The effect of expanders on lead-sulphate formation and reduction

The influence of some organic expanders on the formation of lead-sulphate h as been studied by means of potentiostatic transients. The experimental dat a have been discussed according to the theories which have been proposed in the literature for the electro-crystallisation of lead-sulphate and lead. The discussion of the data obtained confirms the inhibiting effect of the e xpanders on lead sulphation. in fact, the tests showed that, when the expan ders are added to the electrolyte, a longer time is required to reach the c urrent maximum of the i(t) curve and a reduction of its intensity. Accordin g to the theoretical interpretation, this finding indicates a decreasing of the kinetic constant of the solid state process. The analysis of the i(t) transients obtained during the sulphate reduction revealed an influence of expanders only when the sulphate layers has been formed in their presence. Thus, it seems that the adsorption of the organic expanders on lead is of p rimary importance for their action while adsorption on lead-sulphate appear s to be negligible. (C) 2000 Elsevier Science S.A. All rights reserved.