Design and Fabrication of Superhydrophobic, Ice-/Snowphobic Coatings for High Voltage Power Lines Application

The formation and accretion of ice and snow on high voltage (HV) power lines components represent a huge problem which can reduce the efficiency of current conduction and whose removal requires expensive and time-consuming treatments. Strong snowfalls can often involve severe drawbacks such as extended blackout and damages to the HV systems due to the accretion phenomena and the subsequent breakup of the lines. Superhydrophobic surfaces (SHSs) - designed with a strict control of the surface chemical composition and morphology, e.g. coupling hierarchical micro-nanostructures with a very low surface energy - work in a stable Cassie-Baxter state preventing water drops from wetting the surface. SHSs have been widely investigated for many applications. Anyway, their potential use as icephobic and snowphobic materials have not been clearly highlighted yet, notwithstanding many recent papers on the subject1,2. In this work, 50 cm-long Anticorodal aluminum alloy (6082) conductors, commonly used in HV lines, were functionalized by dip coating into a ceramic oxide nanoparticles suspension, synthesized by sol-gel route, and chemically modified with fluoroalkylsilane (FAS) solution to obtain SHSs by the typical Lotus leaf approach. Some of them underwent an additional infusion step in a fluorinated oil (Krytox 100), according to the so-called SLIPS approach. Both the design approaches provided materials with high dynamic performances (contact angle hysteresis < 10°), while the infused samples showed a static water contact angle of about 120°, much lower than the value of 170° reached by SHS samples. However, the presence of the fluorinated oil as outer layer involves a greater homogeneity of the coating with a decreasing of local defects. To evaluate the influence of roughness on nucleation and accretion of the ice as well as on snow deposition, the functionalization was performed on smooth (Ra = 0.3 ?m) and sandblasted (Ra = 3.6 ?m) conductors, either by SHS and SLIPS approach. The ice adhesion strength has been evaluated by shear stress analysis and the results exhibit a decrease of adhesion for both SHS and SLIPS samples with respect to the untreated ones. During the last winter, coated samples were exposed outdoor at experimental facilities located in the west of Italian Alps, at an altitude of 959m asl. Under the recorded snowfall events and conditions (T = -2°C, dry snow with low liquid water content (LWC) and spherical snowflakes), sandblasted SH cables showed a significant delay in snow deposition and snow/ice layer accretion, with a complete detachment of this layer before the end of the observed event. This behavior has to be underlined with respect to that of the other coated cables, whether smooth or sandblasted. However, in different conditions (i.e. -2°C < T < 0°C, wet snow with high LWC), sandblasted SHSs seem to lose the ability of delaying show and ice accretion.