Copper redistribution during corrosion of aluminum alloys

We describe a new quantitative electrochemical technique for measuring the copper redistribution that occurs during corrosion and pretreatment of high-strength copper-containing aluminum alloys. Underpotential deposition (upd) of Pb on Cu was used to assay the surface coverage of Cu. Model experiments using samples of known Al-Cu ratios were used to evaluate the accuracy of the technique and develop a calibration curve. The results demonstrated the accuracy of the method to within 2%. The elemental copper remaining on the surface of Al 2024-T3 samples after various pretreatment/corrosion procedures was determined using the upd technique. A simple treatment involving open-circuit etching of the alloy surface in 3 M HNO₃ was found to be most efficient for the removal of Cu from the Al alloy surface. In accord with a recent observation of Bucheit et al.,¹ convection was found to enhance copper redistribution on an Al 2024-T3 sample in 0.5 M NaCl solution.