Microstructure-corrosion resistance relationship of direct and pulse current electrodeposited Zn-TiO2 nanocomposite coatings

Zinc–TiO2 nano-composite coatings were synthesized by Direct Current (DC) and Pulse Current (PC) electrodeposition techniques. The effects of the plating parameters on the microstructure, codeposition percentage of TiO2 and corrosion behavior were investigated. The coatings morphology presents hexagonal grains perpendicularly oriented to the surface. Under DC conditions, TiO2 content of the coatings decreased with increasing TiO2 concentration of the electrolyte. Increasing applied current and TiO2 concentration in the bath leads to a fine microstructure with corrosion currents as low as 2.7 µA/cm2. Under PC conditions, incorporation rate of nanoparticles tends to increase with increasing pulse frequency and decreasing current density. Incorporation of TiO2 increases microhardness of the zinc coatings by improving deposit structure.