Improving the corrosion performance of epoxy coatings by chemical modification with silane monomers

In this communication, commercial epoxy resins were chemically modified with various silane monomers under the catalysis of organotin compound, aiming to enhance the corrosion resistance of epoxy coatings on 2024-T3 aluminum substrates. Immersion studies conducted in 3.5 wt.% NaCl solution showed that the coating capacitance (Cc) decreases significantly after the silane modification, as measured by electrochemical impedance spectroscopy (EIS), indicating the higher resistance to water permeation. EIS measurements also indicated an enhancement in protectiveness of silane-modified epoxy coatings against substrate corrosion, which was characterized by higher charge transfer resistances (Rct) and lower double layer capacitance (Cdl) at substrate/electrolyte interface. The adhesion of epoxy coatings was also found to improve after the modification with silane components. The best performance was observed for coating system modified by 3-glycidoxypropyltrimethoxy silane (GPTMS).