Silica based organic-inorganic hybrid nanocomposite coatings for corrosion protection

Silica based organic-inorganic hybrid nanocomposite coatings have been developed for corrosion protection of 1050 aluminum alloys by dip coatings technique. The hybrid sols were prepared by hydrolysis and condensation of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and tetramethoxy silane (TMOS) in the presence of an acidic catalyst and bisphenol A (BPA) as cross-linking agent. Such prepared hybrid coatings were found to be relatively dense, uniform and defect free. Structural characterization of the hybrid coatings were performed using optical microscopy, scanning electron microscopy (SEM) and attenuated total reflectance-infrared (ATR-IR) spectroscopy. Corrosion resistance properties of the hybrid sol-gel coatings were studied by potentiodynamic scanning (PDS) and salt spray testing methods. The results indicate excellent barrier protection performance of the coatings. In addition, the effect of molar ratio of GPTMS-BPA (silane content) on corrosion resistance of the coatings was investigated. The PDS results demonstrated that the corrosion resistance of hybrid coatings improved by decreasing of silane content.