Mechanism of a MIC probe

Interaction of bacterial biofilms with stainless steel is expected to alter electrochemical behaviour compared with that obtained under sterile conditions and under non-biological deposits. In principle, electrochemical signals can monitor biofilm formation and microbial activity. In this study, attempts were made to understand the mechanism by which an electrochemical sensor using periodic mutual polarisation of two similar stainless steel electrodes responds to biofilm formation. This probe is believed by others to respond to cathodic depolarisation by the biofilm, but the present study using natural fresh water showed that an increase in the galvanic and applied currents of two similar, coupled AISI Type 304 SS electrodes took place only after biofilms had initiated corrosion on the anodically polarised electrode. Comparison of electrodes with natural biofilms and deposited rust layers showed that both the films showed evidence of crevice action, but with a lower ionic resistance than a conventional crevice, therefore permitting rapid propagation of localized corrosion even in dilute chloride media.