Synthesis of Silane Functionalized LDH-Modified Nanopowders to Improve Compatibility and Enhance Corrosion Protection for Epoxy Coatings

Novel modified Zn-Al LDH/epoxy coatings are synthesized and applied to steel substrates, providing active corrosion protection and improved barrier properties. This protective coating is made by combining Epon 828 as a polymer matrix with modified layered-double-hydroxy (LDH) nanoparticles acting as corrosion inhibitor containers. To synthesize the coatings, nitrate was intercalated into Zn-Al-LDH layers through an aqueous co-precipitation method to obtain Zn-Al LDH-NO3, and decavanadate replaced nitrate within the LDH layers through an anion exchange process to obtain Zn-Al LDH-(V10O28)6−. The intercalated LDH was functionalized by silanization with (3-aminopropyl)triethoxysilane (APTES) to increase the compatibility of the LDH inhibitor nanocontainers with epoxy resin and produce a protective coating. To protect the mild steel substrate, functionalized LDH nanopowders were dispersed into the epoxy resin, mixed with a polyamide hardener (Epikure 3571), and applied and cured to the metal surface. Surface morphology, structure, and chemical composition were determined for the modified LDH nanopowders using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Corrosion protection of the coating system was studied using long-term immersion testing and potentiodynamic polarization studies in a 3.5 wt.% NaCl solution.