Seamlessly embedded microcapsules in self-repairing coatings: Improved compatibility and enhanced corrosion resistance recovery

Microcapsules, with polyether amine as the core repairing agent and polyether amine-cured epoxy as the shell, were prepared via the multiple emulsion polymerization and applied in an epoxy/polyether amine coating system on carbon steel surfaces. The microcapsules and the coating substrate have the same composition and are seamlessly connected by chemical bonds, akin to the direct injection of liquid healing agents into the substrate. When the repairing agent flows out, it will crosslink and cure with the epoxy groups in the substrate to achieve no difference self-repair. The characteristics of microcapsules were studied by scanning electron microscope (SEM), Fourier transform infrared (FTIR) and Thermal gravimetric (TG). The mechanical properties and corrosion resistance recovery of coatings loaded of coatings with different weight percentages of loaded microcapsules were investigated using tensile testing, electrochemical impedance spectroscopy (EIS) and neutral salt spray test (NSS). Results indicate that the 7 wt% microcapsules composite coating shows a 37.7 % increase in tensile strength and a 71.4 % increase in fracture toughness over pure epoxy coating. After immersing in saltwater for 7 days, the scratch sealing efficiency can reach 99.85 %. The coating system not only improved the compatibility between microcapsules and the substrate, but also enhanced the toughness of thermosetting brittle epoxy materials, giving it long-lasting anti-corrosion capability.