A Study on Zinc-Iron Alloy Electrodeposition from a Chloride Electrolyte

The electrodeposition of zinc-iron alloys from a chloride-based electrolyte has been studied using electrochemical polarisation techniques, Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDXA) and Computer Assisted Pulse Plating (CAPP). A change in the electrodeposition mechanism from equilibrium codeposition to anomalous codeposition with a change in cathodic current density has been observed. Zn-Fe alloys with compositions ranging from 5 wt-% to more than 75 wt-% Fe have been electrodeposited from a single electrolyte, making this system ideal for production of compositional modulated alloy (CMA) electrodeposits. Chloride content, pH and agitation of the electrolyte have been observed to have a strong influence on the reaction at the cathode surface, just as the use of pulse reversal current during electrodeposition. A theory on the electrodeposition mechanism, accounting for the above observations, is presented.