Development of Corrosion Resistant Zn-Ni-TiO2 Composite Coatings

The Zn-Ni-TiO2 composite coatings were developed on mild steel by electrodeposition method. The bath constituents (ZnSO4.6H2O, NiSO4.6H2O, TiO2, thiamine hydrochloride) and operating conditions (temperature and pH) were optimized by Hull cell method, for peak performance of the coating against corrosion. The coatings were prepared by galvanostatic method at room temperature. The effect of current density (CD), on coating parameters, such as corrosion resistance, thickness and throwing power were studied. The micro hardness of the composite coating was investigated. Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion resistance of Zn-Ni-TiO2 composite coatings at different current densities. Surface morphology and composition of the composite coatings was investigated using Scanning Electron Microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Atomic force microscopy (AFM) analysed the topographical surface of the coatings. A new and economical sulphate bath, for bright Zn-Ni-TiO2 composite coating on mild steel has been proposed, and results are discussed.