A superhydrophobic composite passivation film and its preparation method

Abstract

This invention discloses a superhydrophobic composite passivation film and its preparation method, belonging to the field of coating preparation technology. The invention involves sequentially forming a zirconium-based chemical conversion film and a fluorinated functionalized silica layer on a substrate surface to obtain the superhydrophobic composite passivation film. The zirconium-based chemical conversion film and the fluorinated functionalized silica layer are connected by Si-O-Zr or Si-O-Al covalent bonds. The zirconium-based chemical conversion film is obtained by deposition through dissociation coordination and interfacial redox reactions using fluorozirconate, fluoride, vanadate, and manganese nitrate as raw materials; the fluorinated functionalized silica layer is obtained by spraying nano-silica after fluorination and functionalization with perfluorosilane. This invention organically couples an inorganic passivation film with a superhydrophobic micro / nano structure, resulting in a superhydrophobic composite passivation film with a static water contact angle ≥150° and a static oil contact angle ≥150°, achieving dual repulsion of water and oil, and reducing the emission of volatile organic compounds during the preparation process.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, specifically relating to a superhydrophobic composite passivation film and its preparation method. Background Technology

[0002] Currently, surface corrosion protection of aluminum alloys (especially high-silicon die-cast aluminum alloys like ADC12) mainly relies on chemical passivation technology. With increasing environmental protection requirements, traditional hexavalent chromium passivation has been gradually replaced by chromium-free passivation technologies, represented by zirconium-based conversion coatings.

[0003] Zirconium-based chemical conversion films primarily provide protection by forming an inorganic layer containing zirconium oxides (such as ZrO2) and metal fluorides on the metal surface. Traditional zirconium-based chemical conversion films have insufficient shielding performance and possess a microporous structure (…). Figure 1 (Figure a), electrolyte (such as Cl) - It can still penetrate to the substrate surface through microcracks in the film layer, causing pitting corrosion.

[0004] To endow surfaces with special self-cleaning or stain-resistant properties, researchers have recently begun to study the construction of superhydrophobic structures on the passivation layer surface to slow down corrosion by reducing the contact area between the electrolyte and the substrate. However, existing technologies mostly focus on achieving "superhydrophobic" properties, specifically, they only have a high contact angle with water. When faced with low surface energy liquids (such as lubricating oil, coolant, and fingerprint oil), the film layer will quickly wet and lose its protective performance. In addition, existing technologies often use nano-modified solutions (for example, silane hydrolysis sol systems directly mixed with silica nanoparticles). However, because silane coupling agents are prone to self-condensation in aqueous or alcoholic systems, they will agglomerate and precipitate, causing the solution to gel or separate in a short time (i.e., short "shelf life"), which not only wastes raw materials but also leads to unstable film quality. Furthermore, existing technologies are limited by the surface polarity of the material and rely on the use of low surface tension organic solvents to achieve uniform dispersion of fluorinated particles, resulting in the continuous release of volatile organic compounds (VOCs) during the use of the film layer, posing safety hazards and environmental risks. Summary of the Invention

[0005] To address the technical problems of existing membranes being hydrophobic only, having unstable quality, and exhibiting high concentrations of volatile organic compounds (VOCs), this invention provides a superhydrophobic composite passivation membrane and its preparation method.

[0006] In this invention, a zirconium-based chemical conversion film and a fluorinated functionalized silica layer are sequentially formed on the surface of a substrate. The silane molecules in the fluorinated functionalized silica layer undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the zirconium-based chemical conversion film and are connected by Si-O-Zr or Si-O-Al covalent bonds to construct a superhydrophobic composite passivation film layer, achieving "dual repulsion" of water and oil.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows.

[0008] The first objective of this invention is to provide a superhydrophobic composite passivation film, wherein a zirconium-based chemical conversion film and a fluorinated functionalized silicon dioxide layer are sequentially formed on the surface of an aluminum substrate, and the zirconium-based chemical conversion film and the fluorinated functionalized silicon dioxide layer are connected by Si-O-Zr or Si-O-Al covalent bonds.

[0009] The zirconium-based chemical conversion membrane is created by dissociating fluorozirconate, fluoride, vanadate, and manganese nitrate in water. The zirconium species exist as zirconium-fluorine coordination ions. Under pH conditions of 2–4, OH... - Replace part of F - A zirconium-based chemical conversion solution is obtained by generating intermediate species containing Zr-OH. An aluminum substrate is then immersed in the zirconium-based chemical conversion solution to promote the dehydration and condensation of the intermediate species containing Zr-OH to form a Zr-O-Zr passivation layer, which is then cured for the first time.

[0010] The vanadate is reduced to the low-valence vanadium species VO under acidic and interfacial oxidation / reduction conditions. 2+ or V 3+ It also participates in film formation, with Mn dissociated from manganese nitrate. 2+ In the localized environment of interfacial oxidation, manganese compounds such as Mn(OH)2 or Mn2O3 may be formed, which together regulate the interfacial reaction rate and film compactness.

[0011] The fluorinated functionalized silica layer is obtained by dispersing nano-silica in water, using perfluorosilane as a fluorinating agent, and carrying out a fluorination reaction under the action of the fluorinating agent to obtain a fluorinated functionalized silica suspension, which is then sprayed onto the surface of a zirconium-based chemical conversion film and cured a second time.

[0012] The thickness of the zirconium-based chemical conversion film is 8 nm to 15 nm; the thickness of the superhydrophobic composite passivation film is 90 nm to 110 nm.

[0013] In a preferred embodiment, the main components of the zirconium-based chemical conversion film are aluminum fluoride, zirconium oxide, aluminum oxide, and vanadium oxide.

[0014] In a preferred embodiment, the aluminum substrate is an aluminum alloy substrate; the fluorozirconate is potassium fluorozirconate; the fluoride is sodium fluoride; and the vanadate is sodium metavanadate powder with a particle size of 2μm to 5μm.

[0015] In a preferred embodiment, the static water contact angle and the static oil contact angle of the superhydrophobic composite passivation film are 150° to 180°.

[0016] In a preferred embodiment, the sliding angle of the superhydrophobic composite passivation film is 0° to 5°.

[0017] Existing methods for preparing superhydrophobic and amphophobic surfaces often rely on high-vacuum environments (such as CVD chemical vapor deposition), energy-intensive processes (such as plasma treatment), or precise etching techniques. These methods are extremely unfriendly to large-sized parts or complex-shaped components (such as die-cast aluminum alloy pump housings and heat sinks), resulting in low production efficiency and high costs. The preparation method of this invention has low equipment requirements, does not require high vacuum or plasma treatment, and can achieve uniform film formation on large-sized or complex-shaped aluminum substrates (such as die-cast pump housings and heat sinks) under normal pressure and low temperature (30°C to 50°C). Simultaneously, the zirconium-based chemical conversion film and the fluorinated functionalized silica layer are covalently bonded at the interface, significantly improving the interfacial adhesion, corrosion resistance, and ease of industrial application of the film while ensuring superhydrophobic and amphophobic properties (water / oil contact angle 150° to 180°, sliding angle 0° to 5°).

[0018] The second objective of this invention is to provide a method for preparing a superhydrophobic composite passivation film, comprising the following steps: When fluorozirconate, fluoride, vanadate, and manganese nitrate are dissociated in water, the zirconium species mainly exist as zirconium fluoride coordination ions. Under conditions of pH 2–4, OH... - Replace part of F - An intermediate species containing Zr-OH is generated to obtain a zirconium-based chemical conversion solution; an aluminum substrate is immersed in the zirconium-based chemical conversion solution at 30℃~50℃, and the aluminum substrate reacts with the H in the zirconium-based chemical conversion solution. + and F - The reaction is carried out, and the interfacial reaction process is controlled by vanadate and manganese salt to form a passivation layer. After the first curing, a zirconium-based chemical conversion film is obtained.

[0019] When the immersion temperature is below 30℃, the interfacial reaction rate is slow, reducing the deposition efficiency of zirconium species on the substrate surface. This can easily lead to insufficient film formation, inadequate thickness, or discontinuous local coverage, which is detrimental to improving film density and corrosion resistance. When the immersion temperature is above 50℃, the interfacial reaction and the hydrolysis deposition process of zirconium species may be too rapid, easily leading to uneven film growth, and even problems such as loose, rough film, increased local defects, or decreased adhesion stability, thus hindering the acquisition of a zirconium-based chemical conversion film with excellent overall performance. Within the temperature range of 30℃ to 50℃, it is more conducive to balancing the stability of the zirconium conversion solution, the interfacial reaction rate, and the dense and uniform growth of the film, thereby obtaining a zirconium-based chemical conversion film with good adhesion and superior shielding performance. Below this range, the film formation motive is insufficient, easily leading to insufficient film formation; above this range, the reaction is too rapid, easily leading to loose, rough, or less uniform film.

[0020] Nano-silica was dispersed in water, a dispersing agent was added, and the supernatant was taken after dispersion. A fluorination reaction was carried out using perfluorosilane as a fluorinating agent to obtain a fluorinated functionalized silica suspension.

[0021] The fluorinated functionalized silica suspension is sprayed onto the surface of a zirconium-based chemical conversion film and then cured a second time to form a fluorinated functionalized silica layer, thus obtaining a superhydrophobic composite passivation film.

[0022] In a preferred embodiment, the ratio of nano-silica to perfluorosilane is 1g:0.3mL to 1.25mL.

[0023] In a preferred embodiment, the perfluorosilane is at least one selected from 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, and vinyltriethoxysilane.

[0024] In a preferred embodiment, the first curing temperature is 60℃~120℃, and the time is 0.5h~2h. The first curing is mainly used to promote the removal of residual moisture in the zirconium-based chemical conversion film and to further dehydrate, stabilize, and densify the film layer, thereby improving the adhesion, density, and corrosion resistance of the zirconium-based chemical conversion film, while providing a stable substrate for the subsequent spraying of the fluorinated functionalized silica layer. When the first curing temperature is below 60℃ and / or the time is less than 0.5h, the film layer may not be fully cured, which may lead to insufficient film layer density and decreased adhesion stability, which is not conducive to improving the overall performance of the subsequent composite film layer. When the first curing temperature is above 120℃ and / or the time is longer than 2h, the film layer may experience problems such as increased shrinkage stress, local embrittlement, or microcracks due to excessive heating, which may affect the subsequent interfacial bonding and is not conducive to obtaining a substrate film with excellent overall performance.

[0025] In a preferred embodiment, the second curing temperature is 60℃~100℃, and the time is 0.5h~2h. The second curing mainly promotes the evaporation of moisture in the fluorinated functionalized silica layer, the fixation of the particle layer, and the further condensation of the fluorinated silane components, thereby facilitating the formation of a stable micro-nano hierarchical rough structure and a low surface energy surface layer, improving the hydrophobic and oleophobic properties of the film and the stability of the interfacial bonding. When the second curing temperature is below 60℃ and / or the time is less than 0.5h, the surface curing may be insufficient, easily leading to poor adhesion of the particle layer and insufficient stability of the surface functional layer; when the second curing temperature is above 100℃ and / or the time is longer than 2h, it may lead to excessively rapid surface curing, damage to the local rough structure, or a decrease in the stability of the low surface energy components, which is detrimental to the maintenance of the superhydrophobic and oleophobic properties and long-term stability of the film.

[0026] In a preferred embodiment, the mass ratio of the nano-silica to the dispersing agent is 1:1 to 4; the dispersing agent is selected from at least one of fatty alcohol polyoxyethylene ether, octylphenol polyoxyethylene ether, polysorbate surfactants, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium citrate, sodium polyacrylate, or sodium polymethacrylate.

[0027] As a preferred embodiment, the soaking is carried out at 45℃~50℃ for 2min~5min, which is beneficial to balance film formation efficiency, film quality and subsequent composite construction effect.

[0028] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a superhydrophobic composite passivation film, which is obtained by sequentially forming a zirconium-based chemical conversion film and a fluorinated functionalized silicon dioxide layer on the surface of a substrate. The zirconium-based chemical conversion film and the fluorinated functionalized silicon dioxide layer are connected by Si-O-Zr or Si-O-Al covalent bonds.

[0029] The fluorinated functionalized silica layer in this invention is formed by the accumulation of fluorinated functionalized silica particles. During the fluorination functionalization process, a dispersant helps the nano-silica to be uniformly dispersed and stably suspended in an aqueous medium. Perfluorosilanes fluorinate and functionalize the surface of the silica particles, grafting fluorine-containing functional groups onto the particle surface. After spraying and curing, the fluorinated functionalized silica particles form a micro-nano hierarchical rough structure on the film surface, which works synergistically with the fluorine-containing functional groups grafted onto the particle surface to reduce the surface free energy of the film. This gives the fluorinated functionalized silica layer excellent hydrophobicity and oleophobicity, and helps reduce the wetting and adhesion of aqueous and oily media to the film surface, endowing the fluorinated functionalized silica layer with superhydrophobic and oleophobic barrier functions. Furthermore, the prepared superhydrophobic and oleophobic composite passivation film has stable quality. In addition, the dispersant added during the preparation process effectively reduces the emission of volatile organic compounds.

[0030] In this invention, the aluminum substrate and the zirconium-based chemical conversion solution contain H + and F - The reaction consumes H + This leads to an increase in interfacial pH, which promotes the dehydration and condensation of intermediate species containing Zr-OH to form a Zr-O-Zr passivation layer. After curing, a zirconium-based chemical conversion film is obtained. Vanadates are reduced to low-valent vanadium species VO under acidic and interfacial oxidation / reduction conditions. 2+ or V 3+ It also participates in film formation, with Mn dissociated from manganese nitrate. 2+In the localized environment of interfacial oxidation, manganese compounds such as Mn(OH)2 or Mn2O3 may be formed. Both compounds jointly regulate the interfacial reaction, forming a dense inorganic film on the substrate surface. The resulting zirconium-based chemical conversion film exhibits good density and adhesion, providing inorganic shielding and passivation protection to the substrate, hindering the transport of corrosive media to the substrate, and inhibiting the electrochemical corrosion process on the substrate surface.

[0031] In summary, in the superhydrophobic composite passivation film prepared by this invention, the fluorinated functionalized silica layer and the zirconium-based chemical conversion film work synergistically to give the superhydrophobic composite passivation film both superhydrophobic and corrosion-resistant properties, thereby effectively reducing the wetting, penetration and erosion of the substrate surface by corrosive media, and achieving long-term corrosion protection of the substrate in complex environments. Attached Figure Description

[0032] Figure 1 The figures show a single zirconium-based chemical conversion membrane and a conventional superhydrophobic membrane. Figure a shows the single zirconium-based chemical conversion membrane, and Figure b shows the conventional superhydrophobic membrane.

[0033] Figure 2 This is a flowchart illustrating the preparation process of the superhydrophobic composite passivation film prepared in Example 1 of the present invention.

[0034] Figure 3 The fluorinated functionalized silica solution is the superhydrophobic composite passivation film prepared in Example 1 of this invention.

[0035] Figure 4 Figure 1 shows a schematic diagram of the superhydrophobic and oleophobic composite passivation film prepared in Example 1 of this invention. Specifically, Figure a illustrates the superhydrophobicity of the superhydrophobic and oleophobic composite passivation film; Figure b illustrates the superoleophobicity of the superhydrophobic and oleophobic composite passivation film; Figure c illustrates the hydrophobicity of the fluorinated functionalized silica layer under 72 hours of neutral salt spray; and Figure d illustrates the hydrophobicity of the superhydrophobic and oleophobic composite passivation film under 72 hours of neutral salt spray.

[0036] Figure 5 The figures show the corrosion of the aluminum alloy surface after 72 hours in a neutral salt spray environment for the films prepared in Example 1 and Comparative Examples 1-2 of this invention. Figure a is an ADC12 blank sample; Figure b is a fluorinated functionalized silica film; Figure c is a zirconium-based chemical conversion film; and Figure d is a superhydrophobic composite passivation film prepared in Example 1. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention and to implement the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. In the description of the present invention, unless otherwise specified, all reagents used are commercially available, and all methods used are conventional techniques in the art.

[0038] To endow surfaces with special self-cleaning or stain-resistant properties, researchers have recently begun to study the construction of superhydrophobic structures on the passivation layer surface to slow down corrosion by reducing the contact area between the electrolyte and the substrate. However, existing technologies still face significant bottlenecks: they mostly focus on achieving "superhydrophobic" properties, meaning they only have a high contact angle with water. When faced with low surface energy liquids (such as lubricating oil, coolant, and fingerprint oil), the film layer quickly wets and loses its protective performance. Commonly used nano-modification solutions (silane hydrolysis sol systems directly mixed with silica nanoparticles) suffer from problems because silane coupling agents readily self-condense in aqueous or alcoholic systems, leading to aggregation and precipitation. This causes the solution to gel or separate within a short time (i.e., a short "shelf life"), wasting raw materials and resulting in unstable film quality. Furthermore, existing technologies are limited by the surface polarity of the material and rely on low surface tension organic solvents to achieve uniform dispersion of fluorinated particles. This results in the continuous release of volatile organic compounds (VOCs) during use, posing safety hazards and environmental risks.

[0039] The technical solution of the present invention will be analyzed in detail below.

[0040] This invention provides a superhydrophobic composite passivation film, wherein a zirconium-based chemical conversion film and a fluorinated functionalized silicon dioxide layer are sequentially formed on the surface of an aluminum substrate, and the zirconium-based chemical conversion film and the fluorinated functionalized silicon dioxide layer are connected by Si-O-Zr or Si-O-Al covalent bonds. The zirconium-based chemical conversion membrane is created by dissociating fluorozirconate, fluoride, vanadate, and manganese nitrate in water. The zirconium species exist as zirconium-fluorine coordination ions. Under pH conditions of 2–4, OH... - Replace part of F - A zirconium-based chemical conversion solution is obtained by generating intermediate species containing Zr-OH. An aluminum substrate is then immersed in the zirconium-based chemical conversion solution to promote the dehydration and condensation of the intermediate species containing Zr-OH to form a Zr-O-Zr passivation layer, which is then cured for the first time.

[0041] The fluorinated functionalized silica layer is obtained by dispersing nano-silica in water, using perfluorosilane as a fluorinating agent, and carrying out a fluorination reaction under the action of the fluorinating agent to obtain a fluorinated functionalized silica suspension, which is then sprayed onto the surface of a zirconium-based chemical conversion film and cured a second time.

[0042] The thickness of the zirconium-based chemical conversion film is 8 nm to 15 nm; the thickness of the superhydrophobic composite passivation film is 90 nm to 110 nm.

[0043] In the above technical solution, the present invention sequentially forms a zirconium-based chemical conversion film and a fluorinated functionalized silica layer on the surface of a substrate. The two layers are connected by Si-O-Zr or Si-O-Al covalent bonds to obtain a superhydrophobic composite passivation film. The micro / nano structure constructed by the fluorinated functionalized silica can trap air and form a stable air layer. According to the Cassie-Baxter composite contact angle model, water droplets and oil droplets mainly contact the top of the micro / nano structure on the surface of the fluorinated functionalized silica layer, thereby achieving superhydrophobic properties and reducing corrosive media (such as Cl). - The zirconium-based chemical conversion coating further enhances the corrosion resistance of the coating system. Even under extreme conditions, when the superhydrophobic properties of the fluorinated functionalized silica layer decrease (Cassie state to Wenzel state transition), the zirconium-based chemical conversion coating can still hinder the transmission of corrosive media to the aluminum alloy substrate through its shielding effect and high electrical resistance, and inhibit the electrochemical corrosion of the aluminum alloy substrate. The synergistic effect of the fluorinated functionalized silica layer and the zirconium-based chemical conversion coating enables the superhydrophobic composite passivation film to possess both superhydrophobic and corrosion-resistant properties, thereby effectively reducing the wetting, penetration, and erosion of the substrate surface by corrosive media, and achieving long-term corrosion protection of the substrate in complex environments.

[0044] The technical solution of the present invention will be further illustrated below through the following embodiments and comparative examples.

[0045] Example 1 A method for preparing a superhydrophobic composite passivation film includes the following steps: S1. Mix 0.4g of nano-silica with 40mL of deionized water, stir and sonicate in an ice-water bath for 0.5h each, then add 0.4g of dispersant sodium dodecyl sulfate; stir again for 0.5h and sonicate for 1h, let stand for 24h, take the supernatant, add 0.5mL of 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and repeat the stirring and sonication in an ice-water bath process to obtain a stable fluorinated functionalized silica suspension.

[0046] S2, 9 g / L potassium fluorozirconate, 0.75 g / L sodium fluoride and 5 g / L sodium metavanadate powder were mixed, and 40 mL / L manganese nitrate solution was added. Then, nitric acid and sodium hydroxide solution were added to adjust the pH value to 3.6 and stirred thoroughly to dissolve, thus obtaining the zirconium-based chemical conversion film stock solution. The concentration of the obtained zirconium-based chemical conversion film stock solution was diluted to 20% to obtain the grooving conversion solution. The pretreated aluminum alloy substrate was immersed in the grooving conversion solution at 45℃ for 5 min, then washed with water for 120 s, and cured and baked at 80℃ for 0.5 h to obtain a zirconium-based chemical conversion film (ZRCC passivation film) with a thickness of 10 nm.

[0047] S3. The prepared fluorinated functionalized silica suspension was uniformly coated onto the surface of the zirconium-based chemical conversion film using a spray gun. The spraying pressure was 0.2 MPa, the spraying angle between the spray gun and the substrate surface was 45°, the distance between the spray gun nozzle and the substrate surface was 15 cm, and the single spraying time was 10 s. After each spraying, the substrate was allowed to stand for 30 s before the next spraying was performed, for a total of 4 sprayings. After spraying, the aluminum alloy substrate was placed in an oven and cured at 80°C for 1 hour to form a superhydrophobic composite passivation film with a thickness of 100 nm on the surface of the aluminum alloy substrate.

[0048] Example 2 A method for preparing a superhydrophobic composite passivation film includes the following steps: S1. Mix 0.4g of nano-silica with 40mL of deionized water, stir and sonicate in an ice-water bath for 0.5h each, then add 0.4g of dispersant sodium dodecyl sulfate; stir again for 0.5h and sonicate for 1h, let stand for 24h, take the supernatant, add 0.5mL of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS-13) and repeat the stirring and sonication in an ice-water bath to obtain a stable fluorinated functionalized silica suspension.

[0049] S2, 9 g / L potassium fluorozirconate, 0.75 g / L sodium fluoride and 5 g / L sodium metavanadate powder were mixed, and 40 mL / L manganese nitrate solution was added. Then, nitric acid and sodium hydroxide solution were added to adjust the pH value to 3.6 and stirred thoroughly to dissolve, thus obtaining the zirconium-based chemical conversion film stock solution. The concentration of the obtained zirconium-based chemical conversion film stock solution was diluted to 5% to obtain the grooving conversion solution. The pretreated aluminum alloy substrate was immersed in the grooving conversion solution at 50℃ for 2 min, then washed with water for 30 s, and cured and baked at 60℃ for 2 h to obtain a zirconium-based chemical conversion film with a thickness of 10 nm.

[0050] S3. The prepared fluorinated functionalized silica suspension was uniformly coated onto the surface of the zirconium-based chemical conversion film using a spray gun. The spraying pressure was 0.2 MPa, the spraying angle between the spray gun and the substrate surface was 45°, the distance between the spray gun nozzle and the substrate surface was 15 cm, and the single spraying time was 10 s. After each spraying, the substrate was allowed to stand for 30 s before the next spraying was performed, for a total of 4 sprayings. After spraying, the aluminum alloy substrate was placed in an oven and cured at 80°C for 1 hour to form a superhydrophobic composite passivation film with a thickness of 110 nm on the surface of the aluminum alloy substrate.

[0051] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows.

[0052] Comparative Example 1 A method for preparing a fluorinated functionalized silica film: 0.4 g of nano-silica was mixed with 40 mL of deionized water. After stirring and sonicating in an ice-water bath for 0.5 h each, 0.4 g of sodium dodecyl sulfate, a dispersant, was added. The mixture was then stirred again for 0.5 h and sonicated for 1 h. After standing for 24 h, the supernatant was collected, and 0.5 mL of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane was added. The stirring and sonicating in an ice-water bath were repeated to obtain a stable fluorinated functionalized silica suspension. The prepared fluorinated functionalized silica suspension was then uniformly coated onto the surface of an aluminum alloy substrate using a multi-coating process. After coating, the aluminum alloy substrate was placed in an oven and cured at 80 °C for 1 h to form a fluorinated functionalized silica film on the surface of the aluminum alloy substrate.

[0053] Comparative Example 2 A method for preparing a zirconium-based chemical conversion film: 9 g / L potassium fluorozirconate, 0.75 g / L sodium fluoride, and 5 g / L sodium metavanadate powder were mixed, and then 40 mL / L manganese nitrate solution was added. Nitric acid and sodium hydroxide solutions were then added to adjust the pH to 3.6 and stirred thoroughly to dissolve the mixture, thus obtaining the zirconium-based chemical conversion film stock solution. The concentration of the obtained zirconium-based chemical conversion film stock solution was diluted to 20% to obtain the grooving conversion solution. The pretreated aluminum alloy substrate was immersed in the grooving conversion solution at 45°C for 5 min, and then cured and baked at 80°C for 1 h to form a zirconium-based chemical conversion film on the surface of the aluminum alloy substrate.

[0054] Figure 1 Figure a shows a single zirconium-based chemical conversion membrane and a conventional superhydrophobic membrane. Figure a shows the single zirconium-based chemical conversion membrane, where water and corrosive ions (Cl-) are present. - The oil droplets directly reach the aluminum alloy substrate through the channel, causing electrochemical corrosion, producing corrosion products and leading to film bulging; Figure b shows a normal superhydrophobic film, where oil droplets cause the "Cassie-Baxter" state to change to the "Wenzel" state, resulting in loss of protective function.

[0055] Figure 2 This is a flowchart illustrating the preparation process of the superhydrophobic composite passivation film prepared in Example 1 of the present invention.

[0056] Solution stability test: like Figure 3 As shown, the fluorinated functionalized silica suspension showed no significant sedimentation after being placed at room temperature for 5 weeks.

[0057] Superhydrophobic performance test: Figure 4Figure 1 shows a schematic diagram of the superhydrophobic and anaphobic composite passivation film prepared in Example 1 of this invention. Figure a illustrates the superhydrophobicity of the superhydrophobic and anaphobic composite passivation film, with a static water contact angle (WCA) of 165°; Figure b illustrates the superoleophobicity of the superhydrophobic and anaphobic composite passivation film, with a static oil contact angle (OCA) of 157°; Figure c illustrates the hydrophobicity of the fluorinated functionalized silica layer after 72 hours of neutral salt spray; Figure d illustrates the hydrophobicity of the superhydrophobic and anaphobic composite passivation film after 72 hours of neutral salt spray.

[0058] The superhydrophobic composite passivation film prepared by this invention exhibits excellent superhydrophobic properties, with a static water contact angle of 150°–180°, a static oil contact angle of 150°–180°, and a sliding angle of 0°–5°. Specifically, the superhydrophobic composite passivation film prepared in Example 1 has a static water contact angle (WCA) of 165° and a static oil contact angle (OCA) of 157°, demonstrating excellent droplet bouncing performance. Furthermore, after 72 hours of neutral salt spray, the film still maintains good hydrophobic properties, indicating that the superhydrophobic composite passivation film prepared by this invention has good surface stability and environmental adaptability.

[0059] Corrosion resistance test: Figure 5 The image shows the corrosion of aluminum alloy surfaces after 72 hours in a neutral salt spray environment for the following samples: ADC12 blank sample, the superhydrophobic composite passivation film obtained in Example 1 of this invention, the fluorinated functionalized silica film obtained in Comparative Example 1, and the zirconium-based chemical conversion film obtained in Comparative Example 2. After 72 hours of neutral salt spray testing, the aluminum alloy surface of the ADC12 blank sample coating in Figure a was covered with deep pits and black products, indicating extremely severe corrosion. Although the fluorinated functionalized silica film in Figure b and the zirconium-based chemical conversion film in Figure c had some protective effect, they still showed large-area corrosion patches and obvious longitudinal corrosion cracks, indicating that both physical barriers and chemical protection have limitations under long-term high salt spray impact. In contrast, the surface of the superhydrophobic composite passivation film prepared in Example 1 in Figure d remained smooth and clean, with almost no corrosion traces, indicating that the fluorinated functionalized silica layer and the zirconium-based chemical conversion film can form a good synergistic protective effect: the fluorinated functionalized silica layer reduces the wetting and penetration of salt water on the film surface through its superhydrophobic properties, and the zirconium-based chemical conversion film further hinders the transmission of corrosive media to the aluminum alloy substrate through its dense inorganic shielding effect, thereby achieving a longer-lasting anti-corrosion effect than a single film layer.

[0060] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0061] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A superhydrophobic composite passivation film, characterized in that, The superhydrophobic composite passivation film is formed by sequentially forming a zirconium-based chemical conversion film and a fluorinated functionalized silica layer on the surface of an aluminum substrate, and the zirconium-based chemical conversion film and the fluorinated functionalized silica layer are connected by Si-O-Zr or Si-O-Al covalent bonds. The zirconium-based chemical conversion film is obtained by dissolving fluorozirconate, fluoride, vanadate and manganese nitrate in water, zirconium species exists in the form of zirconium fluoride coordination ion, OH - Substituted moiety F - An intermediate species containing Zr-OH is generated to obtain a zirconium-based chemical conversion liquid, an aluminum base material is immersed in the zirconium-based chemical conversion liquid, and the intermediate species containing Zr-OH is caused to undergo dehydration and polycondensation to form a Zr-O-Zr passivation layer, and a first solidification is performed to obtain; The fluorinated functionalized silica layer is obtained by dispersing nano-silica in water, using perfluorosilane as a fluorinating agent, and carrying out a fluorination reaction under the action of the fluorinating agent to obtain a fluorinated functionalized silica suspension, which is then sprayed onto the surface of a zirconium-based chemical conversion film and cured a second time. The thickness of the zirconium-based chemical conversion film is 8 nm to 15 nm; the thickness of the superhydrophobic composite passivation film is 90 nm to 110 nm.

2. The superhydrophobic composite passivation film layer according to claim 1, characterized in that, The main components of the zirconium-based chemical conversion membrane are aluminum fluoride, zirconium oxide, aluminum oxide, and vanadium oxide.

3. The superhydrophobic composite passivation film layer according to claim 1, characterized in that, The aluminum substrate is an aluminum alloy substrate; the fluorozirconate is potassium fluorozirconate; the fluoride is sodium fluoride; the vanadate is sodium metavanadate powder with a particle size of 2μm to 5μm.

4. The superhydrophobic composite passivation film layer according to claim 1, characterized in that, The static water contact angle and static oil contact angle of the superhydrophobic composite passivation film are 150° to 180°.

5. The superhydrophobic composite passivation film layer according to claim 1, characterized in that, The sliding angle of the superhydrophobic composite passivation film is 0° to 5°.

6. A method for preparing a superhydrophobic composite passivation film according to any one of claims 1 to 5, characterized in that, Includes the following steps: The fluorozirconate, fluoride, vanadate and manganese nitrate are hydrolyzed, the zirconium species mainly exists in the form of zirconium fluoride coordination ion, OH - Substituted moiety F - The intermediate species containing Zr-OH is generated, and a zirconium chemical conversion solution is obtained; the aluminum base material is soaked in the zirconium chemical conversion solution at 30-50°C, the H + and F - react, and the interface reaction process is regulated by the vanadate and manganese salt to form a passivation layer, and a zirconium chemical conversion film is obtained after the first solidification; Nano-silica was dispersed in water, a dispersing agent was added, and the supernatant was taken after dispersion. A fluorination reaction was carried out using perfluorosilane as a fluorinating agent to obtain a fluorinated functionalized silica suspension. The fluorinated functionalized silica suspension is sprayed onto the surface of a zirconium-based chemical conversion film and then cured a second time to form a fluorinated functionalized silica layer, thus obtaining a superhydrophobic composite passivation film.

7. The method for preparing the superhydrophobic composite passivation film according to claim 6, characterized in that, The ratio of nano-silica to perfluorosilane is 1g:0.3mL~1.25mL.

8. The method for preparing the superhydrophobic composite passivation film according to claim 6, characterized in that, The perfluorosilane is at least one selected from 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, and vinyltriethoxysilane.

9. The method for preparing the superhydrophobic composite passivation film according to claim 6, characterized in that, The first curing temperature is 60℃~120℃ and the time is 0.5h~2h; the second curing temperature is 60℃~100℃ and the time is 0.5h~2h.

10. The method for preparing the superhydrophobic composite passivation film according to claim 6, characterized in that, The mass ratio of the nano-silica to the dispersing agent is 1:1 to 4; the dispersing agent is selected from at least one of fatty alcohol polyoxyethylene ether, octylphenol polyoxyethylene ether, polysorbate surfactants, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium citrate, sodium polyacrylate, and sodium polymethacrylate.

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