Incongruent dissolution of copper in an Al-Cu assembling. Influence of local pH changes.

ABSTRACT The aim of this work is to show that the presence of a crevice between copper and aluminium and the differential pH values inside and outside the crevice can induce copper dissolution and replating. This was first observed on an assembly between an AA2024 aluminium sheet and a rivet of same composition. The conditions encountered in a crevice were then obtained using a thin-layer electrochemical cell, in which a thin electrolyte layer of 150 µm was trapped between a pure copper and a pure aluminium electrode. A mechanism is suggested involving local acidification in the crevice, due to Al dissolution, pH increase towards the crevice opening and selective dissolution of cuprous oxide at the mouth. Cuprous oxide formation is replenished outside the crevice where oxygen reduction maintains an alkaline interface. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]