Effects of Organic Additives on Initial Stages of Zinc Electroplating on Iron

Abstract

Effects of organic additives such as benzoic acid (BA) and poly(ethylene glycols) (PEGs) on the initial stages of zinc electroplating were investigated at an iron electrode using cyclic voltammetry, energy-dispersive spectroscopy, soft X-ray absorption spectroscopy, and electrochemical impedance spectroscopy in an acidic zinc chloride solution. BA mainly contributed to the roughness control of the zinc layer with a relatively weak interaction with zinc ions. However, PEG molecules raise the overpotential for reduction of both zinc ions and protons by effectively blocking the electrode surface. Soft X-ray absorption spectroscopic results confirmed that the iron oxide layer was reduced to metallic iron by electrodeposited zinc prior to zinc bulk deposition. Impedance measurements helped reveal the roles of BA and PEG molecules during the zinc deposition on the surface and also in determining the corrosion behavior of zinc plated iron. (C) 2003 The Electrochemical Society.