This investigation is concerned with the effect of chromium and molybdenum on the formation of the passive film of stainless steels, and its corrosion resistance to the chloride ion. The corrosion resistance to the chloride ion was estimated by the potential decay method and the measurement of the anodic polarization curve. The composition analysis of the passive film was performed by Auger Electron Spectroscopic Analysis. The following conclusions were obtained from the test results: (1) The passive film was more resistant in the environment containing chloride ions as the chromium content in the passive film increased, and (2) molybdenum was observed on AES analysis to have an effect on the increment of the chromium content in the passive film and to promote the passive film formation of stainless steels, probably adsorbing on the active metal surface in the form of molybdate.

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change in the diffusion layer, that is, formations of voids and cracks. The dezincification reaction proceeded through three stages. In stage I, the weight loss obeyed the parabolic rate law as expected from an ordinary diffusion mechanism. In stage II, the dezincification rate was accelerated. In stage III, the weight loss was nearly proportional to the square root of time. These three stages were characterized by the amount of structural change.reaction proceeded (1) only by stage 1, (2) by stage 1 and stage 11, and (3) by stage I through stage II] Type (3) was observed only in the specimens with higher zinc contents during dezincification a higher temperatures.the zinc content increased.

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