Copper nucleation and growth during the corrosion of aluminum alloy 2524 in sodium chloride solutions

Copper clusters, as nodules and micro dendritic masses, were observed to nu cleate and grow on Al 2524 surfaces after corrosion immersion experiments f or up to 5 days in 0.6 M NaCl solutions; with pH values ranging from 3 to 1 1. Cu clusters observed by SEM on the corroded surfaces and confirmed by ED X analysis were extracted or stripped from their original sites and examine d in detail utilizing TEM and EDX spectrometry. These observations confirm a mechanism contributing to pitting corrosion in copper-rich aluminum alloy s involving the plating or cementation of Cu2+ from solution as an electroc hemical displacement reaction, resulting in nucleation and growth of Cu clu sters on the aluminum alloy surface, and causing additional aluminum dissol ution and pitting around the Cu deposits. (C) 2001 Kluwer Academic Publishe rs.