Effect of KCl deposits in high‐temperature corrosion on chromium‐rich steels in SO 2 ‐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%SO 2${\text{SO}}_{2}$ /99.5% Ar gas atmosphere at560 ° C $560^\circ {\rm{C}}$ . Postexposure characterization was done by X‐ray diffraction and scanning electron microscopy. In a pureSO 2${\text{SO}}_{2}$ /Ar environment a protectiveCr 2 O 3${\text{Cr}}_{2}{{\rm{O}}}_{3}$ scale was formed by all samples. The introduction of KCl deposits causes the scale to be nonprotective and multilayered, consisting of CrS, FeS,Cr 2 O 3 , Fe 3 O 4${\text{Cr}}_{2}{{\rm{O}}}_{3},{\text{Fe}}_{3}{{\rm{O}}}_{4}$ , andFe 2 O 3${\text{Fe}}_{2}{{\rm{O}}}_{3}$ . The impact of the microstructure and alloying elements is discussed.