Materials performance with Na 2CO 3-V 2O 5-CaSO 4 deposit under moist synthetic air

Heavy fuel oils used in diesel engines contain residues of e.g. vanadium, sodium, calcium, sulfur, nickel and aluminum. Their amount varies depending on the source of the crude oil, refining methods as well as mixing ratio and handling process. During combustion these residues become concentrated in the ash. The sodium and vanadium levels are of major concern since they cause high temperature corrosion at temperatures over 500°C. During combustion, these elements oxidize and contribute to formation of semi-liquid and low melting salts causing increased fouling and corrosion of components. Higher efficiency and therefore higher operation temperature, and also lower quality fuels for economic reasons are future targets, and these create additional material challenges under already demanding conditions. The corrosion resistance of various currently used and new alternative materials under simulated medium speed diesel engine exhaust system environments was experimentally clarified. The selected materials were exposed at 650 and 750°C under moist synthetic air with Na 2CO 3-V 2O 5-CaSO 4 deposit up to 1000 h. The specimens were analyzed by means of cross-section microscop