Superhydrophobic Coatings by Suspension Flame Spraying for Outdoor Conditions

This research focuses on the development of superhydrophobic TiO₂-based coatings by suspension flame spraying. Also, HVOF-, flame-, and plasma-sprayed powder coatings were studied as ref [erences. Furthermore, their hydrophobicity was improved by applying stearic acid to functionalize surfaces. In the flame spray process, both powder and suspension feedstock were studied, and the suspensions modified by adding epoxy and polydimethylsiloxane (PDMS) to examine their impact on coating properties. Among the conventional processes, plasma-sprayed coatings achieved a water contact angle (CA) of 145° while the suspension flame-sprayed coatings had CAs as high as 165°. This improvement was linked to structural changes like the formation of nanostructures. Coatings produced with solid powder feedstock did not show water droplet mobility, whereas the sliding angle decreased with the suspension feedstock and was reduced to less than 5° with epoxy and PDMS-modified suspensions. Incorporation of these polymers increased the stability of coatings under UV exposure and at low temperatures. Coatings with PDMS were more durable and stayed superhydrophobic for at least 180 days under UV exposure. In contrast, coatings without modifications became superhydrophilic within 23 days. This study demonstrates the potential of suspension flame-sprayed coatings for applications where robust superhydrophobic surfaces and environmental durability are needed.