Comparative study of the surface oxide films on lean duplex and corresponding single phase stainless steels by XPS and ToF-SIMS

The surface oxide films formed after mechanical polishing on duplex stainless steel and corresponding single phase alloys were characterized by XPS and ToF-SIMS. The native oxide films are mixtures of oxides and hydroxides composed of Fe(III), Mo(IV) and Mo(VI) in the outer region and Cr(III) in the inner region. Nickel, molybdenum and nitrogen are enriched in the underlying metal while chromium and molybdenum are enriched in the oxide layer. The contents of alloying elements in the oxide layer and/or in the underlying metal are found to be directly related to their content in the bulk of the alloys.