Icing and Anti-Icing Performance of Superhydrophobic-Coated Steel Members in Long-Span Transmission Towers

Long-span transmission towers in the Yangtze River basin are exposed to coupled low-temperature, high-humidity and strong-wind conditions, which promote nonuniform ice accretion on steel members and increase structural loads and ice-shedding risks. Although superhydrophobic coatings are promising passive anti-icing materials for civil infrastructure, most existing evaluations use idealized flat or cylindrical specimens and do not capture the geometry, substrate condition and coating uniformity of in-service tower members. Here, a multifactor coupled icing simulation system was developed, and comparative icing tests were conducted on three representative steel members (aged plain circular steel tube, new galvanized circular steel tube and new galvanized angle steel) under controlled temperature, wind speed, spray rate and icing duration. For uncoated members, ice mass increased with supercooling degree and spray rate, first increased and then decreased with wind speed, and exhibited a decelerating growth pattern within 24 h. The superhydrophobic coating reduced ice mass, ice thickness and circumferential nonuniformity under all tested conditions, but its effectiveness depended strongly on environmental loading and member geometry. Under reference conditions, the ice-reduction rates reached 41%, 45% and 38% for the three members, respectively, and remained 27-32% after 24 h of icing. Smooth circular substrates showed the best coating response, whereas angle steel was less effective because edge-induced flow distortion and poor coating uniformity promoted local wetting failure. Performance degradation under harsh conditions was associated with accelerated freezing, water-film formation and localized wetting failure. These findings define the applicability and durability limits of superhydrophobic coatings for passive anti-icing protection of long-span transmission tower steel members.