Anodic treatment of aluminum in nitric acid containing aniline, previous to deposition of polyaniline and its role on corrosion

Anodic activation of aluminum in nitric acid solutions containing aniline makes the aluminum surface porous containing pits filled with polyaniline (PAni). The advantages of this method of pre-treatment are: (1) polyaniline deposited in the pores and pits can promote the formation of closed polymer films covering the electrode, and (2) a short time anodization at high current density produces an optimization in porosity which allows a rapid growth of the polymer film. Corrosion tests in 0.1 M NaCl showed that the polyaniline coatings on aluminum, prepared from aniline containing sulfuric acid after pre-anodization in nitric acid with aniline, are more resistant to corrosion than the films prepared without pre-treatment. The corrosion current density decreases by a factor of 1/57 compared to bare aluminum. It was a] so possible to obtain films with the ability to separate their pitting potentials from the corrosion potentials, by shifting them to more positive values. (C) 2003 Elsevier Science B.V. All rights reserved.