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The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel (SDSS) in simulated marine environment was investigated by electrochemical measurements, periodic wet–dry cyclic corrosion test, scanning Kelvin probe force microscopy, atomic force microscopy, and X-ray photoelectron spectrometry. The results show that the occupation ratio of γ phase increases with the decrease in cooling rate, whereas the content of α phase reduces gradually. In addition, the σ precipitated phase only emerges in the an-nealed steel. The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases. The σ precipit-ated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel. For vari-ous microstructures, the pits are preferentially distributed within the σ and γ phases. The corrosion resistance of 2507 SDSS prepared by differ-ent cooling methods is closely related to the microstructure and structure (stability and homogeneity) of the passive film. Normalized steel shows an optimal corrosion resistance, followed by the quenched and annealed steels.