Surface treatment process of high-hydrophobic weather-resistant aluminum veneer

Abstract

The application discloses a high-hydrophobic weather-resistant aluminum veneer surface treatment process and belongs to the technical field of metal material surface modification. The application adopts an integrated process of surface micro-nano structuring pretreatment, composite passivation bottoming, fluorosilicon modified hydrophobic weather-resistant coating gradient coating and low-temperature curing densification modification, builds a multilayer dense and excellent bonding force micro-nano composite protective coating system on the surface of the aluminum veneer substrate by accurately controlling the aluminum veneer surface micro-roughness, optimizing the passivation film component structure, matching the gradient coating material ratio and coating parameters. The aluminum veneer surface prepared by the application has excellent super-hydrophobic, self-cleaning and anti-fouling properties, and the coating has greatly improved ultraviolet aging resistance, high-low temperature cycle resistance and salt mist corrosion resistance, effectively prolongs the outdoor weather-resistant service life, solves the problems of easy corrosion, easy dust accumulation and fast weathering attenuation of traditional aluminum veneers, is suitable for harsh outdoor scenes and has extremely high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of surface modification technology for metal materials, and in particular to a surface treatment process for highly hydrophobic and weather-resistant aluminum single-panel panels. Background Technology

[0002] Aluminum single-layer panels are widely used in high-rise building curtain walls, outdoor venue decoration, rail transit, municipal engineering and other fields due to their advantages such as light weight, high strength, easy processing and good decoration. At present, the mainstream surface treatment processes of aluminum single-layer panels on the market mainly include anodizing, electrostatic powder coating, ordinary fluorocarbon coating and electrophoretic coating. Among them, the oxide film formed by the anodizing process has high porosity and extremely poor hydrophobicity, and the surface is prone to water and dirt accumulation. Long-term outdoor use is prone to oxidation spots. Ordinary powder coating has insufficient coating density and poor UV aging resistance. After 3-5 years of use, problems such as chalking, fading and cracking will appear. The traditional fluorocarbon coating process has relatively good weather resistance, but the coating surface is flat and has a low hydrophobic angle. It does not have self-cleaning ability. Outdoor use is prone to dust, oil stains and acid rain stains, resulting in extremely high maintenance costs. Moreover, the bonding strength between the traditional fluorocarbon coating and the aluminum substrate depends on a single pretreatment process. Under long-term temperature change environment, the coating is prone to peeling and flaking.

[0003] Some existing technologies attempt to improve the hydrophobic properties of aluminum panels by adding hydrophobic additives, but they have significant technical drawbacks: First, the hydrophobic effect is achieved only through simple coating modification without constructing a micro-nano structure on the aluminum substrate surface. The hydrophobic layer lacks microstructural support, resulting in poor wear resistance and loss of hydrophobicity with slight rinsing. Second, the hydrophobic coating and weather-resistant coating show obvious delamination, with weak interfacial adhesion, making them prone to interlayer peeling under alternating hot and cold conditions. Third, the pretreatment process is simplistic, involving only basic degreasing and cleaning, leaving residual oxide scale and impurities on the substrate surface, severely affecting coating adhesion and overall weather resistance. Fourth, the curing process involves high temperatures and high energy consumption, which can easily cause stress deformation of the aluminum panel substrate, affecting product dimensional accuracy.

[0004] In summary, a surface treatment process for aluminum single panels that combines ultra-high hydrophobicity, ultra-long weather resistance, high adhesion, and energy-saving and environmentally friendly technology is being developed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings and defects in existing technologies, this invention proposes a surface treatment process for highly hydrophobic and weather-resistant aluminum panels. This process employs a segmented approach of low-temperature pre-curing and constant-temperature densification curing to avoid stress deformation and coating aging and embrittlement of the aluminum panels caused by high temperatures. Simultaneously, it promotes full cross-linking of coating molecules and penetration and filling of micro-nano pores in the matrix, thereby improving the density, uniformity, and overall stability of the coating. This process is intended to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A surface treatment process for highly hydrophobic and weather-resistant aluminum single panels includes the following steps: Step S1: Pretreatment of aluminum single-panel substrate: Select the formed aluminum single-panel substrate, smooth it with mechanical grinding, and ultrasonically degrease and clean it with a neutral degreasing agent for 8-12 minutes at a cleaning temperature of 40-50℃. Then, use a 5%-8% sodium hydroxide solution for alkaline micro-etching at an etching temperature of 25-30℃ for 30-60 seconds. After rinsing with deionized water, activate it with a low-temperature plasma treatment of 80-120W for 3-5 minutes to obtain an activated and clean aluminum single-panel substrate. Step S2, Composite Passivation Treatment: The pretreated aluminum single-panel substrate is immersed in a zirconium-titanium composite passivation solution for passivation treatment. The passivation temperature is 35-45℃, and the passivation time is 8-15 minutes. After rinsing and drying, a dense inorganic composite passivation transition film is formed on the surface of the aluminum single-panel substrate. The zirconium-titanium composite passivation solution is composed of the following raw materials in parts by weight: 4-8 parts of fluorozirconic acid, 2-5 parts of potassium titanate, 1-2 parts of organosilicon coupling agent, 0.5-1 parts of corrosion inhibitor, and 85-92 parts of deionized water. Step S3, Gradient Composite Coating Application: A dust-free electrostatic spraying process is used, with two layers of gradient composite coating applied. Step S31, Applying Weather-Resistant Primer: Uniformly spray a fluorocarbon weather-resistant primer onto the passivation film surface of the aluminum single-panel substrate. The spray thickness is 15-20 μm. After spraying, allow it to stand for 3-5 minutes to level. It has high adhesion and UV aging resistance. The fluorocarbon weather-resistant primer is a PVDF fluorocarbon resin primer with a solid content of 55%-60%. Step S32, Spraying a hydrophobic topcoat: Spray a nano-modified fluorosilicone hydrophobic topcoat onto the leveled primer surface, with a spray thickness of 8-12 μm. After spraying, allow it to stand for 3-5 minutes to level. It has superhydrophobic properties, is hydrophobic and oil-transferring, resists water stains and rain streaks, and has self-cleaning properties. The nano-modified fluorosilicone hydrophobic topcoat is composed of the following raw materials in parts by weight: 35-45 parts of fluorosilicone resin, 8-12 parts of modified nano silica, 3-5 parts of perfluorinated hydrophobic additive, 2-3 parts of curing agent, and 35-50 parts of organic solvent.

[0007] Step S4, Segmented Low-Temperature Curing Treatment: The coated aluminum single-panel substrate is cured using a segmented low-temperature curing process. First, pre-curing is performed, with the temperature controlled at 80-90℃ and held for 15-20 minutes to allow the coating to initially set and the solvent to fully evaporate. Then, the temperature is raised to 110-120℃ and kept constant for 30-40 minutes to promote the cross-linking reaction of coating molecules and fill the micro-nano pores of the substrate. After curing, the substrate is naturally cooled to room temperature to obtain a highly hydrophobic weather-resistant aluminum single-panel.

[0008] Step S5, Finished Product Inspection: The obtained high hydrophobic weather-resistant aluminum single panel is inspected on an optical contact angle measuring instrument, and samples are taken for UV aging resistance test and neutral salt resistance test.

[0009] Furthermore, in step S1, mechanical polishing is performed by progressively polishing with 800-1200# waterproof sandpaper.

[0010] Furthermore, in step S2, the passivation temperature is controlled at 35-45℃, the passivation time is 8-15 min, the passivation film thickness is 0.8-1.5 μm, the drying temperature is 60-70℃, and the drying time is 10-15 min.

[0011] Furthermore, in step S3, the temperature of the spraying environment is 22-28℃ and the humidity is 40-60%RH.

[0012] Further, in step S32, the modified nano-silica is a silane coupling agent modified powder with a particle size of 20-50 nm.

[0013] Furthermore, in step S4, the segmented low-temperature curing process is carried out in a constant-temperature tunnel curing oven.

[0014] Furthermore, the prepared highly hydrophobic weather-resistant aluminum single panel exhibits superhydrophobic properties (water contact angle WCA: 152-160°, roll-off angle SA≤5°), coating adhesion grade 0, and after UV aging test (duration ≥6000h) and neutral salt resistance test (duration ≥5000h), the surface remains intact, demonstrating excellent UV aging resistance and salt spray corrosion resistance.

[0015] Furthermore, this highly hydrophobic and weather-resistant aluminum single panel is suitable for surface protection and decoration of building curtain walls, outdoor decoration projects, rail transit, and municipal outdoor facilities.

[0016] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention constructs a multi-layer integrated protection system consisting of a micro-nano structured substrate, an inorganic composite passivation transition layer, and an organic weather-resistant hydrophobic composite coating. The hierarchical structure has strong adaptability, achieving a progressive improvement in anti-corrosion, weather resistance, and hydrophobic properties from the substrate to the surface layer, thus solving the problems of single-layer coating performance and weak interlayer bonding in traditional single-layer coatings.

[0017] 2. This invention uses a micro-nano rough structure and nano-fluorosilicone modification to achieve superhydrophobic properties, which allows rainwater, oil stains and dust to slide off automatically, and has a long-lasting self-cleaning function; zirconium titanium passivation and fluorocarbon fluorosilicone composite coating work together to improve weather resistance, and no cracking or peeling is observed in high and low temperature cycle tests, and the weather resistance life far exceeds that of products made by traditional processes.

[0018] 3. This invention uses low-temperature processing throughout the entire process, without high-temperature sintering, which greatly reduces energy consumption and avoids deformation and performance degradation of the aluminum substrate. The pretreatment, passivation, coating and curing processes are closely connected, with high automation adaptability, making it suitable for large-scale mass production. The passivation system is free of heavy metals, making it green and environmentally friendly, and in line with national environmental protection production standards.

[0019] 4. The coating of this invention has strong adhesion and excellent wear resistance. After long-term wind and sand erosion and rain immersion, its hydrophobicity and weather resistance do not significantly decrease, greatly extending the product's maintenance-free period and significantly reducing the later operation and maintenance costs of outdoor projects. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the surface treatment process for highly hydrophobic and weather-resistant aluminum single-panel proposed in this invention. Figure 2 This is a flowchart illustrating step S3 of a highly hydrophobic and weather-resistant aluminum single-panel surface treatment process proposed in this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example

[0022] Reference Figure 1-2 As shown, a surface treatment process for highly hydrophobic and weather-resistant aluminum single panels includes the following specific steps: Step S1, Pretreatment of aluminum single-panel substrate: Select the formed aluminum single-panel substrate, use 800#, 900#, and 1000# waterproof sandpaper to mechanically grind it flat step by step, use a neutral degreaser for ultrasonic degreasing and cleaning for 8 minutes at a cleaning temperature of 40℃, use a 5% sodium hydroxide solution for alkaline micro-etching at an etching temperature of 25℃ for 30 seconds, rinse with deionized water, and then use 80W low-temperature plasma activation treatment for 3 minutes to obtain an activated and clean aluminum single-panel substrate; Step S2, Composite Passivation Treatment: The pretreated aluminum single-panel substrate is immersed in a zirconium-titanium composite passivation solution for passivation treatment. The passivation temperature is controlled at 35℃ and the passivation time is 8 minutes. The passivation film thickness is 0.8 μm. The drying temperature is 60℃ and the drying time is 10 minutes. After rinsing and drying, a dense inorganic composite passivation transition film is formed on the surface of the aluminum single-panel substrate. The zirconium-titanium composite passivation solution is composed of the following raw materials in parts by weight: 4 parts fluorozirconic acid, 2 parts potassium titanate, 1.5 parts organosilicon coupling agent, 0.5 parts corrosion inhibitor, and 92 parts deionized water. Step S3, Gradient Composite Coating Application: A dust-free electrostatic spraying process is used, with two layers of gradient composite coating applied. The spraying environment temperature is 22℃ and the ambient humidity is 40%RH. Step S31, Applying Weather-Resistant Primer: Uniformly spray a fluorocarbon weather-resistant primer onto the passivation film surface of the aluminum single-panel substrate. The coating thickness is 15µm. After spraying, allow it to stand for 3 minutes to level. It exhibits high adhesion and resistance to ultraviolet aging. The fluorocarbon weather-resistant primer is a PVDF fluorocarbon resin primer with a solid content of 55%. Step S32, Spraying a hydrophobic topcoat: Spray a nano-modified fluorosilicone hydrophobic topcoat onto the leveled primer surface. The spray thickness is 8 μm. After spraying, allow it to stand for 3 minutes to level. It has superhydrophobic properties, is hydrophobic and oil-transferring, resists water stains and rain streaks, and has self-cleaning properties. The nano-modified fluorosilicone hydrophobic topcoat is composed of the following raw materials in parts by weight: 36 parts of fluorosilicone resin, 9 parts of modified nano silica, 3 parts of perfluorinated hydrophobic additive, 2 parts of curing agent, and 50 parts of organic solvent. The modified nano silica is a silane coupling agent modified powder with a particle size of 25 nm.

[0023] Step S4, Segmented Low-Temperature Curing Treatment: The coated aluminum single-panel substrate is cured in a constant temperature tunnel curing oven using a segmented low-temperature curing process. First, pre-curing is performed, with the temperature controlled at 80℃ and held for 15 minutes to allow the coating to initially set and the solvent to fully evaporate. Then, the temperature is raised to 110℃ and kept constant for 30 minutes to promote the cross-linking reaction of coating molecules and fill the micro-nano pores of the substrate. After curing, the substrate is naturally cooled to room temperature to obtain a highly hydrophobic weather-resistant aluminum single-panel.

[0024] Step S5, Finished Product Inspection: The obtained high hydrophobic weather-resistant aluminum single panel is inspected on an optical contact angle measuring instrument, and samples are taken for UV aging resistance test and neutral salt resistance test.

[0025] The prepared highly hydrophobic weather-resistant aluminum single panel exhibits superhydrophobic properties (water contact angle WCA: 156°, roll-off angle SA: 3.6°), with a coating adhesion grade of 0. After UV aging test (duration: 4600h), there was no chalking or fading, and the surface remained intact. After salt spray corrosion test (duration: 3200h), there were no corrosion spots. After 500 cycles of high and low temperature (-30℃-60℃), there was no cracking or peeling, demonstrating excellent UV aging resistance and salt spray corrosion resistance. Example

[0026] Reference Figure 1-2 As shown, a surface treatment process for highly hydrophobic and weather-resistant aluminum single panels includes the following specific steps: Step S1, Pretreatment of aluminum single-panel substrate: Select the formed aluminum single-panel substrate, use 900#, 1000#, and 1100# waterproof sandpaper to mechanically grind it flat step by step, use a neutral degreaser for ultrasonic degreasing and cleaning for 10 minutes at a cleaning temperature of 45℃, use a 7% sodium hydroxide solution for alkaline micro-etching at an etching temperature of 28℃ for 45 seconds, rinse with deionized water, and then use 100W low-temperature plasma activation treatment for 4 minutes to obtain an activated and clean aluminum single-panel substrate; Step S2, Composite Passivation Treatment: The pretreated aluminum single-panel substrate is immersed in a zirconium-titanium composite passivation solution for passivation treatment. The passivation temperature is controlled at 40℃ and the passivation time is 12min. The passivation film thickness is 1.2um. The drying temperature is 65℃ and the drying time is 12min. After rinsing and drying, a dense inorganic composite passivation transition film is formed on the surface of the aluminum single-panel substrate. The zirconium-titanium composite passivation solution is composed of the following raw materials in parts by weight: 6 parts of fluorozirconic acid, 3 parts of potassium titanate, 2 parts of organosilicon coupling agent, 1 part of corrosion inhibitor, and 88 parts of deionized water. Step S3, Gradient Composite Coating Application: A dust-free electrostatic spraying process is used, with two layers of gradient composite coating applied. The spraying environment temperature is 25℃ and the ambient humidity is 50%RH. Step S31, Applying Weather-Resistant Primer: Uniformly spray a fluorocarbon weather-resistant primer onto the passivation film surface of the aluminum single-panel substrate. The coating thickness is 17µm. After spraying, allow it to stand for 4 minutes to level. It exhibits high adhesion and resistance to ultraviolet aging. The fluorocarbon weather-resistant primer is a PVDF fluorocarbon resin primer with a solid content of 58%. Step S32, Spraying a hydrophobic topcoat: Spray a nano-modified fluorosilicone hydrophobic topcoat onto the leveled primer surface. The spray thickness is 10 μm. After spraying, allow it to stand for 4 minutes to level. It has superhydrophobic properties, is hydrophobic and oil-transferring, resists water stains and rain streaks, and has self-cleaning properties. The nano-modified fluorosilicone hydrophobic topcoat is composed of the following raw materials in parts by weight: 40 parts of fluorosilicone resin, 10 parts of modified nano silica, 5 parts of perfluorinated hydrophobic additive, 3 parts of curing agent, and 42 parts of organic solvent. The modified nano silica is a silane coupling agent modified powder with a particle size of 35 nm.

[0027] Step S4, Segmented Low-Temperature Curing Treatment: The coated aluminum single-panel substrate is cured in a constant temperature tunnel curing oven using a segmented low-temperature curing process. First, pre-curing is performed, with the temperature controlled at 85℃ and held for 18 minutes to allow the coating to initially set and the solvent to fully evaporate. Then, the temperature is raised to 115℃ and kept constant for 35 minutes to promote the cross-linking reaction of coating molecules and fill the micro-nano pores of the substrate. After curing, the substrate is naturally cooled to room temperature to obtain a highly hydrophobic weather-resistant aluminum single-panel.

[0028] Step S5, Finished Product Inspection: The obtained high hydrophobic weather-resistant aluminum single panel is inspected on an optical contact angle measuring instrument, and samples are taken for UV aging resistance test and neutral salt resistance test.

[0029] The prepared highly hydrophobic weather-resistant aluminum single panel exhibits superhydrophobic properties (water contact angle WCA: 152°, roll-off angle SA: 2.4°), coating adhesion grade 0, and after UV aging test (duration: 5200), it showed no chalking or fading, and the surface remained intact. After salt spray corrosion test (duration: 4000h), it showed no corrosion spots. After 500 cycles of high and low temperature (-40℃-80℃), it showed no cracking or peeling, demonstrating excellent UV aging resistance and salt spray corrosion resistance. Example

[0030] Reference Figure 1-2 As shown, a surface treatment process for highly hydrophobic and weather-resistant aluminum single panels includes the following specific steps: Step S1, Pretreatment of aluminum single-panel substrate: Select the formed aluminum single-panel substrate, use 1000#, 1100#, and 1200# waterproof sandpaper to mechanically grind it flat step by step, use a neutral degreaser to ultrasonically degrease and clean it for 12 minutes at a cleaning temperature of 50℃, use an 8% sodium hydroxide solution to perform alkaline micro-etching at an etching temperature of 30℃ for 60 seconds, rinse with deionized water, and then use 120W low-temperature plasma activation treatment for 5 minutes to obtain an activated and clean aluminum single-panel substrate; Step S2, Composite Passivation Treatment: The pretreated aluminum single-panel substrate is immersed in a zirconium-titanium composite passivation solution for passivation treatment. The passivation temperature is controlled at 45℃ and the passivation time is 15min. The passivation film thickness is 1.5um. The drying temperature is 70℃ and the drying time is 15min. After rinsing and drying, a dense inorganic composite passivation transition film is formed on the surface of the aluminum single-panel substrate. The zirconium-titanium composite passivation solution is composed of the following raw materials in parts by weight: 8 parts of fluorozirconic acid, 5 parts of potassium titanate, 2 parts of organosilicon coupling agent, 1 part of corrosion inhibitor, and 84 parts of deionized water. Step S3, Gradient Composite Coating Application: A dust-free electrostatic spraying process is used, with two layers of gradient composite coating applied. The spraying environment temperature is 28℃ and the ambient humidity is 60%RH. Step S31: Applying weather-resistant primer: Uniformly spray fluorocarbon weather-resistant primer onto the passivation film surface of the aluminum single-panel substrate, with a spray thickness of 20µm. After spraying, allow it to stand for 5 minutes to level, exhibiting high adhesion and resistance to ultraviolet aging. The fluorocarbon weather-resistant primer is a PVDF fluorocarbon resin primer with a solid content of 60%. Step S32, Spraying a hydrophobic topcoat: Spray a nano-modified fluorosilicone hydrophobic topcoat onto the leveled primer surface. The spray thickness is 12 μm. After spraying, allow it to stand for 5 minutes to level. It has superhydrophobic properties, is hydrophobic and oil-transferring, resists water stains and rain streaks, and has self-cleaning properties. The nano-modified fluorosilicone hydrophobic topcoat is composed of the following raw materials in parts by weight: 45 parts of fluorosilicone resin, 12 parts of modified nano silica, 5 parts of perfluorinated hydrophobic additive, 3 parts of curing agent, and 35 parts of organic solvent. The modified nano silica is a silane coupling agent modified powder with a particle size of 50 nm.

[0031] Step S4, Segmented Low-Temperature Curing Treatment: The coated aluminum single-panel substrate is cured in a constant temperature tunnel curing oven using a segmented low-temperature curing process. First, pre-curing is performed, with the temperature controlled at 90℃ and held for 20 minutes to allow the coating to initially set and the solvent to fully evaporate. Then, the temperature is raised to 120℃ and kept constant for 40 minutes to promote the cross-linking reaction of coating molecules and fill the micro-nano pores of the substrate. After curing, the substrate is naturally cooled to room temperature to obtain a highly hydrophobic weather-resistant aluminum single-panel.

[0032] Step S5, Finished Product Inspection: The obtained high hydrophobic weather-resistant aluminum single panel is inspected on an optical contact angle measuring instrument, and samples are taken for UV aging resistance test and neutral salt resistance test.

[0033] The prepared highly hydrophobic weather-resistant aluminum single panel exhibits superhydrophobic properties (water contact angle WCA: 160°, roll-off angle SA≤4.8°), coating adhesion grade 0, and after UV aging test (duration: 4000), it showed no chalking or fading, and the surface remained intact. It also showed no corrosion spots after salt spray corrosion (duration: 3000h). After 500 cycles of high and low temperature (-20℃-40℃), it showed no cracking or peeling, demonstrating excellent UV aging resistance and salt spray corrosion resistance.

[0034] Comparative Example 1 (Traditional Fluorocarbon Coating Process): The process employs traditional fluorocarbon spraying technology for aluminum panels, involving only simple degreasing and cleaning, followed by a single-layer fluorocarbon coating that is cured at 180℃. Product testing revealed: a water contact angle of 92°, no self-cleaning ability; slight powdering after 3600 hours of UV aging, and localized corrosion after 2800 hours of salt spray corrosion; coating adhesion grade 1, prone to fine peeling after long-term temperature changes.

[0035] Comparative Example 2 (Ordinary hydrophobic modified spraying process): Conventional pretreatment was used, followed by single hydrophobic fluorosilicone coating spraying and conventional high-temperature curing. Finished product testing: The initial water contact angle was 135°, but after 300 abrasion rinsing cycles, the contact angle dropped to 102°, indicating a significant decrease in hydrophobicity; slight chalking occurred after 3800 hours of UV aging, and fading occurred after 2700 hours of salt spray corrosion, indicating weak interlayer adhesion and localized delamination after thermal cycling.

[0036] Comparing Examples 1-3 with Comparative Examples 1-2, it can be seen that the process of the present invention (Examples 1-3) can produce aluminum single panels with stable superhydrophobicity, high adhesion, long-term weather resistance, corrosion resistance and resistance to temperature change cracking compared with traditional fluorocarbon spraying (Comparative Example 1) and ordinary single-layer hydrophobic fluorosilicone spraying (Comparative Example 2).

[0037] Comparison of hydrophobic and self-cleaning performance: Comparative Example 1: The water contact angle of the traditional fluorocarbon coating is only 92°, and it does not have superhydrophobicity and self-cleaning ability; Comparative Example 2: The initial contact angle of the ordinary hydrophobic process is 135°, but the hydrophobic durability is poor, and the hydrophobic performance decays rapidly after wear and erosion; In contrast, Examples 1-3 use nano-modified silica and perfluorinated hydrophobic additives to construct a surface micro-nano rough low surface energy structure, and use a gradient coating structure to protect the surface hydrophobic functional layer. The water contact angle is >150° and the roll-off angle is <5°, which meets the superhydrophobic standard and stably achieves the self-cleaning effect.

[0038] Comparison of coating interface adhesion: Comparative Example 1 has an adhesion of only level 1 and is prone to peeling under long-term temperature changes; Comparative Example 2 has only a single layer of hydrophobic coating with weak interlayer adhesion and local delamination after thermal cycling; In contrast, Examples 1-3 use step-by-step grinding, alkaline etching, and low-temperature plasma activation to improve the surface activity of the substrate. The zirconium-titanium composite passivation film serves as an inorganic transition layer to eliminate the interfacial stress between the aluminum substrate and the organic coating. The gradient structure of the fluorocarbon weather-resistant primer and the fluorosilicone topcoat achieves interfacial compatibility. Segmented low-temperature curing avoids internal stress caused by high temperature, resulting in a stable coating adhesion of level 0. The coating does not crack or peel after 500 high and low temperature cycles.

[0039] Comparison of UV aging resistance: Comparative Example 1 showed slight chalking after 3600h of UV aging resistance test, and Comparative Example 2 showed slight chalking after 3800h of UV aging resistance test; Examples 1-3 used a bottom layer of PVDF fluorocarbon resin combined with a top layer of fluorosilicone resin and modified nano-silica to form a synergistic UV-resistant system, which greatly improved the outdoor aging resistance. In the UV aging resistance test (time: 4000-5200h), the coating was intact, without chalking or fading.

[0040] Comparison of salt spray corrosion resistance: Traditional fluorocarbon process (Comparative Example 1) showed localized corrosion under 2800h salt spray corrosion test, and ordinary hydrophobic spraying (Comparative Example 2) showed fading and weak interlayer bonding under 2700h salt spray corrosion test; while Examples 1-3 used zirconium titanium passivated inorganic film to block the penetration of corrosive media, and the double-layer composite coating formed multiple barriers, which significantly improved the corrosion resistance of aluminum single panel. Therefore, the salt spray corrosion resistance test can reach 3000-4000h without corrosion spots.

[0041] In summary, this invention overcomes the performance bottlenecks of existing technologies through innovative micro-nano structured pretreatment, zirconium-titanium composite passivation transition, fluorosilicone gradient composite coating, and segmented low-temperature curing integrated process, achieving three core technological breakthroughs: First, it solves the problems of poor wear resistance and easy failure of traditional hydrophobic coatings by physically anchoring the substrate through micro-nano structures, significantly improving coating stability; second, it solves the problem that traditional coatings cannot simultaneously achieve both weather resistance and hydrophobicity, with gradient coatings achieving layered functional adaptation; third, it solves the problems of high energy consumption at high temperatures, easy substrate deformation, and poor environmental performance of traditional processes, with low-temperature green processes suitable for large-scale production. The highly hydrophobic weather-resistant aluminum single-layer panels prepared by this invention exhibit superhydrophobic properties, with comprehensive performance far exceeding industry standards, and have broad market prospects.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A surface treatment process for highly hydrophobic and weather-resistant aluminum single panels, characterized in that, Includes the following steps: Step S1: Pretreatment of aluminum single-panel substrate: Select the formed aluminum single-panel substrate, smooth it with mechanical grinding, and ultrasonically degrease and clean it with a neutral degreasing agent for 8-12 minutes at a cleaning temperature of 40-50℃. Then, use a 5%-8% sodium hydroxide solution for alkaline micro-etching at an etching temperature of 25-30℃ for 30-60 seconds. After rinsing with deionized water, activate it with a low-temperature plasma treatment of 80-120W for 3-5 minutes to obtain an activated and clean aluminum single-panel substrate. Step S2, Composite passivation treatment: The pretreated aluminum single-panel substrate is immersed in zirconium-titanium composite passivation solution for passivation treatment. After rinsing and drying, a dense inorganic composite passivation transition film is formed on the surface of the aluminum single-panel substrate. The zirconium-titanium composite passivation solution is composed of the following raw materials in parts by weight: 4-8 parts of fluorozirconic acid, 2-5 parts of potassium titanate, 1-2 parts of organosilicon coupling agent, 0.5-1 part of corrosion inhibitor, and 85-92 parts of deionized water. Step S3, Gradient Composite Coating Application: A dust-free electrostatic spraying process is used, with two layers of gradient composite coating applied. Step S31, Applying Weather-Resistant Primer: Uniformly spray a fluorocarbon weather-resistant primer onto the passivation film surface of the aluminum single-panel substrate. The spray thickness is 15-20 μm. After spraying, allow it to stand for 3-5 minutes to level. It has high adhesion and UV aging resistance. The fluorocarbon weather-resistant primer is a PVDF fluorocarbon resin primer with a solid content of 55%-60%. Step S32, Spraying a hydrophobic topcoat: Spray a nano-modified fluorosilicone hydrophobic topcoat onto the leveled primer surface, with a spray thickness of 8-12 μm. After spraying, allow it to stand for 3-5 minutes to level. It has superhydrophobic properties, is hydrophobic and oil-transferring, resists water stains and rain streaks, and has self-cleaning properties. The nano-modified fluorosilicone hydrophobic topcoat is composed of the following raw materials in parts by weight: 35-45 parts of fluorosilicone resin, 8-12 parts of modified nano silica, 3-5 parts of perfluorinated hydrophobic additive, 2-3 parts of curing agent, and 35-50 parts of organic solvent. Step S4, Segmented Low-Temperature Curing Treatment: The coated aluminum single-panel substrate is cured using a segmented low-temperature curing process. First, pre-curing is performed, with the temperature controlled at 80-90℃ and held for 15-20 minutes to allow the coating to initially set and the solvent to fully evaporate. Then, the temperature is raised to 110-120℃ and kept constant for 30-40 minutes to promote the cross-linking reaction of coating molecules and fill the micro-nano pores of the substrate. After curing, the substrate is naturally cooled to room temperature to obtain a highly hydrophobic weather-resistant aluminum single-panel. Step S5, Finished Product Inspection: The obtained high hydrophobic weather-resistant aluminum single panel is inspected on an optical contact angle measuring instrument, and samples are taken for UV aging resistance and neutral salt resistance tests.

2. The surface treatment process for highly hydrophobic and weather-resistant aluminum single panels according to claim 1, characterized in that, In step S1, mechanical polishing is performed by using 800-1200# waterproof sandpaper for progressive polishing.

3. The surface treatment process for highly hydrophobic and weather-resistant aluminum single panels according to claim 1, characterized in that, In step S2, the passivation temperature is controlled at 35-45℃, the passivation time is 8-15 min, the passivation film thickness is 0.8-1.5 μm, the drying temperature is 60-70℃, and the drying time is 10-15 min.

4. The surface treatment process for highly hydrophobic and weather-resistant aluminum single panels according to claim 1, characterized in that, In step S3, the temperature of the spraying environment is 22-28℃ and the humidity is 40-60%RH.

5. The surface treatment process for highly hydrophobic and weather-resistant aluminum single-panel according to claim 1, characterized in that, In step S32, the modified nano-silica is a silane coupling agent modified powder with a particle size of 20-50 nm.

6. The surface treatment process for highly hydrophobic and weather-resistant aluminum single panels according to claim 1, characterized in that, In step S4, the segmented low-temperature curing process is carried out in a constant-temperature tunnel curing oven.

7. The surface treatment process for highly hydrophobic and weather-resistant aluminum single panels according to claim 1, characterized in that, The prepared highly hydrophobic weather-resistant aluminum single panel exhibits superhydrophobic properties (water contact angle WCA: 152-160°, roll-off angle SA≤5°), coating adhesion grade 0, and after UV aging test (duration ≥3500h) and neutral salt resistance test (duration ≥2500h), the surface remains intact, demonstrating excellent UV aging resistance and salt spray corrosion resistance.

8. A highly hydrophobic weather-resistant aluminum veneer prepared by any one of the processing methods described in claims 1-7, characterized in that, This highly hydrophobic and weather-resistant aluminum single panel is suitable for surface protection and decoration of building curtain walls, outdoor decoration projects, rail transit, and municipal outdoor facilities.

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