Correlation between electrochemical characteristics and microstructures of nickel

In order to relate some electrochemical characteristics of nickel to the microstructural features of nickel surfaces, impedance measurements were performed in addition to steady-state curves for pure nickel single, bi- and polycrystals and for sulphurized nickel. The current intensities corresponding to the different samples differ more strongly in the active domain than in the transpassive one. Whatever the domain, the influence of the nickel composition on the current-potential curves is much more pronounced than microstructural differences. Impedance diagrams, acquired in the transpassive domain for stationarity and reproducibility conditions, were found to be similar for all the samples, proving that the reaction mechanism involved in the transpassive dissolution is the same for pure and sulphurized Ni samples, as long as the sulphur content is very low. (C) 1998 Elsevier Science S.A. All rights reserved.