Synthesis of self-healing composite coating due to development of corrosion-resistant of 2024 Al alloy

The aim of this research is to improve the corrosion resistance and create the active inhibitory in hybrid-silane coatings. Therefor the graphene oxide (GO) nano-sheets and the methylene triphosphonic acid (ATMP) were used as a protective pigment and organic inhibitor carrier in the coating, respectively. The peaks appearing in 1059, 1380, 1730, and 3430 cm-1 belong to hydroxyl stretching, carbonyl, hydroxyl bending, and epoxide groups confirmed the successful synthesis of GO nanoparticles by infrared transfer spectroscopy (FTIR). The displacement of two peaks of 230 and 250 nm in GO to 261 and 360 nm in GO-ATMP represent the successful reduction of graphene oxide by ATMP molecules. Then, the corrosion resistance of GO-ATMP coating was evaluated using electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that the ATMP inhibitor improves the corrosion resistance properties of the coating, and the corrosion current density is reduced as 50%. After successfully inhibiting adsorption on GO plates, the coating (GO-ATMP) was applied on 2024 aluminum alloy sheets. The results of EIS and salt-spray tests showed that the corrosion resistance properties of GO-ATMP coatings improved due to restrict the access of corrosive environment to the metal surface. The intelligent releasing of the inhibitor during electrolyte penetration in scratched area of the coating was confirmed by the formation of a protective film in the scratch area in the electron microscope image of the sample. This caused to restrict the electrochemical reactions.