The influence of rare earth mercaptoacetate on the initiation of corrosion on AA2024-T3 Part II: The influence of intermetallic compositions within heavily attacked sites

• Effect of intermetallic clustering was investigated on the surface of AA2024-T3.
• Both rare earth mercaptoacetate inhibitors stifled the corrosion ring formation.
• Surface area and the number of domains were critical for severely corroded sites.
• Most clustered sites were not always the most severely attacked sites.

Localised corrosion is typical on AA2024-T3 due to intermetallic particles embedded in the alloy. The effect of intermetallic compositions on corrosion are not yet fully understood. EPMA data on AA2024-T3 surfaces before and after a 16 min immersion, analyses the influence of intermetallic clustering on the severity attack at local sites. While sites with a high number of domains and a large S-phase surface area typically lead to severe attack, maximising these features did not always lead to severe corrosion attack. Cerium or praseodymium mercaptoacetate inhibited corrosion ring formation. The common trends observed from such attack sites was also discussed.