Development of self-healing coatings based on PDA@BTA@MOF active fillers for low-temperature corrosion protection

Motivated by the demand for enhanced coating toughness and self-healing capabilities in polar low-temperature environments, a pH-responsive active filler, which was named as PDA@BTA@MOF, was synthesized through the layer-by-layer self-assembly of a metal–organic framework (MOF), benzotriazole (BTA) corrosion inhibitor molecules, and polydopamine (PDA). And then, the obtained fillers denoted as, was incorporated into an epoxy resin to prepare a composite coating (termed the PDA coating) that exhibited superior toughness and excellent low-temperature corrosion protection. Physicochemical characterization revealed that the PDA@BTA@MOF filler possesses a core-shell structure with cubic BTA@MOF as the core and PDA nanoparticles forming the shell, and the special structure ensure that the PDA@BTA@MOF filler could uniformly disperse within the PDA coating matrix. The active filler could significantly enhance the toughness, barrier properties against corrosive media penetration, and adhesion under various conditions of the PDA coating, primarily attributed to mechanisms such as the “pinning effect”. Electrochemical impedance spectroscopy (EIS) and salt spray tests reveals that the PDA coating containing PDA@BTA@MOF filler possesses more excellent anti-corrosion resistance that the pure epoxy coating (EP coating). Even under harsh alternating freeze-salt spray test conditions, where the diffusion of corrosive media through the is coating significantly accelerated and adhesion was substantially degraded, the PDA coating maintained remarkable protective efficacy. Furthermore, immersion tests and EIS analysis on scratched samples confirmed the pH-responsive release behavior of the PDA@BTA@MOF particles and the effective self-healing functionality of the PDA coating.