Effect of covalent organic framework modified graphene oxide on anticorrosion and self-healing properties of epoxy resin coatings

Graphene oxide (GO) can enhance the corrosion resistance of epoxy coating, but there are problems such as poor filler dispersion and mechanical damage that will reduce the coating corrosion resistance. To resolve these problems, here, we used a facile and green liquid-phase synthetic strategy to grow covalent organic framework (COF) on GO sheets with 1,3,5-Triformylphloroglucinol and p-phenylenediamine as monomers for the COF synthesis. The COF could not only improve the compatibility of GO with epoxy coating, but also act as a nanocontainer for loading corrosion inhibitors. Electrochemical impedance spectroscopy showed that the low-frequency impedance of GO/COF-2% coating immersed in 3.5 wt% NaCl solution for 60 days was 8.58 × 108 Ω cm2. This was one order of magnitude higher than that of GO-2%, showing excellent corrosion resistance. Then, corrosion inhibitor of benzotriazole (BTA) was loaded into GO/COF, where the adsorption and release of BTA was controlled by environmental pH values. Results proved that the GO/COF@BTA-2% reinforced epoxy coating had superior corrosion resistance as well as self-healing ability because of the good compatibility, greater crosslinking density and controllable release of BTA.