Optimizing the annealing process of sol–gel hybrid coating technology for corrosion barrier protection of Al

Abstract Corrosion, commonly associated with ferrous materials, also affects aluminum alloys. Given the degradation that corrosion can inflict on aluminum structures, this study focuses on optimizing nanostructured sol–gel silica-zirconia coatings to mitigate the diffusion of the electrolyte, thereby also limiting oxygen availability at the substrate. Using aluminum AA2024 T3 rod specimens of 3.5 mm thickness as substrates, coatings were synthesized via a sol–gel technique, employing tetraethylorthosilicate, 3-glycidoxypropyltrimethoxysilane, tetra-n-propoxyzirconium, and ethyl acetoacetate as precursors. The coatings, composed of a silicon matrix integrated with dispersed ZrO ₂ particles, were applied to the substrate through the dip-coating technique. Various temperatures were subsequently evaluated during the annealing process to achieve stabilization of the coatings. Surface roughness of the aluminum samples was evaluated before and after coating, alongside microhardness measurements. Surface morphology, coating thickness, and electrochemical impedance spectroscopy measurements (conducted in a 3.5% NaCl solution to simulate a marine environment) were assessed via scanning electron microscopy, highlighting the utility of these type of coatings for anti-corrosive protection of aluminum.