Electronic structure study of ac modified passive film on stainless steel

Abstract

The semiconductor properties, electronic structure and reduction susceptibility of passive films on AISI type 304 stainless steel in dilute sulphuric acid solutions have been studied by electrochemical impedance spectroscopy measurements, Mott-Schottky analysis and the photoelectrochemical technique. The passive film shows features of an amorphous or highly disordered n type semiconductor. The donor level is in the range of 10²⁶-10²⁷ m^-3 and increases with the amplitude of ac potential. The passive film thickness increases linearly with the amplitude of the applied ac potential. The reduction susceptibility of the passive film is also decreased with the amplitude of the applied ac. The photoelectrochemical measurements also indicate that the passive film is n type semiconductor and the photcurrent is decreased after ac modulation. It might be related to the surface chromium accumulation.