Photothermal and pH dual-responsive self-healing coating for smart corrosion protection

Abstract

• Sandwich-like rGO@MS-P-BTA microcapsules are designed to achieve both the pH-sensitive and photothermal-responsive actions. • rGO@MS-P-BTA microcapsules are incorporated into epoxy to prepare a self-healing coating. • The photothermal effect of rGO can not only activate the shape memory effect of epoxy, but also facilitate the release of BTA to suppress the corrosion activity. • PDMAEMA as a pH-driven “gatekeeper” realizes the controlled release of BTA. • The self-healing coating shows a fast healing effect and a prominent healing efficiency. A novel self-healing coating with photothermal and pH dual-responsive properties has been designed to protect carbon steel against corrosion by loading the stimuli-responsive microcapsules into a shape memory epoxy coating. The sandwich-like microcapsules were based on reduced graphene oxide/mesoporous silica (rGO@MS) assembled with a pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) layer, and were loaded with benzotriazole (BTA) inhibitors (abbreviated as rGO@MS-P-BTA). Under near-infrared (NIR) light irradiation, the prominent photothermal effect of rGO could not only elevate the coating temperature to activate the shape memory effect and close the coating scratch, but also facilitate the release of corrosion inhibitors to suppress the corrosion activity. Moreover, the PDMAEMA as a pH-driven “gatekeeper” realized the controlled release of BTA from microcapsules at acid conditions. The surface morphology analysis, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) were performed to evaluate the self-healing performance of the composite coatings. The results showed that the combination of NIR light and pH-responsive self-healing effects endowed the coating with short healing time and prominent healing efficiency.