Improved corrosion resistance of AA2024 alloys through hybrid organic-inorganic sol-gel coatings produced from sols with controlled polymerisation

摘要

In this work we present the development of a nanocomposite material composed by silica nanoparticles in a hybrid organic-inorganic sol-gel matrix for corrosion protection of aluminium alloys. The sol-gel matrix was produced from an inorganic precursor, tetraethoxysilane (TEOS), a hybrid precursor organically functionalized with C=C groups, 3-metacryloxypropyltrimethoxysilane (MPS), and an organic bi-functional monomer, ethyleneglycol-dimethacrylate (EGDMA) used to increase the cross-linking network. Silica nanoparticles, on the other side, increase the density and provide a major mechanical performance through the reinforcement of the coating. The evolution of the sol, mainly the chemical structure, during the processes of hydrolytic condensation and organic polymerisation was studied as a function of the sol concentration through Fourier transformed infrared spectroscopy (FTIR), rheometry, laser diffraction analysis and contact angle. Mono and multilayer coatings were deposited by dipping onto AA 2024 substrates and characterised by profilometry. The corrosion behaviour was followed through potentiodynamic tests and Electrochemical Impedance Spectroscopy (EIS).