bluuebunny/crossref_metadata_2025 huggingface dataset:
The Oxidation off Iron, Nickel and Cobalt-Base Alloys Containing Aluminum
Authors: HAGEL W. C.
Published: February 2013

By conducting continuous weight-gain measurements from 500 to 1300 C on a variety of Fe-Al, Fe-Cr-Al, Ni-Al and Co-Al alloys in oxygen at 100 torr and examining the reaction products which form, reasons for the enexpected ineffectiveness of preferential aluminum oxidation have been explored.

With Fe-4.4 percent Al and Fe-12 percent Al, there are two different regions of parabolic growth- these are associated with the appearance of γ-A12O3 below 900 C and α-Al2O3 above. The latter is normally more protective but possesses a greater tendency for cracking and spalling; adding 24.6 percent chromium promotes its formation at lower temperatures. With Ni-5.0 percent Al, two displaced regions are also found; here, nickel penetrates alumina to provide intermediate NiO · Al2O3 and an outer layer of NiO. With Co-4 percent Al, somewhat less cobalt penetrates γ-Al2O3 to provide CoQ · Al2O3 and an outer layer of Co3O4. When both CoO and α-Al2O3 are stable phases, the latter grows mainly by internal oxidation and offers little protection.
The Effect of Cold Work on the Stress-Corrosion Cracking of Type 302 Austenitic Stainless Steel
Authors: GREELEY P. J. , RUSSO V. J. , SAXER R. K. , MYERS J. R.
Published: February 2013

The effect of cold work on stress-corrosion cracking of Type 302 austenitic stainless steel wire exposed to boiling (154 C, 309 F) 42 weight-percent aqueous magnesium chloride solution was determined. Wire specimens of 0.02-in diameter were stressed in uniaxial tension using specially designed glass test cells containing the corrosive environment. Tests were conducted at five applied stresses over the range 10,000 to 30,000 psi with laboratory-annealed wire and as-received (bright-annealed) material which had been cold worked 10, 20 and 30 percent.

It was established that: (1) failure generally occurred in the vapor phase above the boiling MgCl2 solution, (2) the time-to-failure varied inversely with the applied stress, (3) the 10 percent cold-worked material exhibited the shortest time-to-failure, and (4) the 30 percent cold-worked material had the maximum resistance to stress-corrosion cracking. The short times-to-failure recorded for the 10 percent cold-worked material were attributed to introduction of large amounts of localized residual stresses in the bright-annealed material by the cold-working process. The longer times-to-failure associated with the more heavily cold-worked material were explained by the transformation of austenite to “quasi-martensite”.

Crack propagation rates, nearly independent of the applied stress, were greatest for 10 percent cold-worked material. Average crack depth decreased with increasing degrees of applied stress and cold work. In general, a positive correlation existed between the crack density (cracks/inch) and the applied stress.
Effect of Grain Size on Carbide Precipitation and Intergranuiar Corrosion in AISI Type 201 Stainless Steel
Authors: DOSHI C. P. , AUSTIN W. W.
Published: February 2013

The grain size of the austenitic stainless steel affects the rate of intergranular attack at high temperatures. While the effect of grain size has been studied for 18-8 chromium-nickel austenitic steels, little work has been done on chromium-nickel-manganese austenitic steels. It is the purpose of this investigation to correlate intergranuiar attack with grain size in these steels.

A commercially available alloy (AISI Type 201) was selected for study. Effect of four different grain sizes (ASTM Grain Size Numbers 1, 2, 3 and 5) at four different sensitization times and four temperatures was studied. Results obtained in terms of weight loss in the boiling nitric acid test and through photomicrography were used to correlate intergranuiar attack with grain size.

Best resistance to corrosion was obtained at a sensitization temperature of 800 F (426 C) for all grain sizes. At elevated temperatures [1000 and 1200 F (537 and 649 C)] corrosion rate increased with increasing sensitization time. Upon comparison of sensitization behavior at 1400 F (760 C) for all grain sizes it was found that exposure for 48 hours produced less severe corrosive attack than did the 16-hr exposure. This was explained in terms of increase in size of carbide particles.
Corrosivity of Cesium
Authors: WINSLOW P. M.
Published: February 2013

Cesium used as a propellant for ion engines was evaluated for compatibility with container materials. These studies were directed toward the corrosive effects on the materials of containment as well as the extent of propellant contamination by the corrosion reactions. The exposures were made in both liquid and vapor environments at a temperature of 400 C for 500 hours. From this investigation a number of alloys were selected that had adequate corrosion resistance. A preponderance of evidence indicated that the chief reaction was oxidation-reduction between cesium oxide in the cesium and the metals under test.
General Corrosion of Stainless Steels and Nickel Base Alloys Exposed Isothermally in Superheated Steam
Authors: WOZALDO G. P. , PEARL W. L.
Published: February 2013

Results are reported for a comprehensive corrosion study sponsored by the Atomic Energy Commission on commercially available materials that might be suitable for nuclear superheat fuel cladding application. Several nickel alloys (Inconel 600, Inconel 625, Incoloy 800, Incoloy 825 and Hastelloy X) and two stainless steels (Types 304 and 406) were exposed isothermally to 1050 and 1150 F (656–621 C) superheated steam in a dynamic corrosion facility. Hydrogen and oxygen content of the steam was controlled to simulate that found in boiling-water reactor steam. Generally an initially high corrosion rate decreased to a lower constant rate. Initial corrosion rate period appeared to vary in time for different materials although most seemed to reach a linear rate in the first 1000 hours.

Hastelloy X, Incoloy 825, Inconel 625 and Incoloy 800 had low initial and long-time linear corrosion rates and formed good protective and tenacious oxides up to 1150 F. Type 406 stainless steel (SS) had a high initial but low long-time linear corrosion rate and formed a protective and tenacious oxide up to 1150 F. Inconel 600 had adequate corrosion resistance to 1050 F but formed a nonprotective oxide film, a significant portion of which was lost to the system at 1150 F. Type 304 SS had significant corrosion rates at 1050 and 1150 F but formed a relatively tenacious oxide at both temperatures that eventually reached a limiting thickness with subsequent spalling.
Superheated Steam Of Zirconium Alloys Containing Small Amounts Of Iron and Copper or Nickel
Authors: GREENBERG S. , YOUNGDAHL C. A.
Published: February 2013

Alloys of zirconium containing small amounts of iron and copper or nickel have corrosion resistance in superheated steam superior to that of the Zircaloys. At 540 C (1004 F) and 600 psi lowest rates are about 4 mdd (2.4 mpy) and at 650 C (1202 F) and 600 psi rates are about 6.8 mdd (4.1 mpy). High initial rates lead to an extrapolated intercept of about 4 mg/sq cm at 650 C (1202 F). The thickening films are subject to cracking at sharp radii. Absorption of corrosion product hydrogen decreases markedly as exposure temperature is raised from 540 to 650 C (1004 to 1202 F). This phenomenon is not understood. Metal embrittlement due to oxygen absorption becomes an increasingly serious problem as temperature is raised. Corrosion rate at 650 C (1202 F) is not affected by flow rate (300 ft/sec) or by presence of oxygen or oxygen-hydrogen mixtures in the steam.
Hydrogen Uptake of Zirconium And Its Alloys During Early Stages Of Corrosion in Steam
Authors: FREER D. W. , SILVESTER D. R. , WANKLYN J. N.
Published: February 2013

Hydrogen uptakes during initial stages of corrosion of Van Arkel zirconium and of two zirconium alloys in steam at 500 C (932 F) and 1 atmosphere pressure are reported. Percentage uptake remains low down to the lowest weight gains examined (~1 mg/sq dm), suggesting that control of hydrogen entry resides in reactions at the oxide/steam interface.
Intergranular Corrosion of Nonsensitized Austenitic Stainless Steels — 1. Environmental Variables
Authors: ARMIJO J. S.
Published: February 2013

Intergranular corrosion of nonsensitized stainless steels is reviewed, with emphasis on corrosion experienced in nitric-dichrornate solutions. Electrical resistance changes occurring during corrosion of Type 304 stainless ' steel in nitric-dichromate solutions are used to measure the rate of intergranular attack. Effects of HN03 concentration, Cr+6 concentration, temperature and stress on the intergranular corrosion reaction have been studied. The over-all corrosion reaction is found to consist of an incubation period, followed by a penetration period in which the rate of intergranular dissolution is linear. Measured activation energies for incubation and penetration periods are identical.

The effect of applied stress is to increase both incubation and penetration rates. Low stress levels have greatest effect on the incubation rate, while high stress levels have greatest effect on the penetration rate.

Appreciable grain boundary hardening is observed in nonsensitized Type 304 stainless steel. The grain boundary hardening is attributed to adsorbed impurities at grain boundaries. This segregation presents another variable which may be important in this type of intergranular attack.
Effect of Oxygen Concentration and pH on Electrode Potential of Stainless Steels and Operation of Microcouples
Authors: KOROVIN YU. M. , ULANOVSKII I B.
Published: February 2013

Using Russian steels of 13 Cr and 18–9 analyses in general experiments are conducted varying pH and oxygen concentrations in sea water to determine the relative effect of these variables on corrosion rates in crevices. Effect of oxygen concentrations in the range 1–9 mg/1 and pH 8.3 to 2.3 are reported.

Changes in pH were found to strongly and changes in oxygen concentration weakly influence the corrosion rate. Authors postulate that anodic passivity is effected after application of tenths of a milliampere per square centimeter whereas when the pH in the anodic space is lowered, critical current density required for passivation increases 40–50 fold.

Heat treatment of the steel does not influence electrode potentials when solution pH is lowered.
An Improved Exfoliation Test for Aluminum Alloys
Authors: LIFKA B. W. , SPROWLS D. O.
Published: February 2013

A new rapid test capable of producing exfoliation in susceptible aluminum alloys within a few days has been developed. This test is useful in studies of corrosion control and alloy development. Most significant is the excellent correlation of this laboratory test with exposures to natural marine environments. It is noteworthy also that the test procedure is applicable to all types of wrought aluminum alloys.

Test conditions involve cyclic exposure to acidified sodium chloride solution and to high relative humidity in a cabinet held at 95 F (35 C). This test is preferable to other laboratory procedures not only because of its speed but also because it produces readily visible exfoliation, does not require extensive specimen preparation and is not restrictive as to specimen size.
Effects of Mo, Cu, Si and P on Anodic Behavior of 17 Cr Steels
Authors: LIZLOVS E. A.
Published: February 2013

Effects of additions of 1–3 percent molybdenum alone and in combination with copper, silicon and phosphorus on the anodic behavior of 17 Cr stainless steel were evaluated by potentio-dynamic polarization measurements and film breakdown studies in sulfuric acid. As molybdenum content increased the critical current density for passivity decreased, passivation potential shifted in the active direction and stability of passive film, as revealed by breakdown times, increased. Copper and silicon additions tended to enhance effects of molybdenum, in general, while phosphorus was detrimental. No addition had significant effect on potential at which transpassive behavior occurs. All samples displayed a wide passive region over which anodic protection could be applied in sulfuric acid medium.
Stress Corrosion Cracking off Ti and Zr in HCl-Methanol Solutions
Authors: MORI KENJI , TAKAMURA AKIRA , SHIMOSE TAKAAKI
Published: February 2013

It was discovered by the authors that Ti is easily attacked by stress corrosion cracking in methanol containing HCl. This is a report on a study to assess quantitatively stress corrosion cracking of Ti in alcohol solutions. At the same time stress corrosion cracking of Zr was studied because of its similarity in chemical behavior to Ti.

Stress corrosion cracking of Ti occurs in methanol solutions containing HCl or H2SO4 and that of Zr is observed in methanol containing HCl or H2SO4 or HCOOH and in ethanol containing HCl. In HCl-alcohol solutions it is observed also that the larger the molecular weight of the alcohol, the longer life the metals have.

Addition of water to HCl-methanol solution prevents stress corrosion cracking of Ti and Zr. Critical concentration of water in 0.4 percent HCl-methanol solution is about 1.5 percent for Ti and about 3 percent for Zr. To prevent stress corrosion cracking by stress relief, annealing temperatures should be higher than 500 C (932 F) for Ti and 450 C (842 F) for Zr.
Polarization and Corrosion of Ferrosilicon Alloys for Iron Ore Beneficiation Media
Authors: ROBINSON F. P. A. , DuPLESSIS D. J.
Published: February 2013

Ferrosilicon alloys containing from 7.5 to 15 percent silicon and alloying additions of Cr, Ni, Cu, C, U and Mo were subjected to weight loss and polarization tests in NaCl/Na2SO4, HCl and H2SO4 electrolytes. Corrosion resistance was found, in accordance with existing knowledge, to increase with silicon content. Chromium was found to be particularly beneficial as regards corrosion resistance, whereas generally speaking, the other elements had little effect. By the judicious addition of the above-mentioned elements, a 12.5 percent silicon alloy was produced with satisfactory resistance and the high specific gravity necessary for heavy medium separation.
Oxidation Characteristics of the Lanthanide Metals
Authors: GREENE N. D. , HODGE F. G.
Published: February 2013

Oxidation rates and rate equations off La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu„ Y were determined in dry and moist air in the temperature range 100–800 C (212–1472 F) by precision weight gain measurements Oxide structures were examined by both metallographie and x-ray analyses.

Observed oxidation characteristics are related to oxide structures and the physico-chemical properties of the rare earth metals.
Polarization of Strained AISI 4340 Steel in Oxygenated NaCl Solutions
Authors: TOY S. M.
Published: February 2013

Electrode reactions involved in the stress corrosion of AISI 4340 steel in sodium chloride solutions were studied by pulse galvanostatic and potentiostatic experiments. The redox cell system involves two principal cathodic reactions and one anodic reaction. These electrochemical reactions are affected by the application of stress, by change in pH, by oxygen content and the heat-treated condition of the materials. The effect of stress is to shift the cathodic polarization curve in an electropositive direction with increasing tensile load. It is equivalent to cathodic control for the conditions investigated and is described by the electrochemical interpretation, based on the coupling of the redox branches which produce the largest corrosion current.
Embrittlement of High Strength AISI 4340 Steel in Boiling NaCl Solution
Authors: LOGAN HUGH L. , WEHRUNG JOHN M.
Published: February 2013

The resistance of high strength AISI 4340 steel tubing, quenched in oil and tempered at 425 F (218 C), to corrosive media has been investigated. The exterior surface of the specimen was exposed to boiling NaCl, the interior cavity was evacuated and the specimen was subjected to a tensile stress. Specimens failed, with little evidence that cracking was developing, after several hours' exposure and after hydrogen had penetrated through the specimen wall. Appearance of the initial fracture and its mode of development indicate it originated within the specimen wall. The data indicate that failure resulted from hydrogen embrittlement.
Use of Ammonia to Supress Oxygen Production and Corrosion in Boiling-Water Reactors
Authors: LESURF L. E. , BRYANT P. E. C. , TANNER M. G.
Published: February 2013

Radiolysis of the coolant in nuclear reactors cooled by boiling water results in oxygen in the steam and recirculated water phases. This has dictated the use of stainless steels as the major circuit materials for these reactors. It is shown that ammonia additions to the coolant eliminate oxygen production, permitting the use of mild steel for circuit construction with consequent savings in capital cost Corrosion data are presented for various out-reactor materials (carbon steel, low alloy steels, stainless steels, Monel alloy 400, Inconel alloy 600) exposed out-of-flux to the coolant of two phase in-reactor loops when operated neutral and with ammonia addition. Activation of corrosion products from different origins is discussed. Intergranular attack is related to the presence of oxygen or oxidizing radiolytic species in the water.
Hot Corrosion of Gas Turbine Alloys
Authors: BERGMAN P. A.
Published: February 2013

Types of hot corrosion encountered in aircraft gas turbines operating in marine environments were reproduced in laboratory tests. Nickel and cobalt-base alloys were tested in the products of combustion of JP-5 and 0, 2 and 200 ppm sea salt between 1600 F (871 C) and 2000 F (1093 C). Higher chromium alloys were generally (but not always) more resistant to hot corrosion. Attack was caused by sodium sulfate, corrosion occurring only in the temperature range in which sodium sulfate was deposited in a molten state. (About 1600 F (871 C) to 1875 F (1024 C)/ 2000 F (1093 C). Effects of another alkali metal and two alkaline-earth metals, sulfur and chlorine also were evaluated.

Microstructural changes were studied by metallographic techniques and chemical compositional changes and sulfides were identified by electron microprobe analyses. The nature of attack is discussed and some concepts of the hot corrosion mechanism postulated. Apparently, depletion of chromium in surface zones through the formation of oxides and sulfides reduces the corrosion resistance of depleted zones, thereby promoting severe hot corrosion.
Corrosion Tunnels in Stainless Steels
Authors: ARMIJO J.S. , WILDE B.E.
Published: February 2013

Corrosion tunnels can form in commercially pure austenitic alloys in the absence of chloride ions and stress corrosion cracking conditions.
Effect of Halide Additions on Anodic Behavior of Nickel in Sulfuric Acid Solutions
Authors: POSTLETHWAITE JOHN , FREESE LEONARD B.
Published: February 2013

A potentiokinetic study, dE/dt = 950 mV/hr, has been made of the effects of sodium chloride, bromide and iodide additions, in the range 0.001 to 0.1 M, on the anodic behavior of pure nickel in deaerated N/10 sulfuric acid. Each experiment comprised a forward and reverse sweep in the potential range (relative to the standard hydrogen electrode) −0.5 to +1.2 V. Halide additions affected the anodic behavior of the nickel in both active and passive regions. All halides studied lowered the corrosion potential, raised the primary passivation potential and increased the critical passivation current density. Additions of 0.01 M and greater resulted in elimination of the normal passive region.

Reactivation was much greater on reverse sweeps with chloride additions than in either plain acid or with other halides. Negative slope marking the active-passive transition on forward sweep sometimes was eliminated but was evident always on the reverse sweep showing that even when attacks in active and passive regions merge there is a change of electrode process at the normal active passive transition.
Anodic Corrosion Characteristics of Aluminum 7075 and 7178
Authors: ROEBUCK A. H. , LUHAN J. V.
Published: February 2013

High-strength alloys 7075 and 7178 are widely used now in the −T6 tempers by the aerospace industry. Several more corrosion-resistant tempers have been developed recently: 7075–T73 (stress corrosion resistant) and 7075–T76 and 7178–T76 (exfoliation resistant).

Electrochemical characteristics as determined by “dynamic” (current versus potential) and “static” (current versus time) tests were found to correlate well with their performance in accelerated corrosion and natural environment marine tests. Attack on the −T6 temper was found to be localized in nature, while that on the resistant tempers (−T76 and −T73) was general, showing crystallographic form. The −T6 tempers polarized more rapidly and were less active than the −T76 or −T73 tempers. Anodic control of the corrosion process is postulated to be more important in 7075 than in the more highly alloyed 7178; the latter showing mixed anodic-cathodic control.
Identification of the Initial Oxide Films on 18-8 Stainless Steel in High Temperature Water
Authors: NAKAYAMA T. , OSHIDA Y.
Published: February 2013

Initial oxide film formed on 18–8 stainless steel in high temperature water at 300 C (572 F) for 1 hour was identical with corundum type crystals like (Cr, Fe)2O3 alone or its coexistence with α-Fe2O3. On the contrary, the oxide film produced by prolonged oxidation (24 hours) consisted mainly of the spinel type crystals containing nickel.
Stress Corrosion of Titanium Alloys In Aqueous Magnesium Chloride Solution at 154 C
Authors: SANDERSON G. , SCULLY J. C.
Published: February 2013

Titanium alloys have been found susceptible to slow intergranular stress corrosion cracking in MgCl2 solutions boiling at 154 C (309 F). Titanium metal suffers from pitting but not from cracking in the same solution. Experiments on Ti-Al alloys have shown that as aluminium is added there is a transition from pits linked by wide fissures to narrow cracking. The effect of chemical polishing of specimens, which creates a surface layer of hydride phase, is to change the mode of cracking in the richer alloys from predominantly intergranular to predominantly trans-granular. This is explained by the formation of reactive dislocations in these alloys particularly at the hydride/matrix interfaces where corrosion attack is initiated. Formation of a hydride phase at the bases of pits during corrosion also will create reactive interfaces. Intergranular cracking arises from segregation to the grain boundaries of solute and possibly impurity atoms.
Optical Microscopy Studies of Anodic Dissolution of Iron In Sulfuric and Hydrochloric Acid Solutions
Authors: FELLONI L , CAMMAROTA G. P.
Published: February 2013

Microscopical observation was made during and after intensiostatic polarization of Armco iron electrodes. A correlation between etching degree and grain orientation was evident in sulfuric acid solutions. In hydrochloric acid solutions a smoothing at the inside of the grains, independently of their orientation and preferential corrosion at the boundaries occurred. It is suggested that in sulfuric acid the dissolution mechanism involving anion participation may be effective, while in hydrochloric solutions a competitive adsorption very probably takes place between Cl− and OH− or water molecules.
Microelectrodes for Corrosion Studies
Authors: CLEARY H. J.
Published: February 2013

Microelectrode technology is currently being developed by medical and biological workers for use in microanalytic and intracellular studies. The possibilities of applying this new technology to investigations of corrosion phenomena are examined in the paper. Oxygen cathode, pH and potential-measuring microelectrodes with working tips ranging from 10 to 100 microns in diameter are being developed for the study of corrosion mechanisms. Techniques for the construction, storage, calibration and use of stable electrodes are described. Probe dimensions and very high impedance characteristics lead to positioning and electrical measurement difficulties which are also discussed.
Influence of Prepolarization on the Electrochemical Behavior of Iron-Carbon Alloys
Authors: WOOD G. C , SOLTZ G. C.
Published: February 2013

The influence of anodic and cathodic prepolarization of electrodes, containing respectively 0.03, 0.48, and 1.3 percent carbon, in de-aerated N and 0.1 N sulfuric acid at 25 C (77 F) on the subsequent open circuit potential-time curves has been determined. Anodic pretreatment always lowers and cathodic pretreatment raises the initial potential on these curves. Magnitude of the potential shift and time required to resume the rest potential are larger the higher the prepolarizing time. The influence of carbon content and acid concentration is complex. Special experiments have indicated the importance of specimen, and especially solution history, and have permitted an interpretation in terms of polarization diagrams. The most likely explanation is the influence of sulfide or noble metal or metalloid ions derived from the alloy or possibly the solution in altering the number of active anodic sites. This is achieved by an increase in the degree of hydrogen poisoning or by accumulation or plating out of metals or metalloids.
Discussion of the De-Alloying Phenomenon
Authors: BROOKS W. B.
Published: February 2013

This brief note is a discussion of the paper “Clarification of the Mechanism of the De-Alloying Phenomenon” by Robert Heidersbach. “Corrosion,” 24, p 38 (1968) February.
Stress Corrosion Cracking and Corrosion Behavior of Ti and Ti-Al Alloys in Methanol Iodine Solutions
Authors: SEDRIKS A. J. , GREEN J.A.S. , SLATTERY P.W.
Published: February 2013

Studies have been made of the corrosion characteristics and susceptibility to stress-corrosion cracking of pure titanium and Ti-Al binary alloys in methanol-iodine solutions. The results indicate that two distinct stress-corrosion mechanisms may be operative, depending on the composition of the solid. In pure titanium and a Ti-2.09 w/o Al alloy failures were found to be intergranular, while in the higher alloys (>5 w/o Al) only the initial part of the crack was intergranular, the part adjacent to the final ductile fracture being largely transgranular. In all the materials examined, the intergranular stress-corrosion process could be inhibited by cathodic polarization or the introduction of water in the methanol-iodine solution. On the basis of these and other observations, it is suggested that this process represents stress-accelerated intergranular corrosion involving dissolution of metal at a crack tip. The transgranular crack propagation stage observed in the higher alloys has the characteristics of mechanical failure, and its occurrence appears to be related to a reduced propensity for cross-slip.
Polarization Behavior of Iron-Cobalt Alloys in Sulfuric Acid Solutions
Authors: MOTTERN M. M. , MYERS J. R.
Published: February 2013

Anodic polarization behavior of iron, cobalt and seven iron-cobalt alloys in H2-saturated 1, 5 and 10 N sulfuric acid solutions was investigated at 22 C using a potentiostatic technique. Cobalt and the 95 w/o cobalt alloy did not passivate in any acid studied. In 10 N acid, specimens containing 60 w/o or more cobalt failed to exhibit a normal active-to-passive transition. Specimens containing 75 and 80 w/o cobalt were passivated only marginally in 5 N acid. Specimens which did not have a normal passive region exhibited “secondary” passivation at potentials just prior to visible oxygen evolution. Tafel slopes for anodic dissolution and oxygen evolution varied from 0.040 to 0.065 and 0.065 to 0.095 volt, respectively and appeared to be composition and pH independent. Corrosion potentials were linear functions of pH over the pH range +1.87 to −1.08; dEcorr/dpH varied from −0.035 to −0.045, independent of composition. Ecorr decreased linearly with composition from a value of −0.360 volt vs SCE for pure cobalt to −0.505 volt for pure iron. Critical current density increased slightly with increasing cobalt content and obeyed the expression: logicr = logicro + kpH. The passive current density increased with both increasing cobalt content and increasing acid concentration. Values of io, H2, icorr and βc” for iron and cobalt in H2-saturated, 1, 5 and 10 N acid were determined from cathodic polarization curves. Hydrogen overvoltage at 1 ma/cm2 for iron and cobalt appeared to increase linearly with pH; dη/dpH ≅ −0.045. Effect of time on the cathodic polarization parameters for iron in H2-saturated 1 N acid was determined.
The Role of Surface Stress on Hydrogen Absorption by 4340 Steel
Authors: PHALEN D. I. , VAUGHAN D. A.
Published: February 2013

The reaction kinetics of stressed, high strength steel with cathodically generated hydrogen are shown to follow the first-order rate equation, with rate constant k = −5 × 105 exp [−9700/RT] in which the activation energy is equivalent to that for diffusion of hydrogen in iron. The pre-exponential constant, however, is several orders of magnitude greater than that obtained for diffusion and is discussed in terms of the number of reactive sites. While the number of incipient sites is believed to be comparable to the number of subgrain (domain) boundaries in martensity (1012 cm−2), a stress of 85 ksi activates approximately 107 sites/cm2. These sites are not activated by a surface tensile stress of less than 40 to 50 ksi. When these sites are activated, however, hydrogen diffuses to the area of higher tensile stress. In the case of ferritic structure, the hydrogen reaction rate does not increase with the magnitude of the tensile stress.
The Effect of Silicon on the Stress Corrosion Resistance of Low Alloy High Strength Steels
Authors: CARTER C. S.
Published: February 2013

The effect of five levels of silicon, within the range 0.09% to 2.15%, on the stress corrosion resistance of 4340 steel was established in 3.5% sodium chloride solution for two tensile strength ranges (280 to 300 ksi and 230 to 240 ksi). At the higher strength range, the threshold stress intensity KISCC was independent of silicon content, but the stress corrosion crack velocity was significantly retarded when the silicon content exceeded 1.5%. At the 230 to 240 ksi strength range, steels containing less than 1.5% silicon exhibited a higher KIscc threshold than steels of higher silicon content. Strength level had a significant effect on crack velocity characteristics.
Discussion: Surface Stress on Hydrogen Absorption by 4340 Steel
Authors: HUDGINS C M.
Published: February 2013

This brief note is a discussion of the paper “The Role of Surface Stress on Hydrogen Absorption by 4340 Steel” by D. I. Phalen and D.A. Vaughan, “Corrosion,” 24, 243–246 (1968) August.
Sulfidation of a Complex Nickel Base Alloy-Inconel 713C
Authors: CHANDER J. , McQUEEN H. J.
Published: February 2013

The reaction between a complex high-temperature nickel-base alloy Inconel 713 C and hydrogen sulphide diluted with air was investigated in the temperature range of 705 C to 927 C under atmospheric pressure. The sulphidation in an atmosphere of 10% hydrogen sulphide between 816 C-885 C has been found to follow a parabolic-rate law with an activation energy of about 55 kcals/mole. Metallographic studies have shown that the scale is composed of two distinct layers. X-ray and electron microprobe analyses demonstrated that the outer layer is composed mainly of Ni3S2 and that the inner layer is a mixture of unidentified sulphides with chromium and aluminum as major components. The reduced rate of corrosion appears to be the result of the formation of the inner layer of scale.
Mechanism of Corrosion Tunnelling With Special Reference to Cu3Au
Authors: SWANN P. R.
Published: February 2013

A flat corrosion interface is unstable on alloys undergoing preferential dissolution of one component. This instability results from the uneven accumulation of the less soluble component which enables pits to develop and grow into corrosion tunnels. Electron microscope observations of CU3AU exposed to a ferric chloride solution suggest that surface diffusion or ionization and re-deposition of gold occurs on the walls of corrosion tunnels and that this accounts for the discrepancy between observed and calculated tunnel diameters. No evidence was found to support the volume diffusion theory of tunnel formation.
Anodic Polarization of Anodized Aluminum
Authors: JONES D. A.
Published: February 2013

Potentiostatic anodic polarization of anodized coatings on aluminum was sensitive to both coating thickness and degree of seal. The polarization behavior of anodized coatings parallels their performance in atmospheric service. Thus, anodic polarization could be used as a test for the atmospheric corrosion resistance of anodized coatings. The advantages of an anodic polarization test are discussed.
Corrosion Behavior of Nickel-Chromium-Iron Alloy 600 in Borated Pressurized Water Reactor Environments
Authors: VAN ROOYEN D. , COPSON H. R. , BERRY W. E.
Published: February 2013

Corrosion tests were run for periods up to 5000 hrs in borated water at 600 F (316 C) in a high velocity loop on strip, tubes, and weldments of Alloy 600. During the first 1000 to 2000 hrs of exposure, corrosion rate differences depending upon surface preparation and in the case of weld metal on composition were observed. However, by 3000 to 5000 hrs, the corrosion rates of all samples tested had decreased to around 1.0 mg/dm2 per month, or to rates of scale formation of about 1.4 mg/dm2 per month. Approximately half the scale was adherent, and half was lost to the stream. Comparison with earlier tests in borate—free water seemed to indicate that the addition of boric acid increased corrosion somewhat during the initial exposure periods, but this was a transient effect, and corrosion rates decreased with time.
Use of Infernal Damping Measurements in the Study of Environmental Cracking
Authors: THIRUVENGADAM A. , GUNASEKARAN M. , PREISER H. S.
Published: February 2013

The problem of environmental cracking of metals and their alloys has become very important and warrants a concentrated study with new ideas for its solution. The major objectives of such a study are, (1) detection of susceptibility, (2) quantitative measurement of susceptibility, and (3) understanding the mechanism of susceptibility. An approach utilizing measurements of the internal damping characteristics of materials prone to environmental cracking is presented to show the feasibility of detecting significant changes occurring in the materials long before any macroscopic evidence of such changes becomes noticeable. Tests on 2024-T4 aluminum, 2024-T3 aluminum, Ti-6Al-4V and Ti-8Al-1Mo-1 V are reported wherein considerable changes in the internal damping of these materials were observed following their exposure in a stressed state to environments in which they are known to be susceptible to cracking. (Corroborative tests on 1020 mild steel and electrolytic copper stressed and exposed to a corroding environment of air saturated synthetic sea water produced no changes in internal damping. These materials are normally immune to stress corrosion cracking under the above conditions of exposure.) Theoretical ideas with supporting experimental evidence are presented in an attempt to arrive at a basic understanding of the phenomenon of environmental cracking by correlating the laws of diffusional mechanics of materials to those pertaining to changes in their internal damping.
Recent Applications of Electrode Potential Measurements in the Thermodynamics and Kinetics of Corrosion of Metals
Authors: POURBAIX M.
Published: February 2013

A brief survey is given of recent applications of electrode potential measurements for the study of the corrosion of metals and alloys in the presence of aqueous solutions, molten salts and gaseous atmospheres. Particularly considered are: (1) cathodic and anodic protection of passivable metals and alloys in the presence of chloride containing solutions; (2) pitting corrosion of copper in the presence of cold water; (3) stress corrosion cracking of titanium alloys in the presence of aqueous solutions; (4) diagrams of electrochemical equilibria in the presence of molten carbonates, as a function of the electrode potential and of log PCO2 or log O−−; (5) diagrams of chemical and electrochemical equilibria in the presence of gaseous oxygen as a function of ΔG° or the electrode potential E, and of temperature T; (6) diagrams of electrochemical equilibria of semi-conductive oxides, as a function of the electrode potential E, and of log O−−. Mention is made of the possible usefulness of these three last types of diagrams for studying problems related to corrosion, fuel cells, and high temperature electrochemistry.
The Initial Stages of Oxide Film Formation on Copper and Some Copper Alloys
Authors: SANDERSON M. D. , SCULLY J. C.
Published: February 2013

The initial stages of oxide formation on thin foils of copper, Cu-2.5Al-2.5Si, and Cu-7.5Al-2Si alloys in moist atmospheres of oxygen and sulfur dioxide have been studied by transmission electron microscopy and electron diffraction over the temperature range 200-380 C (392-716 F). On the Cu-2.5Al-2.5Si alloy grain boundaries and twin boundaries are preferential sites for oxide nucleation. On the Cu-7.5Al-2Si alloy no preferential sites are observed. The relative reactivities of different crystallographic planes are the same for the alloys as for the metal. On oxidized thin foils a prenucleation thermal pitting phenomenon has been observed at temperatures very much lower than the thermal pitting observed by other workers. Oxide nuclei have been observed to form on a thin amorphous layer of oxide even when there is no metal directly underneath. These results are discussed with reference to current theories on the initial stages of oxide formation. It is concluded that in the prenucleation stage the metal surface is covered with a highly mobile layer of cations and anions.
Film and pH Effects in the Stress Corrosion Cracking of Type 304 Stainless Steel
Authors: BAKER H. R. , BLOOM M. C. , BOLSTER R. N. , SINGLETERRY C. R.
Published: February 2013

Rapid stress corrosion cracking of 304 stainless steel in MgCl2-FeCl3 solutions at 125 C has been shown to occur only when the pH of the corrodent liquid within the crack lay between 1.2 and 2.5. A film of more acidic corrodent solution is raised to pH = 1.2 by reaction with the metal within a few seconds after isolation in a pit, crack, or crevice. MgCl2 solutions of pH higher than 2 became more acidic when in contact with stainless steel as a result of corrosion processes. The pH of small amounts of such solution isolated in pits or crevices eventually fell to near 1.5, where stress corrosion cracking could occur. This pH range is considered to be critical for stress corrosion cracking of 304 stainless steel because it is the range in which a corrosion resistant protective film is formed in the presence of the corrodent solution. This film is essential to crack propagation. If there is added to a corrodent , solution in this pH range an organic complexing agent such as glycerine or glycol which prevents-formation of the protective oxide film, the general corrosion process continues unchecked but no stress corrosion cracking occurs. The data support a model in which stress corrosion cracking is driven by a highly localized galvanic cell within the crack. The cell operates in such a way that there is no large change in pH of the solution in the crack. These results emphasize the importance of the corrosion resistant film in the chemical aspect of the stress corrosion mechanism.
Use of Precracked Specimens in Stress Corrosion Testing of High Strength Aluminum Alloys
Authors: HYATT M. V.
Published: February 2013

Resistance to stress corrosion cracking of 10 high strength aluminum alloys in a variety of heat treatment conditions has been measured using precracked double cantilever beam (DCB) specimens. A new technique is described, and stress corrosion crack growth rates for the alloys tested are presented as a function of the plane-strain stress intensity KI. Crack growth rates for alloys in the T3 and T6 tempers showed both KI-independent and KI-dependent behavior, whereas alloys in the more resistant tempers showed only KI independent behavior over the KI range studied. Double cantilever beam specimen data correlated with established trends from smooth specimens tested by alternate immersion in 3.5% NaCl solution. From the crack growth rate data and the speed and simplicity with which it is obtained, it is concluded that the DCB specimen will be highly useful for (1) comparing and rating alloys, (2) developing new alloys and heat treatments, (3) comparing the effects of environments, (4) achieving or ensuring product uniformity, and (5) studying mechanisms of cracking.
Acceleration of Liquid Mercury Embrittlement of Titanium Alloys by Ultrasonic Oscillations
Authors: CHEN C. M. , KIRKPATRICK H. B.
Published: February 2013

Ultrasonic oscillations were found to markedly accelerate the fracture in liquid mercury of Ti-8Al-1Mo-1 V and Ti-6Al-4V alloys. Unalloyed RMI 70 titanium was unaffected. Likewise, fracture by CH3OH-HCl-H2O solution was unaffected. The results are taken as indicating a stress-sorption failure mechanism.
Effect of Time on Corrosion Rates in Sulfuric Acid Predicted from Electrochemical Data
Authors: WAGNER A. H. , MYERS J. R.
Published: February 2013

Effect of time on the cathodic polarization behavior of Ni, Cr, Ti, Al, and six Ni-Cr-Al and Ni-Cr-Ti alloys was determined in hydrogen saturated, 1N sulfuric acid at 22 C (71 F). Corrosion current densities (icorr) obtained for these specimens, using the beta-extrapolation technique, were generally found to be strongly time dependent. Corrosion current densities for Ni, Cr, and the six ternary alloys decreased with time and approached steady state values after about 72 hours exposure to the electrolyte. Corrosion current density for Al decreased markedly during the initial 24-hour period; further exposure did not appreciably affect the corrosion current density. The corrosion current density for titanium decreased only slightly as the exposure time was increased. All materials exhibited steady state corrosion current densities after sufficient exposure to the acid. Corrosion rates predicted using the steady state corrosion current densities correlated well with rates obtained from long time, weight loss tests. It was established that accurate corrosion rates can be predicted from electrochemical data only after steady state corrosion current densities have been obtained.
Effect of pH on Sea Water Stress Corrosion Cracking Behavior of the Ti-7Al-2Cb-1Ta Alloy
Authors: LITVIN D. A. , HILL B.
Published: February 2013

The purpose of this investigation was to determine the effect of varying the pH of a sea water environment on the stress corrosion cracking behavior of the Ti-7Al-2Cb-1Ta alloy. Various pH levels of 1.0, 3.0, 5.0, 7.4, 9.0, 11.0, and 11.6 were studied by additions of HCl and NaOH to the as-received sea water (pH = 7.4). The titanium specimens were beta-fabricated (rolled 1900 F, 1038 C), and tested using a cantilever weight test. It was found that an increase in the pH level of the sea water from 1.0 to 7.4 decreased the stress corrosion susceptibility of the Ti-7Al-2Cb-1Ta alloy. In all cases, the mode of cracking was transgranular; yet, differences in the angle of cracking through the titanium platelet structure were observed. A distinct low ductility zone on the fracture surface of the sea water samples was noted, but no correlation could be made between the size of this zone and the pH of the solution. Photomicrographs of the specimens are included, along with macrographs of the fractured surfaces.
Effect of Corrosive Environment on Crack Propagation in Alpha Brass and a Copper-Beryllium Alloy
Authors: SYLWESTROWICZ W. D.
Published: February 2013

Notched specimens of a copper-beryllium alloy and of α-brass were tested in tension in an ammonia-containing solution. Specimens were strained at rates ranging from 0.5 cm/min to 5 × 10−4 cm/min. Formation of a plastically deformed zone at the root of the notch appears to be essential to the formation and propagation of the crack. A smaller amount of plastic deformation was needed to start a crack in the corrosive solution than in air. The observation that the effect of the corrosive solution seems to be independent of the strain rate suggests that an adsorption process contributes to specimen failure in stress corrosion fracture.
Sulfide Stress Corrosion Cracking of Steels
Authors: DVORACEK L. M.
Published: February 2013

Critical nominal stress and critical stress intensity factors for sulfide stress corrosion cracking of various steels were determined using fatigue-precracked, laboratory, cantilever beam specimens and short lengths of oil field casing and tubing pressured to failure. The laboratory critical constants were found to be lower than those obtained from short lengths of casing and tubing containing longitudinal internal surface notches. Acceptable steels were defined by statistical methods as those which did not crack in sulfide environments when stressed to their yield strength. The effects of sodium chloride, pH, hydrogen sulfide concentration, temperature, cold working, heat treatment and strength of the steel on these critical constants were determined. Critical flaw sizes which can be used for inspection were calculated from the critical stress intensity factors.
The Role of Sodium and Sulfur in the Accelerated Oxidation Phenomena–Sulfidation
Authors: BORNSTEIN NORMAN S. , DeCRESCENTE MICHAEL A.
Published: February 2013

The oxidation kinetics at 900 C (1652 F) of a sulfur impregnated, a Ni-Ni3S2 eutectic coated, and a NaNO3 coated nickel base alloy were studied. It was determined that Na2O/substrate interactions are more influential than sulfur/substrate interactions on the accelerated oxidation phenomena, sulfidation.
Passivation of Nickel Monocrystal Surfaces
Authors: LATANISION R. M. , OPPERHAUSER H.
Published: February 2013

Steady state potentiostatic polarization measurements on low index nickel monocrystal surfaces in 1N H2SO4 indicate a strong anisotropy in passive current densities. The nature of this orientation dependence appears to be related to such properties of the solid state as the crystal growth axis. For example, in the case of crystal growth parallel to the 〈110〉 axis, the degree of protection provided by the passive film on a {111} surface is greater than that on either {110} or {100} faces, i.e., the passive current densities are in the following order: {111}<{110}<{100}. It is interesting to note than an identical anisotropy has been reported in the rates of gaseous oxidation on nickel surfaces. On the other hand, precisely the reverse dependence is observed in passivation studies when the growth direction of the monocrystal is parallel to the 〈100〉 axis. The above results are examined in terms of the crystallography and defect structure of the film, the metal/film interface, and the metal substrate and their relevance to current theories of passivation is considered.
Observations on Sustained Load Environmental Crack Growth of a Titanium 8Al-lM0-lV Alloy
Authors: BUCCUI R. J. , PARIS P C
Published: February 2013

Sustained load environmental cracking of a mill annealed titanium 8Al-1Mo-1V alloy was investigated by methods amenable to fracture mechanics. Two environments were considered: 3.5% NaCl solution and distilled water, both at room temperature. Varying amounts of crack propagation followed by subsequent crack arrest were detected at K levels considerably below an apparent KIscc (almost 2 to 1) that would be determined from a time to failure test technique. At crack arrest locations along the specimen surface, minute amounts of crack division were often observed under magnification.