Investigation of the mechanical and thermal fatigue properties of hybrid sol–gel coatings applied to AA2024 substrates

This research article reports on the response of various hybrid sol–gel materials when applied as coatings to pre-treated bare AA2024 substrates, to mechanical indentation and cyclic thermal stimuli, in order to determine their usefulness in aeronautical applications. Three groups of hybrid sol–gel-coated samples were prepared using various organosilanes and transition metal oxides. The characterization of the materials revealed that the presence of the organic functionalities, especially the methacrylate group, has a noticeable effect on the mechanical response of the hybrid coatings, in particular their flexibility. The presence of methacrylate group in the cured material gives it ability to flex which influenced the thermal fatigue characteristics of the coatings which are able to withstand the cyclic temperature regimes of 82 ± 3 to −37 ± 3°C over 25 2 h cycles. This capability to maintain substrate protection is reflected in the corrosion resistance of the coatings as measured using electrochemical impedance spectroscopy and accelerated exposure testing. This result is important, as it shows that hybrid sol–gel materials can be used in applications where protecting a metal or ally substrate is paramount, especially in thermally volatile environments.