At present

the preparation of superhydrophobic surface with fluorinating agents is not environmentally friendly. To solve this problem

a new method for fabricating fluorine-free superhydrophobic surface on aluminium alloy for drag-reduction at solid-liquid interface was proposed. First

chemical etching technology was used to fabricate micro- and nano-scale surface roughness on the substrate. Then natural rosin solution and carbon black suspension were used to modify the surface to replace traditional fluoride. In terms of characterization

scanning electron microscopy (SEM)

contact angle measurement instrument

and X-ray energy spectrum analysis (EDS) were used to characterize the microstructure

surface wettability

and elemental analysis respectively. By continuously optimizing the surface structure and the concentration of the modified solution

the superhydrophobic surface with a contact angle of 155° and a rolling angle of 1.38° in the Cassie model state was achieved on the substrate. The experimental results indicated that the surface with the new method had good integrity after 80 cycles of immersion and extraction. In addition

it maintained good superhydrophobic property under continuous water drop impact at the velocity of 1.4 m/s for 3 h. Through the test of drag-reduction and scouring experiment

compared with untreated surface

the drag-reduction rate of the fluorine-free superhydrophobic surface could reach 20%~30% in the scouring velocity range of 0.5~3.5 m/s

which verified the effectiveness of the new method. The whole process is simple

cost-effective

and environmental friendly

which is conducive to large-scale production and application.