Superheater surfaces in oil shale steam boilers, constructed from pearlitic or austenitic alloys, are subject to intensive corrosion, primarily from the presence of chlorine in external deposits. The applicability of martensitic alloys X10CrMoVNb91 and X20CrMoV121 for superheaters has been examined and empirical equations to predict alloy corrosion resistance have been developed for the operational temperature range. Alloy 10CrMoVNb91 is found highly suitable for superheaters in boilers firing fossil fuels that contain alkaline metals and chlorine. An abnormal dependence of corrosion resistance of martensitic alloys on temperature is revealed, namely that corrosion in presence of oil shale fly ash is more severe at 580°C than at 620°C.

Standards for the Determination of Corrosion Resistance of Boiler Alloys at Elevated Temperature-RTM 108.030.116-78 (in Russian).
Steam Boilers. Standardized Methods of Corrosion Testing-OST 108.030.01-75 (in Russian).
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