An X-ray photo-electron spectroscopic study of surface treatments of stainless steels

The effects of surface treatments on the surface composition and structure of Type 304 and 316 stainless steels were studied by X-ray photo-electron spectroscopy. The content of chromium and iron in the surface film depends considerably on the surface treatment method, while the nickel content in the film is significantly lowered compared to bulk composition regardless of the method. Some surface treatments which result in a significant enrichment of chromium in the surface film on the steels give the highest pitting potential. When the specimens were left for at least a day in contact with air, a certain amount of a magnetite-like compound was formed in the surface film. This fact is responsible for the ennoblement of the pitting potential by ageing after treatment.