Mechanism of Copper Passivation in Aqueous Sodium Carbonate−Bicarbonate Solution Derived from Combined X-ray Photoelectron Spectroscopic and Electrochemical Data

X-ray photoelectron spectroscopy (XPS) was used to characterize the passivating films anodically formed on copper in NaHCO3 and Na2CO3 aqueous solutions (9−11 pH range). The influence of potential and solution pH on the composition and protective characteristics of the passivating layers was considered. The analysis of the experimental data supports the composed nature of the formed films. Direct evidence regarding the addition of carbonate species to the surface layers in potential ranges positive to the onset of Cu(II) oxides formation was achieved from XPS data. Specific components of the XPS signals attributable to carbonate species present in the passivating films could be identified.