Solid State NMR and EIS Examination of SiO<sub>2</sub>-Epoxy Hybrid Coatings on Stainless Steel

Abstract

Sol-gel SiO2 and hybrid films were deposited on 316L stainless steel by the dip process. Epoxy bisglycidyl hydroquinone (EBH) was used as an organic component in hybrid films. Both coatings were uniform and homogeneous and displayed good adhesion to the substrates. The thickness of hybrid coatings was greater than that of SiO2 coatings. Thermal condition preparation has significant influence on spectroscopic properties of samples. These features are due to changes of morphology of epoxy-silica hybrid compared to unmodified silica-gels and are related to decomposition at higher temperature. The corrosion behaviour of 316L stainless steel samples coated with SiO2 and hybrid films was studied in Ringer’s solution by electrochemical impedance spectroscopy. SiO2 and silica-based hybrid coatings produced by the sol-gel method offers a good protection against corrosion of stainless steel in Ringer’s solution. In contrast to the SiO2-coated samples and the hybrid coating heated to 200°C, the behaviour of the hybrid coating heated to 300°C changed from resistive to a barrier-like one during exposure to the solution. This change was found to be a transient effect only. During 1-month exposure to Ringer’s solution the coating lost its barrier properties.