Cyclic Potentiodynamic Polarization Study of Ternary Pb-Sn-Ca Alloy in 2M H_2SO_4 Solution

摘要

In this paper redox reaction processes and phase formation on ternary Pb-2Sn-0.08Ca alloy utilized as insoluble lead anodes in copper electrowinning cells, were investigated in 2M H_2SO_4 electrolyte, using cyclic voltammetry technique (CVA). A potential interval between - 1.3V to 2.6V was chosen at various scan rates in order to study the anodic behaviour and phase composition of the oxide layers on Pb-2Sn-0.08Ca 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 (PbO_2) formed at a much slower rate when exposed to 2M H_2SO_4 solution, whilst its degradation due to a reduction in the applied potential occurred at a much faster rate. Hence, PbO_2 did not remain stable, when the externally applied potential dropped below 1.5V and as a result, pitting initiated sporadically on the surface of the electrode.