Chemical etching is a common method for preparing superhydrophobic surface. In this work, the superhydrophobic surface of AP2 was prepared by adopting a two-step chemical etching method of alkali followed by acid to construct the micro and nano structure of the surface, and the fluorosilane solution was used to fluorinate and deactivate the etched surface, providing a reference for the industrial preparation method of superhydrophobic surface. In order to find the most suitable acid-base concentration and acid-base reaction time, 9 groups of experiments were carried out with the orthogonal experimental design method. The surface hydrophobic angle after the completion of etching deactivation was taken as the criterion to evaluate the etching results of these 9 groups of experiments, and the scanning electron microscopy (SEM) was used to observe the etched-surface in these 9 groups of experiments. The microstructure of the surface was analyzed by white light interferometer (WLI). Among the 9 groups of experiments, the hydrophobic angle of the second group was 157° and the rolling angle was 5.67°. In the third experiment, the hydrophobic angle was 152° and the rolling angle was 7°. Both experiments successfully constructed superhydrophobic surfaces. When the concentration of alkali solution was 1 mol/L, the concentration of acid was 9 mol/L and the etching time of acid and base was 1 min, the maximum hydrophobic angle could be obtained. The spectral analysis of AP2 cast aluminum alloy showed that the main elements and their mass fractions of AP2 cast aluminum alloy were as follows: Al was 84.3wt.%, Si was 10wt.%, Cu was 4.4wt.%, Mg was 0.6wt.%, Fe was 0.25wt.% and Mn was 0.25wt.%. This composite metal Al-Si alloy was a subeutectic cast aluminum alloy. After grinding and polishing, the alloy was observed under OM and analyzed by energy dispersive spectrometer. It was obvious that a large number of primary silicon and intermetallic compounds were distributed in the grain boundary of the alloy on the basis of dendritic α-Al phase. Through comparison of the polished aluminum alloy, the etched aluminum alloy and the etched deactivated aluminum alloy, the three samples were measured by XRD respectively. It was found that the three samples were mainly composed of α-Al phase, Si phase and Al2Cu phase. The intensity of the diffraction peak of Al2Cu phase changed obviously before and after etching, and it was judged that it was more corrosion resistant. Subsequently, the surface roughness of these three samples was measured, and it was found that the surface roughness of the samples after chemical etching had a significant change compared with that after polishing, but the change of the surface roughness between the samples after deactivation and the samples after etching was not obvious, indicating that the rough surface was successfully constructed after etching. It paved the way for water droplets to reach Cassie state on the matrix surface. Subsequently, XPS analysis and surface chemical composition analysis were carried out on the three surfaces. Through high-resolution spectral analysis, it was found that the composition of chemical elements on the surface was closely related to the size of the hydrophobic angle. The larger the substrate surface energy, the smaller the surface hydrophobic angle. Conversely, the smaller the surface energy, the larger the surface hydrophobic angle. The highest surface energy was found on the etched surface, where the surface was Wenzel state, the hydrophobic angle was 3°, and the droplet was super hydrophilic. The lowest surface energy appeared the reduced surface, the hydrophobic angle was 157°, and the water droplets were super hydrophobic. This experiment also illustrates the construction process of superhydrophobic surface from the direction of molecular dynamics. After that, the mechanical properties of polished surface, etched surface and etched deactivated surface are analyzed, and the corrosion resistance of these three groups of experiments is analyzed. In the corrosion resistance experiment, the corrosion resistance of the etched surface is similar to that of the polished surface, or even stronger, which is caused by the larger surface contact area. However, compared with the former two, the corrosion resistance of the reduced surface has been significantly improved. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.
