Anticorrosive Coatings Prepared Using Epoxy–Silica Hybrid Nanocomposite Materials

Organic–inorganic nanocomposite protective coatings were prepared by sol–gel method using 3-glycidoxypropyl-trimethoxysilane (GPTMS), tetramethoxysilane (TMOS), or tetraethoxysilane (TEOS) as silane precursors to compare the effect of two types of alkoxysilane (i.e., methoxy or ethoxy functional group) on aluminum substrate properties. In addition, the TiO2 and AlOOH nanoparticles were derived from tetra-n-butyl titanate and aluminum butoxide, respectively, and the protective effect of these nanoparticles on the GPTMS based coatings was investigated. The formation of AlOOH and TiO2 nanoparticles and the uniform distribution of nanoparticles in the coatings were characterized by dynamic light scattering (DLS) and different microscopic techniques. Potentiodynamic scanning (PDS) and 2000 h salt-spray testing methods were used to investigate the corrosion resistance of these hybrid sol–gel coatings. The PDS results demonstrated that the corrosion protection of hybrid coatings depends mainly on the silane content, type of the silane precursor, and type of nanoparticles. The coating protective effect improved by increasing polarization resistance (Rp) for about one decade by replacing silane precursors from TEOS to TMOS. In addition, the incorporation of TiO2 in comparison with AlOOH nanoparticles in the GPTMS based coatings showed improving effect on polarization resistance. However, the simultaneous incorporation of TiO2 and AlOOH nanoparticles led to high protective coatings.