The thermal stability of the hydrogen passivation of aluminum accepters in p-type silicon carbide is investigated. After passivation by Tow energy ion implantation, annealing experiments are performed under the influence of an electrical field in a reverse biased Schottky diode. At temperatures around 500K, Al accepters become reactivated. To study the influence of temperature, p-type doping level, and hydrogen isotope ((1)H or (2)H), a mathematical model is developed and applied to simulate experimental data. Both the diffusion constant of free H as well as the dissociation rate turn out to be thermally activated with activation energies of 2.1 eV and 1.2 TV, respectively.