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Formicary Corrosion And EAC Of Copper Tubes In Contact With Building Sealant

Picture for Formicary Corrosion And EAC Of Copper Tubes In Contact With Building Sealant
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Blue discoloration of off-white sealant in contact with copper tube at medical facilities under
construction was observed. The copper tube was being installed to transport medical-grade gasses and the sealant was used as an acoustical and smoke sealant at through-wall penetrations. In some areas of one facility, galvanized steel pipes inserts were used as sleeves for the copper pipes through the drywall, while in other areas, the copper pipe penetrated directly through the drywall. Observations of the discoloration prompted an evaluation of the copper tube, sealant, and potential adverse interactions.

Product Number: 51322-17846-SG
Author: Kimberly Steine
Publication Date: 2022
Industries: Corrosion Monitoring and Control , Coatings and Linings , Coatings
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$20.00
$20.00

Copper tubes for carrying medical-grade gasses were installed during construction in multiple medical facilities. Where the tubes penetrated drywall separating individual rooms, the perimeter surfaces of thetubes were sealed with building sealant to suppress noise, smoke, and fire transmission. Duringconstruction, discoloration of the copper tube where sealant had been applied was observed. Alaboratory investigation determined the observed discoloration was copper corrosion product. Furtherlaboratory evaluation of the system was performed to characterize the discoloration, the underlying copper tubes, and sealant using a variety of techniques. Evaluation of the copper tubes indicated nitrogen-containing deposits on the outside diameter (OD) surface as well as features consistent with formicary corrosion and environmentally assisted cracking (EAC). While through wall-cracking or corrosion had not occurred, the investigation indicated that failures were possible if the discolored pipes were placed into service as constructed. Evaluation of the sealant indicated it contained nitrogencontaining compounds and formic acid. Certain nitrogen-containing compounds are associated with EAC of copper, and formic acid is associated with formicary corrosion of copper. The results of the investigation determined that the sealant was not compatible with the copper tubes.

Copper tubes for carrying medical-grade gasses were installed during construction in multiple medical facilities. Where the tubes penetrated drywall separating individual rooms, the perimeter surfaces of thetubes were sealed with building sealant to suppress noise, smoke, and fire transmission. Duringconstruction, discoloration of the copper tube where sealant had been applied was observed. Alaboratory investigation determined the observed discoloration was copper corrosion product. Furtherlaboratory evaluation of the system was performed to characterize the discoloration, the underlying copper tubes, and sealant using a variety of techniques. Evaluation of the copper tubes indicated nitrogen-containing deposits on the outside diameter (OD) surface as well as features consistent with formicary corrosion and environmentally assisted cracking (EAC). While through wall-cracking or corrosion had not occurred, the investigation indicated that failures were possible if the discolored pipes were placed into service as constructed. Evaluation of the sealant indicated it contained nitrogencontaining compounds and formic acid. Certain nitrogen-containing compounds are associated with EAC of copper, and formic acid is associated with formicary corrosion of copper. The results of the investigation determined that the sealant was not compatible with the copper tubes.

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