Electrochemical Data on the Effect of Extreme Temperatures on 2101 Duplex Steel Corrosion Performance in Chloride-Sulphate Environment

Abstract

The detrimental outcome of heat treatment operation at 1200oC on 2101 duplex stainless steel was studied in 2 M H2SO4/0%-1.75% NaCl by potentiodynamic polarization, open circuit potential measurement and optical microscopy analysis. Result reveal the processes heightened the corrosion vulnerability of the duplex alloy with maximum corrosion rate result of 11.3 mm/y at 0.5% NaCl for the annealed steel (A2101ST), followed by quenched steel (Q2101ST) with corrosion rate value of 9.03 mm/y. These values were significantly lower than the peak corrosion rate of the as received steel (ASR2101ST) at 5.785 mm/y. The corrosion rate of all the duplex steels generally decreased beyond 0.5% NaCl. ASR2101ST sustained it passivation characteristics till 1.75% NaCl due to the resilience of its oxide protective film while the passive film of Q2101ST and A2101ST were completely destroyed due to alteration in the metallurgical configuration of the heat treated duplex steels. While the surface of ASR2101ST mildly deteriorated, severe intergranular and pitting corrosion was observed on Q2101ST and the surface of A2101ST was marginally pitted in the presence of SO42- ions. In Cl-/SO4 ion solution ASR2101ST showed an etched morphology with ferrite and austenite phases appearing in addition to superficial pitting. Q2101ST and A2101ST were severely deteriorated in the solution.