Characteristics of hydrophobicity transfer in the Tangential Direction of Silicone Rubber

Applying RTV coatings on insulator is a widely used strategy for anti-pollution flashover. Field experience indicates that coating damage is a common issue. Preliminary tests have shown that for mm to cm scale damages, the overall hydrophobicity transfer capability of the coating is not significantly affected, and the damaged area still possesses excellent hydrophobic capabilities. This phenomenon suggests the possibility of tangential hydrophobic transfer of SiR. Consequently, this paper designed a simplified RTV-Glass plate model to simulate coating damage and conducted hydrophobic transfer tests in normal and tangential directions for up to 130 days. The test results show that for the sample with 25 mm of RTV on the left side and 25 mm of Glass on the right side, after 80 h of hydrophobic transfer, the sample was in an entirely hydrophobic state, with an average SCA of 131.89 degrees above the Glass interface. The 25 mm damage did not significantly affect the overall hydrophobic transfer capability of the coating. However, the SCA increase rate in the damaged area's pollution layer was slightly slower, related to the smaller concentration gradient during the tangential diffusion process of LMW and the longer diffusion distance required. Overall, this paper robustly demonstrates tangential hydrophobic transfer behavior of SiR and preliminarily establishes 25 mm as the permissible size for coating damage, providing new insights for the operation and maintenance of RTV-coated insulators.