(217er) Anticorrosive Conductive Polyurethane Multiwalled Carbon Nanotues Nanocomposites

In the paper, conductive polyurethane (PU) nanocomposite coatings filled with multiwalled carbon nanotues (MWNTs) prepared via an in situ surface-initiated-polymerization method were evaluated for anticorrosion purpose. Scanning electron microscopy (SEM) reveals a uniformly dispersed MWNTs nanoparticles in the PU matrix. Thermogravimetric analysis (TGA) shows an enhanced thermal stability of the composite as compared to pure PU. The nanocomposite exhibits a good response of electrical conductivity change to the varying strain during the cyclic strain test. The anticorrosion tests in 3.0 wt% NaCl aqueous solution suggest that the composite coatings possess a good chemical stability over long immersion time in the corrosive environment. A significantly positive shift of nearly 1.0 V in the open current potential, E_ocp, was observed from the E_ocp-time curve of MWNTs/PU composite-coated stainless steel electrode. Extrapolation of Tafel plots gave a much more positive corrosion potential (E_corr) and much lower corrosion current (I_corr). A protection efficiency as high as 97.70% was obtained. Electrochemical impedance spectroscopy (EIS) was conducted as well to investigate and obtain the anticorrosion mechanism of the composite coating. An equivalent circuit of the coating was proposed to fit the EIS data, confirming an effective corrosion protection for the stainless steel. The results indicate that the polyurethane matrix combined with the well dispersed MWNTs reinforcements provides an effective physical barrier against the attack of corrosive ions in the solution for the stainless steel.