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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In order to investigate atmospheric corrosion of stainless steel, exposure tests were carried out at several locations. By analysis of the test results, it is considered that the distance from the shoreline can be the most significant factor affecting corrosion. Utilizing a developed evaluation method in laboratory and exposure tests, a new alloy of ferritic stainless steel as bright annealed surface was developed, based on the finding that amorphous silicon oxide film is more corrosion resistant against marine atmosphere. The proposed alloy is a type of highly purified 19% chromium ferritic stainless steel covered with a corrosion resistant bright annealed surface film.

The structure of passivated film on electrolytic tinplate by a cathodic treatment in a dichromate solution has been investigated by anodic potential measurement and Auger-electron spectroscopy.

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