Synergistic effect between 8-hydroxyquinoline and benzotriazole for the corrosion protection of 2024 aluminium alloy: A local electrochemical impedance approach

• 8-HQ and BTA present a synergistic effect for the corrosion protection of AA2024.
• 8-HQ mainly acts on the aluminium matrix.
• Action of BTA is limited to copper-rich particles.
• Mixing the two compounds, the galvanic coupling between the Al matrix and the particles disappears.

This work is devoted to the corrosion inhibition of the 2024 aluminium alloy (AA2024) in neutral aqueous solution by 8-hydroxyquinoline (8-HQ) and benzotriazole (BTA). First, current-voltage curves and global electrochemical impedance measurements confirmed that 8-HQ and BTA are two effective corrosion inhibitors for AA2024. Mixing the two compounds led to a synergistic effect for the corrosion protection of the alloy. From the impedance data analysis, it was shown that 8-HQ acted mainly on the aluminium matrix with an additional action of the BTA on the intermetallic particles. Then, to analyse the role of the inhibitors on the galvanic coupling between the aluminium matrix and the particles, local electrochemical impedance measurements were performed on a model system (Al/Cu couple). It was shown that in the presence of 8-HQ or BTA alone, the galvanic coupling between copper and aluminium was little reduced while in the presence of both compounds together it was strongly limited. The local impedance results confirmed the specific inhibition of the 8-HQ and of the BTA on Al and Cu respectively.