Microbiologically Induced Cathodic Depolarization

Abstract Aerobic acetic-acid-producing bacteria can cause the depolarization of an Allegheny-Ludlum 6X stainless steel electrode cathodically polarized to -900 mV vs. SCE in a synthetic seawater solution. Formation of a calcareous film and initial settlement of microorganisms on the electrode surface resulted in decreased current density as a result of impeded oxygen transport and respiration. Subsequent colonization of the electrode resulted in increased current density, i.e., cathodic depolarization. The impact of bulk pH changes on current density during polarization was measured. It appears that colonizing bacteria can accelerate corrosion by producing acetic acid which destabilizes or dissolves the protecting calcareous film that forms during cathodic polarization.