#350 – Guide to Corrosion-Resistant Fire Sprinkler Heads

Fire sprinkler heads corrode quickly in certain environments—here are the models that resist it

Corrosion converts compounds such as iron, brass, and bronze from their metallic states into less reactive molecules, often oxides and sulfides. Iron oxide (rust) is the most familiar example of this. Corrosion slowly weakens and destroys equipment as metal dissolves or flakes away.

Depending on the environment, fire sprinkler systems require special protection against corrosion. Metallic fire sprinkler pipes can corrode particularly readily because oxygen dissolved in water corrodes metal. Depending on the severity, a corroded fire sprinkler pipe can constitute a critical deficiency or an impairment. A light coating of rust won’t cause an immediate problem, but it will reduce the lifespan of the system. Thinning walls, pinhole leaks, or more significant holes are significant issues.

The same goes for fire sprinkler heads. As the business ends of sprinkler systems and with specified coverage areas, every fire sprinkler head must work properly in a fire. Corrosion of sprinklers both reduces their lifespan and creates deficiencies and/or impairments. In this article, we:

  • List the environments where corrosion resistance is needed in fire sprinkler heads
  • Explain how corrosion resistance is applied to fire sprinklers
  • Give a brief guide to the Viking, Victaulic, and Tyco sprinkler heads that are available with corrosion-resistant materials or finishes

Corrosive environments and the types of fire sprinkler heads that work in them

In many environments, corrosion-resistant sprinkler heads are an unnecessary extra expense. To understand how corrosion resistance works and whether you need it, first understand why it happens.

The National Fire Sprinkler Association (NFSA) explains that corrosion, like fire, depends on three factors. Instead of heat, fuel, and oxygen, the “corrosion triangle” includes exposed metal, oxygen, and an electrolyte. Electrolyte levels—ions dissolved in water—will often determine the risk. Reducing the amount of exposed metal is the core way that corrosion is prevented in sprinkler heads.


Picture of the Corrosion Triangle
Corrosion requires exposed metal, moisture, and oxygen. It is prevented by removing one or more of these factors. Source: Zerust

Corrosive environments

Specific environments promote corrosion. Because of the moist salty air, exposed metal in coastal areas corrodes more quickly. The atmosphere in industrial settings can contain metal oxides, chlorides, sulfides, acids, and other compounds that serve as electrolytes and promote corrosion.

The National Fire Protection Association (NFPA) provides an extensive list of corrosive environments in the 2019 edition of NFPA 13: Standard for the Installation of Sprinkler Systems:


Examples of such locations include the following:

  • Paper mills

  • Packing houses

  • Tanneries

  • Alkali plants

  • Organic fertilizer plants

  • Foundries

  • Forge shops

  • Fumigation, pickle, and vinegar works

  • Stables

  • Storage battery rooms

  • Electroplating rooms

  • Galvanizing rooms

  • Steam rooms of all descriptions, including moist vapor dry kilns

  • Salt storage rooms

  • Locomotive sheds or houses

  • Driveways

  • Areas exposed to outside weather, such as piers and wharves exposed to salt air

  • Areas under sidewalks

  • Areas around bleaching equipment in flour mills

  • All portions of cold storage buildings where a direct ammonia expansion system is used

  • Portions of any plant where corrosive vapors prevail

  • The area over and around swimming pools, chlorine storage rooms, and pool pump rooms

In such environments, NFPA 13 says listed corrosion-resistant fire sprinklers should be installed: Listed corrosion-resistant sprinklers shall be installed in locations where chemicals, moisture, or other corrosive vapors sufficient to cause corrosion of such devices exist.

Corrosion-retarding coatings and platings cover and protect underlying brass or bronze (common materials for fire sprinkler heads) from the environment. With no metal exposed to oxygen, less corrosion can occur. Common sprinkler head finishes include:

  • Polyester paints
  • Electroless nickel (ENT)
  • PTFE (“Teflon”)
  • Electroless nickel-PTFE
  • Wax
  • Lead
  • Wax over lead

Not all coatings provide corrosion resistance. Fire sprinkler heads used in corrosive environments should carry a UL listing for the purpose. The rigorous testing standards in UL 199: Standard for Automatic Sprinklers for Fire-Protection Service require sprinklers to pass a heat sensitivity test after 30-day exposure to:

  • 20% salt fog
  • Moist hydrogen sulfide air mixture
  • Moist CO2-sulfur dioxide air mixture

FM approval is sometimes found alongside a UL listing.

Only the manufacturer may coat, paint, or finish a fire sprinkler. With an exception for repairs made following manufacturers’ instructions, NFPA 13 forbids such aftermarket additions to sprinklers:

From the 2019 edition of the NFPA 13 Handbook

FAQ []

Who can apply corrosion-resistant coatings to sprinklers?

A corrosion-resistant sprinkler can be designed with corrosion-resistant materials or, as is common, have a corrosion-resistant coating, such as wax or lead, applied to it. The manufacturer can only apply a corrosion-resistant coating except as permitted for the repair of a damaged coating if the damage occurred during installation. The sprinkler manufacturer should be consulted on proper repair procedures.

The alternative to a corrosion-resistant coating is a corrosion-resistant fabrication. And the main alternative to brass or bronze in fire sprinkler construction is stainless steel.

In general, stainless steel gives the best corrosion resistance. A nickel-PTFE plating, however, also offers extensive protection. Wax, especially over polyester paint or lead, provides decent coverage. And polyester paint on its own is better than bare brass or bronze.

If you need a primer on what a SIN is and how to find it on a sprinkler, check out our guide to sprinkler identification numbers.

Viking offers “next-generation” XT1 fire sprinklers

Hailed by Viking as the “next generation” of fire sprinklers, the XT1 series provides enhanced corrosion resistance. The deflector consists of stainless steel, and the spring and seal assembly has a PTFE seal. Viking also offers sprinklers, including those in the XT1 series, with listed corrosion-resistant white polyester, black polyester, and ENT coatings.

Picture of a Viking XT1 Fire Sprinkler
Viking’s XT1 series of fire sprinklers offer corrosion resistance through stainless steel fabrication of the deflector and a PTFE seal on the spring and seal assembly. XT1 sprinklers can be purchased with corrosion-resistant finishes for further protection.

Viking’s XT1 sprinklers

The XT1 series covers all your needs for pendent and upright sprinklers in 1/2″ and 3/4″ NPT sizes with a range of temperature responses. QRFS offers the following pendent XT1 sprinklers with or without a white corrosion-resistant finish in a variety of response temperatures:

  • VK1021 (1/2” NPT)
  • VK2021 (3/4” NPT)
  • VK3021 (1/2” NPT)
  • VK3521 (3/4” NPT)

Upright XT1 sprinklers have these SINs:

  • VK3001 (1/2” NPT)
  • VK1001 (1/2” NPT)
  • VK2021 (3/4” NPT)
  • VK3501 (3/4” NPT)
  • VK2001 (3/4” NPT)

Viking’s corrosion-resistant sidewall sprinklers

Though not part of the XT1 series, QRFS carries the following sidewall Viking sprinkler heads that are available with corrosion-resistant coatings.

  • VK102 (pendent, 1/2” NPT)
  • VK305 (sidewall, 1/2″ NPT)
  • VK319 (sidewall, 1/2″ NPT)

To inquire about other finishes or other Viking sprinkler heads, contact us at +1 (888) 361-6662 or support@qrfs.com.

Victaulic’s Firelock sprinklers available with corrosion resistance

Victaulic offers its Firelock sprinklers in coatings that are UL-listed for corrosion resistance, including white paint, black paint, custom paint colors, and nickel PTFE. The company’s proprietary VC-250 coating, a multi-layer nickel-based treatment, is both UL-listed and FM-approved.

Victaulic pendent sprinkler SINs

Victaulic has the following pendent sprinklers in a range of temperature responses with options for corrosion-resistant coatings:

  • V2708 (1/2” NPT)
  • V2707 (1/2” NPT)
  • V3405 (3/4” NPT)
  • V3406 (3/4” NPT)

Victaulic upright sprinkler SINs

Victaulic’s upright sprinklers with options for corrosion-resistant coatings come in a range of response temperatures and have the following SINs:

  • V2703 (1/2” NPT)
  • V2704 (1/2” NPT)
  • V3401 (3/4” NPT)
  • V3402 (3/4” NPT)

Victaulic sidewall sprinkler SINs

Victaulic’s corrosion-resistant sidewall sprinklers, which QRFS stocks mainly in white finishes, have the following SINs:

  • V2709 (1/2” NPT)
  • V2710 (1/2” NPT)
  • V3409 (3/4” NPT)
  • V3410 (3/4” NPT)

Contact us to inquire about purchasing other colors, nickel PTFE, and VC-250 coatings.

Picture of Victaulic Corrosion Resistant Fire Sprinkler
Victaulic offers corrosion resistance via custom paint colors, nickel PTFE coating, or VC-250 finishes for their fire sprinklers.

Tyco’s corrosion-resistant fire sprinklers

Tyco offers pendent, upright, and sidewall sprinklers with corrosion-resistant polyester finishes, lead coats, and wax-over-lead coats. The manufacturer’s polyester-coated sprinklers carry UL listings, and lead-coated sprinklers have FM approval.

Picture of Tyco Corrosion Resistant Fire Sprinkler
Out of the brands listed here, Tyco sprinklers are the only ones available with wax and wax-over-lead coats in addition to polyester paint finishes, as pictured here.

Tyco pendent sprinkler SINs

Tyco’s pendent sprinklers are available in pure white and signal white corrosion-resistant polyester finishes. QRFS stocks the following SIN numbers:

  • TY323 (1/2” NPT)
  • TY325 (1/2” NPT)
  • TY313 (3/4” NPT)
  • TY315 (3/4” NPT)

Tyco upright sprinkler SINs

Upright sprinklers with the following SINs are available from Tyco with pure white and signal white corrosion-resistant polyester finishes:

  • TY313 (1/2” NPT)
  • TY315 (1/2″ NPT)

Tyco sidewall

Tyco’s sidewall sprinklers are offered with polyester coatings. (pure white, signal white, and jet black colors available). TY3331 (1/2” NPT) is also available with a lead coat. TY3351 can be purchased with a lead coat, a wax coat, or a wax-over-lead coat in addition to these colors.

To inquire about purchasing lead and wax-over-lead finishes, contact us.

In the right environments, use corrosion-resistant sprinklers

If your environment demands it, make sure your fire sprinkler system stands ready to suppress fires for years to come by investing in corrosion-resistant sprinkler heads. Fire sprinklers listed for use in corrosive environments are either made of non-corroding materials such as stainless steel or have corrosion-retarding finishes or coatings like polyester paint, nickel, PTFE, wax, lead, or others.

Victaulic, Viking, and Tyco offer fire sprinklers that have passed intensive corrosion tests according to UL 199. Viking’s XT1 sprinklers feature corrosion-resistant deflectors and optional polyester and ENT coatings. Victaulic’s sprinklers are available with polyester, nickel, and their proprietary VC-250 coating. Tyco offers polyester finishes, and it is the only company among these three to provide wax and wax-over-lead coatings.

Outfit yourself with corrosion-resistant sprinklers by referencing the sprinkler identification numbers (SINs) listed above and shopping our full selection of commercial fire sprinklers.

If you have questions or you’d like to find other finishes or models, call us at +1 (888) 361-6662 or email support@qrfs.com.


This blog was originally posted at blog.qrfs.com. If this article helped you, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.

8 thoughts on “#350 – Guide to Corrosion-Resistant Fire Sprinkler Heads”

  1. Looking for recommendation for sprinkler heads over plating area with presence of fugitive amounts of nitric acid in air stream precipitating failure of heads after about 12 years after installation, Is there a product that you would recommend?

    • Francis — This is a tough question that may be a little complex. First, you’d need to specify what caused the failure of heads: for example, the frame or other structural elements corroded or the heat-sensitive element lost its functionality. Second, while fire sprinkler manufacturers make sprinklers with frames and certain structural components that are resistant to corrosion and various chemicals, we haven’t seen nitric acid explicitly mentioned. These materials, as indicated above, include polyester paint, stainless steel with a nickel-PTFE coating, and wax coatings. Quickly looking at various chemical resistance charts shows that while nickel is not resistant to nitric acid, PTFE and polyester are. Thus, it’s a good bet that these materials will provide some resistance to that environment. But you should be certain before purchasing. So, the best bet is to make a list of corrosion-resistant sprinkler models based on the material mentioned above and contact the manufacturer to see if they have any specific data on nitric acid resistance.

  2. I’m looking for a storage sprinkler with min K11.2 for a salt storage room.
    Ideally stainless steel but at the very least PTFE coated.
    My searches so far have come up with nothing.
    Do you know of any manufacturers that have this type of head as a standard part of their range?

  3. I have been trying to understand the application of wax coated heads as opposed to other corrosion-resistive heads that are more common. In what situations would you utilize a wax coating instead of other methods of corrosion resistance?

    • Aaron — with the caveat of not directly looking up and comparing the up-to-date costs, the general answer would be cost and whether are they good enough to resist the specific environment. As this Viking data bulletin shows, wax-coated and wax-over-polyester finishes beat PTFE coatings in overall corrosion resistance, but lag behind Electroless Nickel PTFE** (ENT) and Stainless Steel (and the latter is significantly more expensive). Also, here is an interesting fire pro exchange on the subject.

  4. Have a need to put sprinklers in a exhaust duct that pulls from a pickling process utilizing Sulfuric acid. 316 SS has performed well but we have found that cast 316SS does not last. The casting process naturally has porosity issues that the sulfuric acid eats out. The temperature is pushing 160-degree F. Any suggestions???

    Thx – Scott

    • Scott — Apologies for the delayed response. Unfortunately, we aren’t sure with certainty what fire sprinklers will stand up to sulfuric acid. This source mentions various stainless steel alloys, and this research paper from FM Global seems to address it (but it’s behind a paywall). Your best bet is to contact the technical departments for Viking, Tyco, etc. and ask about this application; likely whether an ENT finish sprinkler will handle the environment well. Otherwise, you can contact FM Global; someone there might have some good suggestions.


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