AP2铝硅合金超疏水表面的制备和耐腐蚀性研究

目的 针对AP2铝硅合金中相组织结构种类较为丰富的特点，通过化学刻蚀的方法，构建出层次丰富、耐腐蚀性强的超疏水表面结构。方法 由于在不同刻蚀溶液中，所构建出的表面润湿性存在较大差距。因此采用正交设计的方法设计试验，找到最适宜的刻蚀浓度和反应时间。由于AP2铝硅合金中含量最多的Al与Si元素之间的固溶度低，NaOH溶液可以对主体α-Al相进行刻蚀，HCl溶液可以腐蚀Al、Cu、Mg、Si等元素形成的金属间相(IMPs)和共晶硅相，采用先碱后酸的刻蚀方法相比使用单一的刻蚀溶液推测能形成更丰富的触突结构。结果 在0.25 mol/L NaOH溶液和9 mol/L HCl溶液中分别刻蚀60 s，在2%(质量分数)十七氟癸基三甲氧基硅烷(FAS-17)溶液表面改性的条件下，成功构建出了表面接触角为157°，滚动角为5.64°的超疏水表面。表面腐蚀电位由抛光后的−1.282 V提高到了超疏水表面制备完成后的–1.228 V，腐蚀速率由抛光后的1.07×10^–4 A/cm²降低到7.44×10^–5 A/cm²，耐腐蚀性显著提高。结论 制备的超疏水表面的耐腐蚀性有显著提高，为亚共晶铝硅合金材料在超疏水方向的应用提供了一定的参考。

Preparation and Corrosion Resistance of AP2 Aluminum-silicon Alloy Superhydrophobic Surface

Chemicaletching 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.