HNO3 passivation treatments on martensitic stainless steels used for surgical instrumentation were studied. The pitting corrosion resistance was determined by electropotentiodynamic experiments. The composition and the thickness of the passive films were investigated by XPS. The pitting corrosion potential was more noble for HNO3-passivated sample than for air-passivated sample. The different methods proposed in the literature to estimate the thickness of passive layers were used and compared. Passive films obtained by HNO3-passivation were thinner (3 nm) than air-passivated films (4-5 nm). The composition of these passive films also differs. HNO3-passivated films were enriched in oxidised chromium which represent half of the metallic elements in the passive layer.