Electrochemical Behavior of Some Electroplates in Solutions for Coulometric Measurements of Their Thickness. III. Passivation Phenomena during the Dissolution of Copper Coatings

摘要

Anodic dissolution of copper in NH_4NO_3 solutions of different concentrations was studied by potentiodynamic and chronoammetric methods. It was found that the nitrate salt film starts to form at the anode when the anodic current density reaches approximately two thirds of its maximum on the voltammograms. Immediately after the maximum, the passivating effect of the salt is enhanced by the presence of copper oxidation products, most probably CuO. Chronopotentiometric study of copper dissolution revealed that the optimum concentration of NH_4NO_3 in the working solution should be in a range from 100 to 200 g/l for reliable coulometric measurements of the copper coating thickness. The current edition of the relevant ISO standard gives no formulation of electrolyte suitable for quick measurement of the thickness of copper coatings.