Self-Reporting and Self-Healing Dual Functional Anticorrosive Coating based on Tannic Acid Additives

Tannic acid molecules are loaded into mesoporous silica nanoparticles (TA-MSNs) by one-step synthesis method to endow them with corrosion sensing and corrosion inhibition dual functions. TA-MSNs are added into the epoxy coatings to explore the self-reporting and self-healing performances of composite coatings. Firstly, the coloration and corrosion inhibition properties of TA are characterized. Then, the morphology and structure of TA-MSNs are investigated, and the release behaviors of TA from TA-MSNs studied. The influence of nanofiller content on the self-reporting and self-healing performances of coatings is comprehensively analyzed. Salt spray test indicates that the self-reporting effect of the coating is positively correlated with the filler content, and the addition of more than 5 %(w) TA-MSNs could give the coating obvious coloration effect. Electrochemical measurement and surface analysis show that the low-frequency impedance modulus (|Z|_{0.01 Hz}) of the damaged coating with 5 % TA-MSNs is two orders of magnitude higher than that of the damaged blank epoxy coating. When the coating is damaged, TA molecules released in the coating can be complexed with Fe³⁺ formed during steel corrosion, resulting in blue-black coloration for corrosion reporting, and the complex adsorbed on the metal surface can form a protective film layer to inhibit further corrosion reaction. In summary, the epoxy coating with 5 % TA-MSNs possesses excellent self-reporting and self-healing performance.