ELECTRODISSOLUTION OF COPPER IN NACL SOLUTION - INFLUENCE OF THE SAMPLE HOLDERS SHAPE

From the many experiments conducted on the behavior of copper in chloride solutions, it seems clear that copper dissolution in the apparent Tafel region is mass transfer controlled, either by CuCl2- from the interface to the solution, for by Cl- in the opposite direction. For a chloride concentration lower than 2 mol.1MIN, CuCl32- complex formation is negligible, and it seems that the mechanism can be described by using the two species CuCl2- and CuCl. This paper deals with the result obtained by voltammetry and potentiostatic steps using two different sample holders. The first sample Holder (Electrode I) consisted of a rod of copper (99.999% pure), 5 mm in diameter, embedded in a resin, and allowing the sample to be on the same plane as the holder. The second sample holder (Electrode II) was a disk cut in the same metal and put in a Teflon sample holder, leaving a disk surface of 5 mm in diameter in contact with the solution. In this case, the sample was slightly (1 mm) shrunken with regard to the holder. The samples were polished with emery paper up to grade 600 and were rinsed with water. A conventional three-electrode cell was used. All the potentials were measured with respect to a SCE. The counter electrode was a large-area platinum sheet. The experiments were conducted in NaCl 3% quiescent solution.