Synthesis and characterization of hydrophobic nano-silica thin coatings for outdoor insulators

The hydrophobic characteristics of outdoor insulator surface have significant influence on the lifetime and performance of the power transmission lines. In this research, a textured silica layer was dip-coated on the surface using a tetraethyl-orthosilicate (TEOS) containing solution in order to create a hydrophobic surface. Subsequently, the created coating was modified by dipping it in an octadecyl-trichloro-silane/ethanol solution to decrease its surface energy. The coating was characterized by field emission scanning electron microscopy, X-ray diffraction method, Fourier-transform infrared spectroscopy and atomic force microscopy. The microstructural studies confirmed the formation of a uniform microstructure with the mean particle size of 19 nm and roughness of less than 80 nm. The results demonstrated that by creating the hydrophobic coating, the contact angle increased from 14 to 120 degrees. The result of leakage current test at 10 kV showed that the leakage current of the coated insulator was about 24.4 mu A, while that of the non-coated one was about 32 mu A. The adhesion strength of the coating was 1.7 MPa.