Photothermally activated self-healing protective coating based on the "close and seal" dual-action mechanisms

In this work, a dual-action self-healing coating with excellent photothermal response to both near-infrared (NIR) laser and sunlight irradiation was prepared. The coating was composed of a shape memory epoxy matrix embedded with poly (epsilon-caprolactone) (PCL) microspheres, the surface of which was covered by titanium nitride nanoparticles (TiN NPs) to achieve the superior photothermal conversion ability. Upon light irradiation, the PCL@TiN composite microspheres could efficiently absorb light energy and generate sufficient heat to induce the shape memory recovery of coating defect as well as the melting of PCL to seal the scratch. Morphology observation and electrochemical measurements proved that the coating incorporated with 10 wt% of PCL@TiN microspheres presented an excellent self-healing performance under 30 s of NIR illumination to recover the barrier property. In addition, the photothermal conversion of PCL@TiN microspheres could accelerate the evaporation of water around the coating scratch, hence restraining the corrosion activity in the damaged region. The outdoor exposure test on the atmospheric corrosion monitor (ACM) covered by the coating confirmed that sunlight also benefited to achieve the prominent self-healing performance and shorten the water evaporation time, leading to much reduced corrosion current outputs hence improved corrosion protection property.