Development of anodes for aluminum/air batteries: Solution phase inhibition of corrosion: Final report

Solution-phase inhibition is a promising strategy for controlling the corrosion of the aluminum fuel in alkaline aluminum/air batteries. Development of effective inhibitors would permit the use of scrap aluminum as fuel and thereby significantly improve the economics of the battery, because the cost of the fuel would have been partly or wholly defrayed by its previous use. In this study, we explored the discharge characteristics of aluminum in inhibited and uninhibited 4 M KOH at 50/degree/C and compared the performance of the fuel with that for two leading alloy fuels that had been evaluated in our previous work, Alloy BDW (Al-1Mg-0.1In-0.2Mn) and Alloy 21 (Al-0.2Ga-0.1In-0.1Tl). The inhibitors employed in this study, SnO/sub 3//sup 2/minus//, In(OH)/sub 3/, Ga(OH)/sub 4//sup /minus//, MnO/sub 4//sup 2/minus//, and binary combinations thereof, are either alloying elements of Alloys BDW and 21 or have been investigated previously. We found that potassium manganate and Na/sub 2/SnO/sub 3/ + In(OH)/sub 3/ are effective inhibitor systems. Particularly at high discharge rates, but at low discharge rates only manganate offers a significant advantage in coulombic efficiency over the uninhibited solution. Alloy BDW exhibits a very low open circuit (standby) corrosion rate, but its coulombic efficiency under discharge, as determined by delineating the particle anodic and cathodic reactions, was found to be no better than that of aluminum in the same uninhibited solution. Alloy 21 was found to exhibit a comparable performance to Alloy BDW under open circuit conditions and a much higher coulombic efficiency at low discharge rates, but the performance of this alloy under high discharge rate conditions was not determined. Alloy 21 has the significant disadvantage that it contains thallium. 36 refs., 14 figs., 2 tabs.