Corrosion behavior of superheater steels in the presence of potassium salts under conditions relevant to biomass combustion

The corrosion resistance of three steels; a ferritic 10CrMo type steel, an austenitic 304L type steel, and a nickel-based Alloy 625 type steel, to both solid KCl and K₂CO₃ was investigated in the laboratory. Samples were covered with either KCl or K₂CO₃ and held for 168h under two different atmospheres: dry air, and air with a water content of 30%. Analyses were performed with SEM/EDXA to determine the extent of corrosion, the elemental distribution, and for the identification of corrosion products. Both salts were found to be corrosive, and furthermore, water vapor was found to affect the reaction behavior of the salts. Alloy 625 exhibited the best corrosion resistance, whereas 10CrMo did not perform well even under the mildest conditions.