The semi-conductive performance of the passive film formed on 22Cr duplex stainless steel in bicarbonate/carbonate buffer solution was investigated by Mott-Schottky analysis, and the factors, including formation potential, formation time, formation temperature and chloride ions, etc., which affect the film semi-conductive property, were also examined. The film compositions were analyzed by the X-ray photoelectron spectra (XPS). The results showed that the passive film formed on 22Cr duplex stainless steel in bicarbonate/carbonate buffer solution displayed an n-p semi-conductive character, and the donor density ND and the acceptor density NA decreased with increasing the formation potential, prolonging the formation time, decreasing the formation temperature, and decreasing the chloride ion concentration. In addition, the protective effect of the passive film on 22Cr alloy was enhanced with the variation of these factors. XPS analysis revealed that the passive film had a double-layer structure, i.e., the outer trivalent iron oxide, and the inner chromium oxide with a little content of divalent iron oxide.

Key words: 22Cr duplex stainless steel, passive film, semi-conductive property, X-ray photoelectron spectra (XPS)