Electrochemical impedance spectroscopy study of nickel-iron deposition .2. Theoretical interpretation

A mathematical model of the anomalous deposition of nickel-iron alloys is,compared to steady state as well as electrochemical-impedance spectroscopy data taken on a rotating disk electrode. A key aspect of the model is the treatment of adsorption phenomena of the nickel and iron species. A modification of a previously proposed rate law for the adsorption of iron is shown to predict correctly the changes in alloy composition with the ferrous-ion concentration in the electrolyte. The model is also successful at predicting qualitatively the dependence of impedance data on bath concentration, degree of agitation, and current density. Discrepancies between theory and experiment are most significant at low current densities and high ferrous-ion concentrations.