Abstract
ABSTRACT In the present investigation, the electrochemical behavior and the semiconducting properties of the 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 for determining the semiconducting behavior of the film formed at different applied potentials. The potentiodynamic polarisation curve indicated that AISI 201 austenitic stainless steel exhibits a passivation property in the potential range of −0.2–0.8 V. The average steady-state current density was calculated by conducting a series of potentiostatic polarisation tests at the selected film-forming potentials. The passive films formed on the surface of metals are mainly made up of metallic oxides and hydroxides, which are envisaged as semiconductors. The Mott–Schottky analysis showed that the passive film exhibits n-type behavior. Based on the point defect model, it was deduced that the primary defects in the passive film formed on AISI 201 steel are metal interstitials and oxygen vacancies. The p-type behavior was not observed, indicating that the concentration of the cation vacancies is not significant in the passive film.
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