The influence of the inhibitor particle sizes to the corrosion properties of hybrid sol–gel coatings

Abstract

The influence of the inhibitor particle size (nano and micro cerium dioxide) embedded in several hybrid sol–gel coating systems for the corrosion protection of aluminium AA2024 alloy was studied, as well as the influence of other parameters like the inhibitor loading level and the method of reticulation. The properties of the obtained coatings were evaluated by means of transmission electron microscopy, accelerated salt spray test and electrochemical impedance spectroscopy. All the varied parameters proved to have an important influence on the corrosion mechanism, and an improvement induced by the use of nanometric inhibitors in comparison with the micrometric ones was demonstrated. In the case of the strong reticulated matrix, an inhomogeneous dispersion of the inhibiting species (micro inhibitor) favours the tension formation, making the coating more vulnerable to the corrosion attack. For the same doping level it was observed that the reticulation with 1-methylimidazole (MI) leads to a slightly better corrosion protection. Concomitantly, it was shown that high loadings with inhibitors have an adverse effect on the corrosion protection.