An experimental study of zinc morphology in alkaline electrolyte at low direct and pulsating overpotentials

A possible mechanism of the formation of spongy zinc electrodeposits is con sidered. The confirmation of the proposed semiquantitative mathematical mod el is performed in zinc electrodeposition onto copper wire from a 0.1 M zin cate solution in 1.0 M KOK at room temperature. It was shown by SEM analysi s of the deposit that the spongy growth was caused by mass transfer limitat ions under low nucleation rate conditions. In this situation, amplification of the surface inequalities on the independently growing grains takes plac e leading to the formation of the spherical agglomerate of filaments, which form a spongy deposit. Also, it was shown that in the case of a square-wav e pulsating overpotential regime, the deposits are less agglomerated than t he ones obtained in the case of a direct overpotential regime. This effect is more pronounced at a higher pulse-to-pulse ratio. This is explained by d issolution of filaments, based on the mathematical model of pulsating overp otential. (C) 2000 Elsevier Science S.A. All rights reserved.