The mechanism of transgranular stress corrosion cracking of pure copper in 0.05M NH₄OH solution at 70°C was investigated by means of stress corrosion tests both under the constant strain rates from 1.0×10^-4min^-1 to 5.0×10^-4min^-1, and under potentiostatic anodic polarization in the range of-90.0mV to-10.0mV (SCE) at a constant strain rate of 1.0×10^-4min^-1. Stress corrosion cracking can be observed only at lower strain rates than 1.0×10^-4min^-1 which is slower than rate of tarnish film growth. Good adherent and protective film is formed over the potential range of -90.0mV to -10.0mV. The susceptibility to stress corrosion cracking is increased by anodic polarization in the potential range of -90.0mV to -50.0mV in which thick and black tarnish film is formed, but is decreased by anodic polarization in the potential range of -30.0mV to -10.0mV in which thin and dark brown film is formed. Weight losses of specimens both on the surface produced by straining and on the surface of static specimens were measured over the potential range of -70.0mV to -10.0mV. These weight losses decrease with the increase of applied potential, and the ratio of these weight losses is nearly constant and independent of applied potential and susceptibility to cracking. These results support the theory that crack propagates with the repetition of formation and rupture of the brittle tarnish films, and the distance of propagation equals the film thickness formed after each rupture.

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In the previous paper the authors reported that compound layers of nitrdied titanium showed high corrosion resistance in hydrochloric and sulfulic acids. In strongly oxidizing nitric acids, however, the nitrided titanium is assumed to exhibit a different behavior because the reduction of nitrate ions will occur as a catholic reaction. The present paper aims to clarify the corrosion behavior of nitrided titanium in nitric acid. The corrosion rate and corrosion potential of the nitrided titanium were measured in nitric acid. Potentiostatic polarization measurements were also performed in hydrochloric acid after a certain time of corrosion in nitric acid. Electron diffraction method was applied to examine the change in composition of the surface layer with time of corrosion in nitric acid. After dissolution of the outer layer of nitrided titanium in nitric acid, the corrosion rate decreased and passivation occurred on a solid solution layer.

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In the first report it was shown that damage of metallic propulsive device (Cu-Al alloy propeller) on FRP ships was caused by electrochemical corrosion and could be prevented by supplying sufficient, cathodic protective current. The purpose of this research are to find the stray current that might cause corrosion of the propeller and to determine the protective current density to Cu-Al alloy. Measurements were carried out on the stray current to Cu-Al alloy and on the dissolution rate of zinc anodes for cathodic protection of propellers while running and while stopping. The following conclusions were obtained: (1) The stray current was not directly related to the corrosion of the propeller. (2) The dissolution rate of zinc anodes for cathodic protection of propeller was closely related to the corrosion of the propeller. (3) The protective current density required for protection of Cu-Al alloy was 425mA/m².

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Carbon steel containing MnS inclusions was rapidly heated and cooled. The effect of this treatment on the localized corrosion susceptibility of those inclusions in 3% NaCl solution was studied. Specimens of which central zones were heated to 1, 100-1, 450°C in air and cooled rapidly were used for this study. Measurements showed that the corrosion potential of the heated zone was lower than that of the non-heated zone. In addition, anodic polarization of the heated zone was smaller than that of the non-heated zone. Localized corrosion was easily caused around MnS inclusions in the heated zone by dipping in 3% NaCl at 40°C, and the heated zone was selectively corroded by testing in artificial sea water for 2 months. The measurement of Mn and S content with EPMA across the MnS inclusion revealed that the matrix surrounding the MnS inclusion in the heated zone was enriched in sulfur. It is thought that this partial enrichment in sulfur is due to the rapid cooling to form the unprecipitated phase of the MnS inclusion melted by electric resistance welding. On the initiation of localized corrosion, this sulfur-enriched part acts as a micro anode for MnS inclusions and the residual matrix as a micro cathode. The effect of normalizing ERW steel pipe at 700-1, 100°C on grooving corrosion resistance of the weld was also studied. Localized corrosion around MnS inclusions in the specimen normalized at 900 and 1, 100°C for 30min did not occur after immersion in 3% NaCl solution at 50°C. No grooving corrosion occured in those specimens tested in artificial sea water at 40°C for 4 months. Electron microprobe examinations revealed that the sulfur-enriched part around MnS inclusion disappeared in normalizing.

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This review makes a survey on that the behaviors and the mechanisms proposed of both the stress generation in oxide films and the plastic deformations of oxides at high temperatures, and discusses a role of the mechanical properties of the oxide films in the oxidation of metals. It suggests that the kinetic studies of some oxidation reactions need to be examined again with the mechanical properties of the oxide included in the considerations.

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