Electrochemical machining of superhydrophobic surfaces on mold steel substrates

Superhydrophobic surfaces on mold steel substrates were fabricated via simple and environment-friendly electrochemical technology followed by fluoroalkylsilane (FAS) modification. The microstructure, crystal structure, chemical composition, and wettability of the sample surfaces were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and optical contact angle measuring instrument. The influences of current density and electrochemical machining time on wettability were also studied. The results show that, after the electrochemical processing, the mold steel substrates were covered with a layer of passive films, which have micro/ nano binary rough structures composed of rugged plateau structures and rupture-like shapes. Before fluorination, the obtained sample surfaces showed superhydrophilicity (the water contact angles were almost 0 degrees), while the sample surfaces became superhydrophobic (the water contact angles were 167.2 degrees and the water rolling angles were 4.3 degrees) after fluorination. The proposed method is simple, economical and environmental-friendly, and has great potential for large-scale industrial applications.