The effects of alloying elements, Sn and Cu, on the corrosion behavior of austenitic stainless steel of type 304 have been investigated by electrochemical techniques aqueous solutions of organic acids as food additive. Corrosiveness of lactic acid to type SUS 304 steel was stronger than that of other organic acids. The corrosion rate of the steel in boiling aqueous solution of lactic acid was reduced by addition of less than 0.5% Sn to the steel, and was further reduced by simultaneous addition of Sn and Cu. The reason why Sn or Cu improved the corrosion resistrance of the steel was based on that the cathodic reaction and the anodic dissolution reaction in the active region were retarded by the surface film formed as a result of deposition of Sn or Cu. Therefore, until the film is formed on the steel surface, addition of Sn or simultaneous addition of Sn and Cu to the steel results in degraded corrosion resistance because of preferntial dissolution of the elements.
