Comparative Study of Anodic Film Formation on High-Strength Aluminium Alloys in Tartaric–Sulfuric Acid Electrolyte

The anodizing behaviour of four high-strength aluminium alloys (AA2024-T3, AA2198-T8, AA2198-T851, and AA7475-T761) in tartaric–sulfuric acid (TSA) under identical constant voltage conditions was investigated. Significant differences were found in current density, anodic film thickness, and anodizing efficiency. An inverse relationship was observed between total charge consumption and film thickness. Among the alloys, AA7475-T761 exhibited the greatest film thickness and highest efficiency, whereas AA2024-T3 showed the highest charge consumption and the thinnest film. The Al–Cu–Li alloys exhibited similar anodizing behaviour. All anodic films revealed porous, sponge-like morphologies attributed to oxygen evolution. Variations in film thickness are correlated to alloy compositions.