CYCLIC POTENTIODYNAMIC POLARIZATION STUDY OF TERNARY PB -SN-CA ALLOY IN ۲M H_۲SO_۴ SOLUTION

In this paper redox reaction processes and phase, formation on ternary Pb-۲Sn-۰.۰۸Ca alloy utilized as insoluble lead anodes in copper electro winning cells, were investigated in ۲M H__۲SO__۴ electrolytes, using cyclic voltammetry technique (CVA). A potential range between - ۱.۳V to ۲.۶V was chosen at various scan rates in order to study the anodic behavior and phase composition of the oxide layers on Pb-۲Sn-۰.۰۸Ca alloy. Potential measurements were carried out with respect to a standard calomel electrode (SCE). The surface examination and phase composition of the lead alloy were determined by electron microscopy analysis (SEM) and x-ray diffraction technique, after- exposure to the cyclic voltammetry tests. The results indicated that the protective oxide layer (Pb۰__۲) formed at a much slower rate when exposed to ۲M H__۲SO__۴ solutions, whilst its degradation due to a reduction in the applied potential occurred at a much faster rate. Hence, Pb۰__۲ did not remain stable, when the externally applied potential dropped below ۱.SV and as a result, pitting initiated sporadically on the surface of the electrode.

Keywords:

Cyclic potentiodynamic polarization , Sulfuric acid , Lead alloys , Electrowinning