Galvanic coupling between AA7075-T6 and AA2024-T3 intensifies local corrosion
M. Mopon (University of the Philippines Diliman, TU Delft - Group Garcia Espallargas)
J.M.C. Mol (TU Delft - Team Arjan Mol)
SJ Garcia (TU Delft - Group Garcia Espallargas)
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Abstract
This study demonstrates that galvanically coupling AA2024-T3 and AA7075-T6 affects localized corrosion even with the alloys’ comparable electrochemical behaviour. In situ reflected light microscopy tracked corrosion initiation and trench propagation, while zero resistance ammeter measurements quantified galvanic current density and potential. This combined approach allowed direct correlation between electrochemical signals and optically detectable surface phenomena. Galvanic coupling increased cathodic activity at AA2024-T3 intermetallic particles (IMPs) and caused the surrounding matrix to dissolve more extensively beyond the trench that formed around the particles. Local activity analysis revealed initial IMP dealloying was unaffected by galvanic coupling. However, lateral growth of trenches in both alloys was accelerated under coupling compared with electrically-isolated conditions. Correlation of optical activity with electrochemical measurements showed that trends and fluctuations in galvanic current and potential reflect different stages of local corrosion, facilitating the morphological and physicochemical interpretation of the electrochemical data.
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