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

Abstract

In this research, the effects of visible-light-driven titanium dioxide (TiO2) nanotube/graphitic carbon nitride (g-C3N4) hybrids on the corrosion protection performance of epoxy coatings both in the dark and under visible-light irradiation are studied. For this, TiO2 nanotube/g-C3N4 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, N2 adsorption/desorption technique, and UV–Vis spectroscopy. TiO2 nanotubes containing 30 wt% g-C3N4 (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.