Acid Corrosion Caused by Chemical Breakdown of Antifreeze
Acid corrosion in antifreeze systems is due to the breakdown of two primary chemicals found in antifreeze – propylene glycol and ethylene glycol. While propylene glycol is required by NFPA to be used in antifreeze and ethylene glycol is not, ethylene glycol is present in common antifreeze mixtures and will contribute to the production of acidic byproducts. In the presence of heat and oxygen, both of these chemicals break down to form acidic byproducts (acetic, lactic, formic, etc.), most of which are highly corrosive to the mild steel in fire sprinkler piping. This process is called thermal oxidation.
Acid corrosion causes a very aggressive, highly localized attack of the sprinkler piping. Leaks can occur in a very short amount of time and is further accelerated if fresh antifreeze is not replenished frequently in the antifreeze system.
Risks of Acid Corrosion
- Rapid, unpredictable metal loss of sprinkler piping leading to pinhole leaks
- Health hazard related to exposure of fire sprinkler water with pH less than 4.0
- Premature failure of sprinkler pipe weld seam
It is clear that the use of antifreeze in fire sprinkler systems is a misapplication of the chemical.