Local scanning electrochemical microscopy analysis of a lithium-based conversion layer on AA2024-T3 at progressive stages of formation

Scanning electrochemical microscopy (SECM) is employed to characterize the evolution of local electrochemical surface activity during lithium-based conversion layer formation on legacy aerospace aluminium alloy AA2024T3. Initially, three types of studied intermetallic particles - S-, 0- and constituent phases - act as active cathodic areas. Subsequently, 0- and constituent phases show passivation preceding that of S-phase particles during the later conversion layer formation stages. The entire surface, including the matrix region, shows a higher reactivity at the beginning and then gradually shows decreasing reactivity. Hydrogen evolution-generated bubbles attach to the alloy surface and locally hinder the conversion layer formation, weakening the corrosion protection the conversion layer provides at those locations.

Automated summary

This study uses scanning electrochemical microscopy (SECM) to characterize the evolution of local electrochemical surface activity during lithium-based conversion layer formation on aerospace aluminium alloy AA2024T3. It finds that different types of intermetallic particles show different levels of activity during different stages of conversion layer formation, and the overall reactivity of the surface decreases gradually over time.