Investigation of corrosion protection performance of poly(N-methylpyrrole)-dodecylsulfate/multi-walled carbon nanotubes composite coatings on the stainless steel

In this study, composite coatings which consist of multi-walled carbon nanotubes (MWCNTs) and poly(N-methylpyrrole)-dodecylsulfate (PTIMPy-DS) were fabricated on a stainless steel. Firstly, electrodeposition of the PNMPy-DS film was performed by potentiodynamic method on a steel substrate in an aqueous solution containing N-methylpyrrole, oxalic acid and sodium dodecylsulfate. Then, a second layer on the polymer-coated stainless steel was formed by two different ways: (a) the dropping of Nafion (R) solution containing MWCNTs and (b) the electrodeposition of MWCNTs at a constant potential. The cyclic voltammetry, FT-IR spectroscopy and SEM techniques were used for the characterization of the PNMPy-DS and MWCNTs modified PNMPy-DS (PNMPy-DS/MWCNTs) coatings. Corrosion protection tests of these coatings were examined in 0.5 mol L-1 H2SO4 solution by potentiodynamic polarization and EIS techniques. These tests exhibit that the PNMPy-DS/MWCNTs composite coatings ensure powerful protection for the stainless steel against corrosion. This result is caused by the negatively charged MWCNTs and Nafion (R) on the surface of polymer layer and dodecylsulfate dopant in the polymer structure electrostatically repulse the corrosive sulfate ions and retard their reach to metal surface. (C) 2015 Elsevier B.V. All rights reserved.