Electrochemical characterization of alloy segregation in the near-surface deformed layer of welded zones of an Al−Cu−Li alloy using scanning electrochemical microscopy

•Characterization of the near-surface deformed layer (NSDL) in FSWelded 2098-T351.•Spatially resolved electrochemical activity in NSDL obtained by potentiometric SECM.•Mg-enriched bands affect the electrochemical behavior of welded areas.•The NSDL has an anodic electrochemical behavior with respect to the bulk material.•Highest activity for Mg2+ dissolution observed in the HAZ of the retreating side. The development of heterogeneous electrochemical activity in the welded zones of aluminum alloy 2098-T351 by friction stir welding (FSW) associated with the formation of a near-surface deformed layer (NSDL) upon exposure to an aqueous chloride-containing solution was characterized using scanning electrochemical microscopy (SECM) in potentiometric operation. A solid-contact Mg2+ ion-selective microelectrode allowed in situ monitoring of the corrosion reactions sites for magnesium dissolution from different zones of the FSW weld upon exposure to a chloride-containing aqueous environment. In this way, localized corrosion reactions developing in the galvanically coupled joint/heat affected zones (WJ/HAZ) of the weld were detected and imaged with spatial resolution. The most active domains for local Mg2+ concentrations were associated with the HAZ of the retreating side (RS), and these corresponded to Mg oxidation from the Mg-enriched oxide bands in NSDL. [Display omitted]