Evaluating the Electrochemical Behavior of Friction Stir-Welded AA2219-O Alloy Joint in 3.5% NaCl Solution

Single-pass friction stir welding of AA2219-O aluminum alloy was carried out at high rotation speed (1180 rpm), and transverse travel rate of 33.5 mm/min was selected. The microstructural, mechanical and electrochemical characteristics of the weldment are investigated in this study. The high rotational tool speed resulted in a less uniform distribution of the intermetallic theta-phase (CuAl2) in the thermo-mechanically affected zone (TMAZ) than in the weld nugget zone (WNZ). The higher transfer coefficient and lower charge transfer resistance (R (ct) + R (theta)) were observed in case of TMAZ as evaluated from potentiodynamic polarization and impedance spectroscopy, respectively. These results confirmed that microstructural variations could deteriorate the electrochemical performance of the weldment. TMAZ provided the least corrosion resistance than the base metal (BM) and WNZ due to the high concentration of cathodic intermetallic particles and possibly due to the large mechanical distortion of the grain structure.