Abstract
The anodic polarization behavior of Pb-Ag-Ca (up to 1 wt% Ag and/or Ca) tertiary alloys was determined insulfuric acid solution (150g H2SO4/1) at a current density of 50mA/cm2 at 40°C. In addition to measurement of electrode potential and the rate of formation of lead dioxide on the alloy, X-ray diffraction analysis and SEM observation of the surface morphology were conducted to characterize the anodic oxide layer.
1) The electrode potential of the rapidly solidified sample decreased with an increase in the content ofcalcium as well as silver in the alloy.
2) Rate of growth of anodic oxide layer increased almost linearly with an increase in the content of calcium (above 0.1%) in the rapidly solidified Pb-Ca binary alloy. Alloying of a small amount of silver, 0.2%, resulted in a remarkably reduced rate of the growth of the anodic oxide layer.
3) The presence of calcium in the tertiary alloys inhibited the formation of PbO2 up to about 0.5% Ca.
4)βA-PbO2 was detected in the anodic oxide layer on Pb-Ca binary alloys and observed to be formed at much lower silver content in Pb-Ag-Ca tertiary alloy compared to the Pb-Ag binary system.
5) At higher calcium content and at low solidification rate, grains having high calcium content, assigned to Pb3Ca, were crystallized and depraved the quality of the alloy anode.
