Macroscopic and local filming behavior of AA2024 T3 aluminum alloy during anodizing in sulfuric acid electrolyte

The anodic film generated in acid electrolytes on high-purity aluminum shows a porous morphology, formed by the packing of approximately hexagonal cells of alumina, containing a centrally located cylindrical pore. Conversely, during anodizing of an AA2024 T3 alloy, the presence of alloying elements, both in solid solution and as second-phase material, influences the filming behavior, with a less regular film morphology developed above the aluminum alloy matrix, and characteristic morphologies generated above and in the zone of influence of second-phase particles. Further, the anodizing behavior of the alloying elements is determined by the applied potential. In this work, the anodizing behavior of AA2024 T3 commercial alloy in sulfuric acid electrolyte has been characterized. Specifically, phenomena related to the oxidation of the second-phase particles have been separated from those associated with the oxidation of the copper-containing aluminum matrix. This has used electrochemical data obtained under potentiostatic and potentiodynamic conditions for the AA2024 T3 alloy, high-purity aluminum, and model Al-Cu alloys, which have been correlated with detailed examination of plan and sectional views of the anodized substrates. (C) 2008 The Electrochemical Society.