Ellipsometric and photocurrent characterization of oxide films formed on copper in borax solution with and without benzotriazol

The effect of the addition of benzotriazol on the passive behaviour of copper in borax solutions was analyzed in the potential region −0.32 to 0.71 V vs. RHE using voltammetric, photocurrent and ellipsometric techniques. Oxide formation can be explained as a sequence of Cu 2O growth (inner layer ippl) and dissolution precipitation of Cu(II), (outer hydrated oxide layer (oppl)). The resulting photocurrent was proportional to the thickness of the ippl. However, significant variations in the amplitude and phase of the photocurrent were detected as a function of the potential region and the composition of the electrolyte. These effects are related to changes in the excess of cations accumulated in the ippl.