Effect of Annealing Temperature on the Pitting Corrosion Behavior of UNS S82441 Duplex Stainless Steel

The pitting corrosion behavior of UNS S82441 duplex stainless steel annealed at six different temperatures ranging from 1,000°C to 1,130°C for 1 h has been investigated by means of the potentiostatic critical pitting temperature. The microstructure evolution and pit morphologies of the specimens were studied using optical/scanning electron microscopy. The results demonstrated that the volume fraction of the austenite phase decreased with the increasing annealing temperature. Lower critical pitting temperature values were obtained after annealing at higher temperatures. Pitting was initiated preferentially inside the ferrite domains, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. The pitting resistance equivalent number of the ferrite phase fell with the annealing temperature, while the values for the austenite phase rose. No equal pitting resistance equivalent number of the ferrite and austenite phases was found for this steel in the range of annealing temperatures.