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 experimen ts using samples of known AI-Cu ratios were used to evaluate the accuracy o f the technique and develop a calibration curve. The results demonstrated t he accuracy of the method to within 2%. The elemental copper remaining on t he surface of Al 2024-T3 samples after various pretreatment/corrosion proce dures 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 c opper redistribution on an Al 2024-T3 Sample in 0.5 M NaCl solution. (C) 19 99 The Electrochemical Society. S0013-4651(98)04-027-0. All rights reserved .