Electrodeposition of Zn-Fe alloys from aqueous acetate baths

Zn-Fe alloys were electrodeposited on steel substrates from baths containing zinc acetate, ferrous sulphate and acetic acid (pH∼4.5). The effects of bath composition, applied current density and temperature on current efficiency of codeposition and composition of deposits were investigated. The data showed that the current efficiencies were high and Zn-rich alloys were plated. The results were consistent with the behaviour of an anomalous plating system with zinc, the less noble metal, being deposited preferentially. The zinc content in the deposit increased with increase in concentration of zinc ion and acetic acid in the bath and applied current density but decreased with increase of iron concentration in the bath and temperature. The structure and morphology of as-deposited alloys were examined by X-ray and SEM. The results revealed that the deposits consisted of three phases namely η, r and ζ-phase and the morphology of the deposits was controlled by the composition of the deposits. The microhardness of the deposits increased with increase in the deposit iron content.