A long-term anti-corrosion and cathodic delamination resistant epoxy coating based on COF grafted GO nanofillers

Here, a long-term anti-corrosive epoxy (EP) coating based on nano-hybrid filler was developed. The surface of graphene oxide (GO) was aminated with (3-aminopropyl) triethoxysilane (APTES), and then the porous covalent organic framework (COF) was in-situ grown on amino functionalized graphene oxide (FGO) nanosheets by Schiff-based reaction to prepare FGO-COF nanofillers. Different characterization methods proved the successful modification of GO nanosheets with COF particles. The excellent water resistance of composite coatings was characterized through contact angle, adhesion, and water uptake tests. Transmission electron microscope (TEM) and molecular dynamics (MD) methods showed that the grafting of COF enhanced the dispersion and compatibility of GO in the coating. EIS measurements, salt spray analysis and cathodic delamination test indicated the significant improvements in the protective properties of the composite coatings compared with pure EP coating. The low-frequency impedance modulus of 1% FGO-COF composite coating reached higher than 6.8 × 10 9 Ω·cm 2 after immersed in sea water for 60 days. In addition, the 1% FGO-COF composite coating performed only 34% delamination ratio after 120 h cathodic delamination test.