DIRECT OBSERVATION OF INTERGRANULAR CORROSION IN AL-4 WT-PERCENT CU ALLOY

Transmission electron microscopy (TEM) was used to study intergranular corrosion of aged Al-4 Wt% Cu by direct observation of identical regions of grain boundary before and after immersion in aqueous corrosion environments containing KCl plus K//2CrO//4 and KCl plus K MnO//4. All experimental results and observations were shown to be consistent with a simple theory of intergranular corrosion based on the location and extent of copper depleted anodic dissolution sites. Furthermore, similarities were shown to exist between intergranular corrosion and intergranular stress corrosion cracking (SCC) of Al-4 Wt% Cu.