Flue gas desulfurization (FGD) systems are frequently used at power plants to remove SO2 from coal combustion. In systems where limestone is utilized, calcium sulfate from the resulting slurry can be concentrated into a valuable byproduct. However, the concentrated slurry containing chloride poses increased localized corrosion risk to the materials of construction in contact with exhaust/combustion stream. Cyclic Potentiodynamic Polarization (CPP) and Critical Crevice Temperature (CCT) present electrochemical methodologies which can be used to assess the relative risk of different conditions in the laboratory. However, the results of these techniques can be dependent on the details of the experimental protocol. In this study, the effect of slurry preparation, potential scan rate, alloy conditioning time, and slurry acidity were examined. A conservative test protocol was developed based on the outcomes of the effects considered, and the critical chloride concentration of Alloy UNS S32205 was determined, enabling optimization of FGD operating conditions.

Subject
Test methods, Materials, Slurry, Evaporation, Repassivation potentials, Flue gas desulfurization, Sodium chloride, Acidity, Crevices, Crevice corrosion, Pitting, Chlorides, Corrosion potential
Keywords:
Alloy UNS S32205, Flue Gas Desulfurization (FGD), Cyclic Potentiodynamic Polarization (CPP), Critical Pitting Temperature (CPT), calcium chloride concentration
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2020
Association for Materials Protection and Performance (AMPP)
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