Abstract
The corrosion behaviour of copper was studied in dilute solutions of sulphate, chloride, and bicarbonate anions as well as in solutions containing mixtures of these anions at concentrations similar to those encountered in soft tap water. During potentiostatic anodic polarisation, a relatively large current was produced in the sulphate containing solutions, while a very small current was generated in other environments. The difference in behaviour was attributed to the effect of the anions on the characteristics of the oxide scale and the mode of corrosion attack. A highly porous oxide scale was formed in the sulphate solution. Severe general corrosion, more intensive at grain boundaries, occurred below the scale. The scalesformed in the chloride and bicarbonate solutions were relatively smooth and well compacted. Hemispherical pits developed in the chloride solution underneath a layer of cuprous oxide and chloride crystals. Only bare metal and grain boundaries werefound beneath the scaleformed in the bicarbonate solution. In solutions containing mixtures of the anions, the corrosion morphology was a combination of the morphologies observed in the single salt solutions.
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