Optimization of deposition conditions for bright zn-fe coatings and its characterization1

Abstract

Sulfate bath having ZnSO<inf>4</inf> ̇ 7H<inf>2</inf>O, Fe <inf>2</inf>(SO<inf>4</inf>)<inf>3</inf> ̇ H<inf>2</inf>O and thiamine hydrochloride (THC) and cit- ric acid (CA) in combination, represented as (THC + CA) was optimized for deposition of bright Zn-Fe alloy coating on mild steel. Bath constituents and operating parameters were optimized by standard Hull cell method, for peak performance of the coating against corrosion. The effect of current density (c.d.), pH and temperature on deposit characters, such as corrosion resistance, hardness and glossiness were studied and dis- cussed. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion behaviors. Surface morphology, and composition of the coatings were examined using Scanning Electron Microscopy (SEM), interfaced with EDXA facility, respectively. The Zn-Fe alloy, with intense peaks corresponding to Zn(100) and Zn(101) phases, showed highest corrosion resistance, evi- denced by X-ray diffraction (XRD) study. A new and cheap sulfate bath, for bright Zn-Fe alloy coating on mild steel has been proposed, and results are discussed. © Pleiades Publishing, Ltd., 2011.