Sprinkler Protection from Corrosion
In the beginning there was brass and it was good. Brass while a good metal for use in water, is was not suitable for corrosive atmospheres found in some industrial facilities.
I live near the coast in Florida and have seen many sprinklers installed in areas such as parking garages, apartment breeze ways, etc. All a nice shade of green. My company makes good money replacing heads in places such as this. Early on in the sprinkler industry they discovered this and worked to develop finishes and coating to protect against corrosion.
Some early sprinklers were coated with materials such as paraffin, asphaltum or wax, with wax being the most successful. Wax coated heads are still used today. The earliest mention I can find is in Gorham Dana’s book “Automatic Sprinkler Protection” from 1914. It indicates that wax coatings were commonly used at that time.
Also tried were lead coatings. Thought still available today, I do not believe they are used often, as I have never seen one ordered in over 30 years in the business. But the companies still carry them so someone must be using them.
Grinnell took a unique approach in the past. They manufactured a sprinkler with a clear glass cover. I have seen this old sprinkler in collections without the glass cover. I had always wondered why the lip and recess around the outside. It was for the insertion of the glass cover. I was fortunate to get one of these sprinklers with remnants of the cover, but have never seen one intact. See Pictures below.
The concept is still used in the form of blow off caps, but limited to open sprinklers and nozzles where detection is separate from the discharge piping.
The only thing new I’ve seen is from Victaulic. They have a new proprietary nickel Teflon coating that is listed by UL.