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Acid Based Corrosion in Antifreeze Fire Protection Systems

Acid Based Corrosion in Antifreeze Fire Protection Systems
While Oxygen corrosion is the primary cause of degradation of fire sprinkler piping in water based fire sprinkler systems, there is another phenomenon that leads to pinhole leaks in antifreeze systems – acid corrosion. Acid corrosion is found in both antifreeze systems and the adjacent fire protection systems that supply fresh water to antifreeze systems and causes a very aggressive, highly localized attack of the sprinkler piping.

Acid corrosion in antifreeze systems is due to the breakdown of two primary chemicals found in antifreeze – propylene glycol and ethylene glycol. 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. Antifreeze chemicals and/or organic acids have been found to “creep” into adjacent wet pipe fire protection systems that supply anti-freeze systems with fresh water for mixing purposes. Once the chemicals and acids enter the wet pipe system, the solutions mix and significant leaks develop.

Note: this white paper appeared in the September 2015 edition of Fire Protection Contractor Magazine

Randomized, sharp-edged pits caused by acid corrosion

Randomized, sharp-edged pits caused by acid corrosion