KINETIC-MODEL OF THE CATHODIC DEPOSITION OF AS-SB ALLOYS

The cathodic deposition of As-Sb alloys onto Ni rotating-disk and stat ionary-sheet electrodes from citric acid solutions has been studied wi th steady-state and impedance methods as a function of the potential E , As(III)/Sb(III) ratio and rotation rate of the electrode. A kinetic mechanism is proposed implying a different reactivity of As and Sb sit es during the deposit growth and a stronger dependence of the reductio n rate on E for As(III) than for Sb(III) ions. The current-potential, composition-potential and a.c. impedance characteristics have been cal culated and numerically simulated for various potentials, solution com positions and diffusion layer thicknesses.