ELECTROCHEMICAL-BEHAVIOR OF THE SUPERCONDUCTOR YBA2CU3O7-X IN SOLUTIONS CONTAINING VARIOUS ANIONS

YBa2Cu3O7-x exhibits high open circuit potentials in aqueous solution over a range of pH with oxygen evolution, and reduction of the superconductor, respectively the anodic and cathodic reactions. Potentiodynamic polarization measurements in solutions buffered at pH 4.6 and 9.2 indicate that the Tafel slopes for these two reactions are 120 and 180 mV decade-1 respectively. The anodic Tafel slope is consistent with oxygen evolution involving a rate-limiting one-electron transfer step. The higher value of the cathodic Tafel slope suggests that the cathodic process is partially diffusion-limited. Addition of Cl-, SO42- and F- ions to the electrolytes indicate that solution pH, film formation on the superconductor surface, the solubility of degradation products and complexing of ions in solution play important roles in the corrosion behaviour of YBa2Cu3O7-x. In particular, additions of sulphate ion and fluoride ion significantly reduce the rate of degradation of YBa2Cu3O7-x.