Corrosion mechanism associated with T1 and T2 precipitates of Al-Cu-Li alloys in NaCl solution

To clarify the corrosion mechanism associated with T1 and T2 precipitates in Al-Cu-Li alloys, the simulated bulk precipitates of T1 and T2 were fabricated through melting and casting, their electrochemical behaviors and coupling behaviors with alpha(Al) in NaCl solution were investigated. Meanwhile, simulated Al-Cu-Li alloys containing T1 and T2 particles, respectively, were prepared and their corrosion morphologies were observed. A corrosion conversion mechanism associated with the precipitates of T1 and T2 was advanced. The precipitates of T1 and T2 are anodic to the alloy base and corrosion occurs on their surface at the beginning. While, during their corrosion process, the preferential dissolution of Li and the enrichment of noble element Cu make their potential move to a positive direction. As a result, the corroded T1 and T2 precipitates become cathodic to the alloy base at a later stage, leading to the anodic dissolution and corrosion of the alloy base at their adjacent periphery. However, due to more amount of active element Li and much less amount of noble element Cu in the precipitate of T2, the electrode conversion of T2 from anode to cathode is more superficial than that of T1, and the corrosion mainly occurs in T2. (c) 2007 Elsevier BX All rights reserved.