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 particles modified with 0.10 wt.% indium by a dry-coating process, or a conventional wet-coating process is examined to clarify the effect on suppressing hydrogen gas evolution due to the self-discharging reactions of zinc in alkaline manganese batteries. The dry-coating process of indium metal modifies the zinc alloy powder, such that oxidation of the powder is less, and hydrogen-gas evolution is suppressed more effectively 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 process suppresses hydrogen gas evolution on a competitive level with zinc powder containing 0.15 wt.% mercury (Zn–Hg).