Technical Note:Microbiologically Induced Increase in Corrosion Current Density of Stainless Steel under Cathodic Protection

1 May 1988

journal article
Published by Association for Materials Protection and Performance (AMPP) in Corrosion

Vol. 44 (5) , 270-274
https://doi.org/10.5006/1.3583936

Abstract

Aerobic acetic-acid-producing bacteria can cause the depolarization of a UNS-N08366 electrode cathodically polarized to −900 mV vs SCE in a synthetic seawater solution. Formation of a calcareous film and initial settlement of micro-organisms on the electrode surface resulted in decreased current density (CD) as a result of impeded oxygen transport and respiration. Subsequent colonization of the electrode resulted in increased CD, i.e., cathodic depolarization. The impact of bulk pH changes on CD 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.

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