Corrosion and Anodizing Behavior of T1 (Al2CuLi) Precipitates in Al-Cu-Li Alloy

T-1 (Al2CuLi) phase precipitates, the main strengthening precipitates in third generation aluminum-copper-lithium (Al-Cu-Li) alloys, play a critical role in determining the corrosion behavior of these alloys. Herein, the T-1 precipitates, sufficiently large to be visualized by scanning electron microscopy, were intentionally grown in a commercial Al-Cu-Li alloy through a high temperature annealing process. The corrosion and anodizing behavior of the alloy associated with individual T-1 precipitate plates was subsequently investigated. It was observed that corrosion initiated instantaneously on T-1 precipitate plates when the alloy was exposed to laboratory air. When immersed in NaCl solution, T-1 precipitate plates corroded through a dealloying process and then, drove anodic dissolution of the adjacent aluminum alloy matrix by forming copper-rich nanoparticles at the sites of dealloyed T-1 precipitates. The T-1 phase precipitates were anodized relatively faster than the aluminum matrix in tartaric-sulfuric acid solution under a constant voltage of 14 V. The anodic film formed from T-1 precipitates was dissolved quickly by the anodizing electrolyte during anodizing at relatively higher temperatures, resulting in cavities of sizes similar to those of T-1 precipitate plates. (C) The Author(s) 2019. Published by ECS.