An active carbon chemistry is observed at the border of photo-dissociation regions
(PDRs), involving small hydrocarbons, polycyclic aromatic hydrocarbon (PAH) macromolecules
and evaporating very small grains (VSGs). In this context, we aim at quantifying the
physical and chemical evolution of PAHs (hydrogenation and charge states, aggregation, and
complexation with heavy atoms) as a function of the local physical conditions (radiation
field, temperature, density, abundances of atomic and molecular hydrogen, electrons and
heavy atoms). We have developed a numerical model that follows the time dependency of the
abundance and internal energy of each species. In this paper, we use this model to
calculate the hydrogenation and charge states of coronene C24H12 as
an interstellar PAH prototype. We take advantage of recent results on photodissociation
and reaction rates and provide guidelines for future laboratory studies. Reaction rates of
coronene-derived radical cations with H and H2 are found to be sufficiently
constrained by experiments, whereas the absence of experimental data for neutral species
is critical.