Anticorrosive conductive polyurethane multiwalled carbon nanotube nanocomposites

Conductive polyurethane (PU) nanocomposite coatings filled with multiwalled carbon nanotubes (MWNTs) fabricated by employing an in situ surface-initiated-polymerization (SIP) method were tested for corrosion prevention of stainless steel (SS). The nanocomposites exhibited a good response of electrical conductivity change to the strain during the cyclic tensile strain test. The anticorrosion properties of these nanocomposite coatings on the SS surface were evaluated in 3.0 wt% NaCl aqueous solution by monitoring the open circuit potential (E-ocp) and tracing quasi-stationary polarization (Tafel) of the nanocomposite-coated stainless steel (MWNT/PU-SS) electrode. Electrochemical impedance spectroscopy (EIS) was also obtained to give an insight into the anticorrosion protection of SS. The nanocomposite displayed a good chemical stability over long immersion in a corrosive environment. A significant positive shift of nearly 1.0 V in the E-ocp was observed from the E-ocp-time curve. Extrapolation of Tafel plots gave a much more positive corrosion potential (E-corr) and a lower corrosion current (I-corr). A protection efficiency as high as 97.70% was obtained. An equivalent circuit of the coating was proposed to fit the EIS data, confirming an effective corrosion protection for SS. The results indicate that the polyurethane matrix combined with the well dispersed MWNT reinforcements provided a significant physical barrier against the attack of corrosive ions in the solution for SS while providing a channel for the conductivity.