Effect of Zinc Addition on the Microstructure of Waste Acid Battery Lead Electrode (Pb-Sb Alloy)

Abstract

In this research an attempt has been made to determine the
microstructure of Pb-Sb alloy system (waste lead electrode from acid
lead battery) by alloying with zinc using sand and metal mould casting
techniques. Lead-antimony alloys having low Sb content provide the
desired strength. However, batteries parts containing 1.5%−3.5%
(mass fraction) antimony show brittle behaviour and tendency for
cracking, apparently because of the coarse dendritic microstructure.
The reduction of Sb content causes a decrease in mechanical properties
and in castability of the alloys. This can be partly compensated by the
introduction of other elements such as Se, As, Zn or Ag (Markandeya et
al, 2004). The Pb-Sb-Zn alloy was formed through casting by
simultaneous addition of zinc and pouring of the molten alloy by
varying zinc from 2-10% with 2% interval. The microstructure of the
alloys was determined using standard techniques. The alloys were
immersed into 0.5M of H2SO4 solution and the weight loss was
determined after one day over an interval of seven days. Results of this
study show that increase in Zn addition (up to 6%) led to decrease in
the grain size of Pb-Sb-Zn alloy occasioned by increased uniform
distribution of the Zn within the Pb-Sb matrix. The alloys cast in metal
mould have the best properties. Hence this work has established that in
the microstructure of Pb-Sb-Zn alloy, the Zinc showed a uniform grain
size up to a maximum level of 6%.