Aniline electropolymerization on platinum and mild steel from neutral aqueous media

Aniline has been electropolymerized on platinum from neutral aqueous electrolytes. The properties of the resulting polyaniline (PANI) films are similar to those obtained in acidic media. PANI films can be generated using multiple cyclic voltammetry or galvanostatically. In the former case, the molecular structure of the films depends on the inversion potential and two types of material can be generated. When potential sweeps are restricted to an inversion potential of 0.8 V, the films do not have a PANI-like structure, whereas an inversion potential of 1 V allows the deposition of short PANI-like chains, as demonstrated by SEC and MALDI-MS techniques. In the galvanostatic mode, the molecular structure of the films depends on the applied current density. There is a current density window which makes it possible to grow PANI films from neutral electrolytes with the same efficiency as in acids and which depends drastically on the experimental conditions. In the case of a 2 M LiClO4 + 0.4 M aniline solution, a very high current density can be used for PANI deposition on platinum. These neutral aqueous electrolytes have been used for the deposition of PANI films on mild steel. The films are generated with less metal dissolution than when acid electrolytes are used and exhibit similar anticorrosion properties. (C) 2000 Elsevier Science S.A. All rights reserved.