Abstract: The phase and microstructure of different areas of 2205 duplex stainless steel welded joints were analyzed using X-ray diffractometer (XRD) and electron back scatter diffraction (EBSD). The corrosion behavior of different areas of the welded joint in a simulated offshore flexible platform cooling system was studied using electrochemical tests and X-ray photoelectron spectroscopy (XPS). The results show that the passivation current density in the potentiodynamic polarization curve of the heat-affected zone (HAZ) of the welded joint was smaller than that of the base metal and weld seam. The HAZ had the largest impedance arc radius and the highest open circuit potential, and the HAZ had the best corrosion resistance; XPS results show that the passivation film of 2205 duplex stainless steel in this environment was dominated by metal hydroxides and oxides.