Abstract: Classical method of loss weight is used for establishing inhibitor K_2CrO_4 concentration in the MH-WRR shield cooling system and studying surface pretreatment technique of the MHWRR shield coolingsystem before first use. The surface analysis technique and the electro--chemical method are used tostudy mechanism of K_2CrO_4 inhibitor. The chemical compounds Cr_2O_3, Fe_2O_3 and Fe--Cr--O formed onthe surface of carbon steel (A_3) can strengthen corrosion resistance of the surface of carbon steel.