Anodic Copper Dissolution in the Presence of Cl- Ions at pH 12

Abstract

The dissolution of copper has been investigated in an alkaline aqueous solution at pH 12 (0.01 M NaOH) containing up to 1 M NaCl at 25 C. During cyclic voltammetry measurements, the first and second anodic peaks correspond to Cu I and Cu II oxide formation, and the reduction processes of those oxides remained slightly affected by the presence of Cl- ions. With NaCl in solution, a large increase of the anodic dissolution current is observed, and, for the cathodic reaction, a third reduction peak appears on the voltammograms. The large increase of the current results from the localized attack of the surface by Cl- ions. The third cathodic peak corresponds to the reduction of CuCl (nantokite) accumulated on the electrode. The presence of CuCl suggests that the copper oxides/solution interface becomes acidic during the dissolution. The morphology of the accumulated CuCl and the presence of holes in it suggest that the corrosion product is non-protective. As flakes of CuCl detach from the surface to fall into the alkaline solution, this compound reacts with the electrolyte, and the final product is a mixture of (Cu2O), (CuCl2)-3Cu(OH)2, and (CuCl2-3Cu(OH)2-3H2O).