Improvements of anode properties of aluminium alloys for aluminium primary cell: heat treatment and corrosion inhibitors

Improvements of anode properties of aluminium alloys were attempted for application to a primary dry cell. Heat treatments were investigated chiefly for the alloy A1—3.0Zn—0.13Sn—0.01Ga—0.07Bi(% w/w) derived from high purity aluminium (99.999%). The solution heat treatment (homogenization) of the alloy at 400°C for 4 h presented the best anode properties, ie the faradaic efficiency and the rate of corrosion in 1 M AlCl₃ aqueous solution as the electrolyte. The average grain size diameters of the alloy specimens were also measured after heat treatment at various temperatures. The electrochemical properties were discussed in connection with the structures of alloy. Corrosion inhibitors were investigated for suppression of corrosion rates. Addition of agar and α-amilase to 1 M AlCl₃ significantly reduced the current loss (100 — faradaic efficiency, %) and the rate of corrosion. The alloy mentioned above treated at 400°C (homogenization) combined with agar (2 g l⁻¹) as a corrosion inhibitor gave the best electrochemical properties; the faradaic efficiency 99.8% and the average rate of corrosion 0.008 mg cm⁻² h⁻¹ (short term) and 0.005 mg cm⁻² h⁻¹ (long term).