The role of coarse intermetallics in the localized corrosion behaviour of AA 2024-T3 in low concentrated chloride media

• Autor(a) principal: Queiroz, F. M.
• Data de Publicação: 2008
• Outros Autores: Costa, I., Magnani, M. [UNESP], De Melo, H. G.
• Tipo de documento: Artigo de conferência
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://nace.confex.com/nace/ICC08/webprogram/Paper3411.html; http://hdl.handle.net/11449/70767
• topic: AA 2024-T3; EIS; Intermetallic compounds; TEM; 2024-T3; Chloride media; Compositional changes; Corrosion behaviour; EDS analysis; Electrochemical investigations; ELectrochemical methods; Electrochemical response; Engineering materials; Heterogeneous composition; Heterogeneous reactions; Localized corrosion; Nominal composition; Selective corrosion; SEM observation; SEM/EDS; Test electrolyte; Aerospace industry; Aluminum corrosion; Chlorine compounds; Corrosion prevention; Corrosive effects; Reaction rates; Transmission electron microscopy; Intermetallics

Aluminium alloy (AA) 2024-T3 is an important engineering material due to its widespread use in the aerospace industry. However, it is very prone to localized corrosion attack in chloride containing media, which has been mainly associated to the presence of coarse intermetallics (IMs). In this work the corrosion behaviour of aluminium alloy 2024-T3 in low concentrated chloride media was investigated using microscopy and electrochemical methods. SEM observations have shown that intermetallics with the same nominal composition present heterogeneous reaction rates, and that both types of coarse IMs normally found in the AA 2024-T3 microstructure corrode. Moreover, EDS analyses have shown important compositional changes in the corroded IMs, evidencing the selective corrosion of their more active constituents and the onset of an intense oxygen peak, irrespective to the IM nature. TEM/EDS observations on non-corroded samples have evidenced the heterogeneous composition within the IMs. On the other hand, the results of the electrochemical investigations, in accordance with the SEM/EDS observations, have evidenced that IMs corrosion dominates the electrochemical response of the alloy during the first hours of immersion in the test electrolyte. © 2009 by NACE International.