Designing a core-shell structured Ce-MOF-based nanomaterial by Schiff base reaction for pH-responsive self-healing coatings.

Nanocontainers involving corrosion inhibitors can confer self-healing capabilities to organic coatings. However, it is still prone to causing spontaneous leakage of these inhibitors during the coating preparation process. Herein, we propose a pH-responsive self-healing anti-corrosion coating system (CTAP-EP) based on the epoxy coating containing polyethyleneimine (PEI) encapsulated Ce-MOF nanocontainer loaded with tannic acid (TA) corrosion inhibitor. The PEI shell was installed through the Schiff base reaction between oxidized TA and PEI. The PEI shell acts as an acid-responsive gatekeeper because of the sensibility of Schiff base under acidic conditions, realizing controllable release of the wrapped TA. Among all the coatings, CTAP-EP has the highest low-frequency impedance modulus (5.53 × 109 Ω·cm2) after 35 days, revealing its robust anti-corrosion performance. The self-healing rate of scratched CTAP-EP turns positive four times, demonstrating its superior self-healing properties. CTAP-EP possesses reinforced active and passive corrosion protection originating from combined effect of TA inhibitor and Ce3+ ions. The pH-responsive core-shell self-healing system will be a potential candidate for practical applications of corrosion protection of metal.