Protecting the metal and alloys from corrosion by surface treatment is the most commonn method for corrosion control. Austenitic stainless steel is one of the most excellent material for corrosion proof, but has a weak point of stress corrosion cracking. To improve the difficulty, Aluminium was coated on the austenitic stainless steel of SUS 304 by wire arc thermal spraying method by which cathodic protection effects were expected. But the porous nature of thermal sprayed coated film would

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... t ions to leave or to approach to the substrate and it can not become a perfect protection film. When diffusion of Aluminium occur between the thermal sprayed Aluminium and the substrate of austenite, the diffused layer would have no porosity except the Kirkendall voids. Thus, 99.9% Aluminium was coated by thermal spraying method and heat treated in natural atmosphere for the diffusion. Reactive diffusion occured and some intermetallic compounds were formed in the substrate. Susceptibility for stress corrosion cracking were tested by SSRT method and the effects of life times upto cracking were estimated by U bend immersing test in 42% MgCl2 boiling solution. The reduction of susceptibility of stress corrosion cracking and prolonging of life time were observed.