Abstract. 7A52 aluminum alloy plate was welded using twin-wire metal inert gas arc welding (TANDEM welding). Corrosion behavior of the welded joint was investigated by immersion in 3.5% NaCl solution. Scanning electron microscopy (SEM) and electrochemical inspections, specifically, polarization curves and electrochemical impedance spectroscopy (EIS), were conducted to understand corrosion behavior of the TANDEM welding joint of 7A52 aluminum alloy. It was found that the heat affected zone (HAZ) exhibited higher corrosion susceptibility than the weld beam (WB), fusion zone (FZ) and base metal (BM). The electrochemical results showed that the WB with higher corrosion potential and larger impedance had highest corrosion resistance. Variations in the composition and grain size might have led to the differences in corrosion resistance because the welding process influenced microstructures of the TANDEM welding joint of 7A52 aluminum.