Effects of hot water on the wettability of superhydrophobic metal surfaces

Abstract

Super-hydrophobic surfaces were used in self-cleaning, anti-corrosion, anti-fog, drag reduction, oil–water separation, etc., but many super-hydrophobic surfaces were not resistant to hot water. Within a certain range, the change of hot water temperature had little effect on wettability, but beyond the range, the effect of water temperature on wettability was very significant. Here, the superhydrophobic metal surfaces of pure titanium, pure nickel, and 304 stainless steel with hierarchical micro-nano structures were prepared by nanosecond laser combined with heat treatment. By immersing in hot water at 25, 50, 75, and 100 °C, it was found that hot water could not significantly change the surface structure. At the same time, the content of total polar bonds on the metal surface increased, resulting in surface free energy rising. Thus, the superhydrophobicity of the surface was transformed into hydrophilicity with a water contact angle between 10 and 20°. This preparation method was non-toxic and pollution-free and was easy to repeat. The experimental results provided a reference for suppressing the change of superhydrophobic surface composition after hot water immersion.