On the Morphology of Zinc Electrodeposition from Alkaline Solutions

Abstract

The morphology of zinc electrodeposition was investigated from alkal ine zineate solutions on single grains of known orientation in polycrystal l ine zinc electrodes under potentiostatic control. The effect of overpotential, solution composition, and substrate orientation were examined. The deposition mor-phology was observed with a scanning electron microscope. It was found possible to disrupt the deposition repeatedly for microscopic observation, and then continue deposition At low overpotential (50 mV) epitaxial ayer type growth was observed; the width of the macrosteps increased l inearly with time. A theory explaining the l inear step widening is proposed, which can also account for the observed effect of substrate orientation. At 100 mV, "boulders" were observed, not all of which were epitaxial with the substrate. They are suggested to be originated by nucleation. The boulder density per cm 2 is first sharply increasing, then slowly decreasing with time. A statistical calcula-tion for this is given, based on the model that large boulders consume the