Corrosion of stainless steels covered by exopolymers

After a biologically induced corrosion in a 304 stainless steel tube electrochemical tests were carried out on the affected areas to characterise the nature of attack of the steel covered by the excreted exopolymers. Once the corrosive attack has been developed, the samples were removed from the solution, dried out for 1 month and re-immersed in the same well water which caused the attack. Polarization curves and impedance measurements made on non attacked welds, reference stainless steel and the metal covered by the exopolymer confirm that a reactivation of the corrosion process in previously damaged welded areas is produced. However, the corrosive attack has not been so severe than the initially produced by bacteria and after 28 days of immersion the progress of the attack is probably due to the previous activation of the steel surface rather than the microbiological activity.