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 spec troscopy 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 adso rption of iron is shown to predict correctly the changes in alloy comp osition with the ferrous-ion concentration in the electrolyte. The mod el is also successful at predicting qualitatively the dependence of im pedance data on bath concentration, degree of agitation, and current d ensity. Discrepancies between theory and experiment are most significa nt at low current densities and high ferrous-ion concentrations.