# Fabrication of an Anti-Icing Aluminum Alloy Surface by Combining Wet Etching and Laser Machining
## 1 Introduction
The experimental results indicated that droplets deposited on the coating at \(-20\)\({}^{\circ}\)C temperature can remain supercooled liquid without becoming frost crystals for up to 50 min, while at \(-10\)\({}^{\circ}\)C, the droplets can remain liquid for more than 2000 min. [PERSON] [16] et al. processed the Al6061 material by laser, and further modified it with a nanostructured Al\({}_{2}\)O\({}_{3}\) thin film so that its surface can reach the dual roughness and porous state. The laser processed Al6061 material was grafted with perfluorooctyltrieboxysilane (PROTES) steam to make it superhydrophobic, which extended the freezing time of water droplets to nearly 4 h at \(-5\)\({}^{\circ}\)C, and showed significant low ice deposition in wind tunnel tests. [PERSON] [17] et al. directly constructed the grating textures of hierarchical tertiary structures on the aluminum alloy surface using picosecond laser processing. These layered texture surfaces showed good hydrophobic properties at low temperatures. In comparison with the original surface of aluminum alloy, the freezing time of water droplets on the surface of the aluminum alloy after laser processing is delayed from 2879 s to 4015 s, and the freezing temperature is as low as \(-23\)\({}^{\circ}\)C, showing excellent anti-icing performance. The key advantage of laser-machined superhydrophobic anti-ice structures is that the morphology of the prepared surface microstructure is highly flexible. [PERSON] [18] et al. simplified the preparation process of the superhydrophobic surface on an aluminum alloy substrate through electrochemical anodic oxidation and chemical etching methods, and conducted anti-icing experiments. Starting from room temperature (16.0 \({}^{\circ}\)C), the icing time of superhydrophobic surface can be delayed from 406 s to 676 s, compared with ordinary aluminum alloy surface. The icing temperature can be reduced from \(-2.2\)\({}^{\circ}\)C to \(-6.1\)\({}^{\circ}\)C. The results showed that the superhydrophobic surface prepared using this method has excellent ice resistance. [PERSON] [19] et al. proposed a method to prepare a coral-like superhydrophobic structure on the surface of aluminum through chemical etching and hot water treatment to improve its ice resistance. The contact angle of the structure can reach 164.8 \(\pm\) 1.1\({}^{\circ}\), and the sliding angle is less than 1\({}^{\circ}\). Water droplets on the surface can remain ice-free for more than 110 min, showing good anti-ice performance. [PERSON] [20] et al., using hydrochloric acid etching at a certain concentration on the surface of aluminum alloy, successfully developed a simple method to prepare the superhydrophobic surface of an aluminum alloy. This superhydrophobic surface also showed significant ice resistance, and the freezing time of droplets on the surface could be delayed to 600-700 s from \(-5\,^{\circ}\)C to \(-8\,^{\circ}\)C. The preparation of superhydrophobic surface through chemical etching method is easy to achieve and takes a short time. However, the hydrophobic structures prepared by the above chemical etching methods typically only had a single-stage structure, thus the anti-icing effect was not as good as the hierarchical structure. The anti-icing surface preparation methods mentioned above had still some limitations, such as low process efficiency, complex process, and difficulty in the efficient preparation of anti-ice surfaces on a large area. However, solving these problems is of great significance to improve the safety performance of aircraft. This paper proposes a hybrid laser machining-wet etching to prepare superhydrophobic micro/nanostructures on the aluminum alloy surface to realize anti-ice function. This method has numerous advantages, such as simple equipment, convenient operation, short process time, environmental protection, low cost, and ease of application. The anti-icing effect of the superhydrophobic surface on the aluminum alloy surface was studied by theicing delay test, ice adhesion experiment, and dynamic water repellency experiment.