Localized corrosion of 2024 T351 aluminium alloy in chloride media

The corrosion behaviour of 2024 T351 alloy was studied in chloride solutions. The polarization curve of this ahoy showed two breakdown potentials, The first was related to the dissolution of the coarse intermetallic Al2CuMg particles. A severe Mg dealloying of the particles resulted in Cu-rich remnants. The matrix surrounding the particles was systematically found to be dissolved. Indeed, the particles are surrounded by a dispersoid-free zone which is anodic in comparison to both the rest of the matrix and the S phase particles. The second breakdown potential corresponded to the matrix breakdown potential. Pits but also intergranular corrosion developed. Grain boundaries were preferentially attacked because they are anodic in comparison to the grain body and the previous dissolution of the intergranular precipitates made them fragile. (C) 1999 Elsevier Science Ltd. All rights reserved.