bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Some Environmental Conditions on Stress Corrosion Behavior of Ni-Cr-Fe Alloys in Pressurized Water
Authors: COPSON H. R. , ECONOMY G.
Published: February 2013

Stress corrosion tests have been run in pressurized water at 600 F (316 C) using double U-bends and double bent beam specimens. The tests were conducted in autoclaves for up to 3000 hours. The composition of the gas phase above the water and the pH were controlled. The materials tested were commercial heats of Inconel (1) 600, Inconel 625, lncoloy(1) 800 and stainless steel Types 304, 304L and 347; some Inconel alloy 600 weldments; and some experimental laboratory compositions. Several heat treatments were included. No attack was observed in specimens stressed at 90 percent of room temperature yield strength. No attack was observed when hydrogen constituted the gas phase. No attack was observed when crevices were absent. The combined action of a high stress, a high oxygen concentration and a crevice did promote intergranular attack and cracking in the crevice area in all alloys tested. The severity of the attack increased with the oxygen concentration. Many specimens heated for 2 hours at 1250 F (677 C) showed deeper attack than annealed specimens. Solution heat treatment, low carbon content or the presence of carbide stabilizers did not eliminate the attack. The behavior of weld metal deposits was not significantly different from that of base plate. Variations in composition within the normal range of Alloy 600 were unimportant. Differences in behavior among the several alloys tested were minor compared to those from environmental effects.
Electrochemical Properties of Ferrite and Cementite in Relation to Stress Corrosion of Mild Steels in Nitrate Solutions
Authors: GREEN J. A. S. , PARKINS R. N.
Published: February 2013

Polarization studies were carried out both at an iron electrode and an iron electrode having a surface layer of cementite. Anodic and cathodic polarization curves were com-pared in nitrate and chloride solutions and the effect of temperature and the addition of acid was examined also. The Fe3C electrode was found to undergo relatively little cathodic polarization at low current densities and the cementite was thought to be acting as an efficient site for cathodic discharge during the corrosion reaction.
Hydrogen-Induced Phase Transformations in Type 304L Stainless Steels
Authors: HOLZWORTH M. L. , LOUTHAN M. R.
Published: February 2013

Electrolytic charging of hydrogen into Type 304L stainless steel at room temperature and 100 C (212 F) induced partial transformation) of the austenite to the some martensitic phases [α′ (bcc) and ε (hep)] as are formed by cold-working hydrogen-free austenite at low temperatures (−196 C) (−321 F). No evidence of a hexagonal hydride was found. The formation of the ε phase by cathodic charging suggests that hydrogen lowers the stacking fault energy of austenite. Hydrogen charging expands the austenite lattice, causes the dislocation and stacking fault density to increase with increasing hydrogen concentration, and causes dislocation movement.
Corrosion of Monel 400 in High CO2 Well Water
Authors: UGIANSKY GILBERT M. , ELLINGER GEORGE A.
Published: February 2013

Dezincification type corrosion of a Monel Alloy well screen in water with 23–54ppm CO2 is discussed in detail. The second phase in the corroded grain boundaries was identified by electron probe microanalysis as nearly pure copper with little or no nickel. It is concluded that Monel may be susceptible to dezincification-type corrosion when used in certain environments.
The Separation of Corrosion and Stress Effects in Stress Corrosion: Ti-Al-4V in Bromine-Methanol Solutions
Authors: COCKS F.H. , RUSSO J.F. , BRUMMER S.B.
Published: February 2013

The time to failure for stress corrosion of Ti-6Al-4V depends strongly on the extent of precorrosion. Corrosion without stress is initially just as effective in causing eventual failure as is corrosion with stress; only during the last 40% of the normal stress, corrosion life is stress critical in causing failure. Thus, only in this last stage can a stress corrosion process be said to occur. A general mechanism to account for this behavior is suggested, and a precorrosion) susceptibility index is defined and used as a quantitative measure of the importance of stress at each stage of the total process leading to failure. The time to failure of Ti-6Al-4V in methanol-bromine solutions depends also on the extent of “aging” of the solution. The time to failure becomes shorter the longer the solution has been kept standing. This effect arises from the influence of the reaction products of bromine with methanol and water.
The Oxidation of Vanadium-Base Alloys by Liquid Sodium Containing Dissolved Oxides in Temperatures Ranging From 500 to 600 C
Authors: BORGSTEDT HANS U. , FREES GUNTER
Published: February 2013

Vanadium-base alloys suffer oxidation by liquid sodium (500 to 600 C) containing 5 to 10 ppm oxides. The effects are different with differing components of the alloys and the degree of purity of liquid sodium. In liquid sodium of a pumped sodium loop, V-Ti alloys with 5 to 20% Ti suffer embrittlement of surface areas. The zones of embrittlement contain up to 7 to 9% oxygen. Unalloyed vanadium does not underly oxygen diffusion into the metal phase. The different behavior is intelligible from thermodynamic reasons. The free energy of oxygen exchange between Na2O and the refractory metals following the equation, Na2O + V = VO + 2 Na, is small in the reaction with vanadium but remarkable in the reaction with titanium in the above range of oxygen concentrations. Depth of the penetration zone of the metallic phase is dependent on Ti content. After 500 hours testing at 600 C (1112 F), the following depths were measured: 200 microns in V-5% Ti, 100 in V-10% Ti, and 70 in V-20% Ti. In alloys with less than 5% Ti, complete embrittlement occurred through the specimen of 0.5 mm thickness. In some tests with cold trapped sodium with plugging temperatures of less than 130 C (266 F), severe corrosion weight losses and oxide layers were observed. Beneath these oxide layers, there were the well known oxygen diffusion layers. X-ray fluorescence analysis showed that oxide layers contained calcium up to 5% concentration.
Effects of Uranium on Stress Corrosion Cracking of Steels in a Nitrate Environment
Authors: McDonald R. D.
Published: February 2013

Corrosion tests in a boiling nitrate environment show beneficial effects of uranium is steed ion quantities up to 0.15%, the preferred level being at 0.09%. Steels included in the tests contained two levels of carbon and three levels sulphur at strength levels within the ramie 135,000 to 155,000 psi.
Passivation and Activation of Iron in the Presence of Molybdate Ions
Authors: CARTLEDGE G. H.
Published: February 2013

In extension of previous studies of the mechanism of the action of XO4n− inhibitors of corrosion, the behavior of MoO42− ions has been investigated. This inhibitor was found to exert a noncathodic action in facilitating anodic passivation, but the phenomena are more complex than those exhibited by CrO42−, TcO4−, and MnO4−. The transition between active and passive potentials comprises several well-defined stages which were identified in potentiostatic measurements. The character of surface films was studied as a function of potential, both by analytical procedures and by electron microscopy and diffraction. The existence of mixed complex species containing Fe(II), Fe(III), and Mo(VI) in solution was established spectro-photometrically and solids having such compositions were synthesized. A super passive state was found to be produced at noble potentials when ferrous ions were present in sufficient concentration, and the dependence of all transition potentials upon pH was established. An interpretation of the processes occurring in the different regions of potential is presented, and deductions from the super passive behavior are extended to a generalized theory of the passive state.
Passivation of Crevices During Anodic Protection
Authors: FRANCE W. D. , GREENE N. D.
Published: February 2013

The protection of crevices poses an important problem in industrial applications of anodic protection. Experimental studies with a special crevice assembly have shown that the interiors of crevices often remain active and corrode at a rapid rate. These experiments, together with theoretical analyses, demonstrate that the ability to passivate crevices during anodic protection is controlled by electrolyte characteristics, crevice geometry, and the electrochemical behavior of the protected metal. Of these, critical anodic current density, ic, is the most important parameter.
The Dissolution of Zinc in the NaNO3-NH4Cl-NH3-H2O System
Authors: GOODRICH J. D. , SCHMID G. M.
Published: February 2013

Zinc dissolves rapidly in NaNO3-NH4Cl-NH3-H2O with rates of 0.375 to 2.16 g./cm2- hr being observed at 25.0 ± 0.1 C. The reaction occurs via complexion of the zinc ion with ammonia in NH4+ buffered solutions. The cathodic reaction is primarily the reduction of NO3− to NO2−, NO2−, NH2OH, and NH2NH2 are shown to be reactive with Zn but not significantly so.
Stress Corrosion Behavior of High Strength Steels
Authors: LECKIE H. P. , LOGINOW A. W.
Published: February 2013

The effect of stress and environment on the susceptibility to failure of HY-80, HY-130(T), 12Ni maraging, and 18Ni maraging steels has been evaluated by using both pre-notched and smooth specimens. Tests were conducted in sodium chloride solution, artificial sea water, and natural sea water, both with and without cathodic charging. Data are presented which show that the apparent susceptibility to failure is dependent on the test method used. Thus, in natural sea water, the most severe environment, notched specimens often showed failure, whereas, specimens of the same material tested in the unnotched condition did not fail. HY-80 steel was resistant to failure in all environments tested. HY-130(T) steel showed a slight reduction in load-carrying ability during cathodic charging, although the applied stress required for failure remained very high. Both 12Ni and 18Ni maraging steels failed as notched specimens in all test environments at applied stresses below the yield strength. In contrast, however, no failures were observed during the test period when these materials were tested as U-bend specimens in natural sea water.
The Electrochemical Behavior of Some Nickel Base and Cobalt Base Alloys
Authors: LEONARD R. B.
Published: February 2013

Potentiostatic anodic polarization curves are provided for Hastelloy Alloys B, C, D, F, and G, Haynes Alloy No. 25 and Haynes Stellite Alloy No. 6B in a variety of media. These data demonstrate that, if oxidizers are present in environments in contact with low chromium alloys, the dissolution rate will increase with increasing oxidizer level. The polarization data also show that copper markedly decreases the dissolution of alloys in reducing media. Also, the presence of grain-boundary precipitates increases the dissolution rate of Hastelloy Alloy C in oxidizing, pitting, and hydrochloric acid media while not affecting the dissolution rate in unaerated sulfuric acid. The effective alloy content of an alloy is altered by the precipitation of new phases, according to the data obtained. A 30% chromium alloy, Haynes Stellite Alloy No. 6B, had higher current densities, hence lower corrosion resistance under oxidizing conditions, than a 20% chromium alloy, Haynes Alloy No. 25. This was causes by the removel of much of the matrix chromium content by the precipitation of chromium containing carbides in the Haynes Stellite Alloy No. 6B.
Apparatus for Stress Corrosion Tests in Boiling Magnesium Chloride Solutions
Authors: STREICHER M. A. , SWEET A. J.
Published: February 2013

Time-to-failure in stress corrosion tests on stainless steels and related alloys depends on the temperature of the boiling magnesium chloride test solution. Small losses of water vapor and condensate from solutions in the range of 40 to 46 wt % MgCl2 lead to rapid increases in boiling temperature. Components of a three-part test apparatus — flask, condenser, and trap — have been designed to reduce losses of water vapor and condensate to negligible proportions. With this apparatus the temperature of the boiling magnesium chloride solution can be held constant, e.g. at 155 C ±1 C (311 F ±1.8 F), for periods of 100 days or more. This apparatus for reducing vapor and condensate losses may also be useful for other solutions whose boiling points are significantly affected by such losses. Design details are given for a 1-liter Erlenmeyer test flask, condenser, and vapor trap. In addition, dimensions are provided for two stress corrosion specimens, a U-bend and a bent-beam, together with holders for these specimens, which fit a 1-liter test apparatus.
Resistance of Explosion-Bonded Stainless Steel Clads to Intergranular Corrosion and Stress Corrosion Cracking
Authors: HILL B. , TRUEB L. F.
Published: February 2013

Intergranular corrosion of stabilized austenitic stainless steel is not accelerated when this material is explosion-clad to carbon steel. Heat-treatment in the sensitization range causes carbon diffusion across the bond interface and precipitation of chromium carbides; this influences the corrosion rates within the diffusion band. Outside of this relatively small area, corrosion rates are similar to those characteristic of nonclad material subjected to the same heat treatment. Stress corrosion cracking of both a stabilized and an unstabilized grade of austenitic stainless steel is not accelerated by explosion cladding to carbon steel. Stainless steel-to-steel explosion clads thus do not appear to pose any special corrosion problems.
Oxidation of 304L Stainless Steel by Steam and by Air
Authors: BITTEL J. T. , SJODAHL L. H. , WHITE J. F.
Published: February 2013

The oxidation of 304L stainless steel has been measured in steam and in air in the temperature range from 1000 to 1375 C (1832 to 2507 F) using a thermogravimetric technique. This temperature range is of interest in the analysis of a reactor loss-of-coolant accident. Experiments in steam showed initial linear weight gain with time for the first 6 to 28 minutes, followed by parabolic rate behavior. The linear reaction rate constant W/t was found to be 1.1 × 105 exp (−44,350/RT) while the parabolic constant W2/t was found to be 2.4 × 101 2 exp (−84,300/RT), where T is in °K and W is in mg/cm2 and t is in sec. The parabolic rate controlling process is diffusion through an Fe-Ni-Cr spinel layer observed in the inner layer of the scale. The oxidation of 304L stainless steel by air from 1100 to 1360 C (2012 to 2480 F) was slow compared to the oxidation by steam in this same temperature range, parabolic rates being lower than those in steam by a factor of ~ 103. Although X-ray diffraction observed Fe3O4 (major) and Fe2O3 (minor) on the surface of the coatings formed in air at temperatures of 1360 C and below, Cr2O3 was found at the metal-oxide interface. The low rates in air thus reflect the formation of a protective Cr2O3 film. The rate in air at 1375 C is exceptionally rapid compared to those at the lower temperatures possibly because of the Fe-FeO liquidus at 1370 C (2498 F).
Environmental Effects of Anthraquinone Derivatives on the Resistance to SCC of AISI 4340 Steel in Aqueous Chloride Solutions
Authors: TIRMAN A , FUGASSI PAUL , HANEY E. G.
Published: February 2013

Polyhydroxy derivatives of anthraquinone adsorbed on AISI 4340 steel foil increase the resistance of the foil to stress corrosion cracking in aerated 0.6 M aqueous sodium chloride acidified with hydrogen chloride to pH 1.5. It is suggested that these compounds act as acceptors of atomic hydrogen or of other intermediates involved in the electrolytic discharge of hydrogen and that the reduced form of the compound is re-oxidized to its original state by dissolved oxygen in the sodium chloride solution.
Mechanism of Chloride Stress Corrosion Cracking of Austenitic Stainless Steels
Authors: RHODES P. R.
Published: February 2013

Electrochemical studies were made in aqueous LiCl, MgCl2, and MgBr2 solutions and in ZnCl2/KCl molten salt to clarify the corrosion reactions related to stress corrosion cracking (SCC) of austenitic stainless steel and to better define environmental variables critical to the occurrence of chloride SCC. Type 304 stainless steel electrodes were employed, with complementary SCC tests made with U-bend Type 304 stainless steel specimens. Several conclusions critical to an understanding of the mechanism of chloride SCC resulted from these investigations: (1) SCC was observed in concentrated MgBr2 solutions, (2) H2O must be present in the electrolyte, as SCC did not occur in dry molten ZnCl2/KCl, and (3) H2 evolution from corroding specimens may be facilitated by anodic polarization. Present studies do not support a model equating crack propagation with stress assisted anodic dissolution. Rather, evidence is presented that hydrogen evolution at the crack tip occurs and is a critical precursor to crack initiation and propagation. A model of SCC requiring hydrogen evolution at the crack tip is proposed, with emphasis being placed on the effect of anodic reactions within the crack in maintaining high acidity near the crack tip. Recent publications suggest that the role of evolved hydrogen in SCC may be related to formation of hydrogen induced martensitic platelets along paths of crack propagation.
Theoretical Considerations in the Measurements of Polarization and Corrosion Potential Curves
Authors: MUELLER W.A.
Published: February 2013

The polarization curve is defined as the current density potential relationship for a given electrode immersed in a given electrolyte. Based on this definition, the use of hemi-spherical or of cylindrical iso-potential test electrodes is proposed for its accurate determination. For these test electrodes, combined with counter electrodes of equal symmetry, drop of the potential in the electrolyte is shown to be: I1 ρr1 (1–r1/rc) for hemi-spherical and l1ρr1 1n (rc/r1) for cylindrical symmetry, where l1 = current density on the test electrode (amp/cm2), ρ = resistivity of the electrolyte (ohm x cm), and Y1,rc = radii of the test and counter electrode (cm), respectively. By adding to either of these values, the potential drop between test electrode and electrolyte and by subtracting the potential drop between counter electrode and electrolyte, the total potential drop between these electrodes is obtained. The product I1ρr1 is found to be the parameter of deciding importance for an exact determination of the potential field which surrounds electrodes and of the potential of test electrodes. For test electrodes of conventional shape, the average potential drop in the electrolyte is estimated and a similar parameter defined. For sets of hemi-spherical or cylindrical test electrodes arranged in circular order with the reference electrode in the center, the potential field is expressed by an equation which provides a sound basis for the use of such multi-test electrode arrangements. Finally, the effect on the course of polarization curves of redox reagents such as originally contained in the electrolyte or produced by corrosion, is reviewed. From the relations derived, some conclusions are drawn and incorporated in the design of various types of experimental equipment for the determination of polarization and corrosion potential curves in laboratory and field studies, including the study of crevice corrosion.
The Application of Electrochemical Techniques to the Study of Corrosion of Automotive Trim Materials
Authors: WALKER M. S. , ROWE L. C.
Published: February 2013

De-icing salts are known to have a contributing effect on the corrosion of automotive trim materials. Various accelerated tests have been developed to evaluate the corrosion resistance of trim materials, but each test has its own limitations. Electrochemical techniques are a valuable supplement to these other methods, not only because they are fast and reproducible but also because they help in determining mechanisms of reactions. A potentiodynamic anodic polarization method was used to show the relative corrosion resistance of four different stainless steels and a chromium plated stainless steel used in trim applications, and the order of corrosion resistance compared favorably with that obtained by conventional chemical tests and by field exposure. Furthermore, the test was used to show distinct differences in the pitting susceptibility of stainless steels exposed to different concentrations of chloride ion. The thermographic test is commonly used to evaluate the corrosion resistance of stainless steels. The effect of specific ingredients in the solution on corrosion was determined by both chemical and electrochemical tests. Chemical tests showed that chloride and thiosulfate ions had the greatest effect on pit initiation, probably because the thiosulfate altered the redox potential of the solution. Potentiodynamic polarization measurements indicated that the chloride ion concentration was rate controlling after corrosion had begun, and the thiosulfate ion caused a shift in potential which placed the material in a corroding region.
Corrosion Behavior of Nickel and Inconel in Acidic Chloride Solutions
Authors: PIRON D. L. , KOUTSOUKOS E. P. , NOBE KEN
Published: February 2013

The corrosion behavior of nickel and Inconel in acidic solutions has been investigated by polarization methods. The cathodic Tafel slope for the h.e.r. of nickel in de-aerated 1N H2SO4 and the corresponding exchange current density were 135 mv and 3.4 μa/cm2. Two cathodic Tafel slopes and exchange currents for the h.e.r. were obtained for Inconel in the same solution: 50 mv and 0.22 /μa/cm2; 115 mv and 7.2 μa/cm2. With increase in concentration of chloride ions, the corrosion potential of nickel decreased and the open circuit differential capacitance increased. Each parameter approached a constant value at the higher chloride ion concentrations. Anodic polarization of both metals showed that the primary passivation potential, the critical and passive current densities increased with increase in chloride ion concentration. The passivity of Inconel was shown to be superior to that of nickel in acidic solutions in the absence and presence of chloride ions.
A New Solution Potential Measurement for Predicting Stress Corrosion Performance of 2219 Aluminum Alloy Products
Authors: HORST R. L. , HOLLINGSWORTH E. H. , KING W.
Published: February 2013

A new electrochemical test for predicting the stress corrosion performance of 2219 alloy products in the T851 and T87 tempers is described. The test requires only a simple measurement of solution potential of an unstressed specimen in a mixture of absolute methyl alcohol and carbon tetrachloride. It is rapid, requiring less than an hour and has the outstanding advantage of providing differences of nearly 200 millivolts between borderline and resistant conditions of stress corrosion susceptibility, as contrasted to differences of less than 20 millivolts in conventional NaCl-H2O2 solution. The test offers an attractive possibility for evaluating stress corrosion performance of 2219 products quickly as an alternate or supplement to the conventional 30-day alternate immersion exposure in 3½% sodium chloride solution. The mechanism of the reaction between 2219 and this organic electrolyte suggests that a similar test can be developed for other aluminum alloys.
Passivity and Anodic Protection
Authors: REINOEHL J. E. , BECK F. H.
Published: February 2013

The possibility for anodically protecting metals is described in terms of degrees of passivity, passivation diagrams, a passivity index, and a passivating parameter. The effects of material and environmental variables are outlined. The passive state of iron is expressed in terms of a variable-composition Fe3O4-γ-Fe2 O3 spinel phase and also in terms of water in the double layer being oxidized to hydroxy- and oxyligands.
Flaw Growth in Ti-6Al-4V in Freon Environments
Authors: RAYMOND L. , USELL R. J.
Published: February 2013

The general and stress corrosion behavior of Ti-6Al-4V alloy in Freon environments were investigated. Intentionally flawed specimens were examined to determine the ability of the metal to sustain defects on exposure to stress and environment. Freon TF and Freon MF were used as base environments for the study. In addition to testing with commercially pure Freons, chlorine-doped Freons were used. Two thicknesses of solution-treated and aged Ti-6Al-4V alloy were used. The crack-bearing properties of a metal in the presence of an environment is based on the framework of fracture mechanics. It is indicated that the primary function of stress intensity in the Ti-6Al-4V/Freon MF interaction is the exposure of fresh titanium surfaces to the environment through plastic deformation at the crack tip.
The Variable Corrosion Resistance of 18Cr-8Ni Stainless Steels: Behavior of Commercial Alloys
Authors: WILDE B. E. , GREENE N. D.
Published: February 2013

The electrochemical and corrosion characteristics of Types 383, 304, and 316 stainless steel in 1N̄ H2SO4 were determined using precision potentiostatic polarization and conventional coupon exposure/weight change techniques. Factors increasing the magnitude of the critical anodic current density, lC, are shown to have a deleterious effect on the passivating tendencies of Type 304 alloys. Statistical analysis of the electrochemical properties of Type 304 alloy has shown that lC is related to chemical constitution by the following relationship: Control of the detrimental effects of sulfur and manganese in Type 304 alloys can be obtained during manufacture by an increase in copper and molybdenum content.
Stress Corrosion Cracking and Corrosion Behavior of Titanium in Methanol Solutions: Effect of Metal Ions in Solution
Authors: SEDRIKS A. J. , GREEN J. A. S.
Published: February 2013

A study has been made of the effect of additions of various metal ions to the environment on the intergranular stress corrosion cracking (SCC) and corrosion of unalloyed titanium in a methanol-hydrochloric acid solution. Separate additions to the solution of Pd, Au, Fe (ferric), and Cu (cupric) ions, in quantities ranging from 0.01 to 1000 ppm, caused substantial increases in both susceptibility to SCC and intergranular corrosion, without the resulting passivity reported for aqueous hydrochloric acid solutions. Electrochemical studies established that these increases resulted from the enhancement of the over-all cathodic process. In the absence of metal ions, the major cathodic reaction appears to be the reduction of dissolved oxygen, although another reaction, tentatively identified as the recombination of hydrogen ions, also contributes to the over-all cathodic process. Pd or Au ions deposited as metal films, detectable by X-ray techniques, and these films, once present, facilitated the recombination of hydrogen ions. No metal films were detected with ferric or cupric ions in solution, the additional cathodic reaction in these cases probably being the reduction of these ions to their lower oxidation states. The observations are discussed in terms of the mechanism of SCC.
Anodic Polarization Characteristics of Phosphated Steels
Authors: CHANCE R. L. , FRANCE W. D.
Published: February 2013

The problem of providing a meaningful evaluation of the corrosion resistance of phosphated steel for the dual purposes of quality control and of improving the phosphate coating has a long and arduous history. The electrochemical characteristics of zinc-phosphated mild steels have been investigated to determine the repeatability, significance, and possible applications of such data. This investigation resulted in a precise electrochemical procedure that can distinguish between steels with zinc phosphate coatings of different quality and crystal structure. When zinc-phosphated mild steels are polarized anodically in 0.6M ammonium nitrate solution, different steels with the same nominal composition and phosphate treatment exhibit active-passive corrosion behavior with current density values that vary considerably over a narrow potential range. These critical current densities, with certain exceptions, vary in relation to the rust creepage corrosion evaluations of coated specimens in salt spray and to phosphate crystal structure. The effects of phosphate ions and of pH changes on the unique anodic polarization characteristics of phosphated steels were studied by simulating conditions that exist at the steel-phosphate-solution interfaces. Anion adsorption is discussed as a basis for the complicated behavior reflected in the anodic polarization data.
The Separation of Corrosion and Stress Effects in Stress Corrosion: The Critical Role of Surface Preparation
Authors: COCKS F. H. , RUSSO J. F. , BRUMMER S. B.
Published: February 2013

The stress corrosion behavior of an Al-Zn-Mg-Cu alloy (7075) has been investigated. Under certain conditions of surface preparation, corrosion alone is found to cause a major diminution in subsequent stress corrosion life. For example, in 7075 in the T651 temper with an as-machined surface finish, the deleterious effect of corrosion is independent of the application of load during the first 80% of its normal stress corrosion life. Only during the last 20% of the normal stress corrosion period is it necessary to apply a load. It is during this latter period that true stress corrosion, as normally defined, can be said to occur. These observations do not result from residual tensile stresses in the material; rather, they are shown to be due to disruption of the grain boundary structure at the surface by machining. The beneficial effects of shot peening and other mechanical surface treatments probably also derive from similar distortions.
Technical Note: Effect of Applied Current on Stress Corrosion of Beryllium
Authors: KING T. T. , MYERS J. R.
Published: February 2013

Effect of galvanostatic anodic and cathodic currents on the stress corrosion of beryllium sheet material in aerated, synthetic sea water at 72 F (22 C) was determined. Applied anodic currents reduced the time-to-failure; cathodic currents prevented pitting and subsequent stress corrosion. Mechanism for premature failure was associated with rapid anodic dissolution along an active path nearly normal to the applied tensile stress. Hydrogen cracking was excluded as a primary factor in the failure mechanism.
Comparison of Chemically and Electrolytically Induced Pitting Corrosion
Authors: FRANCE W. D. , GREENE N. D.
Published: February 2013

Pitting of zirconium and stainless steel in acidic and near-neutral chloride media has been investigated. It is shown that controlled potential and conventional chemical corrosion tests do not yield similar rates or types of attack under identical environmental conditions. Such discrepancies limit critical pitting potential measurements and related techniques for evaluating and comparing pitting in halide environments. A theoretical explanation based on the accumulation of chloride at anodically polarized electrode surfaces is presented.
Thermochemistry and the Oxidation of Refractory Metals at High Temperature
Authors: GULBRANSEN EARL A.
Published: February 2013

Recent developments in the thermochemical data for the condensed oxide phases and volatile oxide species for the refractory metals has made possible an analysis of the several types of high temperature oxidation processes. The analyses show the following factors to be important: (1) the presence or absence of oxide films or scales on the metals, (2) the melting points of the one or more oxide phases, (3) the equilibrium pressures of the several volatile oxides, and (4) the flow rate of reactant gases. The thermochemical predictions are compared to experimental observations for molybdenum and tungsten.
Effect of Alloy Composition on Stress Corrosion Cracking of Fe-Cr-Ni Base Alloys
Authors: STAEHLE R. W. , ROYUELA J. J. , RAREDON T. L. , SERRATE E. , MORIN C. R. , FARRAR R. V.
Published: February 2013

This study investigated the effect of alloying on the behavior of Fe-Cr-Ni base alloys in boiling MgCl2 solutions. Alloys included commercial Fe-Cr-Ni alloys; ternary Fe-Cr-Ni alloys to 40% Cr; fourth-component alloys with specific alloy bases; fourth-, fifth-, and sixth-component alloys. The primary experimental measurements were time-to-breaking of wire specimens. In addition, polarization, potential time, current decay, constant potential cracking, and metallographic studies were conducted. Alloys of very substantial improvement in resistance to cracking were found. The most effective alloy additions were found to be aluminum, beryllium, and carbon. Lowering chromium to the 10-15% range was also found to be very effective in preventing cracking. The results are discussed in terms of the slip-step dissolution model of stress corrosion cracking.
Resistance of 18Cr-18Ni-2Si Stainless Steel to Stress Corrosion Crack Propagation in Boiling Magnesium Chloride
Authors: DAVIS J. A.
Published: February 2013

The propagation resistance of a steel cannot be determined by conventional testing procedures if the steel is resistant to crack initiation. Since conventional techniques were used to develop 18-18-2 stainless steel for resistance to stress corrosion cracking, its resistance to crack propagation was determined by means of pre-initiated cracks. Two laboratory heats of steel were prepared, one with the typical 18-18-2 stainless steel composition and the other with essentially the same composition but with high phosphorus and molybdenum contents, to make it susceptible to cracking. The steels were roll-bonded together and sheet specimens were prepared in the annealed, cold worked, and sensitized conditions. U-bend specimens were prepared, half of them with the susceptible steel on the tension side and the other half with the resistant steel on the tension side. The specimens were exposed in boiling magnesium chloride (150 C, 302 F). When cracks appeared, the specimens were retained in the solution for a minimum of 3 to 4 additional weeks to allow the cracks to propagate. No cracks initiated in 18-18-2 stainless steel under any of the conditions tested during five months of exposure. Cracks that initiated in the susceptible steel propagated to the interface and stopped. No cracks were observed that propagated into 18-18-2 stainless steel, even for specimens that cracked in 70 hours and were not removed for five months. These test results indicate that 18-18-2 stainless steel is resistant to crack propagation.
Effect of Dissolution of Oxide Film on Oxidation of Zr-1%Nb Alloy in Air and Pressurized Steam at 450 C
Authors: EL-SHANSHOURY I. A. , EL-DAHSHAN M. E.
Published: February 2013

The corrosion behavior of oxidized and vacuum annealed Zr-1%Nb alloy was investigated at 450 C (842 F) in air and pressurized steam. The corrosion resistance of partially dissolved oxide films was found to decrease with the increase in the vacuum annealing temperature up to 600 C (1112 F). A linear relationship between the logarithm of the oxidation rate and the annealing temperature was obtained from which an activation energy of 39.5 K.cal/mole was calculated. The activation energy was found to be independent of the corrosive medium. The increase in corrosion rate is explained on the fact that oxygen ion vacancy gradient increases with the increase in the annealing temperature. The decrease of the corrosion rate in steam after vacuum annealing is attributed to the release of H2 and H during the treatment process.
Stress Corrosion Cracking of Ti-8Al-lMo-lV Alloy: Electrochemical Behavior in Aqueous Solutions
Authors: CHEN C. M. , BECK F. H. , FONTANA M. G.
Published: February 2013

The electrochemical behavior of material/environment systems has a significant effect on susceptibility to stress corrosion cracking. The present investigation is concerned with electrochemical processes associated with stress corrosion cracking of Ti-8-1-1 in aqueous environments. Also included are fresh surface potentials measured by an erosion corrosion method; the slope of potential vs pH was about 59 mV/pH. Potential decay curves in sulfuric acid display two arrests and, the slope of potential vs pH for both was about 55 mV/pH. In chloride containing solution, chloride ion attack occurred at potentials more noble than about 2000 mV. A plot of logarithmic current and time yields the linear relationship, InJ = At + B, where A and B are constants and t is time.
Effect of Polarization Rate in Potentiokinetic Anodic Polarization of iron in 1N H2SO4
Authors: REINOEHL J. E. , BECK F. H. , FONTANA M. G.
Published: February 2013

Potentiokinetic data are reported for single crystal and polycrystalline specimens of high purity (56 ppm total impurities) and sulfurized (150 ppm sulfur) iron in 1N H2SO4. Eight polarization rates, ranging from 20 to 1100 mV/min, were investigated. The shape and position of potentiokinetic anodic polarization curves were found to vary appreciably and reproducibly with polarization rate. The observed logarithmic variation of three characteristic passive and transpassive current densities (ix) with polarization rate (η̇) can be expressed by a relation of the form where k and r are constants. The exponent r is given the name “polarization-rate-sensitivity.” At faster polarization rates, current densities tended to be higher and secondary passivity more pronounced. Secondary passivity merged with ordinary passivity at a material-dependent “critical” polarization rate, at which passive current densities were nearly independent of potential. Passive current densities increased with increasing potential at faster polarization rates, corresponding to Langmuir adsorption conditions, and decreased with increasing potential at slower polarization rates, corresponding to Temkin adsorption conditions. The presence and absence of sulfur and of grain boundaries had a negligible quantitative effect on the appearance of the potentiokinetic anodic polarization curve of iron in dilute sulfuric acid solution. However, a small effect of these chemical and physical variables could be expressed by different relations between currents and polarization rate.
Stress Corrosion Cracking of Ti and Ti-6Al-4V Alloy in Dinitrogen Tetroxide
Authors: MORELAND P. J. , BOYD W. K.
Published: February 2013

The stress corrosion cracking behavior of titanium and Ti-6Al-4V alloy in liquid N2O4 has been investigated from thermodynamic considerations and autoradiographic, chemical, and potential studies. Studies were concerned with the N2O4-H2O-O2 system which is believed to produce HNO3 and the N2O4-O2 system to cause stress corrosion cracking. A hydrogen embrittlement mechanism involving HNO3 in the commercial N2O4 appeared improbable. An electrochemical mechanism in which O2 plays a major role has been proposed.
Anodic Polarization Measurements of Active-Passive Nickel Alloys by Rapid-Scan Potentiostatic Techniques
Authors: MORRIS P. E. , SCARBERRY R. C.
Published: February 2013

Conventional methods for measuring corrosion behavior by potentiostatic polarization techniques failed to yield complete anodic curves for some commercial nickel alloys that passivate in nonoxidizing test media. (Cathodic curves for these alloy-media systems contained inflections suggesting the existence of the S-shaped anodic curve.) Modification of potentiostatic techniques, including a drastic increase in potential-scan rate, enabled primary passive potentials and anodic critical-current densities to be measured before the specimen reached a steady state.
Selective Oxide Films of a 5% Aluminum-Iron Alloy in a Low Oxygen Potential Atmosphere
Authors: NAKAYAMA T. , KANEKO K.
Published: February 2013

Selective oxide films on a 5% Al-Fe alloy in the temperature range 700–900 C (1292–1652 F) for 1 hour in an atmosphere of hydrogen-water vapor mixture with a constant dewpoint as low as 20 C (68 F) were identical with the spinel type crystals, γ-Al2O3, containing small amounts of iron. Oxide films however, produced after heating at higher temperatures than 920 C (1688 F) in the same oxidizing atmosphere consisted only of corundum type crystals, α-Al2O3, having iron. It is probable that the iron ions contribute to the formation of the corundum type oxide at the temperature of the stable region of pure γ-Al2O3.
Effect of Cold Rolling on Resistance of Ni-Fe Alloys to Hydrogen Cracking
Authors: MARQUEZ J. A. , MATSUSHIMA I. , UHLIG H. H.
Published: February 2013

Low carbon 10–19% Ni-Fe alloys become considerably more resistant to hydrogen cracking after severe cold rolling. The observed resistance decreases with increasing carbon content. The improvement is directional, the optimum effect applying to specimens stressed parallel to the rolling direction. Other iron alloys, e.g., 15.1% Co-Fe, martensitic 18-8 stainless steel, 7.5% Mn-Fe, 19.8% Cr-Fe, 0.2% Cu-Fe alloys, in that order, also show a directional improvement conferred by cold rolling. For a cold rolled 19% Ni-Fe alloy of maraging composition, alloyed Co has no effect, but alloyed Mo, Al, or Ti decrease resistance. Pure carbon steels are markedly susceptible to hydrogen cracking indicating that susceptibility of commercial steels is not caused by normal impurities and inclusions. The mechanism of hydrogen cracking is related to microvoids at the interface of precipitate particles and plastically deformed metal which perform as crack nuclei. Cold rolling presumably aligns such nuclei accounting for greater resistance of specimens stressed parallel to the rolling direction.
Solubility and Distribution of Tritium in Annealed and Cold Worked 304 Stainless Steel in the 100 to 300 C Temperature Range
Authors: POWELL G. W. , BRAUN J. D. , CHANEY K. F. , DOWNS G. L.
Published: February 2013

The solubility of tritium in annealed and cold worked 304 stainless steel in the temperature range 100 to 300 C (212 to 572 F) was determined by equilibration of sheet specimens with a tritium-containing gaseous atmosphere. It was found that the solubility is unaffected by cold work in this temperature range. A series of autoradiographs which were made of a cold worked specimen which was equilibrated at 300 C showed that the tritium is distributed homogeneously throughtout the microstructure at 300 C but that partitioning of the tritium between the regions of low and high defect concentration in the cold worked microstructure takes place at ambient temperature.
Concept of the Occluded Corrosion Cell
Authors: BROWN B. F.
Published: February 2013

It is proposed that the various localized forms of corrosion (pitting, stress corrosion cracking, intergranular corrosion, crevice corrosion, filiform corrosion, tuberculation, and exfoliation) have the common feature of local acidification by hydrolysis. The acidity is viewed as having a responsible role in the self-perpetuating character of these corrosion forms. Three possible benefits of this rationale are offered.
An Investigation on the Anodic Behavior of Low Alloy Steels
Authors: BOMBARA G. , AGABIO G.
Published: February 2013

The anodic behavior of three low alloy steels and one mild steel was evaluated by potentiodynamic polarization measurements in bicarbonate, sulfate, and bisulfate solutions. Some significant features differentiated the steels as to their corrosion behavior in these media. These features were dependent on the alloying elements and were related to the practical performance of the steels in atmospheric corrosion tests. The effect of weathering on the anodic behavior of these materials in sulfate solution was evaluated by the use of polarization measurements on specimens artificially weathered by prolonged anodizing treatments at very low current densities.
An Electrochemical-Statistical Study of Mild Steel Corrosion Inhibition in Oxygen Containing Environments
Authors: LEGAULT R. A. , MORI S. , LECKIE H. P.
Published: February 2013

The dissolution behavior of mild steel in a given environment is related to the competitive adsorption of available species onto the metal surface. The nature of the adsorbed species determines the direction in which the dissolution behavior is altered. An earlier study described the effect of chemical inhibitors in oxygen-free environments; this study examines the role of oxygen in these processes. Two anions, chloride and sulfate, were selected as aggressive adsorption species and two, nitrite and chromate, as passivating species. All four anions, in the presence of dissolved oxygen, were evaluated singly over a concentration range of five orders of magnitude in order to obtain the effect of concentration in each case. These four anions were then studied in groupings of two and three to ascertain the relative proportions of inhibiting and noninhibiting ions necessary to ensure passivity. Instantaneous corrosion rates measured by the linear polarization method were used as the criteria in comparing the effect of environmental changes. Multiple regression analysis techniques were utilized to obtain quantitative relationships between the concentrations of the four anions studied and the corrosion rates observed. The results are compared to those obtained in oxygen-free systems and are applied to a consideration of the mechanism of formation and maintenance of a passive film. This is discussed in terms of electrochemical polarization, competitive adsorption and passive film stability.
Effect of Various Modes of Loading on the Stress Corrosion Cracking of a Maraging Steel
Authors: HAYDEN H. W. , FLOREEN S.
Published: February 2013

An 18Ni (280) maraging steel has been tested in 3.5% NaCl solution under various modes of loading. The most severe condition was plane strain loading of fatigue precracked samples. The severity of stress corrosion cracking (SCC) of unnotched samples decreased in the sequence: plane strain bending, tension, plane stress bending, and torsion. The most consistent explanation for the various observations is that SCC results from hydrogen embrittlement. Under certain circumstances anodic dissolution processes can result in beneficial crack blunting effects rather than SCC failure.
Observations on the Stress Corrosion Crack Propagation Characteristics of High Strength Steels
Authors: CARTER C. S.
Published: February 2013

The relationship between stress corrosion crack velocity and crack-tip stress intensity is discussed. In most high strength steels, there is a wide range of stress intensity over which crack velocity is essentially constant. Methods of estimating this velocity are described. Values for a variety of high strength steels are presented and the effects of metallurgical variables are indicated. Implications with regard to testing procedure, crack morphology, and service performance are outlined.
Stress Corrosion Cracking of Ti-8Al-lMo-1V Alloy: Aqueous and Methanol Environments
Authors: CHEN C. M. , BECK F. H. , FONTANA M. G.
Published: February 2013

Stress corrosion cracking of Ti-8-1-1 alloy was studied using controlled potential techniques in aqueous and methanol environments with and without halogen ions. The alloy was observed to display susceptible zones in aqueous solutions containing halogen ions—susceptible zones are in the corrosion potential and pitting potential regions. Also, potential zones of anodic and cathodic protection exist. In methanol environments, the alloy displays both potential regions of cathodic protection and anodic susceptibility—the anodic susceptible region is aggravated by the presence of halogen ions. The dependence of cracking susceptibility and immunity to cracking on potential suggests that anodic dissolution, catalytic action of halogen ions, and hydride formation may be important in aqueous solutions; whereas, in methanol solutions, anodic dissolution and halogen ion attack are of primary importance.