Corrosion resistance of alloyed powder metallurgy austenitic stainless steels in acid solutions

Sintered stainless steels of types similar to AISI 304L and 316L were produced in a laboratory furnace at two different temperatures (1150 and 1250 degrees C). Electrolytic copper and prealloyed bronze were added in different concentrations up to 20% and the effect of alloying concentrations and sintering temperature on the corrosion resistance of the steels was studied. The corrosion behaviour was characterised by immersion in three different acids (H2SO4, HCl, and HNO3) at room temperature and by electrochemical reactivation tests. Both copper and bronze experienced improved corrosion resistance in HCl, small copper additions (4 and 8%) had a positive effect in H2SO4, but alloyed stainless steels showed worse corrosion behaviour than unalloyed ones in HNO3. The electrochemical reactivation tests showed a tendency towards passivity. (C) 1996 The Institute of Materials.