Experimental Study on the Preparation of Superhydrophobic Titanium Alloy Surfaces via Combined Chemical Etching-Anodization Method

TC4 titanium alloy has low density, corrosion resistance, high strength ratio, good fracture toughness and other characteristics, so it is widely used in the aerospace field. When the aircraft passes through the low-temperature cloud in the air, the intake part of the engine will freeze due to the existence of supercold water droplets, which will affect the flight safety. Therefore, it is particularly important to prepare superhydrophobic surface on TC4 titanium alloy. In order to improve the hydrophobicity, corrosion resistance and mechanical properties of the superhydrophobic surface of TC4 titanium alloy, a combined method of chemical etching and anodic oxidation was proposed to prepare the superhydrophobic surface. Firstly, TC4 titanium alloy was treated with chemical etching to prepare micron-scale structure, and then nano-scale structure was prepared by anodic oxidation method. Finally, superhydrophobic surface with micro-nano structure was prepared on the surface of the sample. The superhydrophobic surfaces prepared by H2O2 etching, strong acid etching, anodic oxidation, H2O2 etching-anodic oxidation and strong acid etching-anodic oxidation were compared by Tafel test, linear wear test, impact resistance test and anti-icing performance test respectively. It can be seen from the experimental results that the contact angle of the superhydrophobic surface prepared by the mixed solution of hydrogen peroxide and sodium bicarbonate is 156.4° and the rolling angle is 2.7°. The contact angle of the superhydrophobic surface prepared by the mixed solution of sulfuric acid and hydrochloric acid is 153.1° and the rolling angle is 7.6°. The contact angle of the superhydrophobic surface prepared by anodic oxidation is 156.3° and the rolling angle is 4.2°. The surface contact angle is 157.6° after etching with hydrogen peroxide and sodium bicarbonate mixed solution and anodizing treatment, and 155.9° after etching with sulfuric acid and hydrochloric acid mixed solution and anodizing treatment, and the rolling angle of both is less than 2°. Scanning electron microscopy (SEM) is used to observe the microscopic morphology of the superhydrophobic surface prepared by the five methods. It can be seen that the superhydrophobic surface prepared by the combined method presents a micro-nano hierarchical structure, which effectively reduces the contact area between the water droplets and the surface and significantly reduces the rolling angle. Therefore, the hydrophobic property of the surface prepared by the method method is superior to that prepared by a single method. The OCP of superhydrophobic samples is higher than that of TC4 titanium alloy. Especially the OCP of superhydrophobic samples after strong acid etching and anodic oxidation treatment is moving to 0.08 V, and the corrosion resistance is significantly improved. According to the polarization curve, the Jcorr of the superhydrophobic surface prepared by the combined method is reduced by one order of magnitude, and the Rp is increased by one order of magnitude, which also indicates that the corrosion resistance has been greatly improved. The superhydrophobic surface prepared by the combined method can still maintain the contact angle above 150° and the rolling angle about 10° after several linear wear and 200 g sand fall impact, and still maintain the superhydrophobic property. Therefore, the superhydrophobic surface with micro-nano hierarchical structure prepared by combined chemical etching-anodizing method has better hydrophobicity, corrosion resistance, wear resistance and impact resistance than the superhydrophobic surface with a single structure. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.