Distinguishing abiotic corrosion from two types of microbiologically influenced corrosion (MIC) using a new electrochemical biofilm/MIC test kit.

Biofilms can cause biofouling, water quality deterioration, and transmission of infectious diseases. They are also responsible for microbiologically influenced corrosion (MIC) which can cause leaks, resulting in environmental disasters. A new disposable biofilm/MIC test kit was demonstrated to distinguish abiotic corrosion of carbon steel from MIC. It used two solid-state electrodes inside a standard 10 mL serum vial to form a miniature electrochemical cell. In this work, abiotic corrosion was exemplified using CO corrosion and acetic acid corrosion. Sulfate reducing Desulfovibrio ferrophilus IS5, nitrate reducing Pseudomonas aeruginosa, and an oilfield biofilm consortium were grown anaerobically as examples of MIC systems. Tafel curves from dual-half scans and continuous upward scans did not differ significantly in each of the two abiotic corrosion systems. However, obvious distortions in Tafel curve shapes with corrosion potentials (E) shifts and corrosion current density (i) deviations (Tafel skews) were observed in each of the three MIC systems. The polarization resistance (R) trend from linear polarization resistance (LPR) for an MIC system decreased in several days due to biofilm buildup while an abiotic system did not have this delay. The abiotic corrosion systems did not respond to electron mediators or biocide injections with negligible R changes, while electron mediators accelerated extracellular electron transfer-MIC but not metabolite-MIC, and biocide injection reduced MIC rates as reflected by R changes. The results in this work demonstrated that the new kit is a useful tool in MIC diagnosis, biofilm/MIC monitoring and assessment of biocide efficacy.