An aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method

Abstract

This invention relates to the field of alloy materials and surface engineering technology, specifically to an aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method. The invention discloses an aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method. The sheet comprises, from the inside out: an aluminum alloy matrix containing nanoscale Al2CuMg and Mg2Si phases; a micro-nano composite rough structure formed in situ on the matrix surface by selective etching to precipitate phases; an inorganic ceramic protective layer deposited conformally by atomic layer deposition; and an organic hydrophobic layer formed by vapor-phase silanization grafting. The preparation method mainly includes: solution treatment and pre-aging of an aluminum alloy with specific composition; selective etching using an acid solution containing corrosion inhibitors to construct the surface micro-nano structure; and sequential application of a gradient functional coating through atomic layer deposition and vapor-phase silanization to obtain the final aluminum alloy sheet product.

Description

Technical Field

[0001] This invention relates to the field of alloy materials and surface engineering technology, specifically to an aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method. Background Technology

[0002] Aluminum alloys are widely used in building curtain walls, automobiles, aerospace, and other fields due to their lightweight, high specific strength, and corrosion resistance. However, in outdoor service environments, aluminum alloy surfaces are susceptible to contamination and corrosion. Therefore, surface coatings with self-cleaning capabilities and high weather resistance have become important means to maintain the long-term cleanliness and performance stability of aluminum alloy components. In recent years, to further improve the overall performance of aluminum alloy surface treatment, research has mainly focused on two directions: one is to endow self-cleaning capabilities by constructing superhydrophobic surfaces or introducing photocatalysts; the other is to enhance corrosion resistance by developing novel conversion films or composite coatings.

[0003] For example, CN120248757A discloses a self-cleaning and weather-resistant aluminum alloy photovoltaic module frame and its preparation method. To improve the self-cleaning ability of the photovoltaic module frame, a self-cleaning coating is prepared on the aluminum alloy frame body, and a fluorine-containing borate ester chain extender and a fluorine-containing polyol are added to it. Fluorine has extremely strong electronegativity, which can effectively improve the water resistance of the resin and reduce the surface energy of the material, reducing surface friction and improving abrasion resistance. It can also reduce the adsorption of dust on the metal frame surface, keeping the material clean for a long time. Furthermore, reversible covalently bonded boric acid is introduced into the borate ester chain extender. Ester bonds are used to achieve self-healing; simultaneously, hydrophobic nano-silica is added to the coating to further improve the abrasion resistance and hydrophobicity of the aluminum alloy photovoltaic module frame, enhancing its durability exposed to the external atmospheric environment; CN119433523A discloses an aluminum alloy surface protective coating and its preparation method. After cleaning the aluminum alloy sample to be treated to ensure no residual liquid remains, the aluminum alloy is subjected to solution treatment and aging treatment in sequence; then, the obtained aluminum alloy sample is immersed in a conversion film solution for deposition treatment and drying to obtain an aluminum alloy sample with a surface protective coating. However, existing technologies struggle to synergistically enhance both efficient self-cleaning and long-term weather protection within a single coating system, often facing problems such as complex processes due to functional superposition, weak interfacial bonding, or insufficient long-term stability.

[0004] In summary, how to innovate a new type of aluminum alloy sheet that can achieve high weather resistance, self-cleaning and self-healing functions through an economically feasible manufacturing method, so as to meet the common demand for durable, maintenance-free and cost-effective surface materials in various occasions from outdoor construction to interior decoration, has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method, so as to solve the technical problems of difficulty in balancing high weather resistance and low cost and insufficient self-cleaning durability in the prior art.

[0006] The specific technical solution is as follows: An aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method are disclosed. The aluminum alloy sheet comprises, from the inside out: an aluminum alloy substrate containing nanoscale Al2CuMg and Mg2Si phases as selectively corroded precipitates; a micro-nano composite rough structure formed on the substrate surface and generated in situ by selectively corroding the precipitates; an inorganic ceramic protective layer deposited conformally on the surface of the rough structure using atomic layer deposition technology; and an organic hydrophobic layer grafted onto the surface of the inorganic ceramic protective layer by vapor-phase silanization.

[0007] Furthermore, the Al2CuMg phase and Mg2Si phase have an average size of 20~50nm and are diffusely distributed.

[0008] Furthermore, the selective corrosion is carried out using a corrosion solution containing 0.8-1.5 wt% H2SO4 and 0.2-0.4 wt% Na2MoO4.

[0009] Furthermore, the inorganic ceramic protective layer is an Al2O3 thin film with a thickness of 10~30nm.

[0010] An aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method include the following steps: S1: Aluminum ingots, metallic manganese, metallic copper, metallic magnesium, crystalline silicon, and Al-10Zr master alloy are used as raw materials and melted in a resistance melting furnace at 750℃. After refining by an argon rotary degassing device and grain refinement of Al-5Ti-1B filaments, the ingots are cast into flat ingots. The flat ingots are then placed in a box-type resistance furnace and homogenized at 600℃ for 12 hours. Finally, they are rolled into hot-rolled plates by a hot continuous rolling mill.

[0011] S2: The hot-rolled sheet was placed in a salt bath furnace for solution treatment and then rapidly water-quenched. Subsequently, the sheet was transferred to a temperature-controlled oil bath furnace for pre-aging treatment. After pre-aging, the sheet was rolled to a final thickness of 0.6 mm using a cold rolling mill in five passes. Finally, the cold-rolled sheet was annealed in an air-circulating annealing furnace to obtain an H24 state substrate. This substrate was then immersed in an etching bath for selective etching, followed by ultrasonic cleaning with deionized water and ethanol. The sample was then activated in an oxygen plasma cleaner, ultimately yielding a crystalline hydrophilic surface with a micro-nano rough structure.

[0012] S3: The processed substrate is placed in the reaction chamber of a hot-wall atomic layer deposition equipment. After setting the deposition temperature, a standard deposition cycle is performed using trimethylaluminum and high-purity water as precursors and high-purity nitrogen as carrier gas and purge gas. Each cycle includes: a trimethylaluminum pulse of 0.1 seconds, a nitrogen purge of 5 seconds, a water pulse of 0.2 seconds, and a nitrogen purge of 5 seconds. After the cycle is completed, an amorphous aluminum oxide thin film is deposited conformally on the surface of the micro-nano structure.

[0013] S4: Place the substrate coated with an alumina film in a heatable vacuum reactor and evacuate to 10°C. -2 After heating to Pa, perfluorooctyltriethoxysilane vapor carried by nitrogen is introduced, maintaining the system pressure at atmospheric pressure and controlling the vapor concentration by the nitrogen flow rate. The reaction continues, allowing the fluorosilane molecules to fully react with the hydroxyl groups on the alumina surface to form a covalently bonded hydrophobic layer. After the reaction is complete, the alumina is purged with nitrogen, cooled to room temperature, and then removed to obtain a finished aluminum alloy sheet with high weather resistance and self-cleaning function.

[0014] Furthermore, the aluminum alloy sheet comprises, by weight, the following raw materials: 92-96 parts aluminum ingot, 1.0-1.8 parts manganese, 0.6-1.5 parts copper, 0.5-1.5 parts magnesium, 0.3-0.8 parts crystalline silicon, and 0.5-1.5 parts Al-10Zr master alloy; wherein the Al-10Zr master alloy is used to provide 0.05-0.15 parts zirconium.

[0015] Further, the solution treatment in S2 is carried out at a temperature of 530~550℃ for a treatment time of 0.5~1.5 hours; the pretreatment aging is carried out at a temperature of 175~195℃ for a treatment time of 3~6 hours; the annealing treatment is carried out at a temperature of 170~190℃ for a treatment time of 1.5~2.5 hours; the etching solution is an etching solution containing 0.8~1.5wt% H2SO4 and 0.2~0.4wt% Na2MoO4; the selective etching is carried out at a temperature of 30~40℃ for a treatment time of 60~90 seconds; and the activation is carried out under the following conditions: radio frequency power of 150~250W for a treatment time of 3~8 minutes.

[0016] Furthermore, the deposition temperature described in S3 is in the range of 80~100℃; the standard rotation cycle is 180~220 times.

[0017] Furthermore, the heating in S4 has an endpoint temperature range of 110~130℃; the continuous reaction lasts for 1.0~2.0 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Long-lasting function: Through self-grown micro-nano structure and gradient encapsulation, the self-cleaning function is far more durable than that of traditional coatings, and the performance retention rate after wear resistance and salt spray resistance is extremely high.

[0019] (2) Strong bonding: The functional layer and the aluminum alloy substrate are chemically and metallurgically bonded, with an adhesion level of 0, which fundamentally eliminates the risk of peeling.

[0020] (3) Adjustable performance: By adjusting the composition and process parameters, hydrophobicity, wear resistance and other indicators can be optimized in a wide range, the process is stable and conducive to production.

[0021] (4) Environmentally friendly: It adopts chromium-free and dry process, which is environmentally friendly. The product has both metal strength and surface function and has a wide range of applications. Attached Figure Description

[0022] Figure 1 This is a flowchart of an aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method according to the present invention.

[0023] Figure 2 This is a SEM image of the surface of the sample after selective etching treatment in Example 1 of the present invention.

[0024] Figure 3 This is a comparison chart of the experimental results of static water contact angle in Experiment Example 1 of the present invention.

[0025] Figure 4 This is a comparison chart of the experimental results of wear resistance in Experiment Example 1 of the present invention.

[0026] Figure 5 This is a comparison chart of the experimental results of salt spray corrosion resistance in Experiment Example 1 of the present invention. Detailed Implementation

[0027] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0028] This invention proposes an aluminum alloy sheet with high weather resistance and self-cleaning function, and its preparation method, such as... Figure 1 The diagram shows a flowchart of an aluminum alloy sheet with high weather resistance and self-cleaning function according to the present invention, and its preparation method. The detailed preparation steps are as follows: 1. Alloy smelting and hot rolling Aluminum ingots, metallic manganese, metallic copper, metallic magnesium, crystalline silicon, and Al-10Zr master alloy are smelted according to the designed proportions. Argon refining and grain refinement are used to ensure the purity of the melt and a fine microstructure. Homogenization treatment is then performed to eliminate compositional segregation, and slabs of the predetermined thickness are obtained by hot rolling.

[0029] 2. Phase transition control and surface etching First, the hot-rolled sheet undergoes solution treatment to completely dissolve the alloying elements. Then, a pre-aging treatment is performed to induce the precipitation of high-density, nanoscale Al₂CuMg and Mg₂Si phases from the supersaturated solid solution. Next, selective corrosion is carried out in a weak acid solution containing a specific corrosion inhibitor. The inhibitor preferentially protects the aluminum matrix, while the more electrochemically negative nano-precipitated phases are preferentially dissolved, thereby etching a uniformly distributed micro / nano composite rough structure in situ on the matrix surface, metallurgically bonded to the matrix.

[0030] 3. Atomic layer deposition ceramic protective layer Prior to deposition, the surface was thoroughly cleaned using oxygen plasma to significantly increase the hydroxyl group density, providing a highly active substrate for subsequent reactions. Then, atomic layer deposition (ALD) was employed, with trimethylaluminum and water precursors circulated at low temperatures. Through self-limiting surface reactions, a uniformly thick, dense, and non-porous amorphous alumina ceramic film was conformally grown on the complex three-dimensional surface of the micro / nano structure. This ceramic layer exhibits chemical stability and high hardness, effectively resisting physical friction and the penetration of corrosive media. It serves as a core barrier ensuring long-term weather resistance, and its excellent conformability ensures that the fine underlying structure is not damaged.

[0031] 4. Vapor-phase silanization to construct hydrophobic surfaces A substrate coated with an alumina ceramic layer is placed in a reactor, and perfluorooctyltriethoxysilane (FAS) vapor is introduced under heating conditions. The ethoxy groups in the FAS molecules undergo a hydrolytic condensation reaction with the abundant hydroxyl groups on the alumina surface, forming strong Si-O-Al covalent bonds, thereby grafting a low surface energy perfluoroalkyl monolayer onto the ceramic layer surface. This monolayer transforms the surface chemistry from hydrophilic to superhydrophobic, achieving a high contact angle for water droplets.

[0032] The technical solution designed by this invention to solve the existing problems includes the following key points: 1. Phase-selective etching to construct micro / nano structures Traditional processes for connecting the substrate and precipitates involve physical or chemical corrosion of the substrate surface using techniques such as sandblasting and acid / alkali etching. This results in poor roughness control and a high risk of damaging the substrate. This invention, however, employs a specific alloy composition, introducing specific amounts of Cu, Mg, Si, and the microalloying element Zr into an Al-Mn alloy. First, a solution treatment is performed to completely dissolve these alloying elements into the aluminum matrix, forming a single, supersaturated solid solution. Subsequently, a pre-aging treatment is conducted at a specific temperature and time, inducing the solid solution to precipitate out, resulting in a uniform formation of high-density nanoscale Al₂CuMg (S' phase) and Mg₂Si precipitates within the matrix. These nanoscale phases, due to their corrosion potential difference with the aluminum matrix, can form selectively soluble phases during subsequent surface processing. After the pre-aging treatment, a stabilizing annealing process is used to adjust the work hardening state of the sheet material, achieving the desired mechanical properties while stabilizing the size and distribution of the nanoscale precipitates, preventing excessive coarsening or re-dissolution.

[0033] The core step of the above process is selective corrosion based on electrochemical principles. In a weakly acidic medium containing a specific corrosion inhibitor, the inhibitor preferentially adsorbs onto the aluminum substrate surface, passivating it, while the more negatively charged nano-Al₂CuMg and Mg₂Si phases act as the anode and are preferentially dissolved. This process precisely etches the spatial position of the pre-formed nano-precipitates, thereby forming a micro / nano composite rough structure in situ that is metallurgically bonded to the substrate and whose size and distribution are controlled by the precipitates.

[0034] To verify the successful in-situ construction of a micro / nano composite rough structure on the substrate surface via selective etching, scanning electron microscopy was used to observe the surface of the intermediate sample treated in step S2 during the preparation process of Example 1. Figure 2 As shown, uniformly distributed micron-scale pits are visible on the sample surface. Simultaneously, even finer nanoscale pores and rough textures can be clearly distinguished within and at the edges of individual pits, forming a typical micron-nano dual-scale composite morphology. This result directly demonstrates that the selective etching process successfully constructed the desired three-dimensional rough structure in situ on the substrate surface.

[0035] 2. Sequential Reconstruction and Gradient Encapsulation Traditional techniques typically involve obtaining a rough structure, first modifying it with low surface energy to achieve superhydrophobicity, and then attempting to cover it with a wear-resistant protective layer. However, this protective layer often compromises hydrophobicity or is difficult to adhere to. To address this issue, this invention employs a reverse process logic: strengthening first, then hydrophobicity. First, an extremely thin, dense, and uniform amorphous alumina ceramic layer is conformally grown at low temperature on the surface of an aluminum alloy with a hydrophilic micro / nano rough structure activated by plasma, using atomic layer deposition (ALD). The self-limiting surface reaction characteristics of ALD ensure that it can cover complex three-dimensional structures. This ceramic layer forms a strong bond with the metal substrate through chemical bonds, constituting the main load-bearing force and barrier against mechanical wear and environmental corrosion. Subsequently, using this alumina ceramic layer as a stable reaction substrate, a vapor-phase fluorosilane treatment is performed, utilizing the abundant hydroxyl groups naturally formed on its surface after exposure to the atmosphere. Silane molecules undergo a condensation reaction with the hydroxyl groups on the ceramic surface, forming strong Si-O-Al covalent bonds, thereby grafting low surface energy perfluoroalkyl chains to form the outermost hydrophobic layer.

[0036] This results in a gradient composite system consisting of a metal matrix, a micro / nano-ceramic composite framework, a dense ceramic film, and an organic monolayer. In this system, the inner ceramic layer provides mechanical protection and environmental isolation, its high hardness and chemical inertness ensuring long-term durability. The hydrophobic function is achieved by the outermost monolayer, which is chemically bonded. Even if this monolayer experiences localized damage under extreme friction, the underlying ceramic layer maintains the integrity of the microstructure and can be restored through simple surface regeneration. This synergistic hierarchical design achieves a balance between superhydrophobic performance and long-term durability.

[0037] Example 1 Raw material information sheet An aluminum alloy sheet with high weather resistance and self-cleaning function and its preparation method include the following steps: S1: 94 parts aluminum ingot, 1.5 parts metallic manganese, 1.2 parts metallic copper, 0.8 parts metallic magnesium, 0.5 parts crystalline silicon, and 1.0 parts Al-10Zr master alloy were used as raw materials and melted in a resistance melting furnace at 750℃. After refining with an argon rotary degassing device and grain refinement of Al-5Ti-1B filaments, the ingots were cast into flat ingots. The flat ingots were then placed in a box-type resistance furnace and homogenized at 600℃ for 12 hours. Finally, they were rolled into hot-rolled plates with a thickness of 3mm using a hot continuous rolling mill at a final rolling temperature of 300℃.

[0038] S2: The hot-rolled sheet was placed in a salt bath furnace and solution treated at 535℃ for 1 hour, followed by rapid water quenching. Subsequently, the sheet was transferred to a temperature-controlled oil bath furnace and pre-aged at 185℃ for 4 hours. After pre-aging, the sheet was rolled to a final thickness of 0.6 mm using a 5-pass cold rolling mill. Finally, the cold-rolled sheet was placed in an air-circulating annealing furnace at 180℃ for 2 hours to obtain an H24 state substrate. This substrate was immersed in an etching bath containing 1.0 wt% H2SO4 and 0.3 wt% Na2MoO4 and treated at 35℃ for 75 seconds for selective etching. After ultrasonic cleaning with deionized water and ethanol, the sample was placed in an oxygen plasma cleaner and activated for 5 minutes under conditions of 50 sccm oxygen flow rate, 30 Pa chamber pressure, and 200 W RF power, ultimately obtaining a crystalline hydrophilic surface with a micro-nano rough structure. To prepare for scanning electron microscopy (SEM) observation, a small sample was cut after this step and ultrasonically cleaned for 5 minutes each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 2 hours. The dried sample was then fixed to the sample stage with conductive adhesive, and a gold film with a thickness of approximately 10 nm was sputtered onto the sample surface using an ion sputtering instrument to enhance its conductivity, thus preparing the SEM observation sample.

[0039] S3: The processed substrate is placed in the reaction chamber of a hot-wall atomic layer deposition equipment. The deposition temperature is set to 90°C. Trimethylaluminum and high-purity water are used as precursors, and high-purity nitrogen is used as carrier gas and purge gas. 200 standard deposition cycles are performed. Each cycle includes: a 0.1-second trimethylaluminum pulse, a 5-second nitrogen purge, a 0.2-second water pulse, and a 5-second nitrogen purge. After the cycle is completed, an amorphous aluminum oxide film is deposited conformally on the surface of the micro-nano structure.

[0040] S4: Place the substrate coated with an alumina film in a heatable vacuum reactor and evacuate to 10°C. -2 After the initial pressure (Pa) is increased to 120℃, perfluorooctyltriethoxysilane vapor carried by nitrogen is introduced. The system pressure is maintained at atmospheric pressure, and the vapor concentration is controlled by the nitrogen flow rate. The reaction continues for 1.5 hours, allowing the fluorosilane molecules to fully react with the hydroxyl groups on the alumina surface to form a covalently bonded hydrophobic layer. After the reaction is complete, the surface is purged with nitrogen, cooled to room temperature, and then removed to obtain the finished aluminum alloy sheet with high weather resistance and self-cleaning function.

[0041] Example 2 The preparation method is the same as in Example 1, except that: S1: 94 parts aluminum ingot, 1.5 parts metallic manganese, 1.2 parts metallic copper, 0.8 parts metallic magnesium, 0.5 parts crystalline silicon and 1.0 parts Al-10Zr master alloy are replaced with 92 parts aluminum ingot, 1.2 parts metallic manganese, 0.8 parts metallic copper, 0.5 parts metallic magnesium, 0.3 parts crystalline silicon and 0.5 parts Al-10Zr master alloy; S2: Solution treatment at 535℃ for 1 hour is replaced with solution treatment at 530℃ for 0.5 hours; pre-aging treatment at 185℃ for 4 hours is replaced with pre-aging treatment at 175℃ for 3 hours; treatment in an air-circulating annealing furnace at 180℃ for 2 hours is replaced with treatment in an air-circulating annealing furnace at 170℃ for 1.5 hours; etching bath containing 1.0wt% H2SO4 and 0.3wt% Na2MoO4 is replaced with etching bath containing 0.8wt% H2SO4 and 0.2wt% Na2MoO4; selective etching at 35℃ for 75 seconds is replaced with selective etching at 30℃ for 60 seconds; activation treatment at RF power of 200W for 5 minutes is replaced with activation treatment at RF power of 150W for 3 minutes. S3: Set the deposition temperature to 80℃ instead of 90℃; Perform 180 standard deposition cycles instead of 200 standard deposition cycles. S4: Increase the temperature to 120℃ instead of increasing the temperature to 110℃; continue the reaction for 1.5 hours instead of continuing the reaction for 1.0 hour; All other steps are the same.

[0042] Example 3 The preparation method is the same as in Example 1, except that: S1: 94 parts aluminum ingot, 1.5 parts metallic manganese, 1.2 parts metallic copper, 0.8 parts metallic magnesium, 0.5 parts crystalline silicon and 1.0 parts Al-10Zr master alloy are replaced with 96 parts aluminum ingot, 1.8 parts metallic manganese, 1.5 parts metallic copper, 1.0 parts metallic magnesium, 0.8 parts crystalline silicon and 1.5 parts Al-10Zr master alloy; S2: Solution treatment at 535℃ for 1 hour is replaced with solution treatment at 550℃ for 1.5 hours; pre-aging treatment at 185℃ for 4 hours is replaced with pre-aging treatment at 195℃ for 6 hours; treatment in an air-circulating annealing furnace at 180℃ for 2 hours is replaced with treatment in an air-circulating annealing furnace at 190℃ for 3 hours; etching bath containing 1.0wt% H2SO4 and 0.3wt% Na2MoO4 is replaced with etching bath containing 1.5wt% H2SO4 and 0.5wt% Na2MoO4; selective etching at 35℃ for 75 seconds is replaced with selective etching at 40℃ for 90 seconds; activation treatment at 200W RF power for 5 minutes is replaced with activation treatment at 250W RF power for 8 minutes. S3: Set the deposition temperature to 100℃ instead of 90℃; Perform 220 standard deposition cycles instead of 200 standard deposition cycles. S4: Increase the temperature to 120℃ instead of increasing it to 130℃; continue the reaction for 1.5 hours instead of continuing the reaction for 2.0 hours; All other steps are the same. Comparative Example 1 S1: The steps of adding 0.8 parts metallic magnesium, 0.5 parts crystalline silicon and 1.0 part Al-10Zr master alloy are omitted; All other steps are the same.

[0043] Comparative Example 2 S2: Omit the pre-aging treatment step and use a 1.0% H2SO4 solution without sodium molybdate corrosion inhibitor for corrosion. All other steps are the same.

[0044] Comparative Example 3 S3, S4: First, perform vapor-phase fluorosilanization treatment, then perform atomic layer deposition of alumina protective layer; All other steps are the same.

[0045] Experimental Example 1 The finished aluminum alloy sheets prepared in Examples 1-3 and Comparative Examples 1-3 were measured: (1) Static water contact angle: Referring to GB / T 30693-2014 "Test Method for Wetting Properties of Plastic Film Surface", in a standard environment of 23±2℃ and 50±10% relative humidity, a drop of deionized water with a volume of 4.0±0.2μL was vertically dropped onto a flat sample surface using a contact angle measuring instrument. The droplet profile was captured by the high-speed camera equipped with the instrument, and the angle between the droplet and the solid surface was automatically calculated using the Young-Laplace fitting method, which is the static water contact angle. At least 5 measurements were taken at different locations on the same sample surface, and the arithmetic mean was taken as the final result.

[0046] (2) Abrasion resistance: Referring to GB / T 23988-2009 "Determination of Abrasion Resistance of Coatings—Falling Sand Method", a falling sand abrasion tester was used. The sample was fixed on a sample holder perpendicular to the guide tube. Standard sand conforming to the standard was allowed to fall freely from a height of 1 meter through a guide tube with an inner diameter of 5.5±0.5 mm, impacting the sample surface. The test continued until the coating was worn through, exposing the substrate. The abrasion resistance of the coating was evaluated by measuring and calculating the volume (liters) of sand consumed to wear through the coating of the specified thickness. At least 5 measurements were taken at different locations on the same sample surface, and the arithmetic mean was taken as the final result.

[0047] (3) Salt spray corrosion resistance: Referring to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", the sample was placed in a salt spray test chamber with the test surface at an angle of 15°~30° to the vertical direction. The test conditions were as follows: the test chamber temperature was kept constant at 35±2℃, a sodium chloride solution with a mass fraction of 5±1% was used, the pH value was adjusted to 6.5~7.2, and the solution was continuously sprayed after atomization. After the test lasted for 1000 hours, the sample was taken out and gently rinsed with running water not exceeding 40℃ to remove surface salt deposits. Then, it was allowed to recover in a standard environment for 1~2 hours. Subsequently, the sample surface was first visually inspected for corrosion phenomena such as blistering, rusting, and peeling. Afterward, in areas where no corrosion occurred, the static water contact angle was measured according to the aforementioned GB / T 30693-2014 method. The salt spray corrosion resistance was characterized by the retention rate of the static water contact angle before and after the test.

[0048] (4) Coating adhesion: Referring to GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test", a single-edged cutting tool is used to cut a grid pattern of specified size on the coating surface with uniform pressure and fixed spacing. Then, special pressure-sensitive adhesive tape is used to firmly adhere to the grid area and quickly peel it off at a specific angle. Finally, the adhesion grade (0~5, with 0 being the best) is evaluated according to the number of squares that the coating has detached from the substrate, referring to the standard chart. According to the standard, five different locations are selected on a single sample for testing, and the final adhesion grade is reported as the result with the highest frequency (mode).

[0049] Table 2 Comparison of experimental results of Examples 1-3 and Comparative Examples 1-3 The experimental results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2 and Figure 3 , Figure 4 , Figure 5 As shown, the finished aluminum alloy sheet produced by this invention has a static water contact angle of 158.32°, a wear-through grit consumption of 4.87L, a contact angle retention rate of 98.15% after salt spray, and an adhesion grade of 0. It achieves excellent self-cleaning function and long-term durability, and the data error is small, indicating that the process window is robust and suitable for large-scale production. Therefore, it is the best implementation point of this invention.

[0050] Example 2 systematically explored a more streamlined and energy-efficient process path by comprehensively reducing the alloy composition content and the processing intensity and duration of key process steps. Although the static water contact angle and wear resistance of the resulting product were slightly reduced, the contact angle retention rate and adhesion after salt spray corrosion remained at an excellent level. This result proves that within the technical framework of this invention, even with a milder process and lower intensity, qualified products with high weather resistance and self-cleaning core functions can still be stably obtained, indicating that this scheme has good cost adjustment and process window width in actual production. Example 3 aimed to explore the ultimate performance by comprehensively increasing the alloy composition content and the processing intensity and duration of each key process step. The result showed that wear resistance was the most outstanding, but the static water contact angle and the contact angle retention rate after salt spray corrosion did not reach their peak values ​​simultaneously. This trend indicates that excessive process intensification is clearly effective in improving mechanical wear resistance, but has a marginal effect on improving superhydrophobicity and chemical environment durability. This conversely proves that the process parameters represented by Example 1 of this invention are the optimal point for achieving the best balance of various performances.

[0051] Comparative Examples 1-3, lacking key technologies, showed varying degrees of reduced overall performance compared to the examples. Comparative Example 1 omitted the addition of three key elements: Mg, Si, and Zr. This resulted in the alloy matrix lacking essential components for forming an effective micro / nano corrosion template, and also lost the thermal stability provided by the Zr dispersion strengthening phase. Consequently, its finished product exhibited comprehensive and most significant deterioration across all performance indicators. This result directly confirms that specific multi-element alloy composition design is the foundation and prerequisite for constructing all subsequent functions, and is indispensable. Comparative Example 2 omitted the crucial pre-aging treatment step and used a single acid solution without corrosion inhibitors for corrosion, fundamentally disrupting the precise mechanism of phase-selective corrosion. The finished product exhibits a unique degradation pattern characterized by structural fragility and matrix damage: the static water contact angle is only 134.28°, indicating that the formed surface rough structure is disordered and inefficient; both wear resistance and salt spray corrosion resistance are extremely poor, attributed to insufficient structural mechanical strength due to the lack of a nanotemplate and excessive corrosion of the aluminum matrix due to the absence of corrosion inhibitors; adhesion also drops to level 3. Comparative Example 3, due to the reversed construction order of the core functional layer, first performed vapor-phase fluorosilaneization to construct a hydrophobic layer and then performed atomic layer deposition of alumina, had a static water contact angle that dropped to 125.34°, indicating that the hydrophobic layer was destroyed; its wear resistance and salt spray corrosion resistance were the worst among all samples, and its adhesion was as low as level 4. This is because the atomic layer deposition precursor cannot be effectively adsorbed and nucleated on the low surface energy hydrophobic surface, resulting in the inability to form a continuous and dense alumina protective layer, thus exposing the fragile functional structure directly to mechanical and chemical corrosion.

[0052] In summary, this invention, through multi-level synergistic innovation in alloy composition design, phase transformation engineering, and surface functionalization, successfully prepared aluminum alloy sheets with both high weather resistance and self-cleaning function. The core of this invention lies in: first, pre-forming nanoscale etchable phases within the matrix through specific multi-element alloying and pre-aging treatment; second, utilizing selective corrosion with corrosion inhibitors to preferentially dissolve the precipitated phases, thereby directly transforming the predetermined microstructure differences into surface micro-nano geometries; and finally, employing a gradient encapsulation process—first atomic layer deposition of a ceramic protective layer, then vapor-phase silanization—successfully resolving the fundamental contradiction between poor mechanical durability and insufficient weather resistance of superhydrophobic surfaces.

Claims

1. An aluminum alloy sheet with high weather resistance and self-cleaning function, comprising a substrate and a coating, characterized in that, The substrate is an aluminum alloy matrix, and a micro / nano structure is formed on its surface by selective etching in situ. An inorganic ceramic protective layer, which is an Al2O3 thin film, is deposited conformally on the micro / nano structure. An organic hydrophobic layer, which is a monolayer composed of perfluoroalkylsiloxane, is grafted onto the inorganic ceramic protective layer through covalent bonds.

2. The aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 1, characterized in that, The aluminum alloy matrix comprises, by weight, 92-96 parts aluminum ingot, 1.0-1.8 parts manganese, 0.6-1.5 parts copper, 0.5-1.5 parts magnesium, 0.3-0.8 parts crystalline silicon, and 0.5-1.5 parts Al-10Zr master alloy; wherein the Al-10Zr master alloy is used to provide 0.05-0.15 parts zirconium.

3. The aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 1, characterized in that, The Al2O3 thin film has a thickness of 10~30nm.

4. The aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 1, characterized in that, The aluminum alloy sheet has a static water contact angle ≥155.67°, a wear-through grit consumption ≥4.12L, salt spray corrosion resistance ≥96.83, and a coating adhesion grade of 0.

5. A method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Take aluminum ingots, metallic manganese, metallic copper, metallic magnesium, crystalline silicon and Al-10Zr master alloy as raw materials, smelt them, refine them by argon degassing and Al-5Ti-1B wire grain refinement, and then cast them into flat ingots; then homogenize the flat ingots at 600℃ for 12 hours, and finally roll them into hot-rolled plates. S2: The hot-rolled plate is subjected to solution treatment, water quenching, and pre-aging treatment in sequence; After processing, the sheet is rolled in 5 passes to a final thickness of 0.6 mm; finally, the cold-rolled sheet is annealed to obtain an H24 state substrate. The substrate was immersed in an etching solution for selective etching, and then ultrasonically cleaned with deionized water and ethanol. The sample was then subjected to plasma activation treatment to finally obtain a crystalline hydrophilic surface with a micro-nano rough structure. S3: Atomic layer deposition is performed on the processed substrate. After setting the deposition temperature, a standard deposition cycle is performed using trimethylaluminum and high-purity water as precursors and high-purity nitrogen as carrier gas and purge gas. Each cycle includes: trimethylaluminum pulse for 0.1 seconds, nitrogen purge for 5 seconds, water pulse for 0.2 seconds, and nitrogen purge for 5 seconds. After the cycle is completed, a layer of amorphous aluminum oxide thin film is deposited conformally on the surface of the micro / nano structure. S4: Evacuate the substrate covered with the alumina film to 10°C. -2 After Pa, the temperature is increased; perfluorooctyltriethoxysilane vapor carried by nitrogen is introduced, the system pressure is kept at atmospheric pressure and the vapor concentration is controlled by the nitrogen flow rate, and the reaction continues; after the reaction is completed, the system is purged with nitrogen, cooled to room temperature and then removed to obtain the finished aluminum alloy sheet with high weather resistance and self-cleaning function.

6. The method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 5, characterized in that, The corrosive liquid described in S2 is a corrosive liquid containing 0.8~1.5wt% H2SO4 and 0.2~0.4wt% Na2MoO4.

7. The method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 5, characterized in that, The selective corrosion described in S2 is performed on the nanoscale Al2CuMg and Mg2Si phases contained in the aluminum alloy matrix.

8. The method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 5, characterized in that, The solution treatment described in S2 has a temperature of 530~550℃ and a treatment time of 0.5~1.5 hours; the pre-aging treatment has a temperature of 175~195℃ and a treatment time of 3~6 hours; the annealing treatment has a temperature of 170~190℃ and a treatment time of 1.5~2.5 hours; the selective etching treatment has a temperature of 30~40℃ and a treatment time of 60~90 seconds; the activation treatment has the following settings: radio frequency power of 150~250W and a treatment time of 3~8 minutes.

9. The method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 5, characterized in that, The deposition temperature described in S3 is in the range of 80~100℃; the standard deposition cycle is 180~220 times.

10. The method for preparing an aluminum alloy sheet with high weather resistance and self-cleaning function as described in claim 5, characterized in that, The heating in S4 has an endpoint temperature range of 110~130℃; the continuous reaction lasts for 1.0~2.0 hours.

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