Copper clusters, as nodules and micro dendritic masses, were observed to nucleate and grow on Al 2524 surfaces after corrosion immersion experiments for up to 5 days in 0.6 M NaCl solutions; with pH values ranging from 3 to 11. Cu clusters observed by SEM on the corroded surfaces and confirmed by EDX analysis were extracted or stripped from their original sites and examined in detail utilizing TEM and EDX spectrometry. These observations confirm a mechanism contributing to pitting corrosion in copper-rich aluminum alloys involving the plating or cementation of Cu2+ from solution as an electrochemical displacement reaction, resulting in nucleation and growth of Cu clusters on the aluminum alloy surface, and causing additional aluminum dissolution and pitting around the Cu deposits.