INVESTIGATIONS OF THE NEGATIVE PLATE OF LEAD ACID CELLS .1. SELECTIONOF ADDITIVES

A procedure is proposed for the selection of inhibitors and expanders used as additives for the negative plate of the lead/acid battery. Inh ibitors were selected by performing d.c. and a.c. measurements at pure metals (Cu, Sb, Ag), which are assumed to act as local active sites f or the hydrogen-evolution reaction at the negative plate. From this st udy anisaldehyde was found to show strong preferential adsorption at C u and Sb. Expanders were selected using a.c. impedance measurements at a Pb electrode at a low anodic discharge current. Selected expanders were Indulin C and Na-1-naphtol-4-sulfonate. From the impedance measur ements information was obtained not only on the expander action but al so on the effect of the additive on the double layer and the diffusion properties of lead sulfate. From a study on the concentration depende nce of the expander (Na-1-naphtol-4-sulfonate) an optimal effect was f ound at a concentration of about 600 ppm.