SOME CHEMICAL ASPECTS OF THE CORROSION INHIBITION OF COPPER BY BENZTRIAZOLE

Measurements of the adsorption isotherm of benztriazole (BTA) on copper reveal that the inhibitor molecule is weakly held on the oxide covered surface until a critical solution concentration of BTA is reached above which good corrosion inhibition results. Consideration of the chemical equilibria between the oxides of copper and the dissociation of the BTA molecule in solution, show that this concentration corresponds closely to that at which the Cu(I)BTA complex is precipitated. The chemical nature of the complexes formed has been found by X-ray photo-electron spectroscopy to correspond closely to Cu(I)BTA for cuprous oxide-covered surfaces but is of a more complicated nature for cupric oxide-covered surfaces, although both seem to be equally effective in preventing the corrosion of copper. No tendency for the Cu(I) complex to oxidize to the Cu(II) state over short times was found. Polarization studies of the inhibition process suggest that the surface is largely covered by the complex; impedance measurements imply a double layer at the surface which forms sequentially with time. © 1979 Pergamon Press Ltd.