Prediction of corrosion rate for alloys exposed to reducing/sulfidizing combustion gases

The presence of reducing/sulfidizing combustion gases in Mle lower furnace of utility boilers can lead to accelerated corrosion wastage on the furnace walls. The corrosion has been attributed to the formation of hydrogen sulfide (H2S) that attacks the furnace walls, primarily via sulfidation. In a previous laboratory study, the corrosion rates of several Fe-base alloys were determined as a function of three key independent variables (i.e., H2S concentration in the flue gas, Cr concentration in the alloy, and metal temperature). The results were used to define the trend of corrosion data, regression of the variables individually. To better utilize the previous corrosion data,regression analysis was performed to correlate the corrosion rates of these alloys with the three variables simultaneously. From this analysis, simple mathematical equations were generated that were capable of predicting corrosion rates of Fe-base alloys exposed lo reducing/sulfidizing boiler environments. The accuracy of the equations was evaluated by comparing predicted and actual corrosion rates of a low-alloy steel from the furnace wall of a partial combustion-fired utility boiler. A reasonable agreement was obtained.