Comprehensive insights into competitive oxidation/sulfidation reactions on binary ferritic alloys at high temperatures

Interpreting high-temperature corrosion induced by mixed-gas atmospheres is challenging due to the different contributions of oxidizing gases. Here, a comprehensive study on the combined oxidation/sulfidation using label molecules is presented. Fe-Cr model alloys with 2 wt% and 9 wt% Cr were isothermally exposed using a volumetric mixture of 0.5%S¹⁶O₂/27%H₂¹⁸O and 0.5%S¹⁶O₂/7%H₂¹⁸O at 650 °C for 5 h and then characterized by secondary ion mass spectroscopy (SIMS). Additionally, the reactions were followed in-situ utilizing energy dispersive X-ray diffraction. The study showed that both S¹⁶O₂ and H₂¹⁸O contribute to the oxidation of the alloys but to different extents depending on the Cr-content.