Surface Characterization of Stainless Steels Prepared with Various Surface Treatments

Abstract

The composition depth-profiles of the surfaces of 304 and 316 stainless steels prepared with a variety of surface treatment have been measured by a simultaneous use of argon ion sputter-etching and Auger electron spectroscopy. Chromium was enriched in the surface oxide films, whereas nickel was enriched at the film/substrate interface. The degree of Cr-enrichment in surface films depended on the surface treatment and increased in the following order; mechanical polishing with emery paper in water33COOH+HClO₄ (20 : 1)3 or chemical passivation in 30%HNO₃. The degree of nickel enrichment at the film/substrate interface increased with increasing degree of chromium enrichment in the film. The surface oxide films on 304 stainless steel were always thicker than those on 316 stainless steel, irrespective of the surface treatments. The aging of specimen for one week in dessicator gave rise to decrease in chromium-enrichment and to increase in film thickness. Discussion was made on the relationship between pitting potential and surface composition of stainless steels.