A valuable additive — boric acid — to eliminate passivation of the active material/grid interface in positive plates of lead–acid batteries has been selected through comparison of single-cell discharge tests. This overcomes the problem of rapid decline in initial performance when using low-antimony (1.7 wt.%) grid alloys. The performance of the oxide film on positive grids, as well as its composition and amount, is determined through cathodic reduction of the film with a linear sweep voltammetric (LSV) method. The results confirm that passivation of the positive grid and rapid decline in the initial discharge voltage are due to a resistive layer of PbSO4, and not PbO n (1≤n≤2). The PbO n layer has little effect on passivation. The findings of this study are useful for the production of lead–acid batteries.