Anticorrosion Performance of TiO2/Epoxy Films with Doped Polyaniline and Poly(o-ethoxyaniline) Applied to Carbon Steel in 3.5 wt % NaCl Acid Solution

Abstract

In an effort to enhance the corrosion resistance of carbon steel in hostile environments, researchers have incorporated doped conductive polymers with sulfo-5-salicylic acid, such as polyaniline (PANI) and poly(ortho-ethoxyaniline) (POEA), into a conventional epoxy resin dissolved with xylene solvent. The primary objective was to develop more effective anticorrosion films compared to traditional zinc phosphate (ZP) coatings. The newly created epoxy resin coatings underwent thorough characterization methods; including techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and immersion tests. To assess the corrosion resistance of these coatings, a range of tests were performed, as did the open circuit potential (OCP), linear polarization resistance (LPR), potentiodynamic polarization curves (Tafel plots), electrical impedance spectroscopy (EIS), and solution iron analysis extended to 3.5 wt % NaCl solution at pH 4.5. The results clearly demonstrated a substantial improvement in the corrosion resistance when the PANI and POEA coatings were applied, outperformed the ZP coating. These enhancements were attributed to a tenfold increase in the impedance of the ZP coating, a significant reduction in substrate degradation, and a threefold decrease in iron loss into the solution. These findings suggest that PANI−TiO₂/epoxy and POEA−TiO₂/epoxy coatings hold great promise as potential replacements for traditional zinc phosphate-based anticorrosion coatings, thanks to their superior protective barrier and enhanced performance.