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

This paper describes the results obtained in an investigation into the corr osion behavior of austenitic stainless steel, surface alloyed with silver a nd exposed to sulphuric acid. The alloy was silver plated with a convention al electrolytic plating technique and heat treated to diffuse the silver in to the material. Exposure of the surface alloyed steel to sulphuric acid so lutions of up to 30% concentration at room temperature resulted in spontane ous 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 bas e alloy under all exposure conditions investigated. A comparision with othe r studies reported in the literature indicated that silver used as a surfac e alloyed addition is not as effective as the platinum group metals ,ruthen ium and palladium, in increasing the corrosion resistance of stainless stee l under reducing acid conditions. (C) 2001 IoM Communications Ltd.