Abstract: Taking the steels ^#10， ^#65 and W6Mo5Cr4V2Al as experimental materials， the grain microstructure and alloying element distribution after corrosion treatment in acid environment were observed and analyzed by optical microscope， scanning electron microscope and electron probe. The effects of existing forms of carbides and alloying elements on the grain corrosion morphology in these steels were also studied. The results show that the corrosion morphology of grains is related to distribution of carbides in steel and that C in the form of solid solution and Cr， Al added in steel can significantly improve the corrosion resistance of the steel. In acid environment with electrochemical corrosion， the electrode potential level of each phase in microstructure is the essence that determines whether or not the grains are liable to be corroded， while grain boundary is apt to be corroded or not is also mainly related to the electrode potential level of phases at grain boundary.

Key words: carbide, alloying element, corrosion morphology, grain boundary, acid liquid film