XPS characterisations of passive films formed on martensitic stainless steel: qualitative and quantitative investigations

HNO3 passivation treatments on martensitic stainless steels used for surgic al instrumentation were studied. The pitting corrosion resistance was deter mined by electropotentiodynamic experiments. The composition and the thickn ess of the passive films were investigated by XPS. The pitting corrosion po tential was more noble for HNO3-passivated sample than for air-passivated s ample. The different methods proposed in the literature to estimate the thi ckness of passive layers were used and compared. Passive films obtained by HNO3-passivation were thinner (3 nm) than air-passivated films (4-5 nm). Th e composition of these passive films also differs. HNO3-passivated films we re enriched in oxidised chromium which represent half of the metallic eleme nts in the passive layer. (C) 2000 Kluwer Academic Publishers.