An intelligent anticorrosion coating based on pH-responsive smart nanocontainers fabricated via a facile method for protection of carbon steel

Morphologically intact hollow mesoporous zirconia nanospheres (HMZSs) with a hollow core mesoporous shell structure were successfully synthesized by a sol-gel protection method and used as scaffolds for smart nanocontainers. L-Carnosine (L-CAR) was proved to be a green, efficient and mixed-type corrosion inhibitor for the protection of carbon steel. Crucially, the net charge on L-CAR molecules is influenced by the solution pH and matches the changing regularity of the zeta potential of HMZSs. Taking advantage of the pH-dependent electrostatic interactions between HMZSs and L-CAR, the smart nanocontainers constructed by directly binding L-CAR to HMZSs easily achieve acid/alkaline-responsive controlled release. The smart nanocontainers, L-CAR loaded HMZSs, were incorporated into a water-borne epoxy coating to assemble the intelligent anticorrosion coatings (IACs). The anticorrosion performances of IACs on a carbon steel surface were systematically evaluated by electrochemical impedance spectroscopy and a scanning vibrating electrode technique. Compared with the pure epoxy coating, IACs demonstrate more excellent corrosion resistance ability. By monitoring the corrosion around artificial scratches, it is observed that IACs display satisfactory self-healing effects, which are attributed to the fact that smart nanocontainers respond spontaneously to local acidification in micro-anodic zones as well as local alkalization in micro-cathodic zones, subsequently releasing L-CAR molecules to compensate the damaged coatings.