Modelling the effect of complex waveform on surface finishing in pulse current electroforming of nickel

A mathematical model has been established for formulating the effect of different types of waveform on surface finishing in pulse current electroforming of nickel. The model describes the change of the concentration profile of electroactive ions, micro-current distribution and the rate of protrusion growth at the cathodic surface. The theoretical predictions are compared with the experimental results: within the range of the study, a maximum discrepancy of 10% on surface roughness values between the two was found. This discrepancy could be due to the evolution of hydrogen gases at the cathodic surface during electrodeposition. The best surface finish was found by using a ramp-down waveform with relaxation time. Both theoretical predictions and experimental results show that the quality of the electroforms, in terms of surface roughness improvement, influenced by the types of waveform is of the order of ramp-down waveform > triangular waveform > ramp-up waveform > rectangular waveform, all with relaxation time. This is also supported by the study of the surface morphology of the electroforms by scanning electron microscopy. (C) 2000 Elsevier Science B.V. All rights reserved.