Corrosion-oriented self-healing coating based on ZnMg MOF for efficient corrosion protection of aluminum alloy via in-situ LDH film formation

A corrosion-oriented self-healing coating system relying on metal–organic framework (MOF) based nanofiller is designed for aluminum alloy protection. The nanofiller is comprise of ZnMg MOF nanoparticle as a framework, salicylaldoxime corrosion inhibitors inside the MOF, and a polydopamine layer on the MOF surface. The Al 3+ ions generated from the aluminum alloy substrate at the damaged coating area can etch the nanofiller, causing the collapse of the nanofiller and releasing the corrosion inhibitors to suppress the corrosion process in time. Subsequently, Zn 2+ and Mg 2+ ions from the nanofiller co-precipitate with Al 3+ to form a dense AlZnMg layered double hydroxide (LDH) film, which provides further protection performance at the exposed alloy surface. Electrochemical impedance spectroscopy results demonstrate that the intact MOF@S/P coating exhibits a remarkable corrosion resistance property. For the damaged coating, the self-healing performance originated from the formation of LDH layer and the release of corrosion inhibitors gradually took effect, with the |Z| 0.01Hz value increasing 2.27 times within 14 days. Moreover, under near-infrared irradiation, the photothermal effect of polydopamine will accelerate the release of corrosion inhibitor, the formation of LDH film, as well as the shape memory effect of coating defect for an efficient recovery of the corrosion resistance property. This novel coating system enables a corrosion-driven and location-specific repair with in-situ deposition of both an inhibitor film and an LDH film. As the first work to fully utilize and consume nanofillers on demand, this approach prevents inadequate use of healing agents, addressing a significant challenge in corrosion-driven self-healing coatings. The self-healing mechanism ensures target-oriented corrosion protection that makes the most efficient use of the healing substances.