Predictive Evaluation of Aluminum Profile Corrosion Using Electrochemical Impedance Spectroscopy

This study investigates the time-dependent corrosion behavior of 6060 aluminum profiles subjected to three industrially relevant surface treatments: clear anodizing, black anodizing, and pre-anodizing followed by polyester powder coating during 30 days of immersion in NaCl solution. Electrochemical Impedance Spectroscopy combined with equivalent electrical circuit modeling was used to monitor corrosion evolution and identify the governing degradation mechanisms. Black-anodized specimens exhibited the highest initial corrosion resistance during the first 4 days of immersion, while clear-anodized specimens provided superior protection between 7 and 15 days due to the formation of a more protective inner oxide layer. Both anodized systems showed evidence of repassivation during prolonged exposure through corrosion product accumulation within the porous oxide structure. The pre-anodized/powder-coated system delayed corrosion initiation beyond 15 days, demonstrating the highest long-term barrier performance. Dynamic perpendicular impact loading after corrosion exposure revealed significant differences in mechanical durability: clear-anodized specimens maintained coating integrity up to 15 days, whereas black-anodized specimens experienced complete coating removal, associated with corrosion-induced microcracks and void formation observed by SEM. Overall, clear anodizing provided the best balance between corrosion resistance and post-corrosion mechanical durability, while the pre-anodized/powder-coated system offered the greatest long-term corrosion protection, demonstrating that the optimum surface treatment depends on the intended service conditions.