Electronic properties of the passive films growth on Cu-Ni alloy from the viewpoint of point defect model and power-law model

The electronic properties of the passive films growth on Cu-Ni alloys were investigated via a sensitive method by employing Mott-Schottky analysis, point defect model (PDM) in conjunction with power-law model (PLM), which was employed to accurately analyze the constant phase element (CPE) behavior of the passive films. Results indicate that the passive films exhibit p-type semi-conductive characteristics with acceptor densities of 1.74–6.47 × 10 20 cm 3 , and the condensation of cation vacancies ( V C u ′ ) is mainly responsibility for the passivity breakdown. The diffusion coefficient ( D ) of the passive films growth on Cu-Ni alloy is of the order of 10 –16 cm 2 s −1 . The Ni cation interstitial ( N i ) i 2 + would occupy a metal lattice site (Ni Cu ) and consume the V C u ′ , resulting in decrease of acceptor density, defect flux and superior corrosion resistance. In addition, the calculated lattice parameter of Cu 2 O (4.17 Å) is acceptably close to the theoretical value (4.26 Å), verifying the veracity of the analytic approach proposed in this paper to describe semi-conductive properties of the formed passive films.