Broken bridge aluminum profile surface anti-corrosion coating technology for curtain wall, broken bridge aluminum profile and building curtain wall system

Abstract

The invention relates to a broken bridge aluminum profile surface anti-corrosion coating technology for a curtain wall, a broken bridge aluminum profile and a building curtain wall system, and belongs to the technical field of building curtain wall materials, the broken bridge aluminum profile surface anti-corrosion coating technology comprises the following steps that S1, surface pretreatment is conducted, specifically, an alkaline cleaning agent and ultrasonic-assisted cleaning are adopted, and micro roughness is formed in combination with sand blasting treatment; s2, chromium-free conversion film treatment: immersing into zirconium-titanium salt chromium-free conversion liquid to form a dense film; s3, coating a nano modified priming coat, and spraying nano ceramic particle modified epoxy resin; s4, coating of a floating coat: coating of a flexible polyester floating coat; s5, coating a fluorocarbon surface coating, and electrostatically spraying the PVDF fluorocarbon surface coating; s6, staged gradient curing is conducted; and S7, performing performance inspection and defect repair. The process improves the binding force and the corrosion resistance of the coating, avoids the harm of chromate, is suitable for a building curtain wall system, and improves the durability and the environmental protection property of the profile.

Description

Technical Field

[0001] This application belongs to the technical field of building curtain wall materials, specifically relating to a surface anti-corrosion coating process for thermally broken aluminum profiles for curtain walls, as well as thermally broken aluminum profiles and building curtain wall systems. Background Technology

[0002] Due to its high strength, light weight, and ease of forming, thermally broken aluminum profiles have become the main frame material for modern curtain walls. However, curtain walls are exposed to wind, rain, ultraviolet radiation, industrial atmospheres, and large temperature differences between day and night for extended periods. Therefore, their surface protective layer must possess high corrosion resistance, high weather resistance, and a lifespan of over thirty years. Currently, the industry commonly uses anodizing or electrostatic powder coating: anodized films are thin and brittle, prone to micro-cracks under complex stress, and residual pores in the sealing layer become sources of pitting corrosion; epoxy / polyester powder coatings offer good decorative properties, but their UV resistance is insufficient, showing chalking, loss of gloss, and discoloration within 3-5 years, making them unsuitable for the harsh environments of super high-rise buildings or coastal areas. More importantly, traditional corrosion-resistant undercoats still rely on chromate conversion films, Cr... 6+ High ion toxicity, expensive wastewater treatment, low membrane density and poor adhesion leading to easy peeling after long-term use, long process flow, high energy consumption, and large batch fluctuations no longer conform to the development direction of green environmental protection and intelligent manufacturing. Therefore, developing chromium-free, high-performance aluminum profile surface treatment technology with controllable process and matching thermal-mechanical load of curtain wall structure has become an urgent pain point to be solved. Summary of the Invention

[0003] To solve the above problems, the technical solution adopted in this application is: In a first aspect, this application provides a surface anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls, comprising the following steps: Step S1, Surface pretreatment: The surface of the thermally broken aluminum profile is cleaned and degreased using an alkaline cleaning agent and ultrasonic-assisted cleaning, followed by sandblasting to form micro-roughness. Step S2, Chromium-free conversion coating treatment: Immerse the pretreated thermally broken aluminum profile in a chromium-free conversion solution mainly composed of zirconium-titanium salt to form a dense chromium-free conversion coating. Step S3, Nano-modified primer coating: Spray a layer of epoxy resin primer modified with nano-ceramic particles (such as silicon dioxide or aluminum oxide) onto the chromium-free conversion film; Step S4, Intermediate Coating Application: Apply a flexible polyester intermediate coating layer onto the cured base coating; Step S5, Fluorocarbon Topcoat Application: Electrostatically spray at least one layer of polyvinylidene fluoride (PVDF) fluorocarbon topcoat onto the intermediate coating layer; Step S6, Staged Gradient Curing: The coated profile is cured by staged temperature increases; Step S7, Performance Inspection and Defect Repair: Perform quality inspection on the cured coating.

[0004] Furthermore, in step S1, the optimal surface roughness Ra of the profile after sandblasting, the profile substrate wall thickness δ, and the total design coating thickness H satisfy the following relationship: , Where k is the process coefficient, ranging from 0.8 to 1.2, and Ra is in μm; The sandblasting process employs a pulsating negative pressure supersonic nozzle, generating a 50-80kHz pulsating jet at 0.4MPa, which creates a gradient micro-pit array along the thickness direction to form a mechanically anchored-chemically bonded dual-synergistic interface. Simultaneously, an online laser scattering roughness meter collects Ra data in real time, providing closed-loop feedback to the spray gun's air pressure servo valve. The Ra deviation is ≤±0.05μm, enabling adaptive locking of the roughness process window.

[0005] Furthermore, in step S2, the treatment time t and treatment temperature T of the chromium-free conversion film follow the Arrhenius kinetic model, and their relationship satisfies: , Where A is the pre-exponential factor, ranging from 0.5 to 2.0 min; Ea is the activation energy of the reaction, ranging from 35 to 45 kJ / mol; and R is the ideal gas constant. The conversion solution is a dicationic sol (Zr). 4+ -Ti 4+ Rare earth cerium corrosion-inhibiting microspheres (particle size 80-120nm, shell layer CeO2, core layer SiO2), with a microsphere addition amount of 0.3-0.8g / L, can reduce Ea by 8-12kJ / mol at a low temperature of 20℃, achieving rapid film formation at room temperature; The online electrochemical impedance microprobe collects the membrane resistance Rp every second. When Rp ≥ 1.5 MΩ·cm², the impregnation is automatically terminated to avoid over-etching, and the membrane weight is controlled at 0.8-1.2 g / m².

[0006] Furthermore, in step S3, the nano-ceramic particles are silicon dioxide or aluminum oxide, and their optimal addition amount ω is related to the particle size d of the nanoparticles and the dry film thickness hb of the undercoat, and satisfies: , Where α is the dispersion coefficient, ranging from 0.1 to 0.3, and β is the baseline addition amount, ranging from 1 to 3; Among them, the nano-ceramic particles have a core-shell structure, with a core size of 30 nm and a shell size of 5 nm. The shell layer is grafted with vinyltriethoxysilane, which can form covalent bridges with epoxy groups. The surface grafting rate of the nano-ceramic particles is ≥15%. Employing an ultrasonic-high-speed shear dual dispersion chamber, with an instantaneous shear rate of 40,000 s.-1 This ensures that the secondary agglomerate particle size D50 ≤ 60 nm and the scattering factor ≤ 0.15, guaranteeing that the transparent topcoat does not fog up; The online dynamic light scattering DLS probe provides real-time feedback ω correction, with an added error of ≤±0.05%.

[0007] Furthermore, in step S4, the thickness hm of the coating in the flexible polyester is proportional to the maximum cross-sectional width W of the profile, in order to counteract the internal stress caused by thermal expansion and contraction. The relationship is as follows: , Wherein, γ is the stress buffer coefficient, with a value ranging from 3 to 5. ; The intermediate coating is a dynamic reversible polyurethane-polysiloxane block, with a storage modulus change of <10% in the range of -40℃ to +80℃, which can offset the 0.12% difference in aluminum thermal expansion. The coating incorporates thermochromic microcapsules, allowing on-site infrared thermal imagers to non-contactly determine whether the stress in the intermediate coating exceeds limits through color changes, thus enabling visualization of service health.

[0008] Furthermore, in the staged gradient curing of step S6, the heating rate V1 of the first stage is inversely proportional to the final total coating thickness H, determined by the following empirical formula: , Wherein, λ is the heating coefficient, with a value ranging from 150 to 250℃·μm / min, to prevent rapid solvent evaporation from causing pinhole defects in the coating; The curing oven employs a segmented magnetic levitation hot air circulation combined with near-infrared auxiliary heating, and the specific steps include the following sub-steps: 0-60s: Near-infrared 2-4µm band, penetration depth 15-20µm, surface solvent flash evaporation, hot air velocity 0.5m / s; From 60 to 180 seconds: the hot air temperature increases in a stepwise manner, and the wind speed decreases by 0.1 m / s every 20 seconds to reduce surface pinholes; The online laser interferometer measures the thermal expansion coefficient of the coating surface in real time. When the expansion coefficient suddenly changes by more than 5%, it automatically reduces V1 to prevent blistering.

[0009] Furthermore, in step S7, an eddy current thickness gauge is used to detect the coating thickness. The validity of the detection data is determined based on a calibration curve between the thickness ht of the fluorocarbon surface coating and the thickness gauge reading R. This calibration curve satisfies a linear relationship within the interval [20μm, 40μm]. , Among them, the eddy current thickness gauge integrates dual-frequency excitation, which can automatically eliminate background drift caused by batch fluctuations in the conductivity of the aluminum substrate, with a baseline drift of ≤0.3µm; When the measured thickness (ht) deviates from the curve by more than 5%, the AGV automatically sends the profile back to the re-spraying station and links the PLC to lower the electrostatic voltage by 2kV, thereby achieving online closed-loop correction of thickness and voltage.

[0010] Furthermore, in step S5, the resin content of the PVDF fluorocarbon surface coating is not less than 70%, and its weather resistance life prediction model is based on the irradiance data of the Atlas climate test chamber. The relationship between its gloss retention rate G and the cumulative ultraviolet irradiance Q conforms to the following decay curve: , Where G0 is the initial gloss level, θ is the aging rate constant, and the value of θ is no greater than 5.0 × 10⁻⁶. -5 m² / MJ.

[0011] Secondly, this application also provides a thermally broken aluminum profile for curtain walls, manufactured using the aforementioned process, comprising an outdoor aluminum alloy section, an indoor aluminum alloy section, and a thermal break strip connecting the two; the outdoor aluminum alloy section includes a main cavity, a glass mounting groove, and a drainage channel, the main cavity having reinforcing ribs inside, and its wall thickness not less than 2.5mm; the thermal break strip is a multi-chamber structure made of polyamide nylon and glass fiber material, and is connected to the outdoor aluminum alloy section and the indoor aluminum alloy section through a roll forming composite process; the outdoor aluminum alloy section and the indoor aluminum alloy section are made of 6063-T5 or 6061-T6 aluminum alloy.

[0012] Thirdly, this application also provides a building curtain wall system constructed using the aforementioned thermally broken aluminum profiles for curtain walls.

[0013] Compared with the prior art, the beneficial effects of this application are as follows: 1. This application provides a surface anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls. This application employs alkaline cleaning agents and ultrasonic-assisted cleaning, combined with sandblasting, to create microscopic roughness, significantly improving the adhesion between the coating and the substrate. The chromium-free conversion film treatment in this application uses zirconium-titanium salts as the main component, forming a dense chromium-free conversion film, effectively improving the corrosion resistance of the profiles and avoiding the environmental and human health hazards associated with traditional chromate treatments.

[0014] 2. This application provides a surface anti-corrosion coating process for thermally broken aluminum profiles for curtain walls. This application deeply integrates real-time online monitoring and closed-loop feedback control into the entire coating manufacturing process, enabling the process to leap from "experience-driven" to "data and model-driven", achieving precision, stability and efficiency in the production process.

[0015] 3. This application provides a surface anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls. Based on Arrhenius dynamics, stress buffering models, and weathering attenuation curves, this application can scientifically predict process results and product lifespan. Utilizing stress visualization technology for the intermediate coating layer, online diagnosis of the component's service health is achieved. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the coating process flow for this application; Figure 2 This is a schematic diagram of the thermal break aluminum profile structure of this application; Figure 3 This is the main view of the thermally broken aluminum profile in this application; Figure 4 for Figure 3 Sectional view along section AA.

[0017] In the diagram: 1. Outdoor aluminum alloy section, 11. Main cavity, 12. Glass mounting groove, 13. Drainage channel, 14. Reinforcing rib, 2. Indoor aluminum alloy section, 3. Thermal insulation strip, 31. Multi-chamber structure. Detailed Implementation

[0018] The present application will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present application.

[0019] Example 1 like Figures 1 to 4 As shown, this application provides a process for applying an anti-corrosion coating to the surface of thermally broken aluminum profiles for curtain walls. Includes the following steps: Step S1, Surface pretreatment: The surface of the thermally broken aluminum profile is cleaned and degreased using an alkaline cleaning agent and ultrasonic-assisted cleaning, followed by sandblasting to form micro-roughness. Step S2, Chromium-free conversion coating treatment: Immerse the pretreated thermally broken aluminum profile in a chromium-free conversion solution mainly composed of zirconium-titanium salt to form a dense chromium-free conversion coating. Step S3, Nano-modified primer coating: Spray a layer of epoxy resin primer modified with nano-ceramic particles onto the chromium-free conversion film; Step S4, Intermediate Coating Application: Apply a flexible polyester intermediate coating layer onto the cured base coating; Step S5, Fluorocarbon Topcoat Application: Electrostatically spray at least one layer of polyvinylidene fluoride (PVDF) fluorocarbon topcoat onto the intermediate coating layer; Step S6, Staged Gradient Curing: The coated profile is cured by staged temperature increases; Step S7, Performance Inspection and Defect Repair: The cured coating undergoes quality inspection. In this embodiment, the process constructs a complete, multi-level coating system from substrate treatment to final quality inspection. Its core significance lies in establishing a process of "pretreatment → chromium-free conversion → nano-modified primer → flexible intermediate coat → fluorocarbon topcoat → gradient curing → intelligent quality inspection".

[0020] In step S1, the optimal surface roughness Ra of the profile after sandblasting, the profile substrate wall thickness δ, and the total design coating thickness H satisfy the following relationship: , Where k is the process coefficient, ranging from 0.8 to 1.2, and Ra is in μm; The sandblasting process employs a pulsating negative pressure supersonic nozzle, generating a 50-80kHz pulsating jet at 0.4MPa. This creates a gradient micro-pit array along the thickness direction, forming a mechanically anchored and chemically bonded dual-synergistic interface. A synchronous online laser scattering roughness meter collects Ra data in real-time, providing closed-loop feedback to the spray gun's air pressure servo valve. The Ra deviation is ≤±0.05μm, achieving adaptive locking of the roughness process window. With a total coating thickness H=110μm and k=1.1, the target Ra is calculated as 1.1 ×ln(3.5×110) ≈ 6.2μm. The online laser scattering meter monitors the process in real-time, and the air pressure is adjusted via the servo valve to stably control the actual Ra at 6.18μm. This embodiment addresses the technical deficiency of traditional sandblasting roughness settings, which rely on experience and cannot scientifically match the profile wall thickness δ and the total coating system thickness H, leading to unstable adhesion. This application's logarithmic model ensures a scientific correlation between roughness Ra and the profile's "structural load" (δ) and the coating's "macroscopic thickness" (H). Thicker profiles with thicker walls and coatings require greater stress and therefore better adhesion; the model calculates the optimal mechanical anchoring depth. A pulsating negative pressure supersonic nozzle generates a gradient micro-pit array, providing superior mechanical and chemical bonding area compared to conventional sandblasting. An online laser scattering roughness meter with closed-loop feedback enables real-time, precise roughness measurement, transforming theoretical calculations into stable process realities and solving the problem of large Ra value fluctuations in traditional processes.

[0021] In step S2, the treatment time t and treatment temperature T of the chromium-free conversion film follow the Arrhenius kinetic model, and their relationship satisfies: , Where A is the pre-exponential factor, ranging from 0.5 to 2.0 min; Ea is the activation energy of the reaction, ranging from 35 to 45 kJ / mol; and R is the ideal gas constant. The conversion solution is a dicationic sol (Zr). 4+ -Ti 4+ Rare earth cerium corrosion-inhibiting microspheres (particle size 80-120nm, shell layer CeO2, core layer SiO2), with a microsphere addition amount of 0.3-0.8g / L, can reduce Ea by 8-12kJ / mol at a low temperature of 20℃, achieving rapid film formation at room temperature; An online electrochemical impedance spectroscopy (EIS) probe collects the film resistance Rp every second. Immersion is automatically terminated when Rp ≥ 1.5 MΩ·cm² to avoid over-etching, and the film weight is controlled between 0.8-1.2 g / m². A zirconium-titanium conversion solution (pH=3.8, 25℃) containing 0.5 g / L rare earth cerium corrosion-inhibiting microspheres (core-shell structure, CeO2 shell) is prepared. Based on the model, A = 1.2 min, Ea = 37 kJ / mol, and the processing time t ≈ 7.5 minutes is calculated. Online EIS monitoring shows that Rp reaches 1.62 MΩ·cm² at 7 minutes and 20 seconds, at which point the system automatically lifts the profile, and the film weight is measured to be 1.05 g / m². This embodiment solves the technical defects of traditional chromium-free conversion processes, such as slow film formation speed, high energy consumption, and difficulty in accurately controlling film quality (thickness / density), leading to insufficient treatment or over-etching. This application dynamically correlates the processing time t with the temperature T through a kinetic model, providing a scientific basis for process setting rather than a fixed time. More importantly, it provides a theoretical target for achieving rapid film formation at low temperatures. Using rare-earth cerium corrosion-inhibiting microspheres as a catalyst directly reduces the reaction activation energy Ea, enabling the desired reaction rate to be reached rapidly even at room temperature (20℃), significantly saving energy and simplifying equipment. The online electrochemical impedance microprobe automatically terminates the reaction by monitoring the membrane resistance Rp in real time, precisely controlling the quality of the conversion membrane (membrane weight 0.8-1.2 g / m²), fundamentally solving the problem of uneven conversion membrane quality or over-etching caused by "timed processing based on experience."

[0022] In step S3, the nano-ceramic particles are silicon dioxide or aluminum oxide, and their optimal addition amount ω is related to the particle size d of the nanoparticles and the dry film thickness hb of the undercoating layer, and satisfies the following: , Where α is the dispersion coefficient, ranging from 0.1 to 0.3, and β is the baseline addition amount, ranging from 1 to 3; Among them, the nano-ceramic particles have a core-shell structure, with a core size of 30 nm and a shell size of 5 nm. The shell layer is grafted with vinyltriethoxysilane, which can form covalent bridges with epoxy groups. The surface grafting rate of the nano-ceramic particles is ≥15%. Employing an ultrasonic-high-speed shear dual dispersion chamber, with an instantaneous shear rate of 40,000 s. -1 This ensures that the secondary agglomerate particle size D50 ≤ 60 nm and the scattering factor ≤ 0.15, guaranteeing that the transparent topcoat does not fog up; The online dynamic light scattering DLS probe provides real-time feedback correction for ω, with an added error ≤ ±0.05%. A core-shell structured nano-SiO2 (30nm core / 5nm grafted shell) modified epoxy primer was configured, with hb=25μm. Based on the model, α=0.25, β=1.8, and ω=0.25×(25 / 30)+1.8≈2.01%. After ultrasonic-high-speed shear dispersion, online DLS monitoring showed D50=52nm and a scattering factor of 0.12, meeting the requirements. Precise spraying was performed to a dry film thickness of 25μm. This embodiment addresses the technical shortcomings of relying on experience for nanoparticle addition, where excessive addition leads to agglomeration, coating atomization, and stress concentration points, while insufficient addition results in ineffective reinforcement. It utilizes a correlation between the addition amount ω and the base coat thickness hb and nanoparticle size d. This ensures that an optimal number of nanoparticles provide reinforcement at a specific coating thickness while avoiding agglomeration. The hb / d ratio essentially controls the distribution density of nanoparticles in the coating. In this embodiment, chemical bonding (covalent bridging) greatly enhances the interfacial bonding force between nanoparticles and epoxy resin, preventing phase separation and maximizing the enhancement effect.

[0023] In step S4, the thickness hm of the coating in the flexible polyester is proportional to the maximum width W of the profile cross-section to counteract the internal stress caused by thermal expansion and contraction. The relationship is as follows: , Wherein, γ is the stress buffer coefficient, with a value ranging from 3 to 5. ; The intermediate coating is a dynamic reversible polyurethane-polysiloxane block, with a storage modulus change of <10% in the range of -40℃ to +80℃, which can offset the 0.12% difference in aluminum thermal expansion. The coating incorporates thermochromic microcapsules, allowing on-site infrared thermal imagers to non-contactly determine if the intermediate coating stress exceeds limits via color changes, thus achieving visualized service health. Based on the model, γ=4.2, and hm=4.2×√150≈51.5μm is calculated. A dynamic reversible polyurethane-polysiloxane intermediate coating containing thermochromic microcapsules is applied, with the dry film thickness controlled at 52μm. This embodiment addresses the issue that the large size of the curtain wall profiles and the difference in thermal expansion coefficients between aluminum and the coating, leading to significant interfacial thermal stress, are the main causes of coating cracking and peeling. Traditional intermediate coatings have a fixed thickness, failing to adapt to the stress requirements of different profile specifications. The intermediate coating thickness should be proportional to the square root of the profile's characteristic width W. This is an optimization design based on stress analysis, showing that to offset thermal stress, the intermediate coating thickness needs to increase with the profile size, but not linearly; rather, it achieves an optimal balance between buffering effect and material cost. The thermochromic microcapsules enable visualized diagnosis of the coating system's service health. This is a revolutionary advancement that allows for the visual visualization of stress concentration areas in a non-contact manner during construction and maintenance, enabling preventative maintenance.

[0024] In the staged gradient curing of step S6, the heating rate V1 of the first stage is inversely proportional to the final total coating thickness H, which is determined by the following empirical formula: , Wherein, λ is the heating coefficient, with a value ranging from 150 to 250℃·μm / min, to prevent rapid solvent evaporation from causing pinhole defects in the coating; The curing oven employs a segmented magnetic levitation hot air circulation combined with near-infrared auxiliary heating, and the specific steps include the following sub-steps: 0-60s: Near-infrared 2-4µm band, penetration depth 15-20µm, surface solvent flash evaporation, hot air velocity 0.5m / s; From 60 to 180 seconds: the hot air temperature increases in a stepwise manner, and the wind speed decreases by 0.1 m / s every 20 seconds to reduce surface pinholes; An online laser interferometer measures the coefficient of thermal expansion of the coating surface in real time. When the coefficient of expansion changes abruptly by more than 5%, V1 is automatically reduced to prevent blistering. After electrostatic spraying of the PVDF topcoat, the coating enters a composite curing oven. Based on the model V1=λ / H, with λ=220, V1 is calculated to be 2℃ / min. The system executes according to a preset multimodal curing curve: first, it heats up to 65℃ at 2℃ / min for near-infrared preheating; then, it gradually heats up to 115℃ to cure the intermediate and bottom layers; finally, the top layer is cured at 225℃. In the second stage, the online laser interferometer detected a localized change in the coefficient of expansion of 5.8%. The system automatically increased the wind speed in that area by 0.15m / s, successfully preventing blistering. This solves a technical problem: for coatings of different total thicknesses, using a uniform initial heating rate can lead to insufficient curing of thin coatings or pinholes and bubbles in thick coatings due to excessive solvent evaporation. By using segmented magnetic levitation hot air circulation combined with near-infrared assistance, precise and efficient energy input is achieved. Near-infrared is used for rapid surface flash evaporation, while hot air is used for overall heating.

[0025] In step S7, an eddy current thickness gauge is used to detect the coating thickness. The validity of the detection data is determined based on a calibration curve between the thickness ht of the fluorocarbon surface coating and the thickness gauge reading R. This calibration curve satisfies a linear relationship within the interval [20μm, 40μm]. , Among them, the eddy current thickness gauge integrates dual-frequency excitation, which can automatically eliminate background drift caused by batch fluctuations in the conductivity of the aluminum substrate, with a baseline drift of ≤0.3µm; When the measured thickness (ht) deviates from the curve by more than 5%, the AGV automatically returns the profile to the repainting station and, in conjunction with the PLC, lowers the electrostatic voltage by 2kV, achieving online closed-loop correction of thickness and voltage. A dual-frequency eddy current thickness gauge detects one painted area, with a reading R = 32.1μm. The calculated true thickness ht = 0.95 × 32.1 + 1.2 = 31.7μm, within the allowable range of the target 32μm. Another area, with a reading deviation exceeding 5%, is automatically returned by the AGV, and the PLC simultaneously lowers the corresponding spray gun voltage by 1.8kV for repainting, resulting in a successful re-inspection. This embodiment solves a series of defects in eddy current thickness gauge readings, such as the influence of the aluminum substrate's conductivity, leading to systematic errors in direct readings; and the reliance on manual adjustments and repairs after detection, resulting in low efficiency and poor consistency. By using a linear correction curve fitted from experimental data, the systematic errors of the measurement system are eliminated, obtaining the true thickness ht of the coating layer and ensuring the accuracy of the test results.

[0026] In step S5, the resin content of the PVDF fluorocarbon topcoat is not less than 70%, and its weather resistance life prediction model is based on the irradiance data of the Atlas climate test chamber. The relationship between its gloss retention rate G and the cumulative ultraviolet irradiance Q conforms to the following decay curve: , Where G0 is the initial gloss level, θ is the aging rate constant, and the value of θ is no greater than 5.0 × 10⁻⁶. -5 m² / MJ.

[0027] Example 2 This application also provides a thermally broken aluminum profile for curtain walls, which is manufactured using the anti-corrosion coating process described above for thermally broken aluminum profiles for curtain walls; it includes an outdoor aluminum alloy section 1, an indoor aluminum alloy section 2, and a thermal break strip 3 connecting the two; the outdoor aluminum alloy section 1 includes a main cavity 11, a glass mounting groove 12, and a drainage channel 13, and the main cavity 11 is provided with reinforcing ribs 14, and its wall thickness is not less than 2.5mm; the thermal break strip 3 is a multi-chamber structure 31 made of polyamide nylon and glass fiber material, and is connected to the outdoor aluminum alloy section 1 and the indoor aluminum alloy section 2 by a roll forming composite process; the materials of the outdoor aluminum alloy section 1 and the indoor aluminum alloy section 2 are 6063-T5 or 6061-T6 aluminum alloy.

[0028] Example 3 This application also provides a building curtain wall system, which is constructed using the aforementioned thermally broken aluminum profiles for curtain walls, and assembled together with insulated glass, sealant, structural adhesive, and supporting components to form a unitized curtain wall system. This curtain wall system, with its core profile's superior durability and stability, significantly improves the safety performance and service life of the entire building envelope, and substantially reduces subsequent maintenance costs.

[0029] This application provides a surface anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls, integrating micro-roughening, chromium-free conversion, nano-modification, flexible intermediate coating, gradient curing, and online monitoring to significantly improve corrosion resistance, weather resistance, and adhesion. Ultrasonic-pulsating sandblasting and laser scattering provide real-time feedback to lock in roughness; zirconium-titanium salt dual-cationic sol + rare earth microspheres rapidly generate a dense, chromium-free film at room temperature, with an electrochemical impedance probe automatically controlling the film formation endpoint; core-shell nano-ceramics are dispersed via ultrasonic-high-speed shearing + DLS closed-loop dispersion, resulting in high transparency; a flexible polyester intermediate coating embeds thermochromic microcapsules, allowing for stress assessment via on-site thermal imaging; segmented magnetic levitation hot air + near-infrared gradient curing, with real-time expansion monitoring via laser interferometer, eliminates pinholes; dual-frequency eddy current thickness measurement + AGV automatic back-spraying ensures a thickness deviation of <0.3µm. The entire process is chromium-free and energy-efficient. The addition of UV-shielding nanowires to the PVDF surface coating increases gloss retention by 60%. Combined with the heat insulation strip roll-forming composite, the profile U-value is ≤1.2 W / (m²·K), extending the lifespan of the curtain wall system by 30%, achieving green, intelligent, and high-quality manufacturing.

[0030] Of course, the above embodiments are not intended to limit this application, and this application is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this application should also fall within the protection scope of this application.

Claims

1. A corrosion-resistant coating process for the surface of thermally broken aluminum profiles used in curtain walls, characterized in that: Includes the following steps: Step S1, Surface pretreatment: The surface of the thermally broken aluminum profile is cleaned and degreased using an alkaline cleaning agent and ultrasonic-assisted cleaning, followed by sandblasting to form micro-roughness. Step S2, Chromium-free conversion coating treatment: Immerse the pretreated thermally broken aluminum profile in a chromium-free conversion solution mainly composed of zirconium-titanium salt to form a dense chromium-free conversion coating. Step S3, Nano-modified primer coating: Spray a layer of epoxy resin primer modified with nano-ceramic particles onto the chromium-free conversion film; Step S4, Intermediate Coating Application: Apply a flexible polyester intermediate coating layer onto the cured base coating; Step S5, Fluorocarbon Topcoat Application: Electrostatically spray at least one layer of polyvinylidene fluoride (PVDF) fluorocarbon topcoat onto the intermediate coating layer; Step S6, Staged Gradient Curing: The coated profile is cured by staged temperature increases; Step S7, Performance Inspection and Defect Repair: Perform quality inspection on the cured coating.

2. The anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls according to claim 1, characterized in that: In step S1, the optimal surface roughness Ra of the profile after sandblasting, the profile substrate wall thickness δ, and the total design coating thickness H satisfy the following relationship: ， Where k is the process coefficient, ranging from 0.8 to 1.2, and Ra is in μm; The sandblasting process employs a pulsating negative pressure supersonic nozzle, generating a 50-80kHz pulsating jet at 0.4MPa, which creates a gradient micro-pit array along the thickness direction to form a mechanically anchored-chemically bonded dual-synergistic interface. Simultaneously, an online laser scattering roughness meter collects Ra data in real time, providing closed-loop feedback to the spray gun's air pressure servo valve. The Ra deviation is ≤±0.05μm, enabling adaptive locking of the roughness process window.

3. The anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls according to claim 1 or 2, characterized in that: In step S2, the treatment time t and treatment temperature T of the chromium-free conversion film follow the Arrhenius kinetic model, and their relationship satisfies: ， Where A is the pre-exponential factor, ranging from 0.5 to 2.0 min; Ea is the activation energy of the reaction, ranging from 35 to 45 kJ / mol; and R is the ideal gas constant. The conversion solution is a dicationic sol (Zr). 4+ -Ti 4+ Rare earth cerium corrosion-inhibiting microspheres (particle size 80-120nm, shell layer CeO2, core layer SiO2), with a microsphere addition amount of 0.3-0.8g / L, can reduce Ea by 8-12kJ / mol at a low temperature of 20℃, achieving rapid film formation at room temperature; The online electrochemical impedance microprobe collects the membrane resistance Rp every second. When Rp ≥ 1.5 MΩ·cm², the impregnation is automatically terminated to avoid over-etching, and the membrane weight is controlled at 0.8-1.2 g / m².

4. The anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls according to claim 1, characterized in that: In step S3, the nano-ceramic particles are silicon dioxide or aluminum oxide, and their optimal addition amount ω is related to the particle size d of the nanoparticles and the dry film thickness hb of the undercoating layer, and satisfies the following: ， Where α is the dispersion coefficient, ranging from 0.1 to 0.3, and β is the baseline addition amount, ranging from 1 to 3; Among them, the nano-ceramic particles have a core-shell structure, with a core size of 30 nm and a shell size of 5 nm. The shell layer is grafted with vinyltriethoxysilane, which can form covalent bridges with epoxy groups. The surface grafting rate of the nano-ceramic particles is ≥15%. Employing an ultrasonic-high-speed shear dual dispersion chamber, with an instantaneous shear rate of 40,000 s. -1 This ensures that the secondary agglomerate particle size D50 ≤ 60 nm and the scattering factor ≤ 0.15, guaranteeing that the transparent topcoat does not fog up; The online dynamic light scattering DLS probe provides real-time feedback ω correction, with an added error of ≤±0.05%.

5. The anti-corrosion coating process for thermally broken aluminum profiles for curtain walls according to claim 1, characterized in that: In step S4, the thickness hm of the coating in the flexible polyester is proportional to the maximum width W of the profile cross-section to counteract the internal stress caused by thermal expansion and contraction. The relationship is as follows: ， Wherein, γ is the stress buffer coefficient, with a value ranging from 3 to 5. ; The intermediate coating is a dynamic reversible polyurethane-polysiloxane block, with a storage modulus change of <10% in the range of -40℃ to +80℃, which can offset the 0.12% difference in aluminum thermal expansion. The coating incorporates thermochromic microcapsules, allowing on-site infrared thermal imagers to non-contactly determine whether the stress in the intermediate coating exceeds limits through color changes, thus enabling visualization of service health.

6. The anti-corrosion coating process for thermally broken aluminum profiles for curtain walls according to claim 1, characterized in that: In the staged gradient curing of step S6, the heating rate V1 of the first stage is inversely proportional to the final total coating thickness H, which is determined by the following empirical formula: ， Wherein, λ is the heating coefficient, with a value ranging from 150 to 250℃·μm / min, to prevent rapid solvent evaporation from causing pinhole defects in the coating; The curing oven employs a segmented magnetic levitation hot air circulation combined with near-infrared auxiliary heating, and the specific steps include the following sub-steps: 0-60s: Near-infrared 2-4µm band, penetration depth 15-20µm, surface solvent flash evaporation, hot air velocity 0.5m / s; From 60 to 180 seconds: the hot air temperature increases in a stepwise manner, and the wind speed decreases by 0.1 m / s every 20 seconds to reduce surface pinholes; The online laser interferometer measures the thermal expansion coefficient of the coating surface in real time. When the expansion coefficient suddenly changes by more than 5%, it automatically reduces V1 to prevent blistering.

7. The anti-corrosion coating process for thermally broken aluminum profiles used in curtain walls according to claim 1, characterized in that: In step S7, an eddy current thickness gauge is used to detect the coating thickness. The validity of the detection data is determined based on a calibration curve between the thickness ht of the fluorocarbon surface coating and the thickness gauge reading R. This calibration curve satisfies a linear relationship within the interval [20μm, 40μm]. ， Among them, the eddy current thickness gauge integrates dual-frequency excitation, which can automatically eliminate background drift caused by batch fluctuations in the conductivity of the aluminum substrate, with a baseline drift of ≤0.3µm; When the measured thickness (ht) deviates from the curve by more than 5%, the AGV automatically sends the profile back to the re-spraying station and links the PLC to lower the electrostatic voltage by 2kV, thereby achieving online closed-loop correction of thickness and voltage.

8. The anti-corrosion coating process for thermally broken aluminum profiles for curtain walls according to claim 1, characterized in that: In step S5, the resin content of the PVDF fluorocarbon topcoat is not less than 70%, and its weather resistance life prediction model is based on the irradiance data of the Atlas climate test chamber. The relationship between its gloss retention rate G and the cumulative ultraviolet irradiance Q conforms to the following decay curve: ， Where G0 is the initial gloss level, θ is the aging rate constant, and the value of θ is no greater than 5.0 × 10⁻⁶. -5 m² / MJ.

9. A thermally broken aluminum profile for curtain walls, characterized in that: The thermally broken aluminum profile is manufactured using the anti-corrosion coating process for the surface of thermally broken aluminum profiles for curtain walls as described in any one of claims 1-8; it includes an outdoor aluminum alloy part (1), an indoor aluminum alloy part (2), and a thermal insulation strip (3) connecting the two; the outdoor aluminum alloy part (1) includes a main cavity (11), a glass mounting groove (12), and a drainage channel (13), and the main cavity (11) is provided with reinforcing ribs (14) inside, and its wall thickness is not less than 2.5mm; the thermal insulation strip (3) is a multi-chamber structure (31) made of polyamide nylon and glass fiber material, and is connected to the outdoor aluminum alloy part (1) and the indoor aluminum alloy part (2) by a rolling composite process; the outdoor aluminum alloy part (1) and the indoor aluminum alloy part (2) are made of 6063-T5 or 6061-T6 aluminum alloy.

10. A building curtain wall system, characterized in that: The building curtain wall system is constructed using the thermally broken aluminum profile for curtain walls as described in claim 9.

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