Pierangela Cristiani*, Giuseppina Bestetti**, Andrea Pranzetti ** BIOCORYS 2007 International Conference on Biocorrosion of Materials Parigi, 11-14 Giugno 2007 * CESI RICERCA ** UNIVERSITÀ DEGLI STUDI DI MILANO BICOCCA The present paper(*) describes a new tool for on-line monitoring of aerobic biofilm growth in on stainless steel the soil. The work concerns the application in soil of the same electrochemical techniques and probes already successfully used in water systems to monitor biofilm growth and mainly based on the cathodic polarisation of stainless steel samples. Experiments at laboratory level with sterilised and unsterilised soils, different soil humidity, different levels of nutrients have been performed by using a set of soil microcosms of 6 kg each ones and each ones containing electrochemical probes burrow in it. Weekly humidity tests and adjustments, chemical and microbiological analyses of the soils have been regularly conducted during six months of testing. Microbiological analyses and microscopy observation performed on the surface of the stainless steel electrochemical probes at the end of the tests confirmed a direct correlation between the increase of cathodic characteristic and the biofilm development on the working electrodes. The results suggest that simple electrochemical techniques are applicable in soil to monitor the early stage of biofilm growth on stainless steel. It was confirmed, in particular, a key role of soil humidity level resulted the most critical and limiting factor for biofilm growth, more than the environment temperature, nutrient and carbon content ones. The best conditions to achieve a quick and full electro-active biofilm on “burrow electrodes” in a “soil microcosms” suitable for experiments and studies at laboratory level have been detailed. (*) Work in the frame of the UE project EA-Biofilms NEST508866 of the 6 th European FP and co-financed by the Italian Ministry of Economic Development with the Research Fund for the Italian Electrical System under the Contract Agreement established with the Ministry Decree of march 23, 2006.