#350 – Guide to Corrosion-Resistant Fire Sprinkler Heads
#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.
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:
Organic fertilizer plants
Fumigation, pickle, and vinegar works
Storage battery rooms
Steam rooms of all descriptions, including moist vapor dry kilns
Salt storage rooms
Locomotive sheds or houses
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:
188.8.131.52 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 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
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.
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 corrosion-resistant white polyester, black polyester, and ENT coatings.
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)
- 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)
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
- 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.
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.
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’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 [email protected].