An analysis of the corrosion resistance of low chromium-steel in a wet CO2 environment by the use of an electrochemical potential diagram

Abstract The corrosion rate of the low Cr-steel was measured as a function of Cr content in a wet CO 2 environment and the role of Cr on corrosion resistance has been analyzed by using the generalized electrochemical potential diagrams of the Fe-C-O-H-e − and Fe-Cr-C-O-H-e − system. The decrease in the corrosion rate with the increase in the Cr content of the steel was observed and it is explained as due to the decrease of the stable region of Fe 2+ in the electrochemical potential diagram by forming the oxide layer of Fe x Cr 3 − x O 4 . The temperature dependence of the corrosion rate showed a maximum around 343 K and it has been discussed using the metastable electrochemical potential diagram including the α-FeOOH phase. The comparison between the present electrochemical potential diagram and the Pourbaix diagram has also been discussed.