Abstract: Scanning electron microscopy and backscattered electron diffraction (EBSD) are used to analyze the microstructure of the 2507 duplex stainless steel welded joint, the electrochemical testing and X-ray photoelectron spectroscopy (XPS) are adopted to explore the corrosion behaviors of different areas of the welded joint in offshore flexible platform cooling system in the simulated sea, and the 1 440 h salt spray test is conducted on the welded joint. The results show that the passivation current densities in the potentiodynamic polarization curves of the weld, heat-affected zone and base metal are equivalent, and that the three areas all show similar capacitive semicircle characteristics, indicating that the corrosion resistances of the three locations are equivalent. The XPS results show that the passivation film of 2507 super duplex stainless steel in this environment is mainly metal hydroxide and oxide. The salt spray test results show that after being in in the corrosion environment for a long time, the surface of the base metal maintains good metallic luster, that there is slight corrosion around the weld, and that the weld is still a weak area prone to corrosion. The results have certain engineering reference significance for the selection of key technical components and the control of joint quality of offshore flexible platforms.