The paper presents most developed methods of prevention of chlorine corrosion of steam superheater tubes during biomass combustion which are based on alkali chlorides sulphation and formation less corrosive sulfates. A new concept of using pure gaseous SO3 for sulphation process of KCl (being one of the main promoters of chloride corrosion) has been described. In currently used methods of limiting chloride corrosion, the addition of sulfur (or its compounds) is used mainly. Sulfur is converted to SO2 and SO3, with SO3 playing the most important role in sulphation of KCI. By introducing the additive directly into the furnace in the SO3 form it is possible to obtain the effect of KCl sulphation with a limited sulfur consumption in the process. Moreover, lower sulfur-based additive dosage shall limit the risk of occurrence of low temperature corrosion. The possibilities of locating nozzles for SO3 dosing, taking into account the main limitations were also presented.