Previously the corrosion of 12Crl7 steel in molten alkali metal carbonates containing different chemical additions was investigated by potentiostatic anodic polarization method. The surface morphology of 12Crl7 steel was studied by X-ray analysis. The mechanism of local corrosion damages was influenced by injecting of corrosion passivators and corrosion activators. Corrosion of the investigated alloy proceeds according to electrochemical mechanism. Steel oxidants were both oxygen dissolved in the melt and carbonate anions. Method of corrosion medium processing (treatment) could be used to protect metal structures from corrosion in high-temperature salt bathes. Combined introduction in salt phase of corrosion activators and passivators allows to form protective layers with high corrosion resistance.