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 considered. The confirmation of the proposed semiquantitative mathematical model is performed in zinc electrodeposition onto copper wire from a 0.1 M zincate solution in 1.0 M KOH at room temperature. It was shown by SEM analysis of the deposit that the spongy growth was caused by mass transfer limitations under low nucleation rate conditions. In this situation, amplification of the surface inequalities on the independently growing grains takes place 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-wave pulsating overpotential regime, the deposits are less agglomerated than the 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 dissolution of filaments, based on the mathematical model of pulsating overpotential.