Mechanical property evaluation of corrosion protection sol-gel nanocomposite coatings

Organic-inorganic nanocomposite coatings were prepared from tetraethylorthosilicate and 3- glycidoxypropyltrimethoxysilane (GPTMS) by sol-gel method. These ormosil films were deposited by dip coating on aluminium alloy 5083. The effect of the concentration of GPTMS on the adhesion, mechanical and corrosion performance of coated samples was investigated. Adhesive strength of sol-gel coatings to the substrate was evaluated using pull-off and tape tests. Bending, impact resistance, pencil scratch and potentiodynamic polarisation tests were employed to characterise mechanical and corrosion performance of coated substrates with different GPTMS content. The chemical composition and the microstructure of the hybrid films were studied by attenuated total reflectance-Fourier transform infrared spectroscopy and field emission scanning electron microscopy respectively. The results indicate that the hybrid films had good mechanical properties, and the coating with minimum organic content had minimum corrosion current density, but the corrosion current density did not have any specific trend with an increased organic content.