Abstract
The effect of pH, dissolved oxygen concentration, ammonia, and morpholine on potentiodynamic polarization curves of copper were investigated under simulated condensate conditions at 80°C and 500 rpm with a rotating cylinder electrode. At pH 9, a passive region was observed in the anodic curve. This was believed to result from the formation of the Cu2O/CuOH film. At pH 7, the passive region disappeared. At pH 11, an active-passive transition peak occurred indicating that the film formation became more difficult. However, better passivation was possible at pH 11 in strongly oxidizing environments. The presence of oxygen increased both the corrosion potential and the corrosion rate. Under air-saturated condition at 80 °C (3.6 ppm dissolved oxygen), spontaneous passivation took place. Results suggested that, under field operating conditions, copper corrosion will be enhanced when ammonia or morpholine are present. Typical copper corrosion inhibitors were also studied in this work. Benzotriazole and tolyltriazole showed good inhibition effects under the experimental conditions.
