Research on UV aging evolution mechanism of metakaolin base geopolymer coatings.

In the process of service, the coating is vulnerable to ultraviolet radiation, which leads to aging failure. The metakaolin base geopolymer coating studied in this paper has excellent mechanical and anti-corrosion properties through the previous mix ratio study. However, the UV aging resistance of the coating is unknown. In response to this issue, the present study devised UV aging experiments for metakaolin based geopolymer coatings. Employing UV irradiation in conjunction with EIS tests, the aging resistance of the geopolymer coatings was assessed through electrochemical fitting and analyses such as SEM. The study delves into the structural evolution of metakaolin based geopolymer coatings under UV aging conditions. After 500 h of ultraviolet irradiation, the resistance of the geopolymer coating is enhanced, its water diffusion coefficient is reduced, two orders of magnitude increase the resistance of the coating, and the protection performance of the geopolymer coating is enhanced. In the control group, the waterproof performance of epoxy resin decreased significantly, the impedance decreased, and the resistance decreased by three orders of magnitude. SEM results show that the post-curing of the coating under UV irradiation continuously generates NASH gels, and the coating microstructure is dense. The results show that geopolymer has strong aging resistance. • This experiment investigates the mechanism of UV ageing resistance of metakaolin base geopolymer coatings. • Comparison with epoxy resin coatings concludes that the geopolymer coatings have very good UV aging resistance. • The system of evaluating the water resistance and porosity of the coatings by capacitance method based on Fick's law of diffusion is applicable to the geopolymer coatings. • UV irradiation induces a post-curing reaction of the geopolymer coatings. [ABSTRACT FROM AUTHOR]