Galvanic Corrosion Assessment of Friction Stir Butt Welded Joint of Aluminum and Steel Alloys

Abstract

Galvanic corrosion assessment of a friction stir welded (FSWed) joint of 5052-H32 aluminum and dual phase (DP) steel alloys is conducted by coupling the top and bottom surfaces of the weld joint with the base metals (BMs) in the presence of a 3.5% NaCl solution. The complex nature of the stir zone (SZ) causes different microstructures and corresponding corrosion behaviors across the top and bottom surfaces of the FSWed joint. From the results, the regions between the DP steel BM and the FSWed joint have larger average potential differences as well as higher corrosion rates due to an increase in martensite content, low-angle grain boundaries (LAGBs) and the presence of the steel pieces in the SZ. On the other hand, the regions between the aluminum BM and the FSWed joint show better corrosion properties with smaller average potential differences and lower corrosion rates, even though the aluminum BM is significantly affected by the chloride ions present in the electrolyte.