Abstract: The corrosion morphology, the corrosion film composition, and corrosion electrochemical characteristics of X60 steel soaking in CO2 and sulfate reducing bacteria (SRB) coexistence environment for different times were investigated respectively. Results showed that the potential of X60 steel increased with the increase of biofilm covering extent, and then decreased with the increase of the content of corrosion product FeS and FeCO3. According to the analytical results of EIS, only a time constant related to electrode potential existed when the content of corrosion product in the film forming on the surface of X60 steel was low, and then an additional time constant related to the corrosion film appeared with the increase of the content of corrosion product in the film. The transferring resistance increased with the increase of the covering extend of biofilm in the early soaking stage. And then the transferring resistance first decreased, and then increased with the increase of the content of corrosion product. With the increase of soaking time, both electrical double-layer capacitance and filmcapacitance increased.

Key words: SRB corrosion, CO2 corrosion, Electrochemical characteristic, Corrosion morphology, X60 pipeline steel