Development of mechanically robust superhydrophobic SUS 316 surfaces through chemical etching and fluorinated self-assembled monolayer

Abstract This study presents a method for fabricating mechanically robust superhydrophobic surfaces on SUS 316 stainless steel by combining chemical etching and self-assembled monolayer (SAM) coating. The etching process was optimized to produce hierarchical structures, and the fluorinated SAM coating lowered the surface energy. The surface morphology, chemical composition, and wettability were characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and contact angle measurements based on the low-bond axisymmetric drop shape analysis (LBADSA) method. The 30 min etched sample achieved superhydrophobicity with a water contact angle of 152° and a sliding angle of 2° at a surface roughness of Ra = 0.52 μm, which is notably lower than those reported in previous chemical etching studies on stainless steel (1.69–4.7 μm). Mechanical durability tests, including scratch and tape peel-off experiments up to 10 cycles, confirmed that the hierarchical structures protected the SAM coating from abrasive damage. Short-term ambient stability tests over a 120 h period showed minimal changes in the contact angle for samples etched for 1 min or longer. The proposed approach demonstrates a practical balance between wetting performance and structural stability for superhydrophobic stainless steel surfaces.