When all intermetallics dealloy in AA2024-T3: Quantifying early stage intermetallic corrosion kinetics under immersion

A hyphenated optical-electrochemical technique and image analysis protocol is used to quantify global and local (intermetallic) corrosion process and kinetics. Our findings reveal an early stage (< 60 s) composition-dependent hierarchical local activation of all IMs that can be attributed to IM dealloying. This is followed by local trenching initiated at matrix locations adjacent to regions of the IMs previously dealloyed, which in turn develops into concentric trenching around the IMs. These stages have quantifiable activation times and kinetics. While dealloying kinetics are found to be strongly dependent on IM composition and slightly dependent on IM size in the case of the S-phases, trenching kinetics are IM composition and size independent.