Effect of KCl deposits in high‐temperature corrosion on chromium‐rich steels in SO2‐containing atmosphere

High‐temperature corrosion was studied under multiple chemical loads on ferritic‐austenitic model alloys (Fe–13Cr, Fe–18Cr–12Ni, and Fe‐25Cr–20Ni) with KCl deposit under 0.5% SO2 ${\text{SO}}_{2}$ /99.5% Ar gas atmosphere at 560°C $560^\circ {\rm{C}}$ . Postexposure characterization was done by X‐ray diffraction and scanning electron microscopy. In a pure SO2 ${\text{SO}}_{2}$ /Ar environment a protective Cr2O3 ${\text{Cr}}_{2}{{\rm{O}}}_{3}$ scale was formed by all samples. The introduction of KCl deposits causes the scale to be nonprotective and multilayered, consisting of CrS, FeS, Cr2O3,Fe3O4 ${\text{Cr}}_{2}{{\rm{O}}}_{3},{\text{Fe}}_{3}{{\rm{O}}}_{4}$ , and Fe2O3 ${\text{Fe}}_{2}{{\rm{O}}}_{3}$ . The impact of the microstructure and alloying elements is discussed.