Abstract

Electrodeposition of bright Zn-Fe alloy on mild steel from acid chloride bath

Author(s): K.Venkatakrishna, A.Chitharanjan Hegde, N.Eliaz

Electrodeposition ofZn-Fe alloy onmild steal substratewas performed under galvanostatic condition from an acid chloride bath. Use of sulphanilic acid (SA) and gelatin was found to show significant effect on homogeneity and brightness of the deposit. Under no conditions of bath composition and operating parameters studied, the codeposition behaviour changed from anomalous to normal type was observed. The experimental results revealed that the corrosion resistance of electroplates depends on both wt. % Fe and structure of the deposit. The dependency of bath composition, current density (c.d.), pH and temperature on wt%of Fe, hardness, appearance and corrosion resistance of deposits were studied and discussed. The corrosion resistance of electroplates were evaluated by direct current (d. c.) and alternate current (a. c.) method. Potentiodynamic cyclic polarisation technique was used to investigate the mechanism of corrosion. The surface roughness and morphology of deposits were studied byAFM and SEM analysis. XPS analysis was carried out to investigate the state of metal in the alloy. The electrochemical impedance spectroscopy (EIS) analysis revealed that superior corrosion resistance of Zn-Fe coatings are due to formation of ntype semiconductor filmat the interface of the metal andmedium, confirmed by Mott-Schottky (M-S) plot.