ELECTROCHEMICAL-BEHAVIOR OF COBALT IN NAOH SOLUTIONS

The electrochemical behaviour of cobalt in 0.001 - 1 M NaOH was invest igated by voltammetric techniques coupled with ESCA examination. The a nodic polarization curve exhibits a well defined peak which correspond s to the formation of Co(OH)(2) or CoO. Further peaks in the transpass ive potential region correspond to the electrooxidation of Co(II) spec ies to CO3O4 and CoOOH, respectively. The heights of the anodic peaks increase with the increase of NaOH concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan consistently shows thre e cathodic peaks which are ascribed to the reduction of CoOOH, Co3O4 a nd CoO oxides, respectively. ESCA examination confirmed the presence o f these oxides in the passive film.