3D Xanthium-like of Ni-Co-Zn ternary alloys as superhydrophobic coatings toward porous Ti surface for its anti-icing performances

Abstract

Super-hydrophobic surface has attracted great interests as functional coatings in spacecraft wings and wind-turbine fans. With the ever-increasing demands of durability and low cost, the scopes for industrial application of hydrophobic coatings have been restricted. Herein we proposed an innovative and simple approach for electroplating Ni0.12Co0.88-xZnx (x = 0–0.36) coatings toward porous Ti substrate. Featuring as 3D Xanthium-like spherical textures, the Ni-Co-Zn ternary alloy coatings were achieved by optimizing the Zn2+ concentration and complexing agent (Na3Cit) in bath. Results validated that its crystal size was refined into ∼300 nm, leading into pinning growth through hole-hole linked porous channel of Ti substrate to increase interfacial strength. Based on the wettability tests, it depicted the water-droplet contact angle (WCA) value of 126.3° attached with sliding angle (SA) of 17.5° for coating samples after being exposed in air for 14 days. Further studies of different ageing treatments on micro structural evolution and super-hydrophobic characteristics were well explored. Through artificial ageing at 200 °C, its attained super-hydrophobic surfaces shorted than 7 days, showing the maximal WCA value up to 153.2° and SA ≤ 7.8° for Ni0.12Co0.88-xZnx (x = 0.24) samples, which was mainly contributed to the self-assembly of multi-tentacles ZnO dendrites. Meanwhile the anti-icing behaviors were compared and featured as peach blossom at −10 °C for all the samples. The icing-delay time of water droplets on coating samples was >1425 s, which was 20 times longer than that of porous Ti substrate. Similarly, it was higher than 90 % for its self-cleaning efficiency based on salt pollutants. Besides the mechanical durability of tested samples against the abrasion-resistant tests and water impact-resistance tests were studied. Results implied that good durability was achieved for Ni-Co-Zn superhydrophobic coatings, but sanded surfaces within a serious decrease of WCA was obtained after a continuous testing for 30 min by abrasion-resistant tests because of the partial destruction of Xanthium-like spherical textures. With the respect to reconstructing of multi-tentacles ZnO dendrites onto the Ni-Co-Zn coatings in air, it was the bio-inspired strategies for self-healing super hydrophobic metal coatings used in warship surfaces, etc.