Highly corrosion protection properties of plasma electrolytic oxidized titanium using rGO nanosheets

In the present study, reduced graphene oxide (rGO)/titanium dioxide (TiO2) composite coatings were successfully prepared on titanium substrate by applying plasma electrolytic oxidation (PEO) process and the effect of anti-corrosion ability of rGO nanosheets synthesized by modified Hummer's method on the physical properties, corrosion and Mott-Schottky behaviors of the coatings was investigated. Structural, composition and morphological characteristics confirmed the full incorporation of large-area rGO nanosheets into the TiO2 coatings with pancake-like morphology. By increasing rGO concentration, the thickness of the coatings was found to increase; whereas both roughness and porosity gradually reduced, compared to the pure TiO2 sample. Meanwhile, the wettability properties revealed a high hydrophobic behavior with a contact angle larger than 90 degrees. The electrochemical measurements using potentiodynamic polarization test featured that the polarization resistance (R-p) experienced a considerable increase from 1.88 x 10(5) to 195.3 x 10(5) Omega.cm(2), with the increment of rGO nanosheets content up to 0.5 g.L-1. While the Mott-Schottky analysis indicated that the rGO nanosheets incorporation drastically diminished the donor concentration of the samples. These results verified that introducing rGO nanosheets into the PEO prepared TiO2 coatings significantly enhanced the anti-corrosion performance of rGO/TiO2 composite coatings, suggesting a tremendous corrosion barrier effect of the coatings.