An XPS and ToF-SIMS study of the passive film formed on a model FeCrNiMo stainless steel surface in aqueous media after thermal pre-oxidation at ultra-low oxygen pressure

A combined X-ray photoelectron spectroscopy, time-of-fight secondary ion mass spectrometry and electrochemical approach was used to investigate the mechanisms of molybdenum chromium enrichment a passive film formed on model austenitic stainless steel single crystal in aqueous acid media effect that thermal pre-oxidation at 250°C plays composition, thickness stratification film. clean FeCrNiMo (1 0 0)-oriented surface, prepared under ultra-high vacuum (UHV), exposed ultra-low pressures oxygen 250°C, forming thin oxide film, rich iron chromium, as well containing molybdenum. An argon-filled glovebox, directly attached UHV system, allowed for alterations be carried out without exposure ambient air. After being held open circuit potential 30 min, hydroxylation promoted, with marked both elements distinct bilayer observed. Anodic polarisation resulted significant growth inner layer further chromium. Pre-oxidation using an pressure oxygen, found promote protection against transient active dissolution during anodic passivation, cause outer