Kinetics of growth of zinc dendrite precursors in zincate solutions

Abstract

By means of microscopic measurements on a rotating disc electrode under potentiostatic conditions it is established that the propagation rate of the precursors is constant within the limits of the diffusion layer boundary. The propagation kinetics follow the expression of Diggle, Despic and Bockris [3] if it is assumed that the radii of curvature at the tip of the growing precursorsr increase proportionally with the height of the precursorsy. The overpotential dependence of the ratioy/r is linear and probably reflects the Kelvin relation. At constant diffusion layer thickness the moment of the visual appearance of the dendrites coincides with the transition time on the potentiostaticI-t curves. The average heighty at this moment is equal to the diffusion layer thickness δ. The average rate of growth of precursors is inversely proportional to δ. An equation for the time of appearance of dendrites which accounts for the effect of diffusion is derived and experimentally tested. The effect of lead ions on the time of appearance is discussed in terms of the kinetic equation.