This study aims at investigating the effect of friction stir welding (FSW) on the electrochemical behavior of pure copper in 0.01 M borax solution (pH = 9.1). For this purpose, pure copper was welded with rotation speeds of 355 and 500 rpm and welding speeds of 20, 28 and 40 mm/min. Before any electrochemical measurements, evaluation of pure copper and welded pure copper microstructures was obtained by X-ray diffraction and scanning electron microscopy. Furthermore, the electrochemical behavior of the samples in 0.01 M borax solution was investigated by using open circuit potential measurements, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The results indicated that FSW led to reduction of the grain size of pure copper and improvement of resistance against the stir corrosion area. Also according to Mott–Schottky analysis, it was found that the calculated acceptor density decreased with decreasing the grain size of the stir zone. These results were consistent with the results of the potentiodynamic polarization and EIS measurements, evidencing that the electrochemical behavior of the stir zone enhanced with decreasing of the grain size.
