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International Journal of Corrosion
Volume 2012 (2012), Article ID 857823, 16 pages
http://dx.doi.org/10.1155/2012/857823
Research Article

Inhibition of Copper Pitting Corrosion in Aggressive Potable Waters

1Department of Mining and Minerals Engineering, Virginia Tech University, 108 Holden Hall, Blacksburg, VA 24061, USA
2Department of Civil and Environmental Engineering, Virginia Tech University, 418 Durham Hall, Blacksburg, VA 24061, USA

Received 2 December 2011; Accepted 23 April 2012

Academic Editor: Flavio Deflorian

Copyright © 2012 Emily Sarver and Marc Edwards. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Copper pitting corrosion can lead to premature plumbing failures, and can be caused by aggressive potable waters characterized by high pH, free chlorine residual and low alkalinity. In such waters and under continuous flow, certain inhibitors including phosphate, silica or natural organic matter may greatly reduce pitting occurrence. In the current work, 1 mg/L phosphate (as P) completely prevented initiation of pits, and 5 mg/L silica (as Si) significantly decelerated pitting. However, much lower doses of these inhibitors had little benefit and actually accelerated the rate of attack in some cases. Effects of organic matter were dependent on both the type (e.g., natural versus ozonated humic substances) and dosage. Dose-response effects of free chlorine and alkalinity were also investigated. Based on electrochemical data, pits initiated more rapidly with increased free chlorine, but even moderate levels of chlorine (~0.4 mg/L) eventually caused severe pitting. High alkalinity decreased pit propagation rates but did not prevent pit formation.