Influence of Iron Oxides and Chlorides on the Corrosion of Stainless Steels and Ni-based Alloys in O₂-H₂O-HCl at High Temperatures

Abstract

Corrosion of stainless steels, SUS304L, SUS310S, and Ni-based alloy, HastelloyC-276, covered with/without Fe₂O₃, FeCl₂ or FeCl₃ powder was investigated for 5 days in O₂-H₂O-HCl atmospheres at 160-210°C under heat transfer conditions. Corrosion rate of SUS304L and SUS310S was much higher than that of HastelloyC-276, and was enhanced considerably by covering with FeCl₃. The enhanced corrosion rate on the FeCl₃-covered specimen was due to the formation of concentrated FeCl₃/HCl solution by absorbing H₂O and HCl into FeCl₃. Corrosion mechanisms of stainless steels are discussed thermodynamically in terms of oxychlorination of iron.