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.
