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 the epoxy coatings on 7N01 aluminum alloy, cerium nitrate and zeolite particles were incorporated into the bis-(triethoxysilylpropyl)tetrasulfide (BTESPT) silane solution to pretreat the substrate. Scanning electron microscope (SEM), electronic probe microanalyzer (EPMA) were used to characterize microstructure of the composite silane film. The corrosion performances of the epoxy coatings were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and microstructure of the interfacial region after salt spray tests. The thickness of the composite silane film by 5 % BTESPT doped with 5×10-3 M cerium nitrate and 0.5 g/l zeolite particles is about 2.1 μm. The composite silane film can provide active protection to the substrate surface beneath the epoxy coating. It promotes 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 high barrier effect of the composite silane film and cerium ions releasing from the silane network and the zeolite particles.