Gas pressure impact

Impact with gas molecules is not a very common test for the degradation of liquid repellent surfaces. However, elevated gas flows could be severe for many coatings. Moreover, this is a test that should be considered for surfaces that target aerospace applications or finishes for outdoor use in regions affected by hurricanes and tornados. 

Applying shear stress is not the only way that a liquid repellent surface can be damaged. Vertical compression or expansion can also lead to degradation of the surface properties. Furthermore, material removal can occur by vertical compression or expansion when two solid surfaces are in contact. In the following section we will describe techniques that apply normal (and not shear) force to the tested surface. 

---