Comparative analysis of the anticorrosive properties of trivalent chromium conversion coatings formed on 2024-T3 and 2024-T351 aluminium alloys. (1st May 2020)

• Record Type: Journal Article
• Authors: Verdalet-Guardiola, X.; Saillard, R.; Fori, B.; Duluard, S.; Blanc, C.
• Is Part Of: Corrosion science. Volume 167(2020)
• Publication Date: 2020-05-01
• Subjects: A. Aluminium -- A. Copper -- A. Intermetallics -- B. EIS -- B. Polarisation -- C. Oxide coatings; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.108508
• Languages: English
• ISSNs: 0010-938X

Abstract

Graphical abstract: Highlights: TCP coated AA2024-T3 had better corrosion resistance than AA2024-T351. The corrosion behaviour of TCP coated samples depended on the surface Cu coverage. High surface Cu coverage θCu led to thicker and/or more defective coatings. The dealloying of large Cu-rich IMCs could lead to Cu-rich sponges, then high θCu . A defective coating formed at grain boundaries decorated by Cu-rich precipitates. Abstract: The anticorrosive properties of the trivalent chromium process (TCP) coatings were studied for a 2024 aluminium alloy (AA2024) in both T3 and T351 metallurgical states. Better corrosion resistance was measured for the TCP coated AA2024-T3 compared to AA2024-T351, which was clearly related to the surface copper coverage measured after the pre-treatments for the different samples. The differences were explained considering the reactivity of both the S-phase coarse intermetallics (IMCs) and intergranular Cu-rich precipitates during deoxidation. Large S-phase IMCs and numerous intergranular Cu-rich precipitates constituted critical metallurgical parameters for the anticorrosive properties of the TCP coatings.