The influence of rare earth mercaptoacetate on the initiation of corrosion on AA2024-T3 Part I: Average statistics of each intermetallic composition

• The effect of intermetallic clustering was investigated on the surface of AA2024-T3.
• Both rare earth mercaptoacetate inhibitors stifled the de-alloying process of S-phase.
• Each intermetallic particle type appeared to participate in local corrosion reactions.
• There was some level of clustering between S-phase and other intermetallic particle types within a 25 μm radius.

De-alloying of S-phase in AA2024-T3 in the presence chlorides, is well-known. However, it is unclear how rare earth mercaptoacetate inhibitors affect this process when immersed in a 0.1 M NaCl solution. This paper analyses data obtained using EPMA on AA2024-T3 surfaces before and after a 16 min immersion period. Cerium and praseodymium mercaptoacetate inhibited the de-alloying process of S-phase particles. Although no significant change in composition was observed for cathodic intermetallics, each appeared to participate in local corrosion reactions as evidenced by the development of surface oxides. Clustering between S-phase and one of the Cu-containing intermetallic domains was also evident.