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COPPER PITTING CORROSION AND PINHOLE LEAKS: A CASE STUDY
LYTLE, D. A., J. PAYNE, AND J. FELDHAUS. COPPER PITTING CORROSION AND PINHOLE LEAKS: A CASE STUDY. Presented at 2005 American Water Works Association Annual Conference, San Francisco, CA, June 13 - 17, 2005.
To inform the public
Localized corrosion, or "pitting", of copper drinking water pipe continues is a problem for many water utilities and their customers. Extreme attack leads to pinhole leaks that can potentially lead to water damage, mold growth, and costly repairs for the homeowners, as well as the potential for lawsuits against the utility. Copper pitting corrosion is very complicated; often, the exact cause of, and solution for, this problem are unknown. A case study involving pipe analysis, plumbing survey, literature review, and bench scale assessment using electrochemical approaches is being conducted. The objective of this work is to present the pipe analysis and plumbing survey portion of that study. Analysis of pipes removed from a community with a widely-known pitting problem showed the pits to be randomly spread across the pipe surface. A cross-section of a zone containing a pinhole leak revealed three distinct components: a pit cap, porous membrane, and pit. The porous (hollow) cap is characterized by the presence of two basic copper sulfate minerals and, in some cases, pure copper metal. A porous membrane is located beneath the cap made of cuprite. The pit itself is deep and bowl shaped and contains cubic cuprite crystals, sulfur, and chlorine.