Corrosion protection of carbon steels by electrochemically synthesized V-TiO2/polypyrrole composite coatings in 0.1 M HCl solution

Polypyrrole (PPy) composite coatings have been effectively synthesized in the presence of TiO2 and V-TiO2 nanoparticles on carbon steel by electrochemical method in aqueous oxalic acid solutions. These coatings were characterized by different surface analysis methods. TEM results confirmed that the size of V-TiO2 nanoparticles (11.91 +/- 1.03 nm) was smaller than that of TiO2 nanoparticles (17.22 +/- 2.84 nm), therefore increasing the interaction between PPy composite coatings and metal surface. The electrical conductivity measurement was carried out to examine the electrical properties of TiO2/PPy and V-TiO2/PPy composite coatings. Besides, the electrochemical behaviors of these coatings were also studied in 0.1 M HCl solution by electrochemical impedance spectroscopy and potentiodynamic polarization measurements. Results showed that the V-TiO2/PPy composite coatings exhibited better anti-corrosion performance than TiO2/PPy composite coatings. The exceptional anti-corrosion performance of PPy composite coatings was associated with the synergistic effect of the increase in physical barrier, prevention of charge transport by TiO2 nanoparticles and the complex passive film on the metal surface. (C) 2018 Elsevier B.V. All rights reserved.