Caulk Corrodes Copper?


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Old 05-28-07, 01:14 PM
A
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Caulk Corrodes Copper?

Hi all,

Three days ago, I put new backing rod and Sashco "Big Stretch" clear caulk around a copper pipe where it exits the brick wall and feeds the outdoor sillcock. Soon after, I noticed a blue color diffusing into the caulking and found an article at copper.org,

"Many silicon caulking materials outgas ammonia and/or methanol during their curing process. The outgassing of ammonia, within the sleeve, can lead to stress corrosion cracking of the copper tube, and eventual failure."

Oh great. Today the diffusion appears to have stopped at 0.5" around pipe.

1. How serious is this? Am I about to have a flooded basement or is it just a few surface molecules? There was no warning on the caulking product.

2. In future, what do you recommend for sealing this kind of opening?

Regards,
~A
 
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Old 05-28-07, 02:14 PM
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Sashco's website specifically says not to use Great Stretch "clear" on copper.

http://www.sashcosealants.com/home_improvement/pdffiles/bigstretch_brochure.pdf

Lexel clear should be used instead. I'm suprised this warning is not on the tube. I'd call the company.
 
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Old 05-28-07, 08:05 PM
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Smile

Thank you. I will call Sashco. I will probably use DAP Alex Plus; it looks safe:

http://www.dap.com/docs/tech/00010019.pdf

I'll try to be a better chemist in future!
 
 

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