PDMAEMA as a pH/temperature- responsive switch enhanced corrosion resistance of self-healing epoxy coatings

A dual-responsive self-healing epoxy coating was developed by incorporating a smart microcapsule (rGO@SiO₂-95S-P). PDMAEMA acted as a responsive gatekeeper, enabling faster 95S release under acidic conditions and at temperatures below its LCST range. Meanwhile, the photothermal conversion of rGO increased the coating temperature under 808 nm NIR irradiation, enhancing epoxy-chain mobility and promoting partial scratch closure. UV-Vis spectroscopy, infrared thermography, optical microscopy, electrochemical measurements, and SEM/EDS were employed to evaluate the responsive release, scratch-recovery behavior, and corrosion protection of the coating. Under NIR irradiation for 600 s, the composite coating reached 48.6 °C and exhibited an average scratch-width reduction of 0.5321 mm. After scratching and NIR treatment, the coating maintains a relatively high |Z| f= 0.01Hz of 5.08 × 10 5 Ω·cm 2 and an R ct of 8.922 × 10 5 Ω·cm 2 . At pH= 3, the composite coating exhibited an I corr of 1.286 × 10 −8 A·cm −2 and an R ct of 2.053 × 10 7 Ω·cm². SEM/EDS observations further revealed a comparatively uniform Q235 steel surface with fewer coarse corrosion products under acidic conditions. These results demonstrate that the combination of responsive inhibitor release, NIR-induced partial scratch closure, and physical barrier protection provides the composite coating with effective corrosion protection, particularly under acidic conditions. Download: Download high-res image (140KB) Download: Download full-size image