In this study, electrochemical behavior of passive films formed on AISI 316L stainless steel (AISI 316L) in three acidic solution concentrations (0.3, 0.6, and 0.9M HNO3) under open-circuit potential conditions was evaluated by potentiodynamic polarization, Mott–Schottky analysis, and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization results showed that the corrosion potentials of AISI 316L shift towards positive direction with increase in solution concentration. Also, these results revealed that the corrosion rate of AISI 316L is enhanced in solutions with higher nitric content. Mott–Schottky analysis revealed that passive films behave as ptype and n-type semiconductors at potentials below and above the flat band potential, respectively. Also, Mott–Schottky analysis indicated that the donor and acceptor densities increased with solution concentration. EIS data showed that the equivalent circuit Rs((RctQdl)(RfQf)) by two time constants is applicable. Moreover, EIS results revealed that charge transfer resistance and passive film resistance decrease with solution concentration.
