Influence of Aging Time at 850°C on Microstructure and Corrosion Resistance of a Cold Rolled 2205 Duplex Stainless Steel

The effect of aging time at 850°C for 300 s, 600 s, 1800 s, and 84600 s on the microstructural evolution and corrosion resistance of 2205 duplex stainless steel (DSS) was studied after cold rolling up to 60% of reduction. X-ray diffraction, scanning electron and transmission electron microscopy were used for microstructural characterization. The corrosion behavior was studied by cyclic potentiodynamic polarization (CPP) and electrochemical impedance technique (EIS) in 3.5% NaCl solution and the susceptibility to sensitization was investigated through the double loop electrochemical potentiodynamic reactivation (DL-EPR) test in 0.5 M H2SO4 + 0.1 M NaCl + 0.002 M KSCN solution. After cold working, increasing aging time led to an increase in sigma phase precipitation and a decrease in pitting corrosion resistance. However, the ultrafine microstructure had a beneficial influence on the self-healing effect in Cr and Mo depleted areas with the increasing of aging time, resulting in higher passivation ability. The DSS 2205 type was not susceptible to intergranular corrosion for the aged conditions applied.