Ice formation on metal surfaces can cause several problems in power lines, planes, aircrafts, industrial refrigerators that could result in unexpected failures and important economic losses. In general, hydrophobic surfaces have weak ice adhesion strength; therefore, it is necessary to investigate the correlations between ice adhesion, surface energy and surface roughness. Fluorinated coatings have a very low surface energy, which makes them the first choice as metal coating in order to create a hydrophobic material. The best coating are represented by fluorinated self-assembly compound which are easily deposited on metals with spin coating, dip coating or mechanical deposition methods. In addition, besides the fluorinated coating, which reduces the metal surface energy, it is often applied a surface roughness modification with anodization process, chemical etching or controlled mechanical polishing techniques. The aim is the creation of superhydrophobic surfaces whose wettability is described by Cassie-Baxter mode.
In our laboratory we perform drop test for the evaluation of ice adhesion strength on several functionalized metal surfaces. The formation of ice is induced by depositing water drops on the fluorinated metal surfaces and freezing into a cooling chamber. Ice adhesion strength is measured using a tailor-made proprietary apparatus, which permit to evaluate the energy of ice detachment after a controlled impact. The specimen are characterized with contact angle measurements before and after each adhesion strength test, in order to find a correlation between the hydrophobic/superhydrophobic behavior and the ice adhesion. Furthermore, lifetime and fatigue behavior of different fluorinated coatings are analyzed looking at the variations of contact angle values, after several ice formation/detachment cycles, on the same sample.