The corrosion behaviour of an exotic duplex stainless steel containing small ruthenium additions in sulphuric acid

The influence of minor ruthenium additions, which can significantly enhance the corrosion resistance of stainless steels in reducing acid media, on the corrosion of duplex stainless steel containing high concentrations of chromium and nickel, has been investigated. Mass loss tests and electrochemical measurements were used to study the spontaneous passivation as well as active corrosion of the alloys at various temperatures and in a number of different concentrations of sulphuric acid. Small additions of Ru (<0.28%) increased the corrosion resistance of the base alloy significantly. it was found that the increased corrosion resistance could be attributed to the simultaneous effect of improved hydrogen evolution efficiency and inhibited anodic dissolution, due to the presence of Ru in the modified alloys. (C) Munksgaard, 1996.