MORPHOLOGIES OF ZINC ELECTRODEPOSITED FROM ZINC-SATURATED AQUEOUS ALKALINE SOLUTION

The deposit morphologies produced during the deposition of zinc from an aqueous solution of potassium hydroxide saturated with zinc oxide have been examined by scanning and transmission electron microscopy. Single crystal substrates of orientations (0001), (121O), (1100) and (2311) were used. The cd was maintained constant in the range 4-100 mA/cm2. The deposit morphologies were found to vary with cd; at 100 mA/cm2 the deposits were dendritic; at 20 mA/cm2 they consisted of layer growths with some granular growths; at 4 mA/cm2 they were mossy growths at a density of 103/cm2. The principal effect of substrate orientation was the lower the density (106/cm2 compared with 108/cm2) of small growths on the basal plane during the early stages of dendritic growth. The density of dendrites after greater passage of charge was found to be independent of the number of small growths and was about the same (∼106/cm2) for all substrate orientations. Examination of dendrites by transmission electron microscopy showed that they were mono-crystalline with the stem and side branches growing in the <121 0 > directions. No evidence for twinning within dendrites was found. The mossy deposits were found to consist of large numbers of small zinc crystals. © 1968.