MULTIELECTRODE PROBE FOR STATISTICAL EVALUATION OF MICROBIOLOGICALLY INFLUENCED CORROSION

Microbial biofilms increase the complexity and spatial variation of the interfacial chemistry occurring at metal surfaces and can facilitate corrosion. A multi-electrode probe was designed to replicate interfacial chemistry by providing multiple interfaces on a single probe. Electrochemical impedance spectroscopy (EIS) was used to examine the electrochemical properties of four-electrode probes containing 430 (USN430000) stainless steel coupons in test solutions. The EIS results obtained with the probe were compared to the ASTM G-106 standard method, and the probe was determined to be accurate. In addition, no interference or crosstalk between electrode channels was observed. In order to demonstrate the utility of the probe, four-electrode probes were used to investigate microbiologically influenced corrosion of C1020 carbon steel. Enrichments of aerobic, fermentative, and sulfate reducing bacteria from a corrosion tubercle were inoculated into the bulk phase of a corrosion cell and formed biofilms on the carbon steel electrodes. A five fold increase in the polarization admittance of carbon steel coupons exposed to biofilms relative to sterile medium was observed, The four-electrode probe provided the necessary degrees of freedom to show the statistically significant differences.