Incorporation of Modified Graphene Oxide into Hybrid Sol–Gel Coatings on Aluminum Alloy to Improve Mechanical and Anticorrosion Properties

Hexavalent chromium (Cr6+) based coatings are currently the industry standard for protecting aluminum surfaces from corrosion while improving the corrosion resistance. As hexavalent chromium compounds are known carcinogens and lead to negative impacts in the environment, there is a need to develop safer coatings with comparable performance. In this study, a suite of corrosion and abrasion resistant composite coatings were prepared via the sol–gel method using 3-(aminopropyl)triethoxysilane (APTES), 3-glycidyloxypropyl trimethoxysilane (GPTMS), and phenyltrimethoxysilane (PTMS), which incorporated graphene oxide (GO) and APTES-functionalized graphene oxide (fGO) coated on an aluminum alloy, AA2024-T3. The effect of the ratio of the incorporated materials and the coating thickness on the corrosion resistance as well as the mechanical properties, including hardness, Young’s modulus, and abrasion resistance, of composite coatings was examined. Electrochemical corrosion testing indicated that all of the developed coatings provided over 95% corrosion protection efficiency, while fGO-containing coatings achieved over 99.9% protection efficiency and a nearly 104 times decrease in corrosion current. Furthermore, hardness of the coatings was improved with incorporation of fGO, from 0.25 to 0.61 GPa, which contributed to the observed increase in abrasion resistance. The abrasion strength remained stable in the fGO-containing coatings under the salt spray test, indicating that the fGO-containing coatings maintain their stability even under harsh conditions.