Polyorganosilazane/GPTMS functionalized silica coatings as an integrated corrosion–resistance system for AA2024-T3 aluminum alloy

Abstract

A hybrid coating based on polyorganosilazane (Durazane® 1800) combined with 3-glycidyloxypropyltrimethoxysilane (GPTMS) was successfully synthesized to improve the corrosion resistance of the AA2024-T3 aluminum alloy. The polymers were cross–linked with the addition of tetra-n-butylammonium fluoride (TBAF), and the hybrid coatings were deposited on aluminum substrates by dip coating and dried at 120 °C. Crack-free films with a thickness of 13 μm were obtained. Field emission electron microscopy (FESEM) analysis indicated that the synthesized hybrid films were smooth, homogenous, and devoid of cracks. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) studies demonstrated that the intensity of the Si–N–Si peak was maintained, showing that the backbone of the polysilazane was preserved after the addition of GPTMS. Nuclear magnetic resonance (NMR) spectroscopy indicated that glycidoxypropyl groups were still present in the Si–O–N network of the modified polysilazane. Contact angle measurements indicated that the hybrid coatings were hydrophobic, with a measured contact angle of 93 ± 6°. The electrochemical results confirmed that the synthesized hybrid coatings improved the corrosion resistance of the aluminum substrate in 3.5 wt% NaCl solution. This suggest that the modified polyorganosilazane coating is an effective solution for developing anti-corrosive coatings on metal substrates, offering excellent adhesion strength and good scratch resistance.