Synchrotron-based near ambient-pressure X-ray photoelectron spectroscopy and electrochemical studies of passivation behavior of N- and V-containing martensitic stainless steel

Passivation behavior of a N- and V-containing martensite stainless steel was studied by synchrotron-based near ambient-pressure X-ray photoelectron spectroscopy, electrochemical analyses, and thermodynamic calculation. The passive film consists of Cr³⁺, Fe^{(2, 3)+}, and V^{(2, 3, 4)+} oxides as inner layer, and Cr³⁺ and Fe³⁺ hydroxides as outer layer. Austenitization at 1080 ^oC (rather than 1010 ^oC) and anodic polarization facilitate transformation of CrN to Cr₂O₃ leading to further enrichment of Cr³⁺ oxide in the passive film. Whereas higher Cl^- concentration promotes film dissolution leading to higher level of point defects and higher fraction of remaining V oxides in the passive film.