Bio-inspiredly fabricating the hierarchical 3D porous structure superhydrophobic surfaces for corrosion prevention

Significance Statement

Superhydrophobic surface are surfaces that are extremely difficult to wet. Effort has been made by various scientists and engineers to attain a more detailed understanding about the internal relationship between solid surface states and it specific properties. Yuebin Lin and colleagues proposed fabricating the hierarchical 3D porous structure superhydrophobic surfaces for prevention of corrosion. Their study was published in Materials and Design.

According to the researchers, Wenzel and Cassie-Baxter models are classical and generally used to describe the wetting condition of rough solid surfaces, especially hydrophobic or superhydrophobic surfaces. The Cassie-Baxter model determine the large amount of air pockets that can be entrapped by the hierarchical micro or nanoscale structures on solid surfaces, resulting in a heterogeneous wetting regime and superhydrophobicity. To break the predicaments of stagnant applications of superhydrophobic technique, that led the team to carry out this study.

The principle for the preparation of superhydrophobic surfaces is governed by the combined action of surface structure and chemical component. The hierarchical 3D porous structures was constructed on Ti6Al4V substrate by combining strategy of sand blasting and two-step chemical etching, an excellent superhydrophobicity after the modification of fluoroalkylsilane was obtained. Their present work focused on a full understanding of the action mechanism of the hierarchical 3D porous structures on the anti-wettability, the systematic characterizations and analyses of the corrosion prevention property, and revealing the underlying corrosion prevention mechanism of superhydrophobic surfaces in details.

The team confirmed that the second step of alkaline etching is highly important in the production of special 3D nanoporous structures when compared with the other operation steps. They found out that under a low concentration of NaOH solution, a layer of 3D nanoporous structures uniformly appear on the sample surface, without affecting the smooth sample surface. Controlling the appropriate technological parameters of alkaline etching technique can effectively adjust the morphologies of the 3D nanoporous structures within a certain range, which also has a guiding significance for the microstructured design and fabrication, explained the research team.

Superhydrophobicity change trend with the variation of alkaline etching time, almost consistent with that under the different concentration of NaOH solution, which are due to the similar micro/nanostructured change trend of the alkaline etching time. The researchers observed that the superhydrophobic treatment on substrate compels the corrosion current density to decrease three orders of magnitude, and the corrosion potential to increase 0.26 V, demonstrating the superhydrophobic surface possessing a certain extent of corrosion prevention capacity.

This study produced and tested fabrication of a hierarchical 3D porous structure superhydrophobic surfaces for prevention of corrosion. The result shows maximum porosity and exhibited a higher capacity to trap a large amount of flowing air pockets, resulting in the excellent anti-wetting properties with the apparent contact angle reaching 160° and the contact angle hysteresis of only 3°.   

About the author

Dr. Yizhou Shen got his Ph.D Degree in Materials Science and Engineering in June, 2016, from Nanjing University of Aeronautics and Astronautics, China. Currently, his research interests mainly focus on Superhydrophobic surfaces, Bio-inspired interfacial materials, Anti-icing coatings, and Surface engineering modification.

Up to now, he has published 30 papers as the first author, and the research results attracted wide attentions from many researchers in the fields of anti-icing technology, superhydrophobic modification, and wetting controlling.   

Journal Reference

Yuebin Lin1, Yizhou Shen2 , Aihui Liu1, Yufu Zhu1, Senyun Liu2, Hailin Jiang3, Bio-Inspiredly Fabricating the Hierarchical 3D Porous Structure Superhydrophobic Surfaces for Corrosion Prevention, Materials and Design 103 (2016) 300–307.

Show Affiliations
  1.  Jiangsu Provincial Key Laboratory for Interventional Medical Devices, Huaiyin Institute of Technology, 1 Meicheng Street, Huaian 223003, PR China
  2.  College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, PR China.
  3.  Faculty of Mechanical and Meterial Engineering, Huaiyin Institute of Technology, 1 Meicheng Street, Huaian 223003, PR China.

Abstract

The fundamental investigations on the bio-inspired superhydrophobic surfaces have been developed for decades, and various functional surfaces with the special wettability have been artificially fabricated under the abundant inspirations from nature, yet it do not still break the predicaments of the stagnant applications of superhydrophobic surfaces. Herein, we developed a facile combined strategy of sand blasting and two-step chemical etching for the creation of hierarchical 3D (three dimensional) porous structures on Ti6Al4V substrate, and obtained excellent superhydrophobicity with the apparent contact angle reaching 160° and the contact angle hysteresis of only 3° after the modification of fluoroalkylsilane. This mainly attributed to the hierarchical 3D porous structures possessing the huge porosity, and exhibiting a higher capacity to trap a large amount of flowing air pockets. Furthermore, based on the mechanism of the trapped air layer restricting the transport of Cl, the superhydrophobic surfaces displayed a great corrosion prevention performance with the corrosion current density (icorr) lowering three orders of magnitude and the corrosion potential (Ecorr) increasing 0.26 V.

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