Application of multisine impedance spectroscopy, FE-AES and FE-SEM to study the early stages of copper corrosion

During the first 24 h of immersion of a pure copper surface in a NaCl containing solution, this surface is in constant evolution. The reactions going on the surface are still not known; discrepancies are found between different published studies. This study resolves these discrepancies using broadband impedance spectroscopy, field emission Auger spectroscopy and field emission electron microscopy. The surface evolution was studied using time series of impedance spectra. Also the experimental variables convection and electrolyte concentration were varied. Parameter evolutions were obtained by fitting the obtained impedance spectra to an equivalent circuit. Combining the calculated parameter values and their evolution with the spectroscopic data led to the identification or replacement of the elements present in the very general equivalent circuit found in the literature: a double layer, two circuit films in parallel and mass transfer.