Anodic film growth on Al–Li–Cu alloy AA2099-T8

• DOI: 10.1016/j.electacta.2012.06.126
• Publication Date: 2012-07-15T23:17:02Z
• Authors: Y. Ma; X. Zhou; G.E. Thompson; M. Curioni; P. Skeldon; X. Zhang; Z. Sun; C. Luo; Z. Tang; F. Lu
• Keywords: Aluminum alloy; Grain orientation; 0103 physical sciences; Anodizing; Lithium; Film detachment; 01 natural sciences

{AA2099-T8} aluminium alloy was anodized at a current density of 5 {mA/cm} 2 to selected voltages in 0.1 M ammonium pentaborate electrolyte at 293 K. It was found that the growth of barrier-type anodic film on the alloy was accompanied by oxidation of intermetallics, formation and rupture of oxygen gas-filled voids in the anodic film and healing of the anodic film at the sites of rupture. It was revealed that the formation of oxygen gas-filled voids was related to the oxidation of copper-rich nanoparticles in the copper-enriched layer at the film/alloy interface, and that the oxidation process of copper-rich nanoparticles depended on grain orientation. Further, the significantly reduced Pilling-Bedworth ratio for formation of anodic lithium oxide compared with that for formation of anodic alumina resulted in the formation of fine voids at the alloy/film interface and sequentially, detachment of the anodic film from the alloy surface. ?? 2012 Elsevier Ltd.