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Abstract: The pitting corrosion behaviors between the constituent phases in F53 super duplex stainless steel (SDSS) in acidified chloride environments were investigated using a critical pitting corrosion temperature test, a potentiodynamic anodic polarization test, and the microstructure analyses through a SEM-EDS and a SAM. As the solution annealing temperature decreased from 1150℃ to 1050℃, the γ-phase fraction increased whereas the α-phase fraction decreased. The pitting potential and the critical pitting temperature increased with a decrease of solution annealing temperature, thereby increasing the resistance to pitting corrosion. The pitting corrosion of the SDSS was selectively initiated at the α-phases because the PREN (pitting resistance equivalent number, PREN = %Cr+3.3%Mo+30%N) value of the γ-phase is much larger than that of the α-phase, irrespective of the solution annealing temperature. The pitting corrosion was finally propagated from the α-phase to the γ-phase. The decrease of solution annealing temperature enhanced the resistance to pitting corrosion greatly in acidified chloride environments due to a decrease of PREN difference between the γ-phase and the α-phase, that is, a decrease of PRENγ by dilution of N in γ-phase with an increase in the γ-phase volume fraction and an increase of PRENα by enrichment of Cr and Mo in the α-phase with a decrease in the α-phase volume fraction.