Synthesis of graphene oxide nanosheets decorated by nanoporous zeolite-imidazole (ZIF-67) based metal-organic framework with controlled-release corrosion inhibitor performance: Experimental and detailed DFT-D theoretical explorations.

For the first time, the zeolite-imidazole (ZIF-67) framework, a new subfamily of metal-organic frameworks (MOFs), is synthesized on the graphene oxide (GO) platform. Co (as a central atom) and 2-methylimidazole (as organic ligands) were assembled to fabricate ZIF-67/GO NPs for providing epoxy-based anti-corrosion coatings with both active (self-healing) and passive (barrier) performance. Also, the ZIF-67/GO NPs were modified by 3-Aminopropyl triethoxysilane (APS) to improve the particles compatibility with the epoxy matrix and control their solubility in saline media. The FE-SEM, FT-IR, UV-Vis, Raman, TGA, and low-angle XRD techniques were used to prove the successful ZIF-67 particles growth onto the GO platforms. Tafel (potentiodynamic) polarization test demonstrated that the ZIF-67/GO@APS NPs could protect the surface of steel through mixed anodic/cathodic type (O reduction/Fe oxidation) mechanisms and the corrosion current density of the iron sample decreased to 1.41 µA·cm. Interestingly, the epoxy coatings containing ZIF-67/GO and ZIF-67/GO@APS particles revealed long-term corrosion protection durability and outstanding self-healing anti-corrosion performance, which were well studied via EIS, salt spray, cathodic delamination, and pull-off techniques. The impedance value at the lowest frequency for the coating containing ZIF-67/GO@APS after 50 days decreased from 10.7 Ω·cm to 10.2 Ω·cm that showed the lowest reduction among the studied samples.