralleled that of steady-state polarization behavior on non-straining electrodes. Data was presented as ratios, in which is the corrosion rate in cm/s and is the corresponding strain rate. This ratio, which was shown in a previously published theory to be numerically equal to the crack advance per film rupture event during film rupture SCC, depended on electrochemical variables such as electrolyte concentration and temperature in a manner similar to the kinetics of caustic cracking. Conditions which are known to be marginal in producing caustic cracking resulted in values for of about 10−7 cm, in excellent agreement with a previously developed theory. It was concluded that strain enhanced corrosion in this system results from repetitive film rupture and repair during straining.
Residual Stresses in Bent Tubes for Nuclear Steam Generators
Authors: BERGE Ph. , BUI H. D. , DONATI J. R. , VILLARD D.
Published: February 2013

Residual stresses in Inconel 600 tubes for PWR steam generators were measured using the strain gauge technique, and the results were checked by a stress corrosion test in boiling MgCl2 performed on stainless steel tubes manufactured according to the same process as the Inconel 600 tubes. It was shown that very high tensile stresses, equal to or even exceeding the yield stress, could exist as a result of the straightening, bending or roll expanding operations. The efficiency of possible stress relieving treatments was also investigated.
Oxalate Coating of Nickel Alloys
Authors: MORRIS P. E.
Published: February 2013

Rapid-scan potentiodynamic polarization techniques were utilized to solve problems encountered in a commercial oxalate coating process for nickel alloy tube and wire products. The electrochemical data provided an explanation for the observed inconsistent coating performance in terms of alloy type and environment parameters. Based on the electrochemical study, the mill operating procedures were modified to yield consistently satisfactory alloy coatings.
Relationship Between Acid Intergranular Corrosion and Caustic Stress Corrosion Cracking of Alloy 600
Authors: THEUS G. J.
Published: February 2013

Modified Streicher and 288 C (550 F) electrochemical caustic stress corrosion tests were performed on Alloy 600 to determine the relationship between acid intergranular attack susceptibility and caustic stress corrosion cracking (SCC) susceptibility. Mill annealed and solution annealed materials with and without a subsequent 621 C (1150 F) heat treatment (simulated stress relief) were evaluated. Susceptibility to attack in the Streicher test was greatest for material that had received a 621 C (1150 F) heat treatment, whereas this heat treatment caused the same material to be least susceptible to cracking in the electrochemical tests. The conclusions drawn from these results are: (1) stress relieving Alloy 600 does improve its resistance to caustic SCC, and (2) resistance of Alloy 600 to acid intergranular attack does not imply resistance of Alloy 600 to caustic SCC. Therefore, the results demonstrate the need for selecting corrosion qualification tests which are relevant to service conditions.
Practical Experiences with Linear Polarization Measurements
Authors: HAUSLER R. H.
Published: February 2013

The linear polarization technique in principle is a convenient and rapid way for determining corrosion rates. In practice, one finds that it is often applied under conditions alien to the assumptions on the basis of which it was derived. This paper will present a series of comparative observations between linear polarization, resistance probe, and weight loss measurements in different systems. The systems studied were: (1) Hydrochloric acid containing acetylenic inhibitors, (2) a two phase system containing hydrocarbon and water saturated with H2S, and (3) tap water containing various inhibitors. An equation will be derived showing the effect of ohmic resistance due to corrosion product buildup. The effect of polarization on the properties of a corrosion product layer will be discussed qualitatively.
Rust Prevention Control by Changing Sulfide Type
Authors: SHIMADA HARUO , SAKAKIBARA YOSHIAKI , OKADA HIDEYA
Published: February 2013

The first stage of rust formation process is the dissolution of α(Mn,Fe)S into dew water at the steel surface. Therefore, rust prevention can be expected by changing the sulfides in steel from the water soluble type, α(Mn,Fe)S, to the water insoluble type. This paper deals with the rust prevention control process. The dissolution tendency of various sulfides into water has been examined by using the electrolytically extracted sulfides from steel, and then the difference of rust resistance of steel sheets due to the change of sulfides type has been studied with acceleration tests in the humid atmosphere. The obtained results revealed that the most appropriate rust prevention can be achieved by fixing all the sulfur in steel as the water insoluble sulfides, (Ce,Mn)(O,S).
Stress Corrosion Crack Growth in Austenitic Stainless Steel
Authors: SPEIDEL MARKUS O.
Published: February 2013

Stress corrosion crack velocity and stress corrosion threshold stress intensity have been measured for Type 304L austenitic stainless steel in water with 42% MgCl2 at 130 C. The stress corrosion crack velocity vs stress intensity curve has a shape similar to the one for other austenitic steels and many other metallic and nonmetallic materials. The threshold stress intensity (KISCC is 8 ± 1 MN·m−3/2, and the plateau crack velocity is 3 to 6 × 10−8 m/s. Linear elastic fracture mechanics techniques can be applied to SCC testing of soft and tough materials, provided the KISCC is low enough, and crack branching can be avoided. Criteria for the formation of single, branched, and circular stress corrosion cracks are indicated.
Further Observations on Sensitization of Chemically Stabilized Stainless Steels
Authors: SAMANS CARL H. , KINOSHITA KAZUHISA , MATSUSHIMA IWAO
Published: February 2013

The solubility product for niobium and carbon in a Type 347 steel is Niobium additions to an 18Cr:8Ni type matrix reduce carbon solubility to such an extent that any “solution treatment” below at least 1150 C causes stabilization. Consequently, no Cr2 3C6 precipitates at lower temperatures to sensitize the structure. Further observations on Type 321 suggest that two types of TiC precipitate from solid solution in an 18:8 type matrix. The size of the TiC nucleus decreases with the precipitating temperature. Above 1050 to 1100 C the initial TiC is probably incoherent, large enough to be stable and resistant to ferric sulfate-sulfuric acid solution. Below 1050 to 1100 C the initial TiC, known as “dot TiC” or “TiC on dislocations”, is probably coherent, not large enough to be stable without further growth, and not resistant to ferric sulfate-sulfuric acid solution. During holding at temperatures below 1050 to 1100 C, stabilization occurs as the TiC on dislocations agglomerates to larger, incoherent particles. The time required increases as the temperature decreases down to the minimum TiC nucleation temperature near 610 C. Cold work makes it easier for the coherent particles to become incoherent, in effect facilitating approach to equilibrium carbon solubility at any temperature. Once chromium carbide forms, dissolved titanium eventually reacts with it, forming TiC and releasing chromium to desensitize the structure. This reaction can occur, given sufficient time for titanium diffusion, at any temperature at which chromium carbide nucleates. It is much more rapid than back diffusion of chromium from the matrix.
The New Fe-Cr-Mo Ferritic Stainless Steels
Authors: STEIGERWALD R. F. , BOND A. P. , DUNDAS H. J. , LIZLOVS E. A.
Published: February 2013

The new Fe-Cr-Mo ferritic stainless steels are reviewed with an emphasis on corrosion behavior. The properties of commercial steels are outlined showing how these alloys can be divided into general purpose (18Cr-2Mo), moderately severe service (26Cr-1Mo), and premium service (29Cr-4Mo) materials. The stress corrosion cracking (SCC), intergranular corrosion, pitting, crevice corrosion, and general corrosion of the Fe-Cr-Mo ferritic stainless steels in general is discussed. The influence of nickel on the corrosion resistance and toughness of ferritic stainless steels is considered.
Potassium Oxalate Inhibits Corrosion of Mild Steel by Ferric Ion
Authors: SUBRAHMANYAM D. V. , HOEY G. R.
Published: February 2013

Potassium oxalate inhibits the corrosion of AISI 1010 steel in 2.5 pH H2SO4 solutions with and without Fe3+ ion at inhibitor efficiencies up to 98%. Ferric ion exerts a synergistic influence with oxalate ion. The minimum oxalate concentration required is directly proportional to the ferric ion concentration in solution. Inhibition is caused by 30.5 to 116.8 μ thick ferrous oxalate film, i.e., β-FeC2O4·2H2O, identified by X-ray diffraction analysis. Based on potential-time and current density-time curves, a three-stage mechanism for inhibition is postulated. Possible applications of this inhibitor in the mineral industry are suggested.
Stress Corrosion Cracking and Corrosion Fatigue in Cr-Mo Low Alloy Steel
Authors: AIYAMA SIGEKI , SHOJI TETSUO , TAKAHASHI HIDEAKI , SUZUKI MASAHIKO
Published: February 2013

Corrosion fatigue crack propagation tests were performed below and above KISCC in AISI 4145 steel heat treated to 1230 MN/m2 and 0.1 N H2SO4 system with particular reference to effects of frequency and stress intensity parameters. The crack growth results above KISCC could not be described by simple linear summation hypothesis, and this fact suggested the importance of the synergestic effect term in crack growth rate. This synergestic effect denoted hereafter as the dynamic SCC rate was strongly influenced by frequency and showed the maximum at a particular frequency. This frequency effect on the dynamic SCC rate suggested that crack growth enhancement under cyclic loading would be induced by dissolution mechanism in spite of the fact that the material had high sensitivity to hydrogen stress cracking under constant load.
Contribution to the Interpretation of Current Maxima in the Passivity Range of Austenitic Stainless Steels
Authors: CIGADA A. , RE G. , SINIGAGLIA D. , BORILE F.
Published: February 2013

Passive current density maxima have been observed by various workers during the anodic polarization of different stainless steels in sulfuric acid solutions and have been explained by many theories. This paper describes the precorrosion time and some other pretreatments of the sample surface which change drastically the anodic polarization curve of AISI Type 304 stainless steel in 2N H2SO4, lowering the critical current density and causing two passive maxima. Our results are used in a critical analysis of the conclusions of other authors. The passive current density maxima are attributed to the oxidation of hydrogen formed during precorrosion and absorbed into the alloy and of ions present in the solution and coming from the alloy dissolution.