Protection and surface modification of metals with sol–gel coatings

Abstract

The preparation and properties of protective sol-gel coatings on metallic substrates are reviewed. Control of the coating microstructure is critical to obtain the desired properties and this requires optimisation of processing parameters that include sol composition, synthesis and processing conditions, deposition method and post-deposition sintering or curing. Current knowledge in these areas, e.g. structure-property-processing relationships, and the characterisation of the coatings produced are discussed. SiO 2 layers have been found to confer good oxidation resistance, but for electrochemical corrosion resistance, mixed oxide layers or hybrid organicinorganic layers are required. Incorporation of alkylalkoxides with polymerisable groups attached has allowed synthesis of hybrid nanostructured coatings consisting of interpenetrating, chemically bonded organic and inorganic networks. Doping of hybrid sol-gel coatings with environmentally friendly inhibitors is also a promising approach combining barrier properties with active inhibition of corrosion. The potential to control functional properties such as biocompatibility is also briefly considered. It is concluded that both fundamental work on new coating compositions and the development of improved industrial technologies are priorities for future research.

Preparation of sol-gel SiO2 coatings on steel and their corrosion resistance

“…(Fig 4-b). The erosion of the coatings becomes stronger after treatment at 500 o C, leading to eruption of some areas of sample C. Duran et al have proved that the SiO2 coatings, deposited on stainless steel and galvanized steel treated at 550 o C were more cracked because of the elimination of organic groups during the treatment reduces the plasticity of the coatings [33]. a b…”

“…Several research groups were also obtained amorphous silica coatings thermally treated at 500 o C and 600 o C [33,34] The SEM photographs of the substrate and silica coated steel before and after corrosion test ae shown in Figures 1-3. (Fig 2-a).…”

Resistencia al desgaste de recubrimientos sol-gel de SiO₂ y SiO₂ - ZrO₂ sobre materiales vitrocerámicos obtenidos por sinterización

“…El proceso sol-gel es una ruta química que permite obtener capas densas y sin defectos [10] que pueden reducir o eliminar la porosidad superficial de los sustratos recubiertos, permitiendo así aumentar su resistencia al rayado y al desgaste. La protección mecánica de sustratos cerámicos o vítreos mediante la deposición de recubrimientos sol-gel permite sellar los defectos superficiales, retrasando el inicio de la fractura y aumentando la resistencia mecánica, evitando de este modo el riesgo de formación de nuevos defectos superficiales [11].…”

The influence of nanoadditives on surface, permeability and mechanical properties of self-organized organic–inorganic nanocomposite coatings

“…[1][2][3][4][5][6][7][8][9] Hybrid organic-inorganic (O-I) nanocomposite materials have been frequently prepared and studied due mainly to the possibility of preparation of tailormade products with properties hardly achieved if only organic-or inorganic-based material is used. O-I polymeric nanocomposites can be formed by two basic methods: either by building-up the inorganic nanofiller in situ (using e.g., the sol-gel process) within the organic phase, or by homogeneous dispersion of previously prepared nanoparticles in the organic matrix, either in a ''finished'' polymer or in a polymerizable monomer(s).…”