New effects of TiO2 nanotube/g-C3N4 hybrids on the corrosion protection performance of epoxy coatings

In this research, the effects of visible-light-driven titanium dioxide (TiO 2 ) nanotube/graphitic carbon nitride (g-C 3 N 4 ) hybrids on the corrosion protection performance of epoxy coatings both in the dark and under visible-light irradiation are studied. For this, TiO 2 nanotube/g-C 3 N 4 hybrids and 3-(aminopropyl)triethoxysilane functionalized hybrids were synthesized and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy , scanning electron microscopy coupled with energy dispersive X-ray spectroscopy mapping, N 2 adsorption/desorption technique, and UV–Vis spectroscopy. TiO 2 nanotubes containing 30 wt% g-C 3 N 4 (H30%) showed the highest photocatalytic performance due to the simultaneous effects of high surface area and band-gap structure; however, the photocatalytic activity decreased after the silane functionalization of H30%. Then, epoxy coatings containing H30% and silane functionalized H30% in different amounts (0.1, 0.3, and 0.5 wt%) were prepared, and their corrosion resistance was investigated by electrochemical impedance spectroscopy in NaCl solution. The results revealed that the epoxy coatings containing 0.3 wt% hybrids have higher corrosion resistance than that of the neat coating, and silane-functionalized nanofillers more effectively enhance the corrosion resistance. However, when these nanocomposite coatings are irradiated with visible light , their corrosion protection performance remarkably reduces owing to the degradation of organic matrix by the oxidizing radicals formed on the photocatalytic hybrid surface.