A new corrosion protection coating with polyaniline–TiO 2 composite for steel

Abstract

Organic coating strategies for corrosion protection with inherently conducting polymers have become important because of restriction on the use of heavy metals and chromates in coatings due to their environmental problems. This work presents the synthesis of polyaniline–TiO 2 composites (PTC) and the corrosion protection behaviour of PTC containing coating on steel. PTC was prepared by chemical oxidation of aniline and TiO 2 by ammonium persulfate in phosphoric acid medium. The PTC was characterized by FTIR, XRD and SEM techniques. Suitable coating with PTC was formed on steel using acrylic resin. Using electrochemical impedance spectroscopy, the PTC containing coating's behaviour in 3% NaCl immersion test and salt spray test has been found out. Results indicate that the coating containing PTC is able to maintain the potential of steel in passive region due to its redox property. The resistance of the coating containing PTC was more than 10 7 Ω cm 2 in 3% NaCl solution after 60 days and 10 9 Ω cm 2 in the salt spray test of 35 days. But the resistance of the TiO 2 containing coating was found to be less than 10 4 Ω cm 2 in both the cases. The high performance of PTC containing coating is attributed to the passivation of steel by polyaniline.