THE BEHAVIOR OF ZINC ELECTRODE IN ALKALINE ELECTROLYTES .1. A KINETIC-ANALYSIS OF CATHODIC DEPOSITION

A model for the cathodic electrode activation is developed so as to account for the polarization curves and impedance plots obtained for zinc deposition in alkaline electrolytes. The reaction pattern involves the two-step discharge of zincate ions through an oxide-containing layer whose ionic and electronic conductivities are potential activated. The sharp electrode activation with increasing cathodic polarization is shown to be related to the spreading and thinning of the conductive layer. These phenomena and the concentration of the monovalent intermediate in the layer account for the three time-constants distinguished in the inductive electrode impedance. The growth of granular compact deposits, favored by trace lead in the electrolyte, is associated with the existence of a uniformly conductive layer on the whole electrode surface. The presence of a fluorinated surfactant (F1110) inhibits the formation of spongy deposits in close connection with modifications to both the kinetic parameters of reactions and the geometrical parameters of the conductive layer.