In the present study, the corrosion behavior of a friction stir welded GOST 5632 lean duplex stainless steel was investigated. For this purpose, the alloy was welded at a constant rotational speed of 800 rpm and different welding speed of 50, 100 and 150 mm/min. The microstructure of all specimens were studied using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy spectroscopy (EDS). The corrosion behavior of the specimens investigated using open circuit potential (OCP), linear polarization, potentiodynamic polarization, cyclic polarization, zero internal resistance ammeter (ZRA), electrochemical impedance spectroscopy (EIS), Mott-Schottky and immersion tests. Cyclic polarization test was employed in 0.1 M H 2 SO 4 + 0.1 M NaCl solution. Immersion test in 1 M H 2 SO 4 was used to evaluate the corrosion behavior of different weld zones. Also, the zero internal resistance ammeter test was used to determine the galvanic corrosion behavior of the base metal and the welded specimens. The results showed that no deleterious phase was formed after friction stir welding. Also, FSW reduced the grain size of both ferrite and austenite phases. The OCP, linear polarization, potentiodynamic polarization, EIS and immersion tests showed that the corrosion resistance improved after FSW. Cyclic polarization tests in 0.1 H 2 SO 4 + 0.1 NaCl revealed that the base metal and weld specimens exhibited positive hysteresis. It was concluded from the ammeter tests with zero internal resistance that the base metal was anode. Mott-Schottky analysis showed that the level of defects significantly decreased in the passive film of stired zones in comparison with the passive film of the base metal. In general, the results revealed that the increase in welding speed in a constant rotational speed decreased the grain size and enhanced the corrosion resistance. Key words : Friction stir welding, Duplex stainless steel, Corrosion behavior
