Corrosion resistant coating with passive protection and self-healing property based on Fe3O4-MBT nanoparticles

This work synthesized novel Fe3O4 nanoparticles loaded with 2-mercaptobenzothiazole corrosion inhibitors (Fe3O4-MBT NPs), which possessed not only photothermal conversion property but also corrosion inhibition ability. The loading percentage of MBT inhibitors in the Fe3O4-MBT NPs was 9.69 wt.%. The obtained Fe3O4-MBT NPs were incorporated into a shape memory epoxy coating to achieve passive protection and self-healing property. The passive protection property of intact Fe3O4-MBT/epoxy coating was assessed using electrochemical impedance spectroscopy (EIS) measurement during immersion in 3.5 wt.% NaCl solution. The low-frequency impedance modulus at 0.01 Hz of the composite coating containing 3 wt.% Fe3O4-MBT NPs was approximately 5 times higher than that of the blank epoxy coating after 240 h of immersion, indicating the superior barrier property of the composite coating. As for the self-healing property, the scratch width on the coating surface could narrow from 80 µm to ∼5 µm after near-infrared (NIR) light irradiation for 30 s, which was ascribed to the excellent photothermal conversion property of Fe3O4 NPs. EIS results verified that both the scratch closure triggered by the photothermal conversion of Fe3O4 NP and the release of MBT inhibitors are beneficial for the suppression of corrosion activity within the coating scratch. The Fe3O4-MBT/epoxy coating with outstanding passive protection and self-healing property holds great potential to achieve long-term corrosion protection.