In this work, the global kinetics and the exchange of protons and free solvent at the film/electrolyte interface were investigated when a PPy film doped with HPA (heteropolyanions) is polarized. The ionic and electronic transfers for the PPy-HPA system are fast because the determined values of the resistances are relatively low (a few ohms). Depending on the applied potential, the global kinetics is controlled by both the ionic and electronic transfers. The transport effects were neglected here because the prepared films were very thin. Protons play an important role in charge compensation whatever the imposed potential on the PPy-HPA film. This phenomenon results from the acidic-basic properties of the SiMo12O404- reduced species. A small quantity of water was also shown to be involved in the film reaction process.