As a rule, air migrates through wet sprinkler piping to the highest points of the system, where it accumulates in pockets under compression due to the water pressure in the system. These “trapped air pockets” are comprised of 20.9% oxygen, which drives the corrosion of the interior pipe wall at the air-water interface.

Another contributor to the corrosion of wet sprinkler piping comes from the highly oxygenated water that fills the system. The dissolved oxygen in the fill water reacts with the steel to form a layer of corrosive black iron oxide (magnetite) along the submerged areas of the interior pipe wall. In addition, the dissolved oxygen can transfer out of the water and into the trapped air pockets, helping to sustain the corrosion reaction at the air-water interface.

Corrosion leads to the formation of localized pinholes and the resulting sprinkler pipe leaks, cause sprinkler head blockage, reduce flow rates, and render fire protection systems completely inoperable in the event of a fire – leading to loss of life and property.