Easy formation process of anatase‐TiO2 coating layer strongly bonded to titanium metal surface

Abstract

AbstractBecause of the formation of a surface passive film (rutile TiO2) on its surface layer, titanium metal shows adequate corrosion resistance. As the surface layer (passive film) of titanium metal is very stable, any functionalization of the titanium metal has been generally performed using relatively complicated methods. This is because any direct oxidation of titanium metal only leads to the formation of rutile TiO2 over the entire temperature range. Chemical reactions using titanium chemicals can easily produce anatase TiO2 at temperatures of ≤600°C. Using precursors is one of the ways of producing an anatase TiO2 coating on titanium metal. However, in previous studies, anatase TiO2 layers easily peeled off when they were used in flowing water. Herein, we describe a simple process for obtaining an anatase TiO2 coating layer strongly bonded to the titanium metal surface. In our process, titanium metal was pretreated with a reducing agent to create a surface TiH2 layer, whose condensation reaction easily proceeds with a precursor (composed of oxalic acid and tetra‐butoxy titanium). Subsequently, the treated titanium metal was calcinated at 550°C in air to achieve strong bonding between the anatase TiO2 coating layer and titanium metal surface. The treated titanium metal exhibited excellent photocatalytic activity.