Early warning and self-repair properties of o-phenanthroline modified graphene oxide anti-corrosion coating

Smart coatings play a crucial role in achieving excellent corrosion protection on metals and alloys. However, the preparation of smart composite coatings with a dual function of self-reporting and self-healing remains a challenge. In this paper, 1,10-phenanthroline-5-amine (Phen) was grafted onto graphene oxide (GO) by the dehydration condensation method, and flaxseed oil crosslinked o-phenanthroline-modified graphene oxide (PGO) was used as the core and polyurea-formaldehyde (PUF) as the wall, and the harvesting emulsion method and in situ polymerization method were used to prepare microcapsules. The effects of stirring speed, temperature, polyvinyl alcohol (PVA) content and core-to-wall ratio on the dispersion of grafting and reaction conversion rate, as well as the microcapsule encapsulation rate, drug loading, and size were investigated to derive the optimal grafting process of PGO and the optimal preparation process parameters of microcapsules. Finally, the prepared microcapsules were incorporated into the epoxy coating, and the early warning, self-repairing and anticorrosive properties of the composite coatings with different microcapsule contents were investigated by impregnation test and electrochemical test. The results showed that the optimal grafting process of PGO was at a temperature of 80 °C, a stirring speed of 750 rpm, and an initial pH of 2. The optimal preparation process parameters of microcapsules were: stirring speed 500 rpm, reaction temperature 50 °C, optimal PVA content 6 % of urea, core to wall ratio 1.25:1. When the addition of PGO was 0.3 wt% and the microcapsule addition amount was 15 wt%, the composite coating showed the best early warning, self-healing and anti-corrosion performance. The warning response time was 5 min, the repair rate was 95.92 %, and the anti-corrosion performance was improved by 10 times.