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

Authors : Amtul NASEER, Athar Yaseen KHAN

Pages : 225-235

Doi:10.3906/vet-1104-26

View : 18 | Download : 7

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Results for passive film formation and breakdown on copper disk electrodes in buffer solutions, pH 9.2 and 8.5, were reported earlier. The present studies were carried out in a buffer solution, pH 8.0, and together these studies make good material for understanding the effect of pH changes on film texture as a function of potential. Cyclic voltammetry insert ignore into journalissuearticles values(CV); and electrochemical impedance spectroscopy insert ignore into journalissuearticles values(EIS); were used to examine passive film and the variations it went through upon being treated potentiostatically in the range of -0.3 to 0.9 V. On the basis of equivalent circuits used for modeling impedance data in this potential range, 4 stages were identified. The proposed circuits for different potential ranges illustrated the Cu/oxide/electrolyte systems and their properties in terms of 2 interfaces. A criterion for the applicability of the equivalent circuit model was discussed. Changes in the film-metal interface as a function of potential were also probed at 30 mHz with Nyquist plots. Diffusion coefficients for ionic movement at 4 potential values in the film, calculated from the EIS data, were of the order of 10-5 cm2 s-1.
Keywords : Electrochemical impedance spectroscopy, model circuits, copper surface, passive film, transition stage, interfaces, diffusion coefficient