In structures, it is probable that the plastic deformation will occur locally by the unexpected large stress, for instance, intensified by discontinuity, or the applied stress superimposed on the residual stress, and so on. The effect of pre-strain on the corrosion-fatigue of steel was investigated in the present investigation.
The experiments were carried out by reversed bending on the tensile pre-strained specimen of a high tensile steel plate. The corrosive was sea water. The fatigue strength in air was remarkably decreased by pre-strain. The results can be explained by the assumption that the fatigue fracture will happen when the sum of the absorbed energy per cycle of stress of a specimen during testing reaches a defined value. In sea water, owing to the corrosive action, the absorbed energy required to fracture will be small compared with that in air, and then the fatigue strengths in the former are inferior to those in the latter.

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Anodic behaviors of pure iron and its oxides in 0.1-36N sulfuric acid solution have been investigated by a potentiostatic method. In the anodic polarization curves of pure iron five current peaks were detected. Although the potentials for these peaks were not affected so large by sulfuric acid concentrations except in the ranges of 12-16N and 28-32N, the current densities at the peaks and in the passive region changed complicatedly. On these anodic phenomena, effects of H⁺, HSO₄^-, SO₄^2- and undissociated sulfuric acid were discussed.

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Effect of some alloy elements on the susceptibility of austenitic stainless steels to stress corrosion cracking was investigated by transmission electron microscopy. Thin-foil specimens of the steels were used to examine corrosion behavior before and after exposure to solutions which should cause stress corrosion cracking.
18-8 stainless steels seemed to have high stress corrosion susceptibility at the maximum solubility rof carbon (0.08% C). Dislocation arrangements were dependent on the relative contents of carbon and titanium in the steels containing titanium, but addition of molybdenum had no pronounced effect. Stainless steels containing nitrogen had a planar arrangement of dislocations. In 18-8 and 18-20 austenitic stainless steels containing both elements of nitrogen and carbon, dislocation distributions were dependent on relative contents of them.
Chemical attack was observed in highly restricted slip steps. It was possible that solute atoms segregated to slip planes with moving of dislocations and excess vacancies created during deformation. The solute atoms, therefore, should be concentrated on the slip planes. Stress corrosion, once initiated at slip steps, would be advanced into the interior of the steel by galvanic corrosion.

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