Microbially influenced corrosion by manganese oxidizing microorganisms
(MIC by MOMOS)

  This project started in 1991 when the TVFA got involved in a corrosion case in a hydroelectric power plant in the Netherlands. After just 2 years of service, severe chloride induced pitting corrosion was observed on the components made of a 13% Cr martensitic stainless steel. The chloride levels in the river water were considered too low to fully explain the attack.

Investigations identified an additional corrosive factor in the system: The metallic surfaces were covered by large amounts of manganese dioxide (MnO2) which is known to be a strong oxidant. It could be demonstrated that this substance causes a shift of the open circuit potential of the steel in the anodic direction close to the pitting potential of the steel in this water, an effect which is also known as "ennoblement".

The formation of the MnO2 could be attributed to the activity of a specific class of microorganisms, the manganese oxidizers. These organisms are capable to selectively extract the dissolved Mn2+ from the water, oxidize it to MnO2 and deposit this insoluble substance at the surface they are attached to.

The case history was first presented at the 7th International Seminar on Hydropower Plants in November 1992 at the TU Vienna.
Research was continued and a general mechanism MIC by MOMOs for this type of corrosion was proposed, expected to be a more common phenomenon in the application of stainless steel in natural waters [1-7,9].

Meanwhile, MIC by MOMOs was observed in hydroelectric power plants in other parts of the world too [8] and it was identified in several cases of stainless steel pipeworks carrying freshwater [10-12].

Research activities continue with focus on the possible electrochemical interaction of these specific microorganisms with the metal surface and on the consequences of the dynamic behaviour of the anodic pitting process linked to the specific biomineralized MnO2 as the cathodic agent. [13]
 

 

   

 

 

References  (see more: Publications)

  1. P. Linhardt, Manganoxidierende Bakterien und Lochkorrosion an Turbinenteilen aus CrNi-Stahl in einem Laufkraftwerk, Werkstoffe und Korrosion 45, 79 (1994).

  2.  P. Linhardt, Failure of Chromium-Nickel Steel in a Hydroelectric Power Plant by Manganese-Oxidizing Bacteria, in: Heitz et al. (eds.) Microbially Influenced Corrosion of Materials, Springer Verlag Berlin Heidelberg, p. 221, (1996).

  3.  P. Linhardt, Pitting of Stainless Steel in Freshwater Influenced by Manganese Oxidizing Microorganisms, DECHEMA Monographs 133, 77 (1996).

  4.  P. Linhardt, Corrosion of metals in natural waters influenced by manganese oxidizing microorganisms, Biodegradation 8, 201 (1997).

  5.  P. Linhardt, Electrochemical Identification of Higher Oxides of Manganese in Corrosion Relevant Deposits Formed by Microorganisms, Mat. Sci. Forum, 289-292, 1267 (1998).

  6.  P. Linhardt, Corrosion processes in the presence of microbiologically deposited manganese oxides, CORROSION 2000, paper no. 398 (Houston TX: NACE International, 2000).

  7.  P. Linhardt, Manganese oxides in pipes of galvanized steel for potable water a potential risk of MIC ?, CORROSION 2002, paper no. 02459 (Houston TX: NACE International, 2002).

  8.  P. Linhardt, A. Nichtawitz, MIC in Hydroelectric Power Plants, CORROSION 2003, paper no. 03564 (Houston TX: NACE International, 2003).

  9.  P. Linhardt, Microbially influenced corrosion of stainless steel by manganese oxidizing microorganisms, Materials an Corrosion 55(2004), p. 158-163.

  10.  P. Linhardt, G. Mori, MIC by Manganese Oxidizers in a Paper Mill, CORROSION 2004, paper no. 04601 (Houston TX: NACE International, 2004).

  11.  P. Linhardt, Corrosion at Welds of Stainless Steel Pipes, Influenced by Manganese Oxidizers, CORROSION 2005, paper no. 05490 (Houston TX: NACE International, 2005).

  12.  P. Linhardt, MIC by Manganese Oxidizers: The Performance of Stainless Steels and the Cathodic Behaviour of Biomineralized Mn-Oxides, CORROSION 2006, paper no. 06527 (Houston TX: NACE International, 2006).

  13. P. Linhardt, MIC of Stainless Steel in Freshwater and the Cathodic Behaviour of Biomineralized Mn-Oxides, Electrochemica Acta 51, 6081 (2006).