Development of electroless Ni–Zn–P/nano-TiO2 composite coatings and their properties

Ni–Zn–P–TiO2 composite coatings were successfully obtained on low carbon steel by electroless plating technique. Deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis (EDS) studies. The hardness and microstructure of as plated and heat treated Ni–Zn–P and Ni–Zn–P–TiO2 composite coatings were analyzed. The change in microstructure and higher hardness was noticed for heat treated composite. The corrosion resistance behavior of as plated and heat treated Ni–Zn–P and Ni–Zn–P–TiO2 coatings was investigated by anodic polarization, Tafel plots and electrochemical impedance spectroscopic (EIS) studies in 3.5 wt% NaCl solution. The composite coating exhibited enhanced corrosion resistance property over Ni–Zn–P coating.