Electrochemical polishing assisted selective laser melting of biomimetic superhydrophobic metallic parts

[Display omitted] •The bio-inspired 316L ss superhydrophobic 3D part was prepared based on SLM.•The obtained superhydrophobic surface exhibits excellent corrosion resistance.•A superhydrophobic square pipeline with excellent self-cleaning ability was processed.•The process principles are also applicable to other metallic 3D printing processes. Metallic superhydrophobic surfaces can be widely used in pipeline transportation, oil–water separation, anti-icing, biomedicine and industrial production owing to their excellent properties. The biologically non-smooth superhydrophobic structure provides a biomimetic prototype for superhydrophobic metal surface processing. However, processing micro-nano biomimetic structures on the internal surface of complex pipelines is difficult because of the limitations of traditional molding processes. Herein, a superhydrophobic butterfly wing is imitated via the selective laser melting technology to print a pit prototype on the surface during the complex parts forming, and then the bio-inspired superhydrophobic internal surface of the 316L stainless steel is successfully prepared by the processes of electrochemical polishing, chemical etching, fluorosilane modification, and low temperature drying, sequentially. The morphology, wettability, corrosion resistance, and elemental composition of the obtained surface are characterized. The results show that a uniform pit-shaped micro-nano composite structure is formed on the surface, the contact angle is up to 155°, the rolling angle is less than 10°, and the corrosion resistance is significantly improved. Finally, a complex superhydrophobic inner surface square tube with application value is successfully prepared, and its excellent superhydrophobicity and self-cleaning properties are verified. This fabrication method provides an idea for the complication of metal superhydrophobic structures, and will promote the application of additive manufacturing in the engineering field.