Coating titanium on carbon steel by in-situ electrochemical reduction of solid TiO2 layer

Ti coating on A3 steel was successfully prepared by direct electrochemical reduction of high-velocity oxy-fuel (HVOF) thermally sprayed and room-temperature dip-coating titanium dioxide coating on A3 steel in molten CaCl2 at 850 °C. The interfacial microstructure and mutual diffusion between coating and steel substrate were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The results show that the precursory TiO2 coating prepared by HVOF has closer contact and better adhesion with the A3 steel substrate. After electrolysis, all of the electro-generated Ti coatings show intact contact with the substrates, regardless of the original contact situation between TiO2 layer and the steel substrate in the precursors. The inter-diffusion between the iron substrate and the reduced titanium takes place at the interface. The results demonstrate the possibility of the surface electrochemical metallurgy (SECM) is a promising surface engineering and additive manufacturing method.