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Controlling microbiologically influenced corrosion in fire sprinkler systems

Microbiologically influenced corrosion (MIC)-causing bacteria seem to be everywhere. Evidence of their presence and by-products was recently reported to be on Mars.1,2 MIC-causing bacteria are present to some degree in almost all of our potable and municipal water supplies.3 It is a worldwide problem, and we are all affected by the effects.

MIC-causing bacteria first became a concern in the fire protection industry in 1998, when their presence was detected in a nursing home in Iowa when the sprinkler system malfunctioned when tripped by a fire.4 The National Fire Protection Association, in updated versions of its NFPA 13, Standard for the Installation of Sprinkler Systems, and NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, quickly addressed this problem. MIC committees were formed and are in existence today.5

We have now identified the problem. The question is, Are we approaching remediation and mitigation in the proper way?

Implications for the future

It is estimated that the fire sprinkler market will continue to grow in the United States, with 35 to 40 million sprinklers being installed annually6 and approximately 70 million7 worldwide. It may be assumed that MIC bacteria infection will also increase, endangering life and property around the world.

A national retailer that recently experienced $3 million in damage at one of its New York outlets contacted WHI USA, Inc. about resolving its continuing pinhole leaks. We found extremely high and aggressive acid-producing bacteria levels. Remediation and mitigation procedures had to be performed to eradicate this damaging problem. This is just one example that illustrates how destructive MIC can be to property. MIC in fire protection systems will not be eradicated, but it can be controlled with proper mitigation and remediation.

MIC bacteria have been reported to be extremely aggressive, with corrosion rates recorded as high as 20 to 100 mils per year (MPY). (3) This makes the integrity of four-inch (schedule 40) pipe subject to failure within one year. What about the risk to the popular thin-walled (schedule-10) pipe? Neither is a long-term asset if MIC is not identified and controlled.


MIC is found in many industries; it has long been a problem in the oil and gas, water treatment, textiles, nuclear, pulp and paper, and numerous other industries where water is used as part of the process. These industries have confronted the MIC problem most commonly by using biocides in the workplace. The fire sprinkler industry recently has adopted biocides for mitigating MIC. There are several problems with using biocides in fire sprinkler systems.

The Environmental Protection Agency (EPA) defines biocides as “a diverse group of poisonous substances, including preservatives, insecticides, disinfectants, and pesticides, used for the control of organisms that are harmful to human or animal health or that cause damage to natural or manufactured products.”8

The EPA requires that biocides be registered. This does not make them less poisonous but allows the chemicals to be used under certain guidelines. Should we be using such methods in fire protection systems that are there to protect the public?

The industries that have historically used biocides have very little, if any, public exposure. Therefore, there have been only a few reported instances of the public having been exposed to biocides in these industrial processes. What happens when a fire sprinkler system is tripped in a crowded retail store or a nursing home and dangerous biocides are atomized in the air and possibly inhaled by people exiting the building?

The fire sprinkler industry must look at this risk differently than other industries. The threat to the public is high, as is the potential for liability and litigation. Biocides also contaminate our land, streams, lakes, and seas. Property owners and managers who use them are liable for environmental remediation of their real estate and facilities.8

The MIC bacteria become “immune” to biocides when used over time, thus creating immunity to the exact bacterium species we are trying to kill. They mutate so that they are not affected by that certain biocide, much in the same way that antibiotics become ineffective if used too often. Biocides must be rotated on a regular schedule to be effective. Eventually, the bacteria become immune to all of the available biocides and ineffective in killing the MIC bacteria, creating “Super-Bacteria.”


Another philosophy for mitigating MIC is to coat the internal diameter of the piping or tubing so bacteria cannot attach to form a colony (biofilm). Why try to kill all the MIC-causing bacteria when you can protect the piping, tubing, and fabricated product? We are trying to control corrosion and protect our assets in an environmentally friendly manner. Let’s look at some of the various kinds of coatings. Not all coatings are created equal.


This group is most familiar to us. We see them every day in the paint on our car and house to tar coatings on pipelines. They create a “physical barrier” to chemical corrosion, such as oxygen-cell corrosion and the formation of “rust.” They protect from MIC-causing bacteria very well. These coatings usually have a polymeric basis and form a coating that is susceptible to microcracking (from film shrinkage), allowing MIC bacteria to enter and start forming corrosive colonies underneath. This affects the integrity of the iron by honeycombing the pipe walls, like Swiss cheese, sometimes not evident to the naked eye. This creates a false sense of protection.

Permanent biostatic

This group, a definite improvement over conventional coatings, contains molecules that ward off MIC bacteria attachment and colony formations. They are a good solution for various applications. However, they have some drawbacks when used in fire protection systems: Most fire protection systems are fabricated on-site. They contain many components, and only the coated part of the system will be protected from MIC. In fact, the new welds, threads, sprinkler heads, and valves will experience an accelerated MIC problem because the bacteria are competing for a place of attachment on a limited surface area. The MPY corrosion rate on these uncoated components may exceed the corrosion rates of a completely unprotected fire protection system; the system’s life can be extremely shortened. Also, some of these coatings present environmental concerns.

Dynamic Biostatic

Dynamic biostatic is a relatively new classification for coatings. They may be applied on fire protection system pipe, tubing, or other components. The dynamic biostatic coating becomes part of the overall fire protection system.

These coatings are somewhat water soluble. When a fire sprinkler system is filled with water, some of the coating becomes soluble and the molecules are equally concentrated throughout the system by a process called “ionic-diffusion.” The dynamic coatings are attracted to the component’s surface through a chemical reaction that bonds the coating to all uncoated metallic surface areas, coating the entire fabricated system.

The coating’s concentration can be measured in the sprinkler system water. When the concentration becomes low, a maintenance canister can be added to boost the level. The coating is environmentally friendly, nonregulated, and nonhazardous to people, land, or bodies of water. The level of dynamic biostatic coating must be maintained periodically, usually once a year.

WHI USA, Inc. has recently been awarded a U.S. patent on a dynamic biostatic coating (U.S. # 6,517,617), Par-Guard. The product, developed for fire sprinkler systems, is nonhazardous, environmentally friendly, economical, and convenient to use. Additional information is available at the Web site (e-mail: Info@

I believe dynamic biostatic coatings can ward off the attachment of MIC bacteria and colony formation in fire protection sprinklers. One thing is certain: We must widen our spectrum in the remediation and mitigation of MIC in fire protections systems. The public and the environment currently are exposed to unnecessary risks.

Printed with permission of FPC/Fire Protection Contractor magazine.


1. Vance, David B. “Life on Mars: 2 the 4 Technology Solutions: The Ubiquitous Vigor of Microbiological Systems,” 2004.

2. Dr. David Noever, “Brewing Sulfur with Martian Water,” Astrobiology: Search for Life in the Universe,

3. “MIC The Greatest Threat to Any Condenser Water System,” Technical Bulletin # C-06, East Coast Industries,

4. “Iowa Authorities Suspect MIC: Nursing Home System Plugged With Rust-Colored Material,” Sprinkler Age, 1998.

5. National Fire Protection Association, “Microbio-logically Influenced Corrosion (MIC) Phase II,”13 MIC Task Group, Roland Huggins.

6. Russell P. Fleming, P.E., National Fire Sprinkler Association, 2002.

7. “Sprinkler Scene,” IFSA, Sept.-Dec. 2003.

8. Environmental Protection Agency FIFRA Pesticide Act, 1972.

DOUG CHARTIER is president/CEO of WHI USA, Inc. He is the co-author of various patents, is a “hands-on” field chemist, and has been involved with MIC for 24 years. He was recently awarded a U.S. Patent on the biostatic coating “FPS MIC remediation & mitigation methods and apparatus #6,517,617.” He is a member of the National Fire Protection Association and the American Chemical Society.

Fire Engineering November, 2004
Author(s): Doug Chartier