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SULFATE-REDUCING BACTERIA,
MICROORGANISMS, ETC...
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Especially the sulfate-reducing bacteria (e.g. desulphovibrio
desulphuricans), which occur under anaerobic conditions
(e.g. deeper soil layers), are important with regard
to underground corrosion. They can catalyse the reduction
of SO4= ions to S=, and this reduction allows a corresponding
oxidation (corrosion) of steel.
Nevertheless, also other microorganisms or biological
life can play a role in underground corrosion, e.g.:
| - | aerobic bacteria that can oxidize iron or form mineral
acids, |
| - | slime-producing microorganisms that form deposits and
cause the formation of local corrosion cells, |
| - | fungi that may attack organic coatings, |
| - | roots that may grow into a protective coating or lining
and cause severe damage. Therefore -in general- underground
structures should as far as possible be laid outside
the limits of the roots of trees and tall bushes. Moreover,
the surface of a bituminous or other coating should
be smooth, since even minor irregularities prevent
deflection of the roots, with the consequence that
these tend to grow into the coating. |
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