Laboratory Studies of Potassium-Halide-Induced High-Temperature Corrosion of Superheater Steels. Part 2: Exposures in Wet Air

In Part 1 of this work, the high-temperature corrosion behavior of three different superheater materials (10CrMo9-10, AISI347, and Sanicro28) under KBr and KF salts in dry air was studied. The results were compared to an earlier published paper in which the same steels were exposed to KCl. In this work, a continuation of the studies with the same steels covered with KCl, KBr, and KF and exposed to wet air (30 vol % H2O) at 450 and 550 °C was carried out. The corrosion behavior of the test steels in both dry and wet air was compared. It was found that the differences in the structure and thickness of the oxide layers formed depend not only on the gas atmosphere and temperature but also on the composition of the steel and the type of potassium halide. Generally, AISI 347 was found to corrode the least, although Sanicro 28 in some cases seemed to perform better.