Corrosion Behavior of X70 Pipeline Steel in 3.5% Nacl Solution under the Synergistic Action of Cathodic Protection and Sulfate-reducing Bacteria

The corrosion behavior of X70 pipeline steel in 3.5% NaCl solution under the synergistic action of cathodic protection (CP) and sulfate-reducing bacteria (SRB) was studied. The growth curves of SRB under various polarization potentials were measured. The results showed that SRB reproduction was suppressed and the bacteria rapidly entered decline phase at an anodic polarization potential. Under the stimulation of cathodic potential of -0.85 VSCE, the reproduction of SRB was promoted. The death of the bacteria was accelerated when CP potential reached -1.0 VSCE. The growth cycle of SRB had significant influence on the CP efficiency. During SRB growth phase, the excess electrons of CP were directly utilized by SRB as electron donors to metabolize. CP current repelled the electronegative SRB, and CP and SRB synergistically mitigate the steel corrosion. When SRB enters the death stage, the metabolite of SRB acted synergistically with CP to promote hydrogen evolution, and CP promoted SRB corrosion.