Copper Plumbing Surfaces: An Electrochemical Study

Abstract

Electrochemical kinetic parameters on copper plumbing surfaces were investigated under hydraulic and water quality conditions typical of distribution systems. The generally reported values of anodic and cathodic Tafel slopes were found to be inapplicable to plumbing surfaces of drinking water systems. Actual values may differ from reported values by up to twofold. Cathodic Tafel slopes vary strongly with the oxidant–disinfectant constituents of the water, whereas anodic slopes are influenced by corrosion inhibitors and aging of the corrosion scale. The corrosion current (corrosion rate) is affected by these and other parameters, including dissolved oxygen, pH, and chlorine residual. Contrary to some reports, orthophosphates were found to significantly reduce corrosion rates on copper surfaces; however, the phosphate scales that provide this protection are prone to rapid dissolution at low pH.