Galvanized steel has been used in a variety of industries for many years to prevent atmospheric corrosion of steel. The galvanizing process involves the application of a thin layer of metallic zinc to the substrate base metal which is typically mild steel. In almost every industrial application, galvanizing is used to protect mild steel, from atmospheric corrosion by oxygen.
In theory, use of galvanized steel tubing in dry pipe fire sprinkler system applications makes sense. The exterior of the tubing will not rust due to atmospheric oxygen corrosion because the zinc carbonate layer forms and protects the external surfaces and the “essentially dry” state of the interior piping should mean that corrosion is minimal.
Unfortunately galvanized steel pipe is NOT more corrosion resistant than black steel piping under normal use conditions in dry and preaction fire sprinkler applications. The atmosphere inside dry pipe fire sprinkler systems presents a persistently moist, oxygen rich environment which means that the galvanized coating corrodes at a very high rate. Galvanized steel tubing performs very poorly when used as dry and preaction fire sprinkler pipe. If water is trapped within the piping network the zinc layer will break down quickly and ultimately lead to a pin‐hole leak.