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  • A silanol-based nanocomposi...
    Gonzalez, E.; Pavez, J.; Azocar, I.; Zagal, J.H.; Zhou, X.; Melo, F.; Thompson, G.E.; Páez, M.A.

    Electrochimica acta, 09/2011, Letnik: 56, Številka: 22
    Journal Article

    • A new silanol-based hybrid coating has been synthesized. • The incorporation of CeO 2 and ZrO 2 nanoparticles into the coating greatly improves the corrosion resistance of the coated aluminium alloy. • The effectiveness of the coating is increasingly evident for long term exposure to the sodium chloride solution. • The silanol-based nanocomposite coatings have self-healing ability. A new hybrid sol–gel type film, composed of tetraethylorthosilicate (TEOS) and tetraocthylorthosilicate (TEOCS), and modified with different nanoparticle systems, has been investigated as a coating for protection of AA-2024-T3 aluminium alloy. The nanoparticle systems considered were either ZrO 2 or CeO 2 or their combination . The zirconia nanoparticles were prepared from a Zr (IV) propoxide sol (TPOZ), using an organic stabilizer, and the CeO 2 nanoparticles were developed spontaneously after adding cerium nitrate solution to the hybrid sol. The chemical composition and the structure of the hybrid sol–gel films were examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion resistance of the coated AA-2024 alloy was examined by potentiodynamic polarization. The results revealed that, for short exposure times in the electrolyte, incorporation of ZrO 2 or CeO 2 nanoparticles in the hybrid film does not provide an increase in the corrosion resistance of the coated AA-2024 alloy. Further, the resistance was significantly reduced by increasing the nanoparticle content. Conversely, by incorporating both nanoparticles (ZrO 2 and CeO 2), the corrosion resistance of the resulting hybrid films increased slightly. The behavior changed significantly when the coated alloy was exposed to the electrolyte for 5 days. The corrosion resistance of the coatings, unmodified and modified with CeO 2 or ZrO 2 nanoparticles, decreased by two or three orders of magnitude, while the film modified with both nanoparticles (CrO 2 and ZrO 2) showed a relatively high corrosion resistance and responsiveness to activation processes during anodic polarization.