AWWA JAW37636

Copper passivation was examined in simple solutions that contained bicarbonate, chloride, perchlorate, nitrate, or sulfate at pH 5.5, 7.0, 8.5, and 10. Copper corrosion rates increased with aging in the presence of sulfate, nitrate, or perchlorate at all pH values, whereas copper passivated in the presence of chloride at pH < 7.0. Bicarbonate ion was discovered to have a dual nature that was pH-dependent, causing activation (increased corrosion rates) after aging at pH < 7.0 and passivation at pH > 8.5. Activation in the presence of bicarbonate was due to catalysis of oxygen reduction (cathodic) reactions, whereas sulfate, nitrate, and perchlorate increased the copper oxidation (anodic) reaction rates after aging. Includes 14 references, table, figures.