Résumé : Distributions of potential and current and variations of crevice environments are studied in a crevice under a simulated disbonded coating in soil extract solutions (SES) with and without sulfate-reducing bacteria (SRB). Results show that forming of the crevice blocks the penetration of cathodic currents in the crevice and weakens the cathodic polarization of the steel Q 235. The cathodic currents in the presence of SRB are nearly three times more than those without SRB at the same cathodic protective potential, which indicates that SRB increases the energy consumption of the cathodic protection systems. SRB leads to basification of the solution in the crevice. The forming of inner electric field enhances the anionic migration into the crevice. The forming of the reversed potential increases the cathodic current.