Silica sol–gel anchoring on aluminum pigments surface for corrosion protection based on aluminum oxidized by copper ammonia complex ion

Abstract

To reduce the volatile organic compounds emission led to the development of waterborne coatings. Correspondingly, waterborne aluminum pigment is desirable to develop. Here, the waterborne aluminum pigments were prepared by sol–gel encapsulation method using tetraethoxysilane and γ-aminopropyl triethoxysilane as precursors with [Cu(NH3)4]2+ as anchoring agent. Fourier transformation infrared and X-ray diffraction results showed that the boehmite formed by [Cu(NH3)4]2+ oxidizing aluminum can successfully react with silanol to make the silica sol–gel film anchored on the aluminum surface in the encapsulation process. The reaction conditions were optimized and the products were characterized by scanning electron microscopy, optical microscopy and stability test. It was found that control the pH of encapsulated media between 8.77 and 10.10, the boehmite on aluminum flake surfaces carried a strong positive charge and the silica sol–gel film carried a negative charge, which conduct the most anchorage efficiency, and the waterborne aluminum pigment exhibit best stability.