There is now a significant body of evidence that suggests that the use of galvanized steel pipe in dry and preaction fire sprinkler systems may expose mission critical facility owners to the risk of premature system failure due to internal corrosion. Conditions that typically exist within dry and preaction fire sprinkler system piping create an environment in which zinc coated mild steel will corrode, sometimes quite aggressively. In the case of mission critical facilities, the risks of premature failure are more pronounced than they might otherwise be because of the sensitivity and costs of the systems that are being protected. A water leak simply cannot be tolerated.
Mild steel piping will also corrode in the environment that is found in dry and preaction fire sprinkler systems. However, in the case of galvanized steel the corrosion mechanism creates highly localized attack of the base metal once the galvanized layer is breached. As a result, although mild steel initially corrodes more quickly than galvanized steel in the persistently moist oxygenated environment that exists within the piping, the corrosion is more uniform and the oxygen attack is distributed over the entire wetted metal surface. In the case of galvanized steel, voids in the zinc coating tend to concentrate the corrosion of the underlying base metal in those portions of the piping where the zinc coating has been dissolved. These areas are subject to aggressive pitting attack and the resultant through the wall pipe penetrations.