Enhanced anti-aging and anti-corrosion performance of waterborne epoxy coating layers over the dual effects of g-C3N4 photocatalysis

To overcome the drawbacks of waterborne epoxy (WEP) films, various fillers were employed to eliminate the microcracks and microporous in the coating layers. Here, photocatalysis (g-C3N4) was incorporated into WEP coating to achieve improved long-term anti-aging and anti-corrosion performance via dual effects, including barrier effects through the formation of dense and uniform composite film as well as the photocatalytic effects. The chemical structure, chemical states, photoabsorption properties, and morphology of g-C3N4/WEP films were analyzed. Effects of g-C3N4 content on the mechanical properties, water resistance, anti-corrosion behaviors, anti-permeation property, and photocatalytic activity of g-C3N4/WEP (x-CN/WEP) composites were investigated by salt spray test, electrochemical impedance spectroscopy, and RhB degradation experiments. 2-CN/WEP coating with the addition of 2% g-C3N4 displayed the optimum mechanical property, water resistance, anti-permeation, anti-corrosion, and anti-aging performance. The anti-corrosion mechanisms of x-CN/WEP composite coating were also summarized, which consists in the formation of chemical bonds between g-C3N4 and WEP, uniform distribution of g-C3N4 in WEP, and the photocatalytic performance of g-C3N4.