Hydrophobic Antioxidant Polymers for Corrosion Protection of an Aluminum Alloy

We explore synthetic polymeric antioxidants as powerful inhibitors of corrosion of metals. Antioxidant copolymers were designed to have polyphenol, gallol, or catechol moieties along with hydrophobic groups brought by hexyl methacrylamide units. The polymers were deposited on aluminum alloy 2024-T3 as submicrometer thick films of individual polymers or as 10 wt % additives to epoxy-based ∼100 μm thick coatings. Thin antioxidant polymer films provided significant corrosion protection of AA2024. Unlike poly­(hexyl methacrylamide), which lacked polyphenol functional units, the antioxidant polymers were compatible with standard epoxy coatings and provided exceptional protection of surfaces in extreme corrosion conditions (0.6 M NaCl solution) for over 100 days. Anticorrosion performance of antioxidant-containing coatings was characterized using scanning electron microscopy, optical microscopy, and electrochemical impedance spectroscopy (EIS) and further evaluated with the equivalent electrical circuit analysis of the EIS data. Importantly, unlike small-molecule analogues, such as tannic acid, antioxidant copolymers were not leachable from epoxy coatings into water or ethanol. Taken together, these results show that antioxidant copolymers are efficient materials for protection of metals against corrosion.