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°. The electrochemical measurements using potentiodynamic polarization test featured that the polarization resistance (R_p)experienced a considerable increase from 1.88 × 10⁵ to 195.3 × 10⁵ Ω·cm², 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.