The morphology of stress corrosion cracking of the ferritic stainless steel was investigated in the concentrated chloride solution. The test result was as followings: (1) Fe-Cr and Fe-Cr-Mo alloys nucleated intergranular SCC for the high test loading. On the other hand, fine transgranular cracking and pitting corrosion grew for the low test loading, and, in this case, the fatal damage was caused by pitting corrosion. (2) The stress corrosion sensitivity of the ferritic steel was increased with nickel addition. At the same time, twin frequency grew with nickel addition. (3) The cracking morphology of Fe-Cr-Mo-Ni alloys depended on the chloride ion concentration and pH of the test solution. Transgranular SCC nucleated and propagated in the deformation twins in case of low pH and high Cl^- ion concentration. On the other hand, intergranular SCC occurs in case of high pH and low Cl^- ion concentration.

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The diffusion coefficient of oxygen through paint film coated onto mild steel was measured in 3wt% sodium chloride solution and the effect of oxygen on corrosion behavior of coated steel was investigated.
Results in this work were (I) The diffusion coefficient of oxygen through paint film was obtained from measuring a time lag of potential change which occurred soon after aerating a deaerated solution. That of epoxy paint film was 1.1×10^-7 to 1.6×10^-7cm²·sec^-1., (II) The amount of oxygen used for cathodic reaction was calculated from the difference between corrosion currents under aeration and deaeration. The amount of oxygen exhausted was much less than the amount of oxygen permeated which was reported by other workers and it increased with immersion service period., and (III) It was found that the corrosion behavior was affected by oxide film formed at the surface of mild steel under paint film. It was suggested that passivated film was formed at the surface of mild steel under film in the presence of enough amount of oxygen.

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More than two hundred galvanized steel pipes which had been in service were collected at 31 buildings in principal cities of Japan. Waters by which the collected pipes had served were mostly soft ones, characterized by low hardness and alkalinity. Examinations of the samples included visual inspection, measurements of pit depth and corrosion potential, and analyses of corrosion products by X-ray and infrared methods. Dense and heavy tuberculation following complete loss of the zinc layer was observed on large-diameter pipes used for delivery and supply mains. On small-diameter pipes used under intermittent flow conditions, localized attack was predominant with galvanized layer on the rest of surfaces. The predominant corrosion product on galvanized layer was a mixture of amorphous zinc silicate and carbonate. In some cases well-crystallized hemimorphite (zinc silicate) was detected. The penetration rate of a maximum pit ranged from 0.12 to 0.14mm/year. In soft waters, loss of carrying capacity due to tuberculation and red water are more frequent troubles than water leakage.

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The impedance of anodic dissolution of iron in nonaqueous formic acid was measured by use of a Lock-in amp coupled with a potentiostat in the high frequency range and Lissajous method in the lower one. In order to obtain the response of the steady-state, the impedance measurements were started after the polarization for 1.5hrs. The potentiodynamic current (i)-potential (E) curves of Fe/HCOOH-0.5mol HCOOK were influenced not only by the contents of water, but also the conditions of cathodic reduction. In the active dissolution range of Fe/HCOOH-0.5mol HCOOK, the two capacitive arcs were observed in the complex impedance (Z) plane. The presence of the capacitive arc in the lower frequency range would be ascribed to an adsorbed intermediate. As for the active range of Fe/HCOOH, the capacitive arc and the inductive one were observed in the Z plane.

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