Silica-Based Coatings for Corrosion Protection of AA7075 Aluminum Alloy

The large economic and environmental impact caused by corrosion of metal structures has demanded new types of anti-corrosion coatings. This study proposes the application of silica-based coatings for corrosion protection of AA7075 aluminum alloy in saline environments rich in chloride ions. These coatings were obtained using the sol-gel technique. The samples were dip-coated in two types of solutions: (a) a mix of tetraethyl orthosilicate (TEOS) with 3-(Trimethoxysilyl)propyl methacrylate (TMPM) (Coating 1); and (b) a mix of titanium (IV) isopropoxide (TIP) with TMPM (Coating 2). The cure temperatures of the coatings were of 25°C, 60°C, 100°C, and 130°C, with treatment times of 1 and 3 hours. Characterization of the coatings was done by potentiodynamic polarization in aqueous saline solution (sodium chloride 3.5 %), nanoscratching, and scanning electron microscopy (SEM). The layers produced were uniform with good scratch resistance and with superior corrosion resistance when compared to the substrate.