ZINC DEPOSIT STRUCTURES OBTAINED FROM SYNTHETIC ZINC-CHLORIDE ELECTROLYTE

Zinc deposits electrowon from synthetic zinc chloride electrolyte were characterized by a morphology which featured clusters of large platelets with rounded edges and by a preferred crystallographic orientation, namely (0 0 2) (1 0 3) (1 0 5). These deposit characteristics persisted over a wide range of experimental conditions which included variations in the current density and changes in anode material, cell design, and the zinc and hydrochloric acid concentrations. Although the addition of HCl to the electrolyte improved the physical characteristics of the deposit, it did not alter the deposit morphology or orientation. The addition of animal glue or tetrabutylammonium chloride resulted in smooth, compact deposits having a (1 1 0) orientation at 0·24 M H+. Jaguar C-13 additions gave a (1 1 2) orientation, while gum arabic and tetraethylammonium chloride only affected the grain size. The various deposit morphologies and orientations obtained showed only some correspondence to changes occurring in the zinc deposition polarization voltages. The presence of metallic impurities, Cu, Co, Fe, and Sb, caused the morphology and orientation of the deposits to become more basal and the current efficiency to decrease. The presence of Cd resulted in a (1 1 2) (1 1 4) orientation and Pb gave a (1 0 1) orientation. © 1979 Chapman and Hall Ltd.