Cause of Major Sprinkler Corrosion in Warehouse?

7/29/2025

Looking for education on the cause of major sprinkler corrosion in a warehouse.

A general warehouse with ESFR heads has a serious corrosion problem on approximately 600 sprinklers, with two inadvertent actuations occurring in the past 6 months. The image is of the worst corroded sprinkler. Others are more lightly corroded, each with a green hue.

The actuated heads were sent to UL for evaluation as well as non-fused corroded heads. Tests indicated the heads functioned within normal range, with one head slightly delayed. The manufacturer confirmed the heads are not counterfeit.

The conditions within the warehouse were unique for approximately 7 years, with very high internal temperatures occurring during the winter months, using once-through heating to ensure forklift exhaust CO ppm levels were kept low.

In addition to elevated temperatures, the warehouse received insect fogging applications as normal practice for stored seed and beans. Fogging has also occurred at other similar warehouses, and no problems have been observed at those locations.

Corrosion is on approximately 15% of all sprinklers in the warehouse building area.

Are there similar experiences with corrosion that is similar to the image?

If so, what was determined to be the primary cause? Heat, chemical, or something else?

All of the corroded sprinklers were replaced with new heads and NFPA guidance was observed for temperature selection near forced air heaters.

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12 Comments

Pete H

7/29/2025 06:09:52 am

No similar experience:

I assume the 15% were in the same part of the warehouse?

Is this fed from an aquafer or something else that might have microorganisms?

Joseph Terranova

7/29/2025 08:09:23 am

It appears to be a chloride reaction with some dust accumulation. The pattern and coloration is similar to what is found in pool filtration rooms.

Chris Logan link

7/29/2025 08:09:28 am

With no obvious environmental concerns, I would check and see if there is electrical ground on the sprinkler system somewhere.

Glenn Berger

7/29/2025 08:20:48 am

Need to review the chemicals involved with the "insect fogging" application mentioned the write-up.

Jesse

7/29/2025 08:25:39 am

This is a fascinating one.

Its ESFR so I'm presuming there isn't a manufacturing process in close proximity that would produce corrosive off-gassing. Chris's comment re: an electrical ground is interesting but I would think more widespread than 15% of the sprirnklers.

I wonder if these 15% of sprinklers affected are contiguous to one area of the system(s), or if these are spread throughout.

I'm gonna follow this post today. Hopefully Dann or Glenn or Franck or anyone of you guys much smarter than I have some insight!

Franck

7/29/2025 08:29:52 am

Could it be related to the products stored in the warehouse ?
Just a guess...
If you had seed and beans in a bulk storage configuration, it could be that dust (generated by transferring the product) from seed and beans could accumulate on the sprinklers, thus having moisture (if the area was heated, the seed and beans would release water by evaporation) accumulated at the same place to increase the corrosion level.
More obvious on sprinklers as this is where the dust tends to accumulate easily compared to piping (that are painted in addition to limit outside corrosion).

Chad

7/29/2025 08:42:08 am

I too wonder what the products are off gassing. Its most likely environmental, possibly whatever they fog it with.

It possible but less likely its the water or its being used as a ground

Dan Wilder

7/29/2025 08:29:54 am

So brass & bronze will corrode green with both chemical and humidity factors. As you stated this is a seed and bean warehouse the chemical factor (typically chlorine) decreases dramatically, however with a high humidity level kept for most of these warehouses, this is more likely the cause. Due to the more uniform rusting on the pipe, the warm humid air rising within the structure will naturally condense on the pipe as shown.

What is the proximity of the units that heat/cool/humidify the air to the effected sprinklers? What about exhaust fan and high points in the roof compared to the corrosion of the sprinklers? What do the hangers look like?

Jack G

7/29/2025 08:49:45 am

I think Chris s explanation of electrical, ( I think the building is not grounded properly ) is the major problem, along with the chemical fogging, the ionization of corrosive particals.,

Jeff Ayers

7/29/2025 10:17:33 am

I had a garage in Baltimore with similar corrosion problems.
The cause for the corrosion and deterioration (more than 50%) was MIC.
https://c1sinc.com/blog/mic-microbiologically-influenced-corrosion-fire-sprinkler-pipes
Microbilogically influenced corrosion: "MIC in fire protection systems can be described as a chemical corrosion process that is concentrated and accelerated by the activity of specific bacteria within a fire-sprinkler system resulting in the premature failure of metallic system components."

The problem was the water supply (supposedly).
The problem was exacerbated by the sprinkler did not have positive fall for drainage at all mains and branches. But the upright heads (it was a dry system in the garage) corroded just as much as the pendant heads in the BOH rooms.

Greg

8/1/2025 08:23:14 am

Thank you for the insight. All responses have been very helpful and prompted further evaluation of makeup air entering the building.

The following corrosion coupon is being considered for the evaluation.

https://corrosionmonitor.com/products/corrosion-classification-coupon-plus

8/15/2025 03:02:32 pm

Also, we verified that a fumigant containing phosphine products was not used in the warehouse's history. Phosphine containing fumigants have been known to cause metal corrosion.

Cause of Major Sprinkler Corrosion in Warehouse?

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