8-hydroxyquinoline directly loaded on graphene oxide for active protective performance of sol-gel coatings on aluminum alloys

The selection of containers and the method of loading corrosion inhibitors are crucial factors in simplifying the preparation process and enhancing the practicality of active protective coatings in the field of corrosion protection research. Using a straightforward solution adsorption method, corrosion inhibitor 8-hydroxyquinoline (8-HQ) was directly loaded onto graphene oxide (GO) to prepare GO@8HQ nanocomposite fillers. On the surface of GO, the adsorption and desorption of 8-HQ were controlled by regulating the pH, enabling the effective loading and release of the inhibitor. This process enhanced the active protective performance of the coating. 8-HQ exhibited a high loading capacity on GO, achieving an adsorption value of 264.1 mg/g at pH=1, and was released from the surface of GO as the pH increased. The GO@8HQ nanocomposite fillers were then applied in sol-gel coatings. Specifically, the coating with GO@8HQ (G@Q) showed minimal surface corrosion after a 72h salt spray test. The impedance modulus at 0.01 Hz (|Z|_0.01Hz) of G@Q was an order of magnitude higher than that of the sol-gel coating, owing to the release of 8-HQ upon the occurrence of corrosion. On the surface of GO, two interaction mechanisms—electrostatic adsorption and π-π conjugation—were confirmed through a molecular dynamics simulation of the adsorption of 8-HQ and GO in an aqueous solution. The results demonstrated that the direct loading method of the corrosion inhibitor offered a straightforward and efficient approach for the preparation of practical and active protective coatings.