The work aims to investigate the chemical corrosion and aging mechanism of methyl-silica superhydrophobic coatings under acidic and alkaline environments and their impact on anti-pollution flashover performance, thus elucidating the evolution of coating hydrophobicity over corrosion time, analyzing the transition between Cassie-Baxter and Wenzel contact modes, and providing theoretical support for enhancing the chemical corrosion resistance and application stability of these coatings. Artificial corrosion tests were conducted by immersing the methyl-silica superhydrophobic coating samples in acidic and alkaline solutions. The static water contact angle and sliding angle were measured at different time intervals to monitor changes in hydrophobicity. X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize the surface chemical composition and microstructural changes during the corrosion process. A geometric model was developed to quantify the variation in the real contact area as the gas-liquid interface height decreased, revealing the interplay between microstructural geometry and corrosion dynamics. Furthermore, the self-cleaning performance was evaluated, and the effects of corrosion duration, contamination levels, applied voltage, corrosion temperature, and wetting time on leakage current were systematically analyzed. The results indicated that the hydrophobicity of methyl-silica superhydrophobic coatings deteriorated significantly with prolonged corrosion time, with alkaline environments accelerating this degradation. For instance, under pH=13 conditions, the coatings lost super hydrophobicity within 25 hours. During the corrosion process, the surface content of low-surface-energy —CH3 groups progressively decreased, leading to higher surface energy. The transition from the Cassie-Baxter mode, where air pockets between the water droplets and the microstructures enhanced hydrophobicity, to the Wenzel mode, characterized by complete wetting of the microstructures, was observed. This transition was accompanied by a significant increase in the actual contact area between the corrosive solution and the coating surface, as the gas-liquid interface height decreased. Larger microstructural dimensions were associated with greater contact areas and accelerated corrosion rates. The self-cleaning performance of the coatings declined markedly after corrosion, with residual contamination mass increasing with both corrosion time and contamination levels. After 360 hours of corrosion, the self-cleaning ability was almost completely lost. Leakage current tests revealed a positive correlation between leakage current and both corrosion temperature and applied voltage, whereas wetting time showed a negative correlation. Coatings exposed to extended corrosion duration exhibited a more pronounced decline in insulation performance, as evidenced by elevated leakage current values. The geometric model provided a quantitative understanding of the corrosion mechanism, demonstrating that the expansion of the real contact area is a critical factor in accelerating corrosion rates. The combined effects of increased surface energy due to the depletion of —CH3 groups and the degradation of microstructural features significantly contributed to the aging of the coatings. To enhance corrosion resistance, strategies such as introducing more stable low-surface-energy groups (e.g., —CF3) and optimizing microstructural designs to extend the Cassie-Baxter mode and reduce contact with corrosive solutions are proposed. These measures aim to mitigate the impacts of chemical corrosion and aging while improving the long-term durability of the coatings. This study provides a comprehensive analysis of the chemical corrosion aging mechanisms and anti-pollution flashover performance of methyl-silica superhydrophobic coatings. The integration of experimental data with theoretical modeling offers valuable insights for advancing the design and application of durable superhydrophobic coatings under complex environmental conditions. The findings contribute significantly to the development of coatings capable of maintaining superior performance over extended periods, even in harsh environments.
Key words
superhydrophobic coating /
methyl-silica /
corrosion aging /
anti-pollution flashover properties
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Funding
National Natural Science Foundation of China (U24B2094)
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