Analysis of PEO coating on AA2024 alloy after immersion in saline solution

The AA2024-T3 aluminum alloy is widely used in aerospace vehicle structures due to its high mechanical strength, resulting from the precipitation of intermetallic phases. However, these phases can cause localized corrosion, necessitating treatments for use in more aggressive environments. In this study, the AA2024-T3 (Alclad) alloy was immersed in a NaCl solution (0.1 M) under two conditions: I) as supplied and II) treated superficially by Plasma Electrolytic Oxidation (PEO), to evaluate the effect of the PEO process on the corrosion resistance of the alloy in a saline environment. For this purpose, ASTM G31 standard and other characterization techniques such as SEM/EDS and FT-IR were used. Both samples exhibited severe corrosion after exposure for 2 months in the saline medium, evidenced by surface darkening and mass loss, with 0.6133 g for the untreated sample and 1.2707 g for the treated one. Due to the characteristics of the PEO process, such as the presence of micro-arcs, the more corrosion-resistant aluminum layer was broken on the surface of the treated 2024 alloy, resulting in the presence of alloying elements and precipitation of coarse intermetallic phases, which allowed for localized corrosion.