Effects of External Stress on High-Temperature Corrosion Behavior of T92 Ferrite Steel with Na2SO4-K2SO4 Molten Salts

This paper reports an experimental study of the oxidation-sulfidation behavior of T92 steel in a complex environment consisting of a combination of high temperature (700 degrees C), SO2, molten sulfate salts, and applied stresses. The corrosion products, morphologies, and element distributions of corrosion scales were investigated in detail by SEM and XRD. Results indicate that the formation of sulfides in the deep layer where the p(O-2) is low-level prevents the reformation of a protective layer after the damage of the Cr2O3 layer. It is also noted that based on the data of maximum corrosion depth, when stresses are applied, the extent of corrosion had been alleviated, which is ascribed to that the applied stress also accelerated the fast formation of Cr2O3. However, the applied stress is also thought to accelerate the damage of the protective layer by inducing more boundaries of products and increasing the possibility of exfoliation of a corrosion scale. Thus, in the limited exposure duration to the corrosive environment in this study, there should be a "critical stress" under which the specimens present the best corrosion resistance.