Studies on the sealing processes of corrosion resistant coatings formed on 2024 aluminium alloy with tartaric-sulfuric anodizing

Anodizing and post-treatment of aluminium alloys can effectively improve their surface corrosion resistance. In this work, we demonstrate the effectiveness a potassium permanganate sealing (M-S) treatment of tartaric-sulfuric anodized 2024 aluminium alloy. This post anodic oxidation process was performed by immersing samples in the electrolyte solution at 70 degrees C for 30 min. Immersion and salt spray tests show such a M-S sealing processing can result in much improved corrosion resistance. The M-S treated samples can resist 240 h of salt spray test without corrosion pitting. Detailed morphological, microstructural and chemical analyses have been used to reveal mechanistic effects of the M-S retreatment. Interfacial electrochemical impedance measurements were performed to directly compare the corrosion behaviors of Al alloys after different post-treatments.