Modeling The Effects Of Different Pulse Current Waveforms On Grain Size Of Electrodeposited Nickel Coatings

A comprehensive mathematical model based on the works reported by Molina et al. [J. Molina, B. A. Hoyos, Electrochim. Acta, 54, 1784-1790 (2009)] and Milchev [A. Milchev, "Electrocrystallization: Fundamentals of Nucleation And Growth" 2002, Kluwer Academic Publishers, 189-215] for galvanostatic pulse electrodeposition of nickel on metallic substrates employing four different waveforms was developed and compared with experimental results. The model is based on progressive nucleation and, unlike other reported models, considers contributions from both nucleation and growth currents. A comparison between the model and experimental results revealed a reasonably good agreement at low peak deposition current densities and low pulse on-times, where the average grain diameter was greater than 50 nm. However, as the pulse on-time or peak deposition current density increased, leading to a decrease in average grain size, the difference between the model and experimental results became more pronounced. At high peak deposition current densities-greater than 400 mA cm(-2)-the ramp-down waveform yielded the highest nucleation rates, confirming the experimental findings in which nickel electrodeposits generated with ramp-down waveform produced the smallest average grain size. (C) 2012 The Electrochemical Society. [DOI: 10.1149/ 2.015211jes] All rights reserved.