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  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. 
References (see more:
P. Linhardt, Manganoxidierende Bakterien
und Lochkorrosion an Turbinenteilen aus CrNi-Stahl in einem Laufkraftwerk,
Werkstoffe und Korrosion 45, 79 (1994).
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).
P. Linhardt, Pitting of Stainless Steel
in Freshwater Influenced by Manganese Oxidizing Microorganisms, DECHEMA
Monographs 133, 77 (1996).
Linhardt, Corrosion of metals in natural waters influenced by manganese
oxidizing microorganisms, Biodegradation 8, 201 (1997).
Linhardt, Electrochemical Identification of Higher Oxides of Manganese in
Corrosion Relevant Deposits Formed by Microorganisms, Mat. Sci.
Forum, 289-292, 1267 (1998).
Linhardt, Corrosion processes in the presence of microbiologically deposited
manganese oxides, CORROSION 2000, paper no. 398 (Houston TX: NACE
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).
Linhardt, A. Nichtawitz, MIC in Hydroelectric Power Plants,
CORROSION 2003, paper no. 03564 (Houston TX: NACE
P. Linhardt, Microbially influenced
corrosion of stainless steel by manganese oxidizing microorganisms, Materials
an Corrosion 55(2004), p. 158-163.
Linhardt, G. Mori, MIC by Manganese Oxidizers in a Paper Mill,
CORROSION 2004, paper no. 04601 (Houston TX: NACE
P. Linhardt, Corrosion at Welds of
Stainless Steel Pipes, Influenced by Manganese Oxidizers, CORROSION 2005,
paper no. 05490 (Houston TX: NACE International, 2005).
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
P. Linhardt, MIC of Stainless Steel in
Freshwater and the Cathodic Behaviour of Biomineralized Mn-Oxides,
Electrochemica Acta 51, 6081 (2006).