Organic–inorganic coatings based on epoxidized castor oil with APTES/TIP and TEOS/TIP

Two series of organic–inorganic hybrid films were prepared from epoxidized castor oil (ECO) and the inorganic precursor titanium(IV) isopropoxide (TIP), combined with silicon precursors, either 3-aminopropyltriethoxysilane (APTES) or tetraethoxysilane (TEOS) with different organic to inorganic proportions. Films were pre-cured at room temperature under an inert atmosphere and subsequently submitted to thermal curing. The macro- and microscopic properties of the films, including adhesion, hardness, microstructure (SEM) and thermal properties, were determined as a function of the proportion of ECO to inorganic precursors. Morphological studies showed that the hybrid films were microscopically homogeneous. The addition of TIP decreases substantially the curing time. The hardness and tensile strength of the films increased with increased concentration of inorganic precursor. The combination of the silicon-rich inorganic precursors with TIP improved substantially the mechanical strength of the films. All of the films exhibited good adhesion to the aluminum surface. Aluminum coated with the films and submitted to intensive corrosion test presented excellent protection.