Influence of annealing treatment on the corrosion resistance of lean duplex stainless steel 2101

The effect of annealing temperatures in the range 1000–1200 °C on the microstructure and corrosion behavior of 2101 lean duplex stainless steel was investigated. The results demonstrated that the volume fraction of austenite phase decreased with increasing annealing temperature. However, lower values for the pitting potential (Epit) and the critical pitting temperature (CPT) were obtained after annealing at higher temperatures. Pitting was initiated preferentially in the ferrite/austenite boundaries or inside the ferrite domains, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase in as-received steel. Moreover, the PRE values of the ferrite phase fell with the annealing temperature, while the values for the austenite phase rose. No equal PRE values in the ferrite and austenite phase were found for this steel in the range of annealing temperatures. This was determined by evaluating the PRE values of both phases from EDS results and the Thermo-Calc database.