Effect of surface alloyed silver on corrosion behaviour of austenitic stainless steel in sulphuric acid

Abstract

This paper describes the results obtained in an investigation into the corrosion behaviour of austenitic stainless steel, surface alloyed with silver and exposed to sulphuric acid. The alloy was silver plated with a conventional electrolytic plating technique and heat treated to diffuse the silver into the material. Exposure of the surface alloyed steel to sulphuric acid solutions of up to 30% concentration at room temperature resulted in spontaneous passivation. The base alloy under the same conditions underwent active corrosion once the concentration of the acid solution was greater than 10%. As the temperature was increased, the surface alloyed steel also displayed active corrosion behaviour under more severe conditions. It was found that the silver surface alloyed steel was more corrosion resistant than the base alloy under all exposure conditions investigated. A comparison with other studies reported in the literature indicated that silver used as a surface alloyed addition is not as effective as the platinum group metals, ruthenium and palladium, in increasing the corrosion resistance of stainless steel under reducing acid conditions.