Kinetic Model of the Cathodic Deposition of As-Sb Alloys

The cathodic deposition of As-Sb alloys onto Ni rotating-disk and stationary-sheet electrodes from citric acid solutions has been studied with 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 sites during the deposit growth and a stronger dependence of the reduction rate on E for As(III) than for Sb(III) ions. The current-potential, composition-potential and a.c. impedance characteristics have been calculated and numerically simulated for various potentials, solution compositions and diffusion layer thicknesses.