Interface reaction mechanism of epoxy resin electrodeposition on aluminum induced by silane coupling agents

Abstract This study systematically investigated the effects of surface treatment with five triethoxysilane coupling agents (TES), combined with heat treatment and electrochemical process parameters, on the adhesion and durability of aluminum (Al)–epoxy resin composites prepared via electrodeposition. The mechanism of TES action on the aluminum surface was analyzed by means of Fourier transform infrared spectroscopy (FTIR), contact angle measurements, atomic force microscopy (AFM), and open-circuit potential measurements. Adhesion strength was evaluated using the surface and interface cutting analysis system (SAICAS), and durability was assessed through the copper-accelerated acetic acid salt spray (CASS) test. The experimental results indicate that TES molecules adsorbed onto the aluminum surface, forming a protective film without significantly altering surface roughness. All TES appeared to treatments improved the adhesion strength of the composite; among them, the combined treatment with aTES and nTES (aTES/nTES) yielded the optimal effect, with adhesion strength reaching 1.17 kN/m after heat treatment. Furthermore, the aTES/nTES treatment effectively inhibited corrosion and significantly enhanced the corrosion resistance of the composite in the CASS test, while showing negligible influence on the adhesion variation induced by electrochemical corrosion. This study suggests that precise selection and application of TES coupling agents can markedly enhance the comprehensive performance of Al-epoxy electrodeposited composites, providing essential theoretical and practical insights for the design and optimization of high-performance composite materials.