All types of fire sprinkler systems are susceptible to some type of corrosion, not just wet systems. Corrosion of any kind can be detrimental to a sprinkler system. It can lead to permanent damage to the piping system and render an entire system inoperable. Corrosion is also the leading cause of maintenance and operation problems for fire protection systems.

The problem is that you can’t see the inside of the pipes of your fire sprinkler system. It’s impossible to know that corrosion is occurring without a professional’s inspection/test.

Microbiologically Influenced Corrosion, or MIC, is a relatively new type of corrosion that affects fire sprinkler systems. It’s an aggressive, accelerated type of corrosion caused by a specific type of bacteria that can be challenging to predict and/or prevent.

Defining Microbiologically Influenced Corrosion (MIC)

Microbiologically Influenced Corrosion, or MIC, can be defined as “an electrochemical corrosion process that is concentrated and accelerated by the activity of specific bacteria within a fire sprinkler system resulting in the premature failure of metallic system components.”

This process of corrosion involves a series of electrochemical interactions, which means electrical and chemical reactions can occur.

In short, this complex and specified type of corrosion is caused by bacteria; aerobic (requires oxygen), anaerobic (does not require oxygen), or a mix of the two. All types of systems can experience MIC.

General corrosion vs. MIC

General corrosion affects a widespread area whereas MIC affects a smaller, more concentrated area. General corrosion occurs in most unprotected metallic systems (think rust). It covers uniformly exposed surfaced. MIC on the other hand is more localized and the result of a specific bacteria. Unlike general corrosion, all surfaces and materials are at-risk for MIC, not just metals.

General corrosion usually occurs in older piping networks or over a longer period of time as a result of the natural aging process. MIC can occur in sprinkler systems as young as 5 years old, up to 20+ years old.

The damage caused by both general corrosion and MIC are similar (pitting, cratering, etc.); these affects just happen at a faster and more aggressive pace when the corrosion is a result of MIC.

Dangers of MIC

Pockets of biological growth, as MIC cause, can affect the overall performance of a fire sprinkler system. There does not need to necessarily be wide sweeping areas of damaged piping as general corrosion would create. Smaller, localized areas of corrosion are just as detrimental as more widespread areas of general corrosion.

Take for example a major damage of MIC: premature failure of the metallic components of an automatic sprinkler system. This damage can lead to failure to hold water (pinhole leaks) or failure of a system to operate as designed to achieve fire control (obstructed sprinkler built up with biofilm/biosludge). The result is a decrease in water flow or complete obstruction of water to flow through the piping network.

A growing problem

MIC was first discovered in the early 1990s. Over these past 20 years, experts still don’t know a lot about this type of corrosion. In fact, studies by FM Global reflect the growth of MIC since it’s discovery. A study from 1988-1997 found MIC was present in 40 percent of systems that failed due to corrosion. When that study was replicated from in 2002, that percentage jumped to 60 percent.

According to the independent rating bureau, WSRB, “factors such as the introduction of thin-walled (Schedule 5 and Schedule 10) piping in the 1980s, changes in the chemicals used by water treatment facilities in the 1980s and 1990s, the proliferation of electroplating, an increased awareness of MIC and the rising number of buildings with sprinkler systems all contribute to the sharp increase in reported cases of MIC.”

Despite the continuation of research into this topic, there are several ways to detect and treat cases of MIC.

Diagnosing MIC

Other than the discovery of pitting corrosion or pinhole leaks by a fire protection professional, a leaking sprinkler system is one of the first indicators that something is amiss.

If MIC is suspected to be the culprit, a licensed professional can conduct water analysis testing and internal pipe investigations. A fire protection professional may find an excessive amount of pinhole leaks in a younger system, for example. This would point to MIC.

Preventing and treating MIC

When caught right away, sprinkler systems can be treated and repaired before more serious damage can occur. If left untreated, however, serious and costly damage can occur that may require an entire system replacement.

Some prevention strategies, as recommended by WSRB, include:

  • Flushing sprinkler systems with a detergent to remove any oils or debris left on the interior of the pipe.
  • Treat the initial fill in a new system with biocides and corrosion inhibitors.
  • Try to schedule any modifications, repairs and maintenance of the system to be done at the same time to reduce the number of times the system has to be drained and refilled. When fresh water and oxygen is introduced into the system, it provides a new food source for bacteria, causing an acceleration of growth.
  • Know what to look for. Leaks, weeping joints and water that is smelly or black when the system is flushed are all indications that you may have MIC.
  • Consider using thick-walled piping if you live in an area that is prone to MIC and are having a new system installed.
  • Schedule regular MIC inspections, whether your system is new or existing.

Fire Systems, Inc.

 A fully functioning fire sprinkler system is a vital component to an effective fire protection strategy. These dynamic systems are often complex, and they require regular inspections and maintenance. We inspect your sprinkler system using Fire Systems, Inc. technicians – with no sub-contracting; this gives us better control over the quality of service we are able to provide.

Our software system keeps track of when inspections are due, so you never have to worry about being late on required inspections. We can also provide training in the proper use and maintenance of your system.

We also perform installations, repairs, and modifications on all types of fire sprinkler systems.

Call us today at 770-333-7979 or visit our website for more information.