EIS study of MIC in three different zones derived from ship ballast tank model system

Microbiologically influenced corrosion (MIC) is a well known phenomenon in aquatic environments [1]. The presence of a biofilm on metal surface often establishes new electrochemical reaction pathways, or promotes reactions which are not normally favored in the absence of microorganisms, resulting in increased corrosion rates and on the performance of the material. A approach was made by using a new developed lab scale model system containing working electrodes in different height levels to simulate sediment, immersion and splash zone of a ship ballast tank with the help of a three dimensional shaking plate. By studying a defined mix culture of aerobic and anaerobic bacteria it was possible to model the corrosion behavior of low carbon steel exposed to bacteria in different zones. Electrochemical impedance data (EIS) provide data to distinguish between general corrosion and MIC impact in a more detailed way. Fluorescent staining in liquid allowed monitoring biofilm development and activity on steel coupons supporting EIS data. By additional study of the electrode surfaces by SEM-EDX the impact of MIC could be shown. © 2011 by NACE International.