Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

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2013-04-01

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Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier, increasing the total impedance by 4 orders of magnitude and reducing the current densities by more than 3 orders of magnitude, compared to the bare steel electrode. © 2013 Elsevier B.V. All rights reserved.

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Carbon nanotubes, Corrosion protection, Electrochemical properties, Hybrid coatings, Photoelectron spectroscopy, Sol-gel process, Acidic solutions, Bare steel, Carbon steel substrates, Carboxylic group, Corrosion barriers, Covalent bonding, Dip coating, Functionalized, Hybrid coating, Hybrid film, Hybrid matrix, Molar ratio, Nano-composite structure, Orders of magnitude, Polymerization of methyl methacrylate, Potentiodynamic polarization curves, Protection efficiency, Similar degree, Thermogravimetric measurement, Carbon steel, Coatings, Corrosion resistance, Electrochemical impedance spectroscopy, Esters, Photoelectrons, Polycondensation, Polymethyl methacrylates, Sols, Substrates, X ray photoelectron spectroscopy

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Progress in Organic Coatings, v. 76, n. 4, p. 601-608, 2013.