Smart coating based on polyaniline acrylic blend for corrosion protection of different metals

Coatings for corrosion protection of different metals considering intrinsically electronic conducting polymers have become important mainly because of restrictions on the use of coatings containing heavy metals, due to their serious environmental problems. This work presents the electrochemical behavior of a blend formed by camphor sulphonate-doped polyaniline and poly(methyl methacrylate) used for iron, copper and silver corrosion protection in acidic environments with or without chloride ions. The results obtained showed the good efficiency of these polymeric coatings against metal corrosion, proved by open circuit potential, linear voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. It was observed that the protection depends on the formation of a passive film between the polymeric coating and the metallic substrate. Raman spectroscopy revealed that the degree of redox conversion of camphor sulphonate-doped polyaniline strongly depends on the reducing power of oxidizable metals, showing a galvanic coupling between the metal and polyaniline. After that, metallic cations form a passivating complex with the dopant anion (camphorsulphonate), which improved the barrier property of different metals modified polyaniline coating system. (C) 2007 Elsevier B.V. All rights reserved.