Photo Gallery B9:  Microbiologically Influenced Corrosion

Microbiologically Influenced Corrosion, commonly termed MIC, can produce excessive corrosion losses of up to 50 MPY and greater, but fortunately it is relatively rare.  Microbiological corrosion is associated with heavily contaminated open condenser water systems where large volumes of rust and debris have settled.  It has also been cited as the cause of premature failure and the blockage of dry and pre-action fire sprinkler systems, although mistaken as such in most cases we have investigated.

The severe corrosion loss caused by MIC is related to the fact certain anaerobic microorganism, classed as sulfur reducing bacteria (SRB), produce highly acidic conditions which in effect dissolve away the steel pipe.  Trapped under rust and other particulate deposits, such microorganisms mutate to become anerobic, meaning that they no longer require oxygen.  Instead, they draw energy from the steel substrate; producing severe wall losses as a result.  Confirmation of an MIC condition is extremely important in order to plan for the correct response, with laboratory confirmation is required.  Field testing kits for MIC are available but require very specialized live sampling methods.

Severe cases of MIC are extremely difficult to eradicate, and the deep pitting damaged caused to the pipe cannot be reversed.  Repeated cleanings and sterilizations are required.  Since biocides only suppress biological growths, sterilization requires the temporary application of chlorine, bromine, or ozone.