Electrochemical behavior of steel A36 under disbonded coating in the presence of sulfate-reducing bacteria

• Microenvironmental variations and corrosion are investigated in crevice.
• Forming of crevice blocks penetration of cathodic currents in crevice.
• Forming of crevice weakens cathodic polarization in the crevice.
• SRB increase energy consumption of cathodic protection systems.
• Corrosion rate with SRB is smaller in early period than that without SRB.

Variation and distribution of the environmental parameters (potential, current, pH and [Cl−]) and electrochemical behavior of steel A36 were studied in a crevice under a disbonded coating in soil extract solutions in the presence and absence of sulfate-reducing bacteria (SRB). Results show that the crevice blocks the penetration of cathodic currents, and weakens the cathodic polarization of the steel in the crevice. The presence of SRB in the crevice leads to alkalization of the solution and increases energy consumption of the cathodic protection system. The forming of the reversed potential increases the cathodic current. SRB restrains corrosion of the steel in the earlier period due to the protective biofilms, whereas it SRB corrosion of the steel in the later period because of exfoliation of the films and the formation of the corrosive microcell.