Electrodeposition of zinc+iron alloys: II. Relation between the stripping results and ex-situ characterization

Zn+Fe alloy electrodeposition under potentiostatic conditions was studied in chloride medium on vitreous carbon from solutions with relatively low metal concentrations. It has been demonstrated that electrochemical stripping techniques can be used to characterize the Zn+Fe alloy deposition process. Morphological and compositional studies, along with structural XRD analysis, enabled the electrodeposition conditions for obtaining a defined coating with defined characteristics to be specified. Anomalous codeposition of Zn+Fe alloy was maintained under gentle stirring conditions until zinc-rich deposits were obtained. In highly zinc-rich deposits, in which only the η-phase is present, a distorted platelet-like shape was seen. The zinc oxidation of these deposits took place in only one peak/plateau region in the electrochemical stripping curves. A slight increase in iron in the deposits (%Fe>4%) caused significant changes in both morphology and structure. For these deposits a second, more negative, peak/plateau region was recorded for the zinc oxidation in the stripping curves. Although the η-phase remains the phase mainly formed, the greater difficulty of zinc oxidation is interpreted as a consequence of the interactions between the η-phase and a new phase that probably has an fcc structure.