The effect of dry passivation treatments on the corrosion resistance, moisture release and structure of the surface oxide film on electropolished stainless steel

Abstract

The objective of the present study is to investigate the effect of dry passivation treatments on corrosion resistance, moisture release behavior and structure of oxide film on electro-polished Type 316L stainless steel. The corrosion resistance was evaluated by measuring the incubation time until H 2 evolution occurred in HCl solution and the linear polarization resistance in boiling 0.005M-Na 2SO 4 solution. The moisture release behavior was investigated by measuring the volume of H 2O desorption with ultra pure N 2 gas purging. The structure of surface oxide film was analyzed using AES, XPS, LRS etc. The corrosion resistance and the moisture release resistance were remarkably improved by the oxidation treatments in oxygen atmospheres controlled with a dew point of below −100°C at temperatures from 400°C to 450°C, compared with as-electropolished surface film. At the treatment temperature over 500°C, those properties changed for the worse. From the results of surface analyses, it was clarified that a fine and amorphous oxide film containing enriched Fe and Cr was formed at the oxidation temperature of 400∼450°C, whereas oxide films crystallized and became coarse at oxidation temperature over 500°C.