Equivalent circuit modelling of Ni-SiC electrodeposition under ramp-up and ramp-down waveforms

摘要

An equivalent circuit model (EC) for pulsed electrodeposition of Ni-SiC composite coatings was formulated and fit to electrochemical impedance spectra data for the system. Two different shaped waveforms, ramp-up and ramp-down waveforms both with relaxation time were applied to investigate the electrodeposition behaviour of Ni-SiC and to validate the equivalent circuit model. It was found that under the same average and peak current density, the shape of current waveform has significant effect on the electrodeposition behaviour. A higher instantaneous peak current for charge transfer was obtained by the ramp-up waveform, which results in finer grain size and enhanced hardness of the composites. The morphological characteristics of the Ni-SiC composites were also examined and the experimental results were in accordance with the predictions of the EC model.