Substrate-adherent polypyrrole films are obtained by electrochemical oxidation of pyrrole on a Zn electrode in an aqueous sodium oxalate medium provided that the zinc surface has been treated previously in a sulfide medium with the view to reduce its reactivity. The best pretreatment was achieved when the electrode was polarized anodically at 0.35 mA cm(-2) for 3 min in 0.2 M Na2S solution. Various electrochemical techniques (cyclic voltammetry, chronopotentiometry, impedancemetry) accompanied by XPS studies were used to characterize the surface modifications of the zinc electrode induced by this pretreatment. It was found that the formation of surface film occurs in two steps. At low anodic potentials, a porous layer is formed and at high anodic potentials the surface film is modified and acquires good protective properties. The surface layer consists of a mixture of ZnS (ca. 65%) and ZnOxHy, (ca. 35%) with 1 less than or equal to x less than or equal to 2, and 0 less than or equal to y less than or equal to 1. Best electropolymerization conditions for obtaining homogeneous and adherent polypyrrole film involved an aqueous solution of 0.9 M pyrrole + 0.1 M Na2C2O4 With galvanostatic polarization and after the substrate metal had been treated as indicated previously.