Effect of Cerium Salt and Zeolite Particle-Doped Silane Film on Corrosion Resistance of Epoxy Coating on 7N01 Aluminum Alloy

In order to enhance the anti-corrosion property of epoxy coatings on 7N01 aluminum alloy, cerium nitrate and zeolite particles were incorporated into a bis-(triethoxysilylpropyl)tetrasulfide (BTESPT) silane solution to pretreat the substrate. Scanning electron microscopy (SEM) and an electronic probe microanalyzer (EPMA) were used to characterize the morphology and chemical composition of the composite silane film. The corrosion performances of the epoxy coatings were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) and based on the morphology and chemical composition of the interfacial region after salt spray tests. The thickness of the composite silane film at 5% BTESPT doped with 5 × 10^-3 M cerium nitrate and 0.5 g/L zeolite particles was about 2.1 μm. The composite silane film can provide active protection to the substrate surface beneath the epoxy coating. It promotes the impedance value of the coating at 10^-2 Hz by two to three orders of magnitude and greatly lessens the interfacial region corrosion between the coating and the substrate. This effect can be ascribed to the strong barrier effect of the composite silane film and cerium ions released from the silane network and the zeolite particles.