Effects of nitrogen on the passivity of Fe–20Cr alloy

Influences of nitrogen on the passivity of Fe–20Cr–(0, 1.1)N alloys were examined by in situ electrochemical techniques. Nitrogen was incorporated in the form of (Fe, Cr)-nitrides in the passive film, and Cr was enriched in the film of the alloy with nitrogen. Photocurrent analysis demonstrated that the structure of passive film formed on Fe–20Cr–1.1N alloy is Cr-substituted γ-Fe2O3 with (Fe, Cr)-nitrides. Mott–Schottky analysis revealed that the film formed on Fe–20Cr–1.1N contained higher Cr6+ and lower Cr3+ vacancy concentrations compared with that on Fe–20Cr alloy. All of these results were associated with the enhanced protectiveness of the film on Fe–20Cr–1.1N.