Abstract: The applicability of cathodic protection criteria was studied by surface observation and electrochemical method while the X80 steel was immersed into seawater solution containing SRB. The results revealed:The corrosion was anode control. The corrosion rate was reduced by increasing the SRB adhesion resistance and the charge transfer resistance on the metal surface in the fifth day. While the metal was protected mainly through changing the charge transfer resistance on the metal surface in the tenth day, and the cathodic polarization potential was more negative, the effect was better. The corrosion products were more and poor adhesion on the metal with no-cathodic polarization, and the corrosion products were less and strong adhesion on the metal surface with cathodic protecting. The cathodic polarization could indeed protect the X80 steel in the presence of SRB. In the fifth day, the protection degree was not up to 85% when the metal was polarized to -850 mV_CSE, and it just could meet the protection requirement while polarized to -950 mV_CSE. And in the tenth day the protection degree was declined, it did not meet the requirement while polarized to -850 mV_CSE and -950 mV_CSE. So it was needed to continue to determine the appropriate cathodic protection potential in the presence of SRB.

Key words: SRB, surface observation, electrochemical method, cathodic protection criteria, protective degree