Evaluation of High Temperature Corrosion in Simulated Waste Incinerator Environments

In this study, high temperature reactions of Fe–Cr alloys at 500 and 600 °C were investigated using an atmosphere of N₂–O₂ 8 vol% with 220 vppm HCl, 360 vppm H₂O and 200 vppm SO₂; moreover the following aggressive salts were placed in the inlet: KCl and ZnCl₂. The salts were placed in the inlet to promote corrosion and increase the chemical reaction. These salts were applied to the alloys via discontinuous exposures. The corrosion products were characterized using thermo-gravimetric analysis, scanning electron microscopy and X-ray diffraction.The species identified in the corrosion products were: Cr₂O₃, Cr₂O (Fe_0.6Cr_0.4)₂O₃, K₂CrO₄, (Cr, Fe)₂O₃, Fe–Cr, KCl, ZnCl₂, FeOOH, σ-FeCrMo and Fe₂O₃. The presence of Mo, Al and Si was not significant and there was no evidence of chemical reaction of these elements. The most active elements were the Fe and Cr in the metal base. The Cr presence was beneficial against corrosion; this element decelerated the corrosion process due to the formation of protective oxide scales over the surfaces exposed at 500 °C and even more notable at 600 °C; as it was observed in the thermo-gravimetric analysis increasing mass loss. The steel with the best performance was alloy Fe9Cr3AlSi3Mo, due to the effect of the protective oxides inclusive in presence of the aggressive salts.