Nowadays, stainless steel reinforcements appear as an effective solution to increase the durability of reinforced concrete structures exposed to very aggressive environments. AISI 304 stainless steel is widely used as reinforcement in concrete. The high corrosion resistance of this type of stainless steel is due to formation of a thin film (a few nm thickness), but highly protective that limits ionic and electronic conductivity. The barrier properties of passive film deteriorates and, consequently breaks down due to presence and diffusion of chloride ions. In this work the properties of passive film formed on AISI 304 stainless steel in 0.2 M NaOH solution was investigated. In the potential rang of passive film formation, growth of the passive film reduced current density and increased polarization resistance. The point defects within the passive film were cation vacancies. Therefor, the passive film was identified as the p-type one. The electron acceptor density decreased with increasing the passive film formation potential. The thickness of the passive film was increased linearly with the film formation potential. These observations were in good agreement with the predictions of the point defect model. Also, it was concluded that, the corrosion current density increased and corrosion potential decreased by increasing the chloride concentrations. The point defect density within the passive film increased with increasing the chloride concentration. The effect of immersion time in the absence and presence of chloride ion was also evaluated using EIS technique. In chloride containing solutions, the impedance parameters were lower than no chloride solution. Also, by increasing the chloride content, impedance parameters were decreased more quickly. Keywords: stainless steel, passive film, electrochemical impedance, pitting corrosion, Mott–Schottky analyses