Insulators for power lines are subject to flashover phenomena caused by the accumulation of contaminants on their surface. This phenomenon necessitates costly and frequent maintenance and long service outages.

To mitigate this issue, insulators are coated with hydrophobic vulcanized rubber, which helps keep the surface relatively dry even in the presence of moisture and facilitates the washing away of deposits when it rains.

Although effective and widely used, hydrophobic coatings tend to degrade over time due to climatic agents and contaminants themselves. Additionally, erosive phenomena lead to the formation of rougher surfaces that can collect larger amounts of contaminants and, over time, cause cracks and fissures in the coating. For these reasons, despite the good industrial results already achieved, it is advisable to seek improvements in both the durability and self-cleaning properties of insulator surfaces.

This report explains the mechanisms of flashover and presents the main types of contaminants that cause it, with particular reference to the Italian context.

To mitigate this phenomenon, three types of coatings with varying wettability are presented, obtained through different sol-gel synthetic processes: low hydrophobicity coating (static contact angle of about 100°), high hydrophobicity coating (static contact angle of about 140° and dynamic <30°), and superhydrophobic coatings (static contact angle of about 160° and dynamic <10°). The synthesized coatings were applied to glass substrates, and their self-cleaning properties were measured through laboratory soiling tests. These tests, performed with various types of pollutants, showed an excellent correlation between the self-cleaning properties of the samples and the measurements of the dynamic contact angle. However, extremely rough surfaces, despite being superhydrophobic, sometimes exhibit poor self-cleaning properties because particulate matter tends to become lodged in the surface roughness.

The prepared samples were exposed outdoors for 30 days to assess their aging. Many samples showed significant degradation of hydrophobic properties, and some detached from the substrate. Other samples, however, maintained high static contact angles and low dynamic contact angles.

Finally, a new procedure for sampling and analyzing deposits on samples exposed outdoors is proposed. Field exposure tests, along with soiling tests, can be a useful tool for evaluating which surfaces are most promising for future development and testing under real conditions.