Anti-icing properties of a superhydrophobic surface in a salt environment: an unexpected increase in freezing delay times for weak brine droplets

Superhydrophobic coatings on the aluminum alloy were fabricated by intensive nanosecond pulsed laser treatment and chemical surface hydrophobization, which are chemically stable in contact with 0.5 M NaCl aqueous solutions and mechanically durable against stresses arising in the repetitive freezing/thawing of brine. The statistics of the crystallization of ensembles of sessile supercooled droplets deposited on above superhydrophobic coatings indicate considerable anti-icing properties. The comparative analysis of crystallization statistics of deionized water and of brine at a temperature of -20 degrees C allows detecting a striking increase in freezing delay times for the latter case with freezing delay for brine droplets reaching more than 6 hours. We explain the observed phenomenon based on the structure of the double electric layer in the vicinity of the hydrophobic surface and the solution/air interface and on the concept of structure making/breaking ions.