Bio-inspired superior barrier self-healing coating: Self-assemble of graphene oxide and polydopamine-coated halloysite nanotubes for enhancing corrosion resistance of waterborne epoxy coating

Bio-inspired dopamine have attracted immense scientific interest in the surface modification field due to the high bio-adhesive properties for varies substrate. Herein, the polydopamine (PDA) was used as a novel pH-response gatekeeper to be coated on the BTA-loaded HNTs hybrids (PBH) via conventional polymerization reaction (Tris HCl/pH=8.5), which can be destroyed in an acidic environment resulting in release of BTA. Further, the as prepared PBH were self-assembled with graphene oxide (GO) through π-π* interaction between GO and PDA. The waterborne epoxy coating (WEC) loaded with GO@PBH possessed superior barrier properties owing to the excellent shielding performance of GO nanosheets against the corrosive ions. The dual self-healing effect of GO@PBH based WEC for the carbon steel substrate mainly originated from release of BTA during corrosion process and the formation of complex between catechol of the damaged PDA polymer network and Fe 3+ . The barrier and self-healing properties of the composite coating were tested by electrochemistry and neutral salt spray test. The results prove that the WEC loaded with GO@PBH hybrids possesses superior barrier properties for the corrosion medium and outstanding self-healing effect as the corrosive ions reached the metal/coating interface.