Copper Tube (Chilled Water) Corrosion Under Phenolic Insulation

[briand2]

Let my first apologise for cross posting; I previously posted this in the Piping & Fluid Mechanics Engineering forum, but I feel members of the Corrosion Engineering forum may well be able to provide more in-depth comments.

I've seen various conflicting articles / reports / papers concerning corrosion of the outer surface of copper pipes (particularly carrying chilled water) insulated with phenolic foam insulation.
On the one hand, the viewpoint of the European Phenolic Foam Association (December 2000) is that "EPFA can state categorically that phenolic foam products manufactured by its members do not present an enhanced corrosion risk in comparison to other commonly used insulation materials."
On the other hand, the (UK) manufacturer Yorkshire Pressfit states "When insulation copper tube with pheolic foam it is important that moisture or condensate does not occur between pipework and insulation. In order to prevent agressive moisture inducing corrosion problems, some lagging manufacturers provide their products complete with a factory applied sodium silicate barrier, whilst others recommend the use of Densopaste."
Also the Copper Development Association states "Some manufacturers of rigid phenolic foam insulation materials recommend that a moisture barrier be installed at the tube/lagging interface. Moisture between the tube and lagging may lead to external corrosion of the copper tube."
Furthermore, the UK Mineral Wool Association states "Mineral wool pipe insulation is chemically inert and compatible with copper and steel pipework...This means that mineral wool, unlike some foamed plastic insulants which are inherently acidic, does not require any special coatings to prevent chemical attack. This chemical neutrality is important when leaks occur, because water picks up chemicals from the insulation material. Problems have arisen with phenolic foam insulation, which has a very low pH factor in the 1.5 to 3.5 range. Water leaching through phenolic foam therefore becomes very acidic and is highly corrosive to steel and copper pipework and fittings."
Finally, Kingspan Industrial Insulation Limited presents in its publication "Insulants and Corrosion" the methodology and results of various independent tests and concludes "In conclusion, based on Kingspan's extensive in-service experience over 17 years and third party tests, it has been proven that phenolic foams manufactured by British Petroleum / Kingspan technology do not give an enhanced corrosion risk compared to other insulation materials."

Given the broad range of (perhaps slightly partisan!) views, I'm a little confused as to what the true situation is. It looks like a HVAC job with which I'm to be involved has a corrosion problem on copper pipes (about two years old) insulated with rigid phenolic foam insulation, and I'd like to be fully prepared when the expected "discussion" begins! Can anyone provide real life examples to support (or otherwise!) the common industry views as presented above?

I've posted this in Piping & Fluid Mechanics; would it have been better posted in Corrosion?

Thanks,

Brian

 

[btrueblood]

from

http://www.mces.com/phenolic report.htm

...regarding phenolic foam roof insulation products that were subjected to class action lawsuits for excessive corrosion during late '80s and '90s.

"Research indicates that the United States-based Phenolic Foam technology used an aromatic sulfonic acid as a catalyst in the process to create the cells of the foam. It appears that the high rate of water absorption by the Phenolic Foam allows the water to dissolve the sulfonic acid, forming a highly-acidic compound. This highly-acidic compound readily breaks down the typical structural metal deck and metal roof component coatings (organic and inorganic). It has also been reported that formic acid gaseous vapors are also released from Phenolic Foam insulation, thus contributing to the corrosion process of metals in the immediate vicinity of the phenolic material. Once the coatings have been destroyed, the corrosion of steel progresses at an accelerated rate. "

Sounds plausible, certainly the blowing agents used in foam production changed quickly in the late '80s due to mandated reductions in the use of CFC's for foam production. I would certainly ask the foam manufacturers for their side of the story, and their testing data that indicates their production method does not use corrosive salts. A fairly simple test would be to soak an insulation sample in distilled water for 24 hours or more, and monitor pH.