1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 CHEC Research Centre, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Department of Mechanical Engineering, Technical University of Denmark4 Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark
An austenitic stainless steel (TP 347H FG) was coated with a synthetic deposit and exposed, under laboratory conditions simulating straw-firing at 560 oC, for one week. Microscopic, diffraction and spectroscopic techniques were employed for cross-sectional and plan view ‘top-down’ microstructural characterization of the corrosion products. The corrosion products consisted of three layers: i) the outermost layer consisting of a mixed layer of K2SO4 and FexOy on a partly molten layer of the initial deposit, ii) the middle layer consists of spinel (FeCr2O4) and Fe2O3, and iii) the innermost layer is a sponge-like Ni3S2 containing layer. At the corrosion front, Cl-rich protrusions were observed. Results indicate that selective corrosion of Fe and Cr by Cl, active oxidation and sulphidation attack of Ni are possible corrosion mechanisms.