Self-alignment of cationic graphene oxide nanosheets for anticorrosive reinforcement of epoxy coatings

Designing coatings with long term anticorrosion performance remains a great challenge. Herein, a newfangled cationic dopamine-reduced graphene oxide (DRGO+) nanosheet is prepared as a filler for epoxy coating via simple dopamine oxidative self-polymerization and ionization reaction. DRGO+ can be dispersed stably in commercial water-based cathodic epoxy emulsion for more than 45 days without precipitation. Due to the presence of –NH3+ in DRGO+, it can be self-aligned parallel arrangement in the composite coating (DRGO+/EP coating) under the electric field. This highly parallel DRGO+ nanosheets tremendously improve the physical barrier effect of the coating and prolong the penetration path of the corrosive medium. Electrochemical impedance spectroscopy (EIS) test showed that the initial low-frequency impedance modulus of 0.5%-DRGO+/EP coating is as high as 4.79 × 1010 Ω cm2 when the content of DRGO+ is 0.5 wt%, which is an order of magnitude higher than that of pure epoxy coating (4.07 × 109 Ω cm2), exhibiting extraordinary corrosion resistance. Finally, the protective mechanism of composite coating is revealed by the identification of corrosion products and local-EIS techniques. In view of the validity of DRGO+, this work highlights the potential route for the large-scale preparation of coatings with superior long-term anti-corrosion.