Ultrasonic assisted rapid preparation of superhydrophobic stainless steel surface and its application in oil/water separation

The preparation of superhydrophobic (SH) surface on stainless steel by chemical etching method is challenging due to the good corrosion resistance of the material. In this work, SH surface with water contact angle (WCA) as high as 163.21 degrees was accomplished on 304 stainless steel surface by a rapid ultrasonic-assisted chemical etching method within 7 min and a low-cost fluorine-free modification treatment. The mechanism of ultrasonic field on the etching process was explored by detecting the cavitation and oscillation energy in the reactor. It is the first time to found that the ultrasonic cavitation effect enhanced the etching process by both chemical and physical facilitation resulting in hierarchical lamellar micro-structures, mountain-like micro-structure clusters and coral-reef-like nano-scale structures on the surface. With the ultrasonic power increasing, the ultrasonic cavitation effect not only enhanced the superhydrophobicity of sample surface, but also improved the uniformity of surface wettability. The samples also showed excellent performance of oil/water separation for various organics (all separation efficiencies up to 96%) and remarkable mechanical stability.

Automated summary

Superhydrophobic surfaces were successfully prepared on stainless steel using a rapid ultrasonic-assisted chemical etching method and low-cost fluorine-free modification treatment, showing a high water contact angle of 163.21 degrees. The ultrasonic cavitation effect enhanced the etching process, resulting in hierarchical micro-structures and improved surface wettability uniformity. The samples exhibited excellent oil/water separation performance and remarkable mechanical stability.