Preparation of dense modified nanosilica superhydrophilic coatings on aluminum alloy surfaces by adjusting amino groups

In this work, a uniform superhydrophilic coating was prepared by grafting N-(2-aminoethyl)-3-aminopropyltriethoxysilane oligomers(AEAOS) onto nanosilica by using silane coupling agent modification and coated on the surface of aluminum alloys to reduce water droplet generation. The grafting and dispersibility of modified nanosilica and aminosilane oligomers were characterised using Fourier transform infrared (FTIR) and dynamic light scattering (DLS). The surface state, composition, and roughness of the coatings were characterised with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and optical profilometer. The hydroxyl and organic content of modified nanosilica was analyzed by Thermogravimetric Analysis (TGA). The compactness of the coating film is analyzed by an electrochemical impedance. The hydrophilicity and adhesion of the coating films were evaluated by contact angle and adhesion testing. By adjusting the concentration of amino groups in the nanosilica sol, the results show that the amino groups promote the silane grafting on the surface of nanosilica. The 10% addition of AEAOS gives the modified silica film a contact angle of <5° with superhydrophilic properties. The polarization resistance of the superhydrophilic coating film is about 10 times higher than that of the original aluminum alloy. The surface of the coated films is homogeneous and dense, showing high resistance to polarization and good corrosion resistance.