Isotherms of water vapor sorption have been experimentally determined for aluminum powders (flitters) of the grades ASD-4, ASD-6, PA-2, PA-4, PAD-2, PAD-4, PAP-1, and PAP-2. Water vapor sorption by ASD, PA, and PAD powders begins at air humidity above 80%. The kinetics of the chemical reaction between water vapor and aluminum is characterized by an induction period, the duration of which depends on the aluminum grade and the relative air humidity. A reaction mechanism between water vapor and aluminum powders is proposed, in which atomic hydrogen plays an important role: it is released in the main reaction and enters into a chemical interaction that destroys the oxide-hydroxide protective film on the aluminum powder granules. The hygroscopicity of PAP flitters is determined by the absorption of water vapor by the fatty coating rather than by aluminum itself.
A.G. Tereshchenko (Wed,) studied this question.