Polyaniline nanotubes: Facile synthesis, electrochemical, quantum chemical characteristics and corrosion inhibition efficiency

This work represents the preparation of polyaniline in its free and self-doped forms. The polymers were formed as nanotubes using template free self-curling preparation. Chemical oxidation polymerization of aniline and 4-aminobenzene sulphonic acid individually as monomers was carried out without adding acids or templates. The electron microscope image of the polymer reveals the nano-tubular structure with inner diameter of 20-30 nm and outer diameter of 80-100 nm. Quantum chemical calculations of the repeating units were calculated to correlate the chemical structure to the mechanism of inhibition. The corrosion inhibition behavior of the polymers in 1 M HCl has been evaluated using Tafel's extrapolation method and electrochemical impedance spectroscopy (EIS). Self-doped polyaniline showed the greater inhibition efficiency compared with un-doped polyaniline. Results of electrochemical impedance and Tafel's polarization measurements consistently showed that both compounds can be effectively used as corrosion inhibitors. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.