From: [REDACTED]
Sent: [REDACTED]
To: [REDACTED]
Subject: Corrosion of copper piping passing thru walls
It has come to our attention on several hospital projects, that the use of USG Sheetrock Acoustical Sealant has been specified for closure around piping penetrations at drywall partitions. This product is causing corrosion on non-insulated copper pipe. It is strongly suggested architectural specifications for this product be reviewed to include products that do not cause this corrosion. The following italics are from a contractor friend's email concerning the issue they are dealing with on a project of theirs.
Because of possible litigation, they asked that I not identify them.
In summary, at every rated wall assembly (smoke and fire) where medical gas copper piping passes through the wall and is sealed using USG Sheetrock Acoustical Sealant, the copper pipe is corroding. There are three types of corrosion of which two are harmless to the integrity of the pipe. Unfortunately the third, formicary corrosion, is highly detrimental to the integrity of the pipe. Our pipe has all three types at each location. This condition was visually observed two months ago and a sample assembly was sent for further analysis and testing. Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy Analysis were used for the tests. The test results were received yesterday and they are not good. In some instances the pipe already has 5 MIL deep pits in them and will only get worse as long as moisture and air are present. Since we don’t live on the moon, humidity and air are very much present. We are likely facing a situation that will require us to replace all exposed copper pipe penetration locations. Thus far it is limited to exposed copper (medical gas system) and a preliminary survey indicates this would be approximately 2,000 locations. Insulated copper pipe (water system) is perfectly fine.
I have also attached a picture of some of the piping that was removed for testing. Looking at the pipe in the picture, areas where the sealant is on the pipe and the pipe has begun to turn blue is corrosion.
They have elected to utilize HILTI 506 rather than the USG product. Needless to say the proper sealant should be utilized for the rated wall assembly that applies.
Here's a link to the Hilti website.
http://www.us.hilti.com/
[REDACTED]
