Effect of Solution Annealing Temperature on Pitting Behavior of Duplex Stainless Steel 2204 in Chloride Solutions

The effect of solution annealing temperature ranging from 950 to 1200 °C on the microstructure and corrosion performance of duplex stainless steel (DSS) 2204 were investigated. The proportion of the ferrite phase increased while the austenite phase decreased and the ferrite stabilizing elements diluted in the ferrite phase with the increase of annealing temperature. The critical pitting temperature (CPT) of specimens annealed at 1000 °C was higher than those annealed at 950 °C, whereas further increasing the annealing temperature to 1200 °C decreased the CPT. The pitting initiation sites were observed in the austenite phase, at the boundary of ferrite/austenite phase and inside the ferrite phase for specimens annealed at 950, 1000 °C and exceeding 1100 °C, respectively. The evolution trend of the CPT and the pit initiation site were analyzed by the pitting resistance equivalent number.