Analysis of pitting corrosion failure of copper tubes in an apartment fire sprinkler system

Title
Analysis of pitting corrosion failure of copper tubes in an apartment fire sprinkler system
Authors
서상희Suh Young Joon윤형국오정한김영준정기민권혁상
Keywords
Springkler; Pitting corrosion; Copper
Issue Date
2016-06
Publisher
Engineering failure analysis
Citation
VOL 64-125
Abstract
Microscopical and structural analyses as well as visual inspection of copper tubes were used to investigate the cause of pitting corrosion failure of copper tubes in the wet pipe sprinkler system. Chemical analysis of the water in the copper tubing and XRF/XRD analysis of its sediments were also used to obtain hints on what was happening in the copper tubing during the progress of the pitting corrosion. It was found from the failed copper tube that a significant amount of pressurized air was present over the water in the copper tubing during operation and a series of corrosion pits were aligned adjacent to the water/air line. The waterline localized corrosion, a type of differential oxygen concentration cell corrosion, induced by pressurized air over the water in the copper tubing was identified as the cause of the pitting corrosion failure. A state of a very low oxygen concentration was maintained under the envelope of a dense layer of malachite, the corrosion byproduct, which was evidenced by the formation of Cu2O crystalline particles inside the corrosion pit. CuO particles observed on the inside surface of the copper tube do not seem to help prevent local as well as general corrosion. Accelerated pitting corrosion of the copper tube in the wet fire sprinkler system was simulated using a differential aeration cell. Finally, measures for stopping or delaying the pitting corrosion of the copper tube in the wet sprinkler system are suggested.
URI
http://pubs.kist.re.kr/handle/201004/64874
ISSN
1350-6307
Appears in Collections:
KIST Publication > Article
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