Corrosion protection of stainless steel by polyaniline electrosynthesized from phosphate buffer solutions

Polyaniline with excellent adherence was electrosynthesized on stainless steel from aniline containing phosphate buffer solutions. The eletropolymerizations were carried out by cyclic voltammetry at 50 mV s(-1) from phosphate buffer solutions at different pH values (1.7-2.2). The main advantage achieved by using phosphate buffer solutions is to maintain the control of the pH at the polymer/electrolyte interface, promoting a very uniform film growth. The most uniform thin film was formed from 1.0 M phosphate buffer solution containing 0.1 M aniline. The corrosion behavior of stainless steel covered by these films was investigated by potentiodynamic polarization in 3% NaCl aqueous solution. A potential shift to noble values, of around 0.170 V, was obtained for undoped polyaniline coatings compared to the bare stainless steel. A scheme for the polymer protective layer formation on stainless and mild steels, with the participation of an intermediate phosphate layer, is proposed. (C) 2003 Elsevier Science B.V. All rights reserved.