Influence of Post-Welding Heat Treatment on the Corrosion Behavior of a 2050-T3 Aluminum-Copper-Lithium Alloy Friction Stir Welding Joint

The corrosion behavior of a Friction Stir Welding joint in 2050-T3 Al-Cu-Li alloy was studied in 1 M NaCl solution and the influence of T8 post-welding heat treatment on its corrosion susceptibility was analyzed. After exposure to 1 M NaCl solution, the heat affected zone (HAZ) of the weld without post-welding heat treatment was found to be the most extensively corroded zone with extended intergranular corrosion damage while, following T8 post-welding heat treatment, no intergranular corrosion was observed in the HAZ and the global corrosion behavior of the weld was significantly improved. The corrosion damage observed on the welded joints after immersion in 1 M NaCl solution was compared to that obtained after 750 h Mastmaasis Wet Bottom tests. The same corrosion damage was observed. Various stationary electrochemical tests were carried out on the global welded joint and/or each of the metallurgical zones of the welded joint to understand the corrosion damage observed. TEM observations helped in bringing meaningful elements to analyze the intrinsic electrochemical behavior of the different zones of the weld related to their microstructure. However, galvanic coupling tests showed that galvanic coupling effects between the different zones of the weld were at least partially responsible for its corrosion behavior.