Self-healing anti-corrosive coating using graphene/organic cross-linked shell isophorone diisocyanate microcapsules

Abstract

To enhance the anticorrosive performance of coatings in harsh corrosive environments, a graphene/isophorone diisocyanate (IPDI) microcapsule is prepared by in-situ polymerization. The self-healing and anticorrosive performance of coatings based on these microcapsules are studied. The microcapsule with cross-linked shells prepared in this study solves the problems of excessive size and insufficient strength of traditional microcapsules. The addition of microcapsules improves the anticorrosive performance of coatings. The shape of the microcapsules is in the form of round balls, and the average particle size and thickness of the microcapsules are in the range of 17–23 μm and 0.5–3.4 μm, which are conducive to the preparation of the coatings. The average strength of microcapsules is 20.64 MPa and the wrap-around rate reaches 68%. The microcapsules have an initial evaporation temperature of 231.3 °C， the graphene organic cross-linking shell enhances the strength and improves the thermal stability of microcapsules. The electrochemical impedance spectroscopy (EIS) indicates that the |Z|_{f=0.01 Hz} value of the coating with 10 wt% of microcapsule after 168 h of immersion is about 9.4 × 10⁹ Ω cm², nearly three orders of magnitude higher than that of the coating without microcapsule (6.9 × 10⁶ Ω cm²). Monitoring the artificial scratches of coating using a scanning electron microscope (SEM) for 24 h reveals that the microcapsule repairs the cracks well. It is demonstrated that the incorporation of graphene/IPDI microcapsules improves the anti-corrosive performance of the coating.