Anodic oxide film on antimony: II. Parameters of film growth and dissolution kinetics in neutral and alkaline media

Abstract

Growth of the anodic oxide film on Sb has been studied in Na 2 SO 4 , NaCl, K 2 CO 3 , Na 3 PO 4 and NaOH solutions. Anodization gives linear potential/time relations (up to 50–60 V) in both sulphate and chloride solutions, particularly at relatively high cds. In alkaline solutions, however, active dissolution occurs before oxide growth. The latter is characterized by two regions in the anodic charging curve. The mechanism of dissolution is discussed on the basis of the experimental Tafel slope (23–27 mV). The results indicate that the formation of HSbO 2 (soluble meta-antimonious acid or passivating surface oxide SbO·OH) is rate-determining. Oxide growth follows the exponential law in all solutions. The parameters of film formation are recorded. The results are explained on the basis of (i) oxide contamination by anions and (ii) partial dissolution of the anode film. Dielectric breakdown by sparking occurs in sulphate solutions only, at 95–96 V.