Synergistic effect of 8-HQ@CeO2 for enhanced corrosion resistance of self-healing polyurethane coating for corrosion protection of mild steel

The anticorrosive qualities of organic coatings can be enhanced by the inclusion of corrosion inhibitors, which is helpful for ensuring the long-term anticorrosive performance of the coatings. Taking advantage of the fact that polydopamine contains multiple functional groups, the 8-HQ@CeO2 polyurethane composite coating was prepared by coating it on the surface of CeO2 and adsorbed with 8-Hydroxyquinoline (8-HQ), and its anticorrosion performance in 3.5 wt% NaCl solution was investigated. After 120 days of immersion, the polyurethane composite coating containing both CeO2 and 8-HQ organic/inorganic dual corrosion inhibitors exhibited excellent long-term corrosion resistance. Its impedance modulus at 0.01 Hz (108 Ω·cm2) was two orders of magnitude higher than that of the polyurethane composite coating containing only CeO2 (106 Ω·cm2). The coating also incorporated dynamic Diels-Alder (DA) bonds to create its self-healing characteristics. The produced composite coatings could exhibit effective self-healing behavior under sunlight thanks to the superior photothermal characteristics of polydopamine (PDA), and their mechanical and anticorrosive properties were substantially unaltered before and after self-healing. The strategy utilizes the synergistic anticorrosive effect of CeO2 and 8-HQ and dynamic DA bonding to achieve the long-term anticorrosive performance of the coating and proposes a new method to protect metal substrates.