Preparation and characterization of TiO2/ZnO composite coating on carbon steel surface and its anticorrosive behavior in seawater

The TiO₂/ZnO composite coatings with various atomic ratios of Ti to Zn were prepared on carbon steel surface via sol–gel process followed by thermal treatment at different temperature. The as-prepared coatings were characterized through X-ray diffraction method, scanning electron microscopy, energy dispersive X-ray spectroscopy, and their anticorrosive behaviors in sterilized seawater were electrochemically assessed. The obtained coatings were quite thin even for the 8-layer samples. The thermal treatment at 500 °C led to severe oxidation of the steel substrate. The incorporation of ZnO avoided crack formation and refined the particles of the composite coatings. The electrochemical measurements of both the potentiodynamic polarization curves and electrochemical impedance spectroscopy revealed a substantial protection of the coatings for the substrate. In particular, the 8-layer TiO₂/ZnO composite coatings with atomic molar ratios of Ti to Zn of 1/1 and 1/3 after thermal treatment at 500 °C showed better anticorrosive performances than others.