Development of conducting polyaniline coating: a novel approach to superior corrosion resistance

The present work was undertaken to study the corrosion behaviour of conducting polymer coating on ferrous material. The synthesis of polyaniline (PAni) powder, its characterization, blending and coating formulation are described in detail. The yield of synthesized polymer was approximately 90% with a conductivity of 0.20-0.40 S/cm. The coating was formulated by incorporating this PAni powder as pigment. The coating conductivity increased with increase in the solid concentration and saturated in the range of 10-15 wt.%. The results of the corrosion tests on PAni coated steel substrate with 1-50 mum coating thickness exposed to 3.5% NaCl solution were also presented. The corrosion resistance of PAni coated steel was found to be more than 10-15 times higher than the bare steel. Electrochemical impedance spectroscopy study revealed that a continuous charge transfer reaction across the metal-coating interface was responsible for the increase in coating capacitance and decrease in polarization resistance. The potentiodynamic study also showed that the current density significantly decreased in PAni coated steel in comparison to bare steel. (C) 2002 Elsevier Science B.V. All rights reserved.