The threshold effect in ozone-induced degradation of superhydrophobic coatings

Coatings with multimodal roughness are created on the surface of an aluminum alloy by using nanosecond pulsed laser processing. The coatings mainly consists of alumina micro- and nanoparticles. Subsequent application of a hydrophobic agent by vapor-phase deposition brings the coatings to superhydrophobic properties. The effect of ozone on the properties of superhydrophobic coatings is studied by infrared reflection spectroscopy. For exposures to ozone at a concentration of 50 mg/m$^3$ that do not exceed 250 min, coating degradation is almost not absent due to their ability to restore their operating parameters during ozonation. For longer durations of ozone exposure, the superhydrophobic coatings undergo irreversible degradation due mainly to desorption of the hydrophobic part of the hydrophobic agent molecule when its Si–C bonds break, with adsorption of ozone on the textured surface also contributing to this process.