Characterization of the oxide layers on a Cu-13Sn alloy in a NaCl aqueous solution without and with 0.1 M benzotriazole. Electrochemical and photoelectrochemical contributions

The aim of our work was to characterise the oxide layers formed on a Cu-13S n (mass%) alloy in a 0.5 M NaCl aqueous solution and to compare their prope rties to those obtained on pure copper and pure tin samples. Coulometric an alyses allowed comparison of the thickness of the layers on the different m aterials, whereas impedance spectrometry provided information on the stabil ity of the layers versus the immersion time. The photoelectrochemical metho d could be applied since both copper and tin oxides show semiconducting pro perties with well defined band gap values. On the Cu-13Sn alloy, Cu2O and S nO2 were simultaneously present at the surface, for short immersion times i n the NaCl solution. This result was confirmed by XPS measurements. Neverth eless the predominance of the copper(I) oxide became clear after 48 h immer sion. For comparison, similar measurements were performed and discussed in the presence of BTA, an inhibitor of the copper corrosion. (C) 1999 Elsevie r Science Ltd. All rights reserved.