Reaction rates and prediction of thermal instability during aluminum alloy 6061 dissolution

Chemical kinetics of dissolution of aluminum alloy 6061 was investigated for the processing of Pu-238 for deep space missions. The rate of dissolution was measured by the heat release and appeared to be controlled by the rate of release of Al(OH)4− from the metal surface. Rates of reaction were measured from 273 to 365 K, giving an activation energy of 72 ± 13 kJ⋅(mol Al)−1 and a pre-exponential factor of 5 ± 3 × 109 dm3mol−1min−1. Minor alloying elements did not appear to affect the reaction kinetics. The average heat of dissolution was −360 ± 70 kJ⋅(mol NaAlO2)−1. When extrapolated to an infinitely dilute solution of aluminum, kJ⋅(mol NaAlO2)−1.