Synergistic effect of graphene oxide@phosphate-intercalated hydrotalcite for improved anti-corrosion and self-healable protection of waterborne epoxy coating in salt environments

Abstract

Waterborne epoxy coatings (WECs), with significant anti-corrosion and self-healable performance, effectively inhibit the corrosion of the metal surface in salt environments and are highly desirable; however, it is still a challenge to achieve them; herein, we have demonstrated graphene oxide (GO) and phosphate (PO₄³⁻)-intercalated hydrotalcite (PIH) formed via electrostatic self-assembly to overcome this problem. The corrosion protective properties were characterized by an electrochemical experiment and a salt spray test. Due to the synergistic effect of the strong barrier performance of GO plus hydrotalcite, good dispersion of PIH enabled by GO, and the formation of a phosphate film at the metal/coating interface owing to sustainable ion-exchange between Cl⁻ and PO₄³⁻, the GO@PIH-based WECs exhibit superior anti-corrosion ability. By comparison, the failure time of the GO@PIH-based WECs was significantly prolonged to 30 days when compared with that of GO/WECs (15 days) and PIH/WECs (7 days). Interestingly, the GO@PIH/WECs also exhibit self-healing performance when the corrosive ions reach the metal/coating interface; this is attributed to PO₄³⁻ released from the PIH nanoplates; hence, the failure time of the GO@PIH/WECs is further prolonged.