Photothermally activated self-healing coatings for corrosion protection: A review

Self-healing coatings with the ability to effectively recover their barrier property upon damage is essential to protect metal substrates against corrosion. This paper provides a comprehensive summary of the research progress for photothermally activated self-healing coatings, which can remotely activate the repair of coating damage and restore their corrosion resistance through convenient light irradiation. Among the different types of photothermal-responsive materials, carbon-based materials, organic species, plasmonic nanomaterials, MXene, and Fe3O4 nanoparticles are commonly used as fillers in self-healing coatings. These photothermal fillers generate abundant heat under specific light irradiation at certain wavelengths, stimulating a series of physical or chemical reactions for recovering the barrier properties of coatings. Based on intrinsic and extrinsic self-healing strategies, several photothermally activated self-healing methods, including the melting of coating matrix or fillers, shape memory effect and thermoreversible reaction of coating matrix, and release of corrosion inhibitors, are introduced. Typical self-healing performance and advantages and weaknesses of different self-healing mechanisms are elaborately discussed. Compared with extrinsic self-healing strategies, intrinsic ones can improve the cyclic self-healing performance under photothermal excitation. Moreover, a combination of multiple healing mechanisms yields excellent self-healing performance, which facilitates the long-term protective capability of coatings. Finally, current difficulties and future development perspectives associated with photothermally activated self-healing coatings are analyzed to promote research development and expand engineering applications.