Abstract
In this paper we discuss electrocleposited polyaniline (PANI) films on stainless steel surfaces made from two different acidic (sulphuric and phosphoric) solutions containing the aniline monomer. The type of counter anion was shown to significantly affect the polymerisation reaction and the formation of an underlying oxide layer. We find that the growth rate and thickness of the PANISO(4) layer are much higher than those of PANIPO(4) layer. Both layers altered the steel potential and passivated the materials when immersed in a hot acid solution. While the oxide underneath the PANISO(4) layer is enriched with Cr, Fe and Ni components the under PANIPO(4) layer is elementally deficient, making the later a less efficient passivating agent. Finally, we show that the first oxide film is superior in protection against pitting in aggressive chloride solutions. (C) 2011 Elsevier B.V. All rights reserved.