The main reaction mechanism that replaces the Al2O3 passivation layer on Al nanoparticles with an energetic AIH salt is demonstrated. The reaction mechanism is pH dependent and utilizes electrostatic forces that occur between the Al2O3 passivation layer and free hydrogen atoms (H+) in solution. When Al particles are added to highly acidic solutions, free H+ polarize the Al-O bonds in Al2O3, resulting in the formation of H2O and free Al3+ cations that are complexed by water molecules and exist as [Al(H2O)6]3+ in aqueous solutions. The concentration of AIH is limited by the amount of [Al(H2O)6]3+ that forms from the polarization reaction between free H+ and the initial Al2O3 concentration. The proposed mechanism describes a stoichiometric reaction, but deviations from the stoichiometric reaction are expected with varying equivalence ratios (ER). The polarization mechanism is confirmed by measuring deviations in concentration of final AIH mixtures as a function of ER. A salt formation theory dependent on pH and pKa is used to demonstrate how the final AIH concentrations can be estimated at ER values that are not stoichiometric.