Localized electrochemical impedance for characterizing welded areas of dissimilar Al alloys 2024-T3 and 7475-T761 joined by FSW

• Autor(a) principal: ABREU, C.P. de
• Data de Publicação: 2017
• Outros Autores: COSTA, I., MELO, H.G. de, PEBERE, N., VIVIER, V., EUROPEAN CORROSION CONGRESS, 11th
• Tipo de documento: Artigo de conferência
• Título da fonte: Repositório Institucional do IPEN
• Texto Completo: http://repositorio.ipen.br/handle/123456789/27315
• topic: electric impedance; electrochemistry; aluminium alloys; friction welding; coupling; electrochemical corrosion

Friction Stir Welding (FSW) is an efficient way to join high strength aluminum alloys avoiding de-fects that are usually found when conventional techniques are adopted. The aeronautic industry has shown great interest in this welding method, either for joining similar or dissimilar alloys. However, FSW generates different microstructural areas that could give rise to galvanic couplings on the weld-ing area. In the present study, FSW was used to join two similar and dissimilar aluminum alloys, the AA2024 and the AA7475 alloys. To evaluate the effect of the welding process on the corrosion re-sistance of the joined alloys, electrochemical impedance spectroscopy studies, either global or local-ized (LEIS), have been carried out in a low corrosive medium (0.1 M Na2SO4) or with a small addi-tion of chlorides (0.1 M Na2SO4 + 0.001 M NaCl). A gel visualization technique was also employed to detect possible galvanic couplings of the different zones formed during the FSW welding. OCP measurements were also performed on both individual aluminum alloys and on the zones affected by FSW. LEIS investigations were performed at different locations above the different microstructural zones induced by the FSW process on both alloys. Galvanic coupling was clearly evidenced at the interface between the two alloys, contrary to the results reported in literature for the welding of simi-lar alloys, for which no galvanic coupling was evidenced.