Microbial cathode fouling

In Chapter 12 micro-organisms in suspension were referred to as "living colloids". It is to be expected therefore, that microbial fouling will be influenced by cathodic protection. Maines [1993] however, suggests that the picture is far from clear with respect to electrode material, types of organism and the technique adopted for cathodic protection. It would appear that in some situations biofouling is increased and in others it is reduced. Where a biofllm is present it would be expected to modify the electrochemical conditions at the metal surface and thereby influence the metal dissolution reactions [Dexter et al 1989]. 

SRB have been implicated in localised pitting corrosion, commonly referred to as microbially influenced corrosion (MIC). These and other anaerobes cause biocorrosion due to production of adds and other by-products (e.g.hydrogen sulphide), that cause cathodic depolarisation of metal surfaces. SRB also cause discoloration problems and production of foul odors. They are susceptible to bioddes, and can be controlled. Many other types of anaerobes may be present in the mill system, including the common helical-shaped, motile bacteria Spirillum. These corkscrew-shaped anaerobes are often seen under the microscope swimming in deposit samples and soured stock. 

A. Mollica and A. Trevis, Correlation between the formation of a primary film and the modification of the cathodic surface of stainless steel in seawater. Proceedings of 4th Int. Cong. Marine Corrosion and Fouling, Antibe, France, 1976, pp. 351-355. A. Mollica, E. Traverso, and D. Thierry, On oxygen reduction depolarisation induced by biofilm growth on stainless steels in sea water. Aspects of Microbially Induced Corrosion (D. Thierry, ed.). University Press, Cambridge, UK, 1996. 

Oxygen reduction current density on stainless steel exposed to natural seawater and continuously polarized at fixed cathodic potentials. The envelopes of curves 1 and 2 correspond to the set of data on clean and already fouled stainless steel surfaces, respectively. (From Mollica, A. et al.. Aspects of Microbially Induced Corrosion, D. Thierry, ed.. University Press, Cambridge, U.K., 1996.)... 

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