A novel smart anti-corrosive coating based on the beanpod-inspired microcontainers with self-reporting and self-healing abilities

The preliminary detection and instant repair of local metal corrosion under protective coatings is of great importance for long-term application of metal materials in their lifecycles and reduction of environmental impact and carbon emissions. Here, inspired by beanpod, a smart anti-corrosive epoxy coating based on pH-responsive microcontainer was fabricated. The beanpod-inspired microcontainer (micropod) was composed of high-capacity hollowed mesoporous silica nanoparticles/graphene oxide (MSN-NH2/GO microcontainer) loading indicator and inhibitor 1,10-phenanthroline (Phen). The pH-responsiveness of the micropod was derived from GO electrostatic valve interacting with MSN-NH2 whose surface charge varied at different pH values to control the release of Phen. When under-coating corrosion happened with increasing pH value, Phen escaped from the detached micropod and coordinated with dissolved Fe2+ to develop red-orange coloration and form passive complex film retarding the corrosion to realize corrosion sensing and inhibition. GO also enhanced the corrosion resistance of coating because of the high aspect ratio which can prolong the diffusion pathway of corrosive media in coatings. The Phen@micropod/epoxy anti-corrosive coating performed well in immersion test and salt-spray test and remained intact in 30-day immersion test, the Rc of which was 1000 times higher than pure epoxy coating.