Study on properties of organic- inorganic hybrid coatings on LY12 aluminum alloy

As a kind of environmental-friendly organic-inorganic hybrid materials, silsesquioxane (SSO) was found to provide good corrosive resistance and show a great potential in replacing toxic conversion coatings which were classic anticorrosive films. SSO was prepared by sol-gel method from vinyltrimethoxysilane (VMS) and was deposited on a plate of LY12 aluminum alloy (AA). The structure of AA with VMS films obtained with different hydrolysis time was characterized by electrochemical impedance spectroscopy (EIS). The spectra of EIS of AA with 3d-hydrolyzed SSO films cured for different time obtained a new time constant and it is confirmed that a new interface layer was formed between SSO layer and AA LY12 layer. Because of the possible condense-polymerization in interfacial region, the interface layer may be composed of large amounts of Al-siloxane (AlOSi) and the film and substrate was chemically bonded. However, no new time constant emerged in the EIS spectra of AA with 9d- hydrolyzed VMS films. EIS spectra of AA LY12 with SSO hydrolyzed at different time revealed that a minimum pre-hydrolysis time of 3d is required for VMS under the fixed reactant conditions, in order to form a cross-link siloxane network and AlOSi bands between SSO layer and AA layer.