Corrosion protection of AISI 1018 steel using Co-doped TiO2/polypyrrole nanocomposites in 3.5% NaCl solution

A polypyrrole nanocomposites (PPy NTCs) have been effectively synthesized in the presence of TiO2 and Co -doped TiO2 nanoparticles (NPs) by an in situ chemical oxidative polymerization. Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy revealed a tube shape structure of the PPy. The TEM results confirmed that the nanocomposite size of Co-doped TiO2/PPy NTCs was smaller than TiO2/PPy NTCs thereby increasing the interaction between the PPy nanotube and the AISI steel surface. The corrosion performance of the coatings was evaluated by electrochemical impedance spec-troscopy (EIS) and potentiodynamic polarization measurements in 3.5% NaCI solution. The EIS results show that the log RI of AISI 1018 coated with Co-doped TiO2/PPy NTCs and TiO2/PPy NTCs reached about 8.2 and 6.0 respectively after 30 days of exposure in 3.5% NaCI solution. This is likely due to the increased surface area of the PPy synthesized in the presence of Co -doped TiO2 NPs. The EIS results are confirmed by the potentiodynamic polarization and open circuit potential values of the Co -doped TiO2/PPy which indicated little changes between 1 and 30 days of exposure which confirms the protection ability of this coating.. It is evident that the presence of Co-doped TiO2 NPs can enhance the resistance against corrosion at the steel/electrolyte interface.(C) 2017 Elsevier B.V. All rights reserved.