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Methyl-silica superhydrophobic coatings have the capability of providing anti-pollution flashover protection for outdoor electrical insulators. However, in practical applications, the deposition and dissolution of atmospheric pollutants on the coating generates acidic or alkaline ions and leads to chemical degradation of the coating's surface property, which in turn causes a decrease in the anti-pollution flashover performance of the coating. Currently, there is a lack of research on the hydrophobic degradation characteristics of superhydrophobic methyl-silica coatings induced by chemical corrosion. Meanwhile, it is not clear how chemical corrosion affects the anti-pollution flashover performance of methyl-silica superhydrophobic coatings. To address the above issues, the static water contact angle and sliding angle on the corroded methyl-silica superhydrophobic coatings were tested to reflect the surface hydrophobicity degradation, and the results were theoretically interpreted; the surface leakage current amplitudes of the coatings aged to different degrees were measured under dirty and wet conditions to characterize the anti-pollution flashover performance of the corroded coatings. The surface leakage current amplitudes of the aged methyl-silica superhydrophobic coating under different corrosion environment temperatures, different applied electric field strengths, and different wetting times of surface pollutants are measured to characterize the anti-pollution flashover performance of the corrosion-aged coating, and the influences of the above factors on the anti-pollution flashover performance of the methyl-silica superhydrophobic coating are analyzed. [Display omitted] [ABSTRACT FROM AUTHOR]

Cleanliness and desiccative are necessary for outdoor insulation surfaces to maintain the voltage withstand capability especially in humid and polluted operation conditions. Once the voltage withstanding capability of insulation coatings is reduced by contaminant electrolyte, flashover accidents would be easier to happen, causing tremendous economy and energy losses. Superhydrophobic coatings, due to their self-cleaning property, are deemed to have great application potential in maintaining outdoor insulation performance, especially in humid and polluted environments. The water patterns on superhydrophobic coating in humid and polluted conditions are obviously different from those on traditional insulation coatings. Flashover voltage is one of the indices for quantifying insulation strength, while to date it is still unclear whether the commonly-used flashover voltage prediction models based on Obenaus's theory are still suitable to be applied in the cases with superhydrophobic surface. Here we proposed a facile and low-cost preparation method of superhydrophobic coating. By analyzing the specific surface condition under humid and polluted conditions, and considering the development of arc path, a novel theoretical model for predicting flashover voltage of superhydrophobic coatings is established from the perspective of electric field. The flashover voltage of the synthesized coating as well as Room Temperature Vulcanized (RTV) silicone rubber coating are tested and compared, for investigating the insulation strength on the synthesized superhydrophobic coating, and verifying the accuracy of the proposed prediction model. It is found the synthesized superhydrophobic coating shows self-cleaning property during the wetting and voltage applying process, the flashover voltage of superhydrophobic coating is higher than that of RTV coating, and is affected less obviously by the change in pollution degree, compared with RTV coating. The established model shows better accuracy in predicting the flashover voltage of superhydrophobic coating than the traditional one, with errors of less than 6%. Based on the proposed model, the flashover voltage of polluted superhydrophobic coating surface is positively and negatively related to the volume and the contact angle of the polluted electrolyte droplet, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

If the apparent contact angle (ACA) of superhydrophobic materials could be significantly affected by drop volume, it would not be reliable to use ACA as an important index to evaluate the wettability of superhydrophobic materials. In order to explore the effect of drop volume on the ACA of hierarchical structured superhydrophobic surfaces, two kinds of hierarchical structured superhydrophobic surfaces, natural lotus leaf surface and superhydrophobic coating, were used for experimental analysis. In addition, a physical model of ACA considering drop volume was established. And the relationship curve between drop volume and ACA was calculated. The experiment and simulation results show that for each kind of drop, the volume has no significant effect on the ACA of hierarchical structured superhydrophobic surfaces. And the ACA can reflect the wettability of the superhydrophobic material effectively. [ABSTRACT FROM AUTHOR]