Study of copper dissolution and passivation processes by electrochemical impedance spectroscopy

The copper electrodissolution and passivation processes in carbonate (CO32-)-bicarbonate (HCO3-) solutions at different tonic strength and hydrodynamic conditions have been studied by electrochemical impedance spectroscopy (EIS). Impedance diagrams suggest the formation of a first porous cuprous oxide (Cu2O) layer. Through this film, there is a diffusional process of Cu(II) soluble species which, together with the electrooxidation of Cu(I) to Cu(II), leads to the formation of a thicker and complex passive film. Capacitance values obtained by the application of a transfer function analysis using nonlinear fitting routines reflect the different stages during the film transformation into a stable passive one. This passive film exhibits a p-type semiconductor behavior.