Research On The Corrosion Resistance Properties Of Stainless Steels In Desulfurization Environment

Because of its high desulfurization rate, mature technology, stable operation of long cycle, small impact when load changes, large gas processing capacity and other characteristics, the Wet Flue Gas Desulfurization(WFGD) environmental technology has become the main method to control SO2 discharge in china. Since the absorption solution contains a large amount of Cl- and SO42-, the system of WFGD raises serious corrosion inside. Therefore, the corrosion and antisepsis problem in the wet process has been an important topic in the field of FGD, which directly affected the construction costs, equipment life and maintenance.For detailed analysis of the corrosion resistance of the materials in desulfurization environment, this paper was studied from the following aspects:(1) The corrosion resistance of 2205,254,2507,316L were analyzed and compared by hanging pieces experiments in the severely corrosive sites of the GGH and absorber on the scene and the immersion test in Laboratory simulation conditions. The stainless steel 316L and 2205 were not recommended,254 and 2507 were preferred in the high concentrations of chloride ion acidic environments.(2) In combination with morphology observation, the effects of temperature and Cl-concentration on corrosion resistance of the materials were researched using potentiostatic and potentiodynamic measurements. The results showed that the CPT of 2205 and 254 decreased with the increasing concentration of Cl-. By comparing the figures of Epit and Eprot versus temperature in different concentrations of NaCl, both of the corrosion-resistance and CPT decreased and the regions of abrupt change became broader and slower With the increasing Cl- concentration. Below the CPT, pitting had occurred, erosion points were in the metastable state, maintaining a dynamic balance between the breaking and repassivation. Above the CPT, the erosion points were in the stable state and the value ofΔE (Epit-Eprot) was temperature and chloride concentration-independent.(3) The effects of SO42-and Cl-concentration on corrosion resistance of the materials were researched.The influences of SO42-and Cl-concentration on general corrosion of stainless steel were two-way impact.Because of the adsorption competition between SO42- and Cl-, the CPT of stainless steel is lower or higher in different concentrations of SO42-. Above the CPT, the Epit increased compared with in NaCI solution without SO42-. The pitting corrosion radius and hole depth were different with the SO42- concentration changed.