علی فردی ایلخچی

In the present investigation, the electrochemical behavior and the semiconducting properties ofthe passive film formed on AISI 201 austenitic stainless steel has been studied using different electrochemical analysis techniques. The passivity of the steel was evaluated by potentiodynamic and potentiostatic polarisation, and electrochemical impedance spectroscopy.Additionally, the Mott–Schottky analysis considering the point defect model was used fordetermining the semiconducting behavior of thefilm formed at different applied potentials. Thepotentiodynamic polarisation curve indicated that AISI 201 austenitic stainless steel exhibits apassivation property in the potential range of−0.2–0.8 V. The average steady-state currentdensity was calculated by conducting a series of potentiostatic polarisation tests at the selected film-forming potentials. The passivefilms formed on the surface of metals are mainly made upof metallic oxides and hydroxides, which are envisaged as semiconductors. The Mott–Schottkyanalysis showed that the passivefilm exhibits n-type behavior. Based on the point defect model, it was deduced that the primary defects in the passivefilm formed on AISI 201 steel are metal interstitials and oxygen vacancies. The p-type behavior was not observed, indicating thatthe concentration of the cation vacancies is not significant in the passive film