Microbiologically influenced corrosion inhibition (MICI) due to bacterial contamination

Microbiologically influenced corrosion inhibition (MICI) has been observed for Al2024, mild steel, cartridge brass and stainless steel when an artific ial seawater (AS) solution containing growth medium was contaminated by bac teria. In this case the test electrodes had been sterilized by immersion in ethanol, while the test cell had been sterilized in an autoclave. In tests in which all parts had been sterilized in an autoclave contamination did n ot occur and the corrosion behavior was similar to that obtained in AS with out growth medium. Impedance data clearly showed that pitting did not occur for Al2024 in the contaminated solution, while for mild steel and brass co rrosion rates were greatly decreased. Analysis of electrochemical noise (EN ) data demonstrated that the power spectral density (PSD) plots of the curr ent fluctuations for Al2024 and mild steel had changed to lower levels. whi le the PSD plots for the potential fluctuations remained unchanged. The slo pes of the potential and current PSD plots were unchanged due to bacterial contamination, while the localization index (LI) was close to zero in all c ases.