Stoichiometry of Anodic Copper Dissolution at High Current Densities

Abstract

l'he influence• of current density, flow rate and electrolyte composition on the stoichiometry of anodic copper dissolution was investigated under conditions comparable to those of electrochemical machining. Weight loss measurements, x-ray diffraction and chemical analysis were used for the characterization of the dissolution reaction. A sharp change in dissolution mechanism.coincidedwith the transition from active to transpassive dissolution. For active dissolution, an apparent valence of the dissolution process of two was found in sulfate and nitrate electrolytes; and of one in chloride electrolytes. For transpassive dissolution, mixed valences lying between 1 and 2 were found in all electrolytes. The mixed valences are interpreted to result from the simUltaneous production of monovalent and divalent reaction products, some of which are in solid form.

Current Oscillations Observed within the Limiting Current Plateau for Iron in Sulfuric Acid

“…The fabrication of these electrodes has been described previously. 6 In addition, a rotating hemispherical electrode was also studied. The radius and active area of each of the,se electrodes are given in Table 1.…”

“…The experimental equipment and setup have been described previously. 6 The procedure used to determine the limiting current revealed a region in the plateau in which current oscillations are observed. Figure 1 is a Table 1.…”

“…al., 5 and Kinoshita et al 6 have studied oscillations for copper electrodes in various electrolytes. Landolt et al 5 observed oscillations for copper cathodes during the evolution of hydrogen.…”

Investigation into the Anodic Dissolution Processes of Copper in Neutral and Acidic Sulfate Solutions with the In-line Digital Holography

“…1 The anodic dissolution of copper in the acidic sulfate solutions have been extensively studied. [2][3][4][5][6][7][8][9][10] In refining process, various concentrations of H 2 SO 4 solutions were used and the term "passivation" was usually applied to describe the limiting current density with increasing the potential.…”

“…Lekie 4 proposed that the composition of the surface film was related to the concentration of the sulfuric acid solution and that the limiting current behavior was controlled by the diffusion of corrosion products (CuSO 4 ·xH 2 O) in 1 M H 2 SO 4 solution, while the passivation was ascribed to the formation of cuprous oxide in 10 M H 2 SO 4 solution. Kinoshita et al 5 detected a cuprous oxide film by the X-ray diffraction method in the sulfate solution and found that the rate-determining step was the mass transfer processes of dissolved dissolution products. Grishina et al 6 studied the oxidation of copper in the concentrated sulfuric acid by the cyclic voltammetry and X-ray diffraction methods and proposed that the passivation was caused by the formation of a resistive porous layer of cuprous oxide via the electrochemical mechanism.…”