AWWA JAW60846

Copper-pitting corrosion in drinking water has beenthe subject of relatively intense research for morethan 50 years. Worldwide, several different watertypes are known to support pitting. In Australia, NewZealand, and some other locations around the world,however, pitting predominates in soft, unbufferedwaters. The pitting corrosion of copper tubes in drinkingwater systems is a sporadic but persistent problemalong, for example, the east coast of Australia.Historically, the lack of an adequate theory forlocalized soft water copper corrosion has made remedialtreatments speculative and based only on longtermfield trials. Even though several pitting modelshave been developed over time, the earlier models hadtheir limitations.Pitting corrosion of copper in soft water is known tobe dependent on water chemistry, particularly pH andbuffering capacity. The randomness of the problem,however, along with the large number of chemical andphysical variables involved in its initiation and propagation,required a better theoretical and practicalframework for understanding more about the essentialcomponents of the pitting process.For this work, the authors used novel microelectrodeelectrochemical techniques, supported by fieldobservations and thermodynamic calculations, to proposea new mechanism of copper-pitting corrosion insoft waters. The proposed model for soft water copperpitting stresses the dependency of pitting on the formationof a suitable cathodic film on the tube surface. Theauthors also discuss how the proposed theory may beapplied to the development of a remedial water treatmentstrategy and used to calculate the optimum pHand alkalinity set points for a soft water. Includes 19 references, figures.

Product Details

Edition:

Vol. 96 - No. 11

Published:

11/01/2004

Number of Pages:

10

File Size:

1 file , 370 KB