Stability study of passive film on copper surface as a function of anodic potential

摘要

Results for passive film formation and breakdown on copperdisk electrodes in buffer solutions, pH 9.2 and 8.5, were reportedearlier. The present studies were carried out in a buffer solution,pH 8.0, and together these studies make good material forunderstanding the effect of pH changes on film texture as a functionof potential. Cyclic voltammetry (CV) and electrochemical impedancespectroscopy (EIS) were used to examine passive film and thevariations it went through upon being treated potentiostatically inthe range of -0.3 to 0.9 V. On the basis of equivalent circuits usedfor modeling impedance data in this potential range, 4 stages wereidentified. The proposed circuits for different potential rangesillustrated the Cu/oxide/electrolyte systems and their properties interms of 2 interfaces. A criterion for the applicability of theequivalent circuit model was discussed. Changes in the film-metalinterface as a function of potential were also probed at 30 mHz withNyquist plots. Diffusion coefficients for ionic movement at 4potential values in the film, calculated from the EIS data, were ofthe order of 10^{-5} cm^2 s^{-1}.