rGO@APTES/hybrid sol-gel nanocomposite for corrosion protection of 2024 aluminum alloy

In this work, Graphene Oxide (GO) nanoplates were silanized using 3-aminopropyltriethoxysilane (APTES) and dicyclohexylcarbodiimide (DCC) through carboxylic and epoxide groups to obtain reduced GO (rGO)@APTES nanoplates. The rGO@APTES nanoplates were characterized by SEM, FTIR, and XRD techniques. Much better dispersion of the functionalized nanoplates in the hybrid silane mixture (prepared by equimolar mixing of TEOS and GPTMS) was revealed by visual and TEM images. Afterward, the hybrid sol-gel nanocomposites containing different concentrations of the rGO@APTES nanoplates were applied on Al 2024 substrate. Uniform, dense, defect-free and adherent sol-gel films were obtained in all cases. Decreasing of the water contact angle on the surface was much lower than expected due to removal of the oxygen-containing polar groups in the GO structure. Also, the corrosion behavior of the nanocomposites was evaluated after different immersion times in 3.5 wt.% NaCl solution by EIS measurements. The corrosion resistance of the sol-gel coating was significantly improved after incorporation of the rGO@APTES nanoplates. The sol-gel nanocomposite with 100 ppm rGO@APTES content showed the highest polarization resistance which this concentration was much lower than that reported in similar works. The results obtained by the EIS measurements were confirmed by the visual and microscopic observations after the corrosion tests.