June 30 2023 0Comment

Understanding the Corrosion Triangle

Article by – Dale Grant – Marketing Specialist-

The Legend of Zelda has the Triforce. Michael Jordan and the Chicago Bulls of the 1990’s had their offense. Frito-Lay has the Dorito. Pythagoras had his theorem. Needless to say, the Triangle and its cousin the pyramid are proverbial rockstars in both the two and three dimensional worlds. There is one triangle you come across regarding your building’s fire sprinkler system. The dreaded corrosion triangle with its sides made up of Metal, Water (electrolytes) and Oxygen.

What exactly is corrosion?

Corrosion is a natural process that converts a refined metal into a more chemically stable oxide, leading to the gradual deterioration of materials by chemical and electrochemical reactions with their environment.

According to the National Fire Sprinkler Association (NFSA), there are generally 9 types of corrosion we see in Fire Sprinkler Systems. These include:

  1. General or Uniform Corrosion
  2. Galvanic Corrosion
  3. Crevice Corrosion
  4. Pitting (Pinholes)
  5. Selective Leaching
  6. Intergranular Corrosion
  7. Microbiologically Influenced Corrosion
  8. Environmental Crack, Including Fretting (Fatigue)
  9. Erosion Corrosion

What causes corrosion in a fire sprinkler system?

It really comes down to the type of corrosion being experienced. In the event of galvanic corrosion, you typically have two different metals in contact with each other. You may also have a difference in oxygen concentration, leading to crevice corrosion.  Corrosion can also be triggered or exasperated by changes in pressure or temperature. Even the process in which piping is shipped can increase the chances of expediting corrosion.

So now that we know what causes corrosion, the question becomes: How do we mitigate it? Well, it all comes down to that triangle. To reduce corrosion, we need to break one of the sides. Let’s look at each side in turn.


Creating a fire sprinkler system completely free of metal parts is going to be an uphill battle. While using CPVC or PEX pipe removes metal from the corrosion triangle, these parts are still susceptible to their own forms of corrosion.

As metallic pipe is the most viable and economical choice for a fire suppression system, utilizing protections through coatings, treatments and galvanization can be the best way to extend the life of your building’s fire suppression system.


Removing oxygen from the corrosion triangle is another way to take control. One increasingly popular method in the industry involves the use of Nitrogen within the system. By replacing the oxygen with a gas known to be benign to metals, the risk of corrosion is significantly reduced. While there are generally higher upfront costs involved for the equipment, nitrogen systems can provide increased longevity to a system, making the initial expense worth the investment.  

Other options include the use of desiccants, which can be costly and labor intensive. Regularly venting the pipes on wet systems is also a recommended practice to help mitigate corrosion.


Removing water from the equation will also help significantly reduce, but not necessarily eliminate the risk of corrosion. This would involve the application of a dry pipe or preaction system. These are systems which eliminate the water in a system, instead filling the system’s pipes with compressed air or nitrogen. When the system is activated, the pressurized air escapes the system and water fills the pipes and flows through the system’s sprinkler heads. This does not completely remove the opportunity for corrosion as factors like condensation and other environmental factors can result in water forming in the pipes and recreating the triangle.


An Important note

Like Dorito’s impact on your waistline, a little corrosion is inevitable in your fire sprinkler system and that triangle isn’t going to cause you too much trouble as long as any issues are addressed before there is a serious problem. This makes the need for regular inspections and service vitally important to the health of your system.

Michael Jordan said, “Always turn a negative situation into a positive situation.” Addressing tiny problems caused by corrosion can save you from major repairs down the road.

Contact Oliver Fire Protection and Security to discuss a customized inspection and service plan for your facility.

Dale Grant