In CO-rich coal gasification atmospheres, sulfidation attack of metallic components can cause severe wastage problems. In these highly reducing environments, Si is one of the elements with a high enough affinity for oxygen to enable a silica-rich scale to be formed which may provide reasonable protection of the alloy substrate, In this study, the corrosion behavior of a commercial 12%Cr ferritic alloy is compared with the resistance of a series of specially cast 12%Cr and 12%Cr-12%Ni “model” alloys having Si levels ranging ffom 1.3 to 4 %.Two higher Cr-Ni austerritic alloys (25%Cr-20%Ni and 20%Cr-32%Ni) have also been tested. Coupons from each material have been exposed to a nonequilibrated CO-based gas mixture containing 0.8% H2S for up to 2000 hours. Weight changes and surface and cross-sectional examinations have been used to measure the kinetics and establish the morphology, type and extent of corrosive degradation.
Keywords: Corrosion, sulfide scales, Si additions, 12%Cr alloys, non-equilibrated CO-richgases