Fire protection in cold storage spaces is uniquely challenging. Temperature-controlled environments like refrigerated facilities and freezer warehouses require specialized fire sprinkler systems—often dry or pre-action systems—to prevent water from freezing inside pipes. However, these systems are susceptible to internal corrosion and ice plugging, which can not only cause leaks, system failures, and expensive repairs, but can also render systems inoperable. 

Let’s explore the leading causes of corrosion in cold storage sprinkler systems and practical strategies for reducing risk. 

Main Factors Contributing to Corrosion in Cold Storage Systems

Corrosion is not caused by a single factor but rather a combination of environmental and operational conditions that accelerate pipe degradation and weaken the system over time. 

Oxygen Exposure

Dry and pre-action sprinkler systems are filled with pressurized gas (often air) to keep water out until activation. Compressed air contains roughly 21% oxygen, which is the primary driver of oxidative corrosion inside steel pipes​. Oxygen reacts with the metal whenever moisture is present, producing rust. Unlike wet pipe systems that are water-filled (and eventually run low on dissolved oxygen), a dry system continuously introduces fresh oxygen to pipe interiors, sustaining corrosion. While desiccant dryers remove some moisture from compressed air, they do not remove oxygen and offer no corrosion protection. 

Moisture and Condensation

Liquid water is required for oxygen corrosion of steel to occur​. Even in cold storage, keeping sprinkler piping completely dry is nearly impossible. Sources of moisture include residual water from periodic trip tests/inspections and condensation from humid compressed air. During the annual NFPA 25 dry system trip test (or any activation), water can become trapped in low spots despite drainage procedures​.

If the supervisory air is not sufficiently dried, water vapor will condense inside cooler pipe sections. This trapped water enables rust to form where it pools. Notably, condensed water in sprinkler piping tends to be “distilled” (very low mineral content and unbuffered), so when carbon dioxide from the air dissolves, the water turns mildly acidic, accelerating corrosion of the metal​.

Temperature Extremes and Fluctuations

The freezer environments (often 0 °F or below) actually inhibit corrosion. At sub-freezing temperatures, water turns to ice and low temperatures slow chemical reactions​. However, cold storage systems also include sections in warmer areas. For example, riser rooms, entry vestibules, loading docks, or ceiling spaces above 32°F experience normal or even elevated temperatures​. These areas are prone to corrosion because they provide liquid water and higher temperatures that speed up the oxidation reaction​.

Furthermore, when warm, humid air infiltrates a cold pipe (during maintenance or pressure changes), it can cool and deposit moisture. Repeated temperature fluctuations can cause cyclical condensation and ice formation, resulting in ice plugging at the entry to the freezer envelope. 

Material Selection

The choice of pipe materials and system components can influence corrosion rates. Most cold storage sprinkler systems use steel piping (either black steel or galvanized steel)​. Galvanized steel is coated with zinc intended to sacrificially protect the steel, but in dry systems it can sometimes fail faster than black steel​. Small defects or pinholes in the zinc layer become focal points for corrosion.

Black steel corrodes more uniformly (producing orange tubercules of rust) and still suffers internal scaling and eventual leaks, just without the flaking zinc issue. Material choice alone only modestly delays the inevitable without additional protective measures.

Effects of Corrosion in Cold Storage Sprinkler Systems

Corrosion inside sprinkler piping is an invisible threat—it remains hidden until it causes a malfunction or leak. Unchecked corrosion can seriously undermine the sprinkler system's reliability and performance in cold storage facilities.

Decreased Reliability

Investigations have shown that corrosion can cause sections of a dry pipe system to rupture in as little as four years—far sooner than the typical life expectancy of about 15 years. As corrosion progresses, it thins the pipe walls and creates rough scale build-up internally. This leads to pin-hole leaks and cracks that reduce the system's integrity.

Even tiny corrosion pinholes will leak supervisory air, causing the dry system’s air compressor to run more frequently. If leaks worsen faster than the compressor can compensate, the system may lose pressure and false-trip, allowing water into the pipes unintentionally. Accidental water discharges can be extremely costly and leave the system empty or in alarm until reset. A single incident could cost thousands to millions of dollars, depending on the extent of structural damage, product losses, and operational downtime.

It's important to note that corrosion isn’t the only factor compromising system reliability—ice plugging can be just as severe. When moisture inside the sprinkler piping freezes, it can create blockages at critical points in the system. These ice plugs can trigger false alarms and, in worst-case scenarios, render entire portions of the fire protection system completely inoperable during a fire. 

Ongoing Maintenance Issues

When corrosion takes hold, it creates an ongoing cycle of maintenance issues, unplanned costs, and operational risks. Instead of functioning as a reliable, long-term fire protection system, the system becomes a constant liability.

• Regular pipe patching: A temporary fix that doesn’t address the root cause.
• Section replacements: Corroded pipes must be cut out and swapped with new ones, often requiring costly system shutdowns.
• Valve replacements: Corroded debris can clog or damage dry pipe or pre-action valves, leading to system malfunctions.
• More frequent low-point drainage: Removal of accumulated moisture that accelerates corrosion.
• Ice plugs

Repeated pipe section replacements and emergency repairs add up over time, making maintenance significantly more expensive than investing in proactive corrosion prevention. Instead of routine maintenance, facilities are stuck in a cycle of constant troubleshooting, increasing labor costs for in-house teams or third-party fire protection contractors.

Impaired Fire Suppression Performance

Corrosion inside fire sprinkler piping directly impacts fire suppression effectiveness, especially in emergencies. As rust deposits and corrosion buildup accumulate inside the pipes, they can partially obstruct sprinkler heads and pipe openings, restricting water flow. Any reduction in flow or pressure means the system may not deliver the required water density to control a fire.

Over time, entire sections of piping can become entirely blocked by corrosion or ice, preventing water from reaching a fire altogether. Even before complete blockage occurs, corrosion increases friction losses inside the pipes, reducing hydraulic efficiency. This means less water reaches distant or elevated sprinklers than originally intended, compromising the system’s overall performance.

Industry incident reviews have traced severe property losses to sprinkler systems that technically activated but did not control the fire due to internal corrosion obstructions or weakened water pressure​.

Compliance and Standards Implications

If a system is unexpectedly taken offline for repairs, the building is left vulnerable to fire hazards—which can lead to non-compliance with NFPA standards, FM Global Guidelines, and insurance requirements.

• NFPA 13: Requires that dry sprinkler systems be designed to minimize trapped water and corrosion. Recent editions include guidance that in areas with corrosive conditions, dry and preaction systems should be filled with at least 98% nitrogen instead of air to inhibit corrosion, using a listed nitrogen generator sized per manufacturer instructions​.
• NFPA 25: Sets specific inspection intervals (often five years) to find and fix corrosion before it causes failure. Corrective maintenance is required to ensure compliance if corrosion or blockages are found.
• FM Global Guidelines: Recommends keeping the pressurized air’s dew point at least 20°F below the freezer temperature (about 30% relative humidity in the piping) to avoid moisture condensing and freezing inside pipes​. FM Global has expressed support for nitrogen inerting technology. Using an FM-approved nitrogen generator can strip moisture (nitrogen gas naturally has a very low dew point) and substantially lower oxygen levels, tackling ice plugs and corrosion risk. Violating FM Global recommendations could potentially impact insurance coverage or lead to mandated remedial work.
  
  

Related: January 2024 edition of 2-81 FM Global Property Loss Prevention Data Sheet, the time between investigations for ice plugs and freeze damage to fire sprinkler piping and fire sprinklers has been extended to 3 years when using nitrogen.

Learn More and Download the 2-81 FM Global Property Loss Prevention Data Sheet ->

Strategies for Minimizing Corrosion and Ice Plugs in Cold Storage

Mitigating corrosion in fire sprinkler systems in cold storage facilities requires a combination of oxygen control, moisture management, and proactive maintenance.

• Use Nitrogen for Supervisory Gas Instead of Air:  Install a membrane-type nitrogen generator to replace oxygen-rich air with nitrogen. Nitrogen has an extremely low dew point (-70°F or lower), meaning it’s much drier than compressed air and helps prevent moisture buildup and ice formation. NFPA 13 recognizes nitrogen as a best practice for dry and pre-action systems.
• Install Oxygen Removal Vents: Special automatic venting devices purge trapped oxygen from the system when nitrogen is introduced.
• Use Corrosion-Resistant Materials: Consider stainless steel or copper piping in high-risk sections, especially where warm air meets cold pipes. While stainless steel is expensive, it is the most durable option for corrosion resistance.
• Regular Inspections and Preventative Maintenance: Conduct routine inspections to catch corrosion before it leads to system failure. Consider installing corrosion monitoring devices to track system health in real-time.
  
  

Let’s Stop Corrosion and Ice Buildup Before It Starts

The effects of corrosion range from nuisance leaks and false alarms to life-threatening suppression failures. By controlling oxygen exposure, limiting moisture ingress, and monitoring for corrosion, facility managers can avoid costly repairs, extend system life, and ensure their cold storage facility remains protected.

Fire sprinkler system corrosion and ice plugging in cold storage is a major threat but is preventable. Reach out today to learn how ECS nitrogen generators can protect your cold storage facility and keep your fire sprinkler system operating at peak performance.