The corrosion behaviors of HR3C pre-coated alkali metal sulphate in SO 2 atmosphere at different temperatures were investigated by means of XRD,SEM (EDS) and EMPA in order to discuss the corrosion resistance mechanism to SO 2 of HR3C.The results show that the corrosion kinetic curves follow parabolic law.The corrosion products are mainly composed of (Fe,Cr) oxides,minor compound oxides with spinel structure as well as (Fe,Ni) sulfides.The increment in SO 2 content increases significantly the oxide films in thickness,and deteriorates the adhesion to the oxide scale and matrix.In addition,the porosities in the corrosion affected zone (the interface between the oxide films and the matrix) increase and a CrS belt exits in the interface between the oxide layer and the corrosion affected zone.The analysis shows that the corrosion of HR3C in SO 2 environment is resulted from the oxidation,sulfidation of the alloy,moreover,the sulfation of metallic oxides and the formation of ternary composed alkali metal sulfate as well as the dissolution of Fe in melted salt also contribute to the corrosion.