Smart self-healing coatings based on halloysite nanotube/reduced graphene oxide loaded with corrosion inhibitors

In the harsh marine environment, epoxy resin is prone to interface mismatch with nano-fillers, leading to rapid failure of anti-corrosion coatings. The excellent thermal stability and bonding ability of hollow nanotubes in halloysite nanotube can enhance the corrosion resistance of the coating. In this paper, graphene oxide (GO) was reduced to reduced graphene oxide (rGO) by reduction-coagulation method and combined with halloysite nanotube (HNT) to become HNT/rGO, then the novel nanofiller HNT-CS/rGO was synthesized by loading the corrosion inhibitor benzotriazole (BTA) in HNT and coating chitosan (CS). The introduction of 2D rGO material not only effectively strengthened the passive barrier ability of the coating, but also improved the interfacial compatibility between the filler and the epoxy resin. In the test of the fracture toughness of the coating, the fracture toughness of the composite coating with HNT/rGO filler reached 1368.78 J/m², which was significantly increased compared with the 586.14 J/m² of the pure epoxy resin coating. The low-frequency impedance mode value of the composite coating with 2 wt% HNT-CS/rGO added exceeded 10¹⁰ Ω.cm² for the first 28 days, providing very excellent corrosion protection. Meanwhile, confocal laser scanning microscope showed that the composite coating with 2 wt% HNT-CS/rGO was significantly better than the pure epoxy coating in terms of corrosion at the scratch, which proved that it had a good self-healing performance. The above shows that HNT-CS/rGO modified epoxy coating has both excellent passive barrier and active repair performance, which can effectively resist the harsh marine environment and realize long-term corrosion protection.