Hybrid organic-inorganic sol-gel coatings produced from sols with controlled polymerization for corrosion protection of AA2024 alloys

N.C. ROSERO-NAVARRO; S.A. PELLICE; Y. CASTRO; A. DURÁN; M. APARICIO

Tours, France

Conferencia; Hybrid Materials 2009. First International Conference on Multifunctional, Hybrid and Nanomaterials; 2009

Elsevier

The sol-gel technology is a synthesis route that allows the preparation of hybrid materials with specific characteristics as a function of the application. In the corrosion protection coatings area, the research has been oriented to the preparation of coatings with higher density and thickness, and improved mechanical behaviour and corrosion resistance. In many cases, the substrates are temperature-sensitive materials as polymers or metallic alloys which could undergo changes of shape or precipitation of second phases during the thermal treatment of coatings, which imposes strong restrictions in coating formulations preventing the use of purely inorganic ones. From this limitation, hybrid organic-inorganic materials, with interpenetrated networks, exhibits the major possibilities of tailoring properties to fulfil the requirements without affecting the integrity of substrates. In this paper we present a detailed description and characterisation of the synthesis process of hybrid organic-inorganic sol-gel coatings reinforced with silica nanoparticles. 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, ethylenglycol-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 AA2024 substrates and characterised by profilometry and field emission scanning electron microscopy (FE-SEM). The corrosion behaviour was followed through potentiodynamic tests and Electrochemical Impedance Spectroscopy (EIS).