Collect. Czech. Chem. Commun. 1994, 59, 2383-2389

Electrochemical Behaviour of Cobalt in NaOH Solutions

Sayed S. Abd El Rehima, Ahmed A. El Basosib, Salah M. El Zeinb and Magda M. Osmanb

a Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
b Petroleum Research Institute, Cairo, Egypt


The electrochemical behaviour of cobalt in 0.001 - 1 M NaOH was investigated by voltammetric techniques coupled with ESCA examination. The anodic polarization curve exhibits a well defined peak which corresponds to the formation of Co(OH)2 or CoO. Further peaks in the transpassive potential region correspond to the electrooxidation of Co(II) species 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 three cathodic peaks which are ascribed to the reduction of CoOOH, Co3O4 and CoO oxides, respectively. ESCA examination confirmed the presence of these oxides in the passive film.