โ Scribed by Y. Hori; J. Takao; H. Shomon
No coin nor oath required. For personal study only.
Aluminium has not widely been used for anode material for primary ceils, despite its attractive properties. Aluminium loses a great part of the potential when anodically polarized, and is easily corroded in aqueous solution with hydrogen evolved. Aluminium alloys derived from high purity aluminium (99.999 ~) were prepared for application to primary dry cell. Small amounts of the following elements were added to aluminium: Zn, Sn, Ga, Bi, In, Mg. The electrode potential, the anode Faradaic efficiency and the rate of corrosion of the alloy specimen sheets (10 x 10 x 0.5) were measured in 1 M AICI3 aqueous solution. The rate of corrosion significantly increased after anodic polarization (anodic dissolution). The electrode potentials at open circuit and anodic polarization (10 mA cm-2) shifted remarkably in the negative direction by alloying. The anode Faradaic efficiency and the rate of corrosion depended upon the alloy composition. The alloy, AI-3.0Zn-0.13 Sn-0.01Ga-0.07Bi (% w/w), gave the best results. The anode efficiency amounted to 99.7 % as compared with 87.4~o for 99.999 ~o AI. The average rate of corrosion was reduced to 0.03 mgcm -2 h-1 (short term)and 0.01 mgcm-2h -~ (long term). These electrochemical properties will improve the characteristics of aluminium dry cells.
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