Alkyd coatings containing polyanilines for corrosion protection of mild steel

A study was carried out to investigate the performance of anti-corrosion coatings obtained from alkyd paints containing polyaniline and polyaniline derivatives applied on carbon steel. The polyaniline, the polyaniline derivates and the paints were characterized through FTIR and Raman spectroscopies and thermogravimetric analysis. Cyclic voltammetry studies showed that polyaniline and its derivates gave electroactive properties to the paints. Accelerated corrosion experiments (salt spray and humidity chamber) revealed a significant improvement in the performance of the coatings which contained the electroactive polymer compared to conventional coatings. These results were verified by evaluation of the electrical resistance and capacitance measurements of the films using electrochemical impedance spectroscopy. For some of the samples, the Raman spectra demonstrated the presence of an oxide layer at the coating/substrate interface composed basically of Fe2O3 and Fe3O4. The results of this study reinforce the possibility of protecting carbon steel against corrosion through the formation of a protective layer of oxides using coatings which contain electroactive polymers.