EFFECT OF ADDITIVES IN ZINC ALLOY POWDER ON SUPPRESSING HYDROGEN EVOLUTION

The addition of 0.025 wt.% bismuth and 0.025 wt.% lead to zinc particl es modified with 0.10 wt.% indium by a dry-coating process, or a conve ntional wet-coating process is examined to clarify the effect on suppr essing hydrogen gas evolution due to the self-discharging reactions of zinc in alkaline manganese batteries. The dry-coating process of indi um metal modifies the zinc alloy powder, such that oxidation of the po wder is less, and hydrogen-gas evolution is suppressed more effectivel y than in the case of the conventional wet-coating process. In the dry -coating process, the bismuth diffuses into the surface to be alloyed with the indium. As a result, zinc alloy powder containing 0.025 wt.% bismuth modified with 0.10 wt.% indium (Zn-In-Bi) by the dry-coating p rocess suppresses hydrogen gas evolution on a competitive level with z inc powder containing 0.15 wt.% mercury (Zn-Hg). (C) 1998 Elsevier Sci ence S.A. All rights reserved.