Photoelectrochemical study of the growth of the passive film formed on Fe-20Cr-15Ni in a pH 8.5 buffer solution

Abstract

The structural change of the passive film on Fe-20Cr-15Ni at its growth stage was examined in-situ using a photoelectrochemical technique. The photocurrent spectra showed that the passive film on Fe-20Cr-15Ni for 0.5 h similar to 25 h in a pH 8.5 buffer solution was composed of (Cr, Ni)-substituted gamma-Fe(2)O(3) mixed with NiO. Photocurrent spectral analysis suggested that a crystalline film of (Cr, Ni)-substituted gamma-Fe(2)O(3) formed before 30 min, with its thickness exceeded that of the space charge layer after 1 h of passivation. NiO particles appeared to have gradually precipitated from (Cr, Ni)-substituted gamma-Fe(2)O(3) film in the early stage of passivation of 1 h.