What is MIC?
It is not uncommon or necessarily an impairment to find corrosion in fire sprinkler systems. Black steel pipes and ferrous fittings naturally react to environmental conditions such as the presence of water, oxygen and the connection of dissimilar metals. Unfortunately, there is another type of corrosion that has become more common the past few years and poses an imminent threat to the function and integrity of systems: Microbiologically Influenced Corrosion (MIC). Since the 1990s, bacterial infections that cause MIC have been found in nearly every part of the United States. MIC attacks all types of metals in a fire sprinkler system, with steel pipes being the most vulnerable.
MIC is caused by biological organisms (microbes) that form bacterial colonies within fire sprinkler system piping. MIC can degrade or cause failure in many different types of systems including boilers, cooling towers, heat exchangers, process piping and of course, fire protection. MIC attacks newer and older installations and is found in both dry - and wet - pipe systems. Once it has been discovered and diagnosed, the only way to treat it is to administer a remediation program that specifically addresses the nature and extent of the infection. Ironically, one of the most common scenarios with MIC infections is that efforts by building owners and maintenance personnel to eradicate the infection by flushing systems with fresh water has exactly the opposite effect. The introduction of fresh water brings a renewed supply of oxygen that reinvigorates the bacteria and accelerates the problem.
If microbiologically influenced corrosion is suspected due to observation of slime, restrictions in flow, or leaks/pinhole leaks in pipes, it is critical that inspection and forensic testing for the presence of MIC be undertaken to determine
Whether bacteria related to MIC are present, and if so, their relative concentration
The extent of the corrosion present
The source of the corrosion
Limits of the MIC affected system components
Once MIC has been confirmed, it must be remediated as soon as reasonably possible. While it's not possible to reverse the effects of corrosion, the good news is that there is a proven and effective process to stop the progression and extend the life of the system for decades.
As a corrosion management specialist, Protection Design and Consulting has developed strategic partnerships and a program based on site-specific field conditions, forensic data and sound chemistry. If you are working with a contractor, ask them to provide corrosion and bacterial test data to substantiate their findings and proposed solution. Be wary of gimmicks such as treatment of wet-pipe systems with nitrogen - the only PROVEN method to kill bacteria and inhibit corrosion is a stepped program of diagnostic testing (including internal inspection and videography), physical repairs and a chemical treatment program tailored to the specific conditions found at that property. Nitrogen is an excellent choice for supervisory air supplies in dry-pipe and pre-action sprinkler systems, but nitrogen bubbles in the water is not a solution to pinhole leaks, scale and corrosion.