EFFECT OF TEMPERATURE ON COPPER DISSOLUTION IN NAHCO3 AND NAHCO3+NACL AQUEOUS-SOLUTIONS AT PH-8

The effect of temperature between 5 and 60-degrees-C on the behavior of copper rotating-disk electrode was investigated in NaHCO3 and NaHCO3 + NaCl solutions of 0.1-0.001 M at pH 8. Temperature rise had little effect on the Cu(0) to Cu(I) oxidation (i.e., the first anodic peak in voltammetric curves) and a strong eff ect at higher potentials of Cu(II) oxidation state. The low activation energy, approximately 10 kJ mol-1, of Cu2O passive film formation is compatible with a poorly structured layer. The Cu(II) passive film provided better protection for the copper surface. The corrosion and breakdown potentials both show a linear relationship with temperature. Corrosion potential decreased while the breakdown potential increased with an increase of temperature. This may be a result of a dual eff ect of temperature: increase of Cu dissolution rate and improved passivity characteristics of the precipitated Cu(II) products. The eff ect of temperature is considerably stronger for 0.1 and 0.05 M concentrations of NaHCO3 and NaHCO3 + NaCl solutions than in more dilute solutions.