Understanding the protective role of a gradient titanium oxide ceramic layer on Ti6Al4V against corrosion via analyses of Mott-Schottky curve and electron work function (EWF)

Thermal oxidation (TO) process was employed to generate a gradient titanium oxide ceramic layer for improving corrosion performance and service safety of Ti6Al4V alloy. The semiconductor characteristic of the TO layer was evaluated in CO2-saturated simulated oilfield brine. The generated TO layer with a thickness of about 20 mu m was dense and continuous without cracks or spalling characteristics. The TO layer mainly comprised of an oxide ceramic layer (rutile TiO2 ceramic phase, minor anatase one, and Al2O3) and an oxygen diffusion layer. The conducted electrochemical analysis suggested that the corrosion resistance of Ti6Al4V alloy was improved using TO surface strengthening process. It was demonstrated that the TO layer with semiconductor characteristics showed a transition from n-type (donor) to p-type (acceptor) with the increasing applied electric potential. The electron work function of the TO layer was higher than that of Ti6Al4V alloy with a naturally formed passive film. The improvement in corrosion properties was attributed to the excellent chemical stability and semiconductor properties of the metal oxide ceramic phases (TiO2, Al2O3) in the TO layer.

Automated summary

The gradient titanium oxide ceramic layer generated by thermal oxidation process significantly improves the corrosion resistance of Ti6Al4V alloy due to its excellent chemical stability and semiconductor properties.