Regenerated aluminum profile spraying process

Abstract

The invention discloses a regenerated aluminum profile spraying process, and relates to the technical field of regenerated aluminum profile surface treatment, and the regenerated aluminum profile spraying process comprises the following operation steps: S1, base material pretreatment: firstly immersing a profile into a sodium hydroxide solution containing a surfactant for chemical oil removal, and then immersing the profile into a hydrochloric acid solution containing a corrosion inhibitor for acid pickling and rust removal; according to the regenerated aluminum profile spraying process, all links of regenerated aluminum profile spraying are optimized in a targeted mode by surrounding the core process logic of base material purification, coating adhesion and performance strengthening, and in the base material pretreatment stage, through cooperative cooperation of chemical oil removal, acid pickling rust removal and phosphating treatment and precise adding of a surfactant and a corrosion inhibitor, the regenerated aluminum profile can be sprayed on the surface of the base material, and the performance of the regenerated aluminum profile can be improved. According to the invention, oil stains, rust and impurities on the surface of the profile can be thoroughly removed, a compact phosphating film can be formed on the surface of the profile, a stable substrate is constructed for subsequent coating adhesion, the binding capacity of a coating and a base material is greatly improved, and the problem of coating falling caused by incomplete traditional pretreatment is avoided.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for recycled aluminum profiles, and particularly to a spraying process for recycled aluminum profiles. Background Technology

[0002] Due to the complex source of raw materials, recycled aluminum profiles are prone to surface contamination with residual oil, rust, and oxidation impurities from the production process. Furthermore, the impurities contained within the matrix result in lower surface smoothness and chemical stability compared to virgin aluminum profiles, posing significant challenges to subsequent surface treatment.

[0003] In traditional spraying processes, the substrate pretreatment stage often suffers from problems such as incomplete degreasing and excessive corrosion of the substrate during rust removal. This not only makes it difficult to form a uniform and dense base, but may also damage the surface structure of the profile, resulting in insufficient adhesion between the subsequent coating and the substrate. This can easily lead to defects such as coating peeling and blistering, and fail to meet the requirements for long-term use.

[0004] Therefore, it is necessary to propose a coating process for recycled aluminum profiles to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a coating process for recycled aluminum profiles to solve the problems that often exist in the substrate pretreatment stage of traditional coating processes, such as incomplete degreasing and excessive corrosion of the substrate during rust removal. This not only makes it difficult to form a uniform and dense substrate, but may also damage the surface structure of the profile, resulting in insufficient adhesion between the subsequent coating and the substrate, and easily causing defects such as coating peeling and blistering, which cannot meet the requirements of long-term use.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a spraying process for recycled aluminum profiles, comprising the following steps:

[0007] S1. Substrate pretreatment: First, the profile is immersed in a sodium hydroxide solution containing surfactant for chemical degreasing. Then, the profile is immersed in a hydrochloric acid solution containing corrosion inhibitor for pickling and rust removal. Finally, the profile is immersed in a zinc phosphating solution for phosphating treatment and then dried after phosphating treatment.

[0008] S2. Electrostatic dust removal: First, low-pressure compressed air with a pressure of 0.2-0.3MPa is used to pre-purge the surface of the profile. Then, a zone adaptation strategy is adopted to perform electrostatic dust removal on different cross-sectional structures of the profile. At the same time, the dust content on the surface of the profile is detected in real time by a dust concentration sensor.

[0009] S3. Preheating treatment: The profiles that have undergone electrostatic dust removal are preheated using a preheating furnace. The preheating furnace is heated from room temperature to 120-140℃ at a heating rate of 5-8℃ / min, and then held at 120-140℃ for 20-30min.

[0010] S4. Primer spraying: Apply epoxy primer to the preheated profile using an electrostatic spraying machine with a nozzle diameter of 1.2-1.5mm. The spraying pressure is 0.4-0.6MPa, the spraying distance is 200-300mm, and the epoxy primer has a solid content of ≥60% and a pigment volume concentration of 30-35%. Preheat the epoxy primer before spraying at a temperature of 50-60℃ for 10-15 minutes.

[0011] S5. Flash-drying treatment: Use a flash-drying oven to flash-dry the profiles after the primer has been sprayed. First, keep the profiles at a low temperature for initial heat preservation, and then transition to the heat preservation temperature. The heat preservation temperature is 80-100℃ and the heat preservation time is 10-15 minutes.

[0012] S6. Topcoat spraying: Within 30 minutes after the primer flash-off, apply fluorocarbon topcoat to the profile using a wet-on-wet process. The relative humidity of the spraying environment is ≤70%, the temperature is 15-30℃, the spraying pressure is 0.3-0.5MPa, and the spraying distance is 250-350mm.

[0013] S7. Curing treatment: Use a curing oven to cure the profile after the topcoat has been sprayed. During the curing process, first raise the temperature to 120-140℃ at a rate of 3-5℃ / min and keep it at that temperature for 5-8 minutes. Then raise the temperature to 160-180℃ at the same rate and keep it at that temperature for 40-60 minutes. At the end of the holding period, lower the temperature to 150-160℃ at a rate of 2-3℃ / min and maintain it for 5 minutes.

[0014] Preferably, in step S1, the sodium hydroxide solution has a mass concentration of 8-12%, the temperature is maintained at 50-60°C, the soaking time is 15-20 minutes, and the surfactant is sodium dodecyl sulfate with a mass concentration of 0.5-1%; the hydrochloric acid solution has a mass concentration of 10-15%, the temperature is maintained at 25-35°C, the soaking time is 10-15 minutes, the corrosion inhibitor is hexamethylenetetramine with a mass concentration of 0.3-0.5%; the zinc phosphating solution has a mass concentration of 5-8%, a total acidity of 20-30 points, a free acidity of 1.5-2.5 points, the solution temperature is maintained at 40-50°C, and the soaking time is 15-20 minutes.

[0015] Preferably, in step S1, the phosphated profile is dried in a drying oven at a temperature of 80-100°C for 20-30 minutes.

[0016] Preferably, in step S2, an electrostatic dust removal gun is used for electrostatic treatment. For the planar area of ​​the profile, the electrostatic dust removal gun scans along the length of the profile with a voltage of 60-80kV, an air pressure of 0.4-0.6MPa, and a dust removal distance of 150-200mm. For the interior of the multi-cavity parts of the profile, the recessed areas of irregular curved surfaces, and the bottom of grooves, the angle between the electrostatic dust removal gun and the surface of the profile is adjusted to fit the contour of the concealed parts.

[0017] Preferably, in step S3, at least three temperature sensors are installed in the preheating furnace, located at the front, middle and rear of the furnace body, respectively, to monitor the temperature of different areas in the furnace in real time. The surface temperature difference of different areas of the preheated profile is controlled within ±5℃, and the surface moisture content of the profile is ≤0.1%.

[0018] Preferably, in step S4, the preheated profile is conveyed using a conveying device, and the conveying speed of the profile matches the spraying speed of the electrostatic spraying machine, while the epoxy primer coating thickness is maintained at 30-40μm.

[0019] Preferably, in step S5, the initial heat preservation time is 3-5 minutes, and a directional airflow auxiliary device is set in the flash drying oven to make the airflow circulate in the multi-cavity interior of the profile, the concave part of the irregular curved surface, and the bottom area of ​​the groove.

[0020] Preferably, in step S6, an electrostatic spraying machine with a nozzle diameter of 1.0-1.2 mm is used to spray fluorocarbon topcoat.

[0021] Preferably, in step S6, the thickness of the fluorocarbon topcoat coating is 20-30 μm.

[0022] Preferably, in step S7, after the constant temperature and heat preservation process is completed, the profile is removed from the curing oven by a conveying device and transferred to a normal temperature environment of 20-25°C to cool naturally to room temperature.

[0023] The technical effects and advantages of this invention are as follows:

[0024] 1. This invention revolves around the core process logic of "substrate purification - coating adhesion - performance enhancement", and optimizes each step of the spraying process for recycled aluminum profiles. In the substrate pretreatment stage, through the synergistic combination of chemical degreasing, pickling and rust removal and phosphating treatment, along with the precise addition of surfactants and corrosion inhibitors, it can thoroughly remove oil stains, rust and impurities from the profile surface, and form a dense phosphating film on the profile surface, thus building a solid base for subsequent coating adhesion, greatly improving the bonding ability between the coating and the substrate, and avoiding the coating peeling problem caused by incomplete pretreatment in traditional methods.

[0025] 2. The electrostatic dust removal process is equipped with a low-pressure air pre-purging and zoned dust removal strategy. First, large particles of phosphating slag and floating dust are removed. Then, the scanning method and parameters are adjusted for the hidden parts of complex cross-sections. At the same time, a real-time dust monitoring and compensation mechanism is used to ensure that the cleanliness of the entire surface of the profile is uniform and stable. This solves the problem that the existing technology is not thorough in removing dust from complex cross-sections such as multi-cavity and irregular curved surfaces, which can easily cause defects such as pinholes and shrinkage cavities in the coating. This provides high-quality surface conditions for the spraying process.

[0026] 3. The preheating process employs segmented heating and multi-point temperature monitoring to ensure uniform surface temperature of the profile, effectively removing residual moisture and preventing spray sagging and coating bubbles caused by uneven temperature. This also adapts to the relatively weak thermal stability of recycled aluminum profiles, reducing the impact of thermal stress on the profile. During primer spraying, preheating and defoaming of the paint are performed, while the profile conveying speed is precisely matched with the spraying parameters. Combined with optimized primer formulation, this ensures a uniform primer coating and sufficient zinc powder dispersion, fully leveraging the sacrificial anode protection of zinc powder to enhance the coating's rust-proof performance. The flash-drying process features segmented temperature control and directional airflow, optimizing the solvent evaporation process for complex cross-sections to prevent localized solvent residue from affecting interlayer adhesion and further strengthening the bond between the primer and topcoat.

[0027] 4. The topcoat is applied using a wet-on-wet process, which shortens the production cycle while ensuring the weather resistance and appearance quality of the topcoat. The curing process uses a stepped heating, dynamic heat preservation and low-temperature transition cooling design to ensure that the coating cross-links evenly and fully, meeting the requirements for corrosion resistance and mechanical properties. It can also effectively reduce the risk of deformation of recycled aluminum profiles due to high temperature, and is especially suitable for the dimensional accuracy requirements of complex cross-section profiles. Attached Figure Description

[0028] Figure 1 This is a flowchart of the recycled aluminum profile spraying process of the present invention. Detailed Implementation

[0029] This invention provides, for example Figure 1 The illustrated coating process for recycled aluminum profiles revolves around the core logic of "substrate purification - coating adhesion - performance enhancement" to achieve efficient surface treatment of recycled aluminum profiles. Specifically, it includes the following steps:

[0030] I. Substrate Pretreatment

[0031] Substrate pretreatment includes three steps: chemical degreasing, pickling and rust removal, and phosphating.

[0032] Chemical degreasing involves immersing recycled aluminum profiles in a sodium hydroxide solution with a mass concentration of 8-12%, maintaining the solution temperature at 50-60℃ for 15-20 minutes. A sodium dodecyl sulfate solution with a mass concentration of 0.5-1% is added as a surfactant. Immersion removes oil and oxide film from the profile surface. The profiles are then rinsed with deionized water until the pH of the residual water on the profile surface reaches 7. The solution is changed after every 50 profiles are treated to ensure effective degreasing.

[0033] For acid pickling and rust removal, the degreased profiles are immersed in a 10-15% hydrochloric acid solution at a temperature maintained at 25-35℃ for 10-15 minutes. A 0.3-0.5% hexamethylenetetramine hydrochloric acid solution is added as a corrosion inhibitor. Immersion removes rust and impurities from the profile surface. The profiles are then rinsed with deionized water until the pH of the residual water on the surface reaches 7, ensuring a corrosion rate ≤0.02 g / (m³). 2 ·h).

[0034] Phosphating treatment involves immersing the rust-removed profiles in a zinc-based phosphating solution with a mass concentration of 5-8%, a total acidity of 20-30 points, and a free acidity of 1.5-2.5 points (tested by titration). The solution temperature is maintained at 40-50℃, and the immersion time is 15-20 minutes. This forms a phosphating film with a thickness of 2-3 μm on the profile surface. Afterward, the profiles are dried in a drying oven at a temperature of 80-100℃ for 20-30 minutes. The phosphating film can withstand salt water immersion time ≥24 hours.

[0035] II. Electrostatic dust removal

[0036] This includes "pre-purging" and "electrostatic treatment";

[0037] First, use low-pressure compressed air (0.2-0.3 MPa) to pre-blow the surface of the recycled aluminum profile after phosphating and drying to remove any relatively large phosphating slag particles that may remain on the profile surface, and at the same time, preliminarily remove the floating dust on the profile surface.

[0038] Pre-purging with low-pressure air can prevent larger phosphate slag particles from remaining due to weak adsorption or scratching the profile surface under static electricity during subsequent high-pressure electrostatic dust removal, thus preventing defects such as pinholes and shrinkage cavities in the coating due to phosphate slag residue during subsequent spraying.

[0039] The pre-purging air pressure is lower than the compressed air pressure of the subsequent electrostatic treatment, which can effectively remove large particulate impurities without damaging the phosphating film due to excessive air pressure.

[0040] Next, electrostatic treatment is performed using an electrostatic dust removal gun. A zoned adaptive dust removal strategy is adopted for different cross-sectional structures of recycled aluminum profiles: For the flat areas of the profile, the electrostatic dust removal gun is kept scanning along a straight line (the length direction of the profile) for dust removal. The voltage of the electrostatic dust removal gun is 60-80kV, the air pressure is 0.4-0.6MPa, and the dust removal distance is controlled at 150-200mm. For hidden parts such as the internal cavities of multi-cavity structures, the recesses of irregular curved surfaces, and the bottom of grooves, the angle between the dust removal gun and the profile surface is adjusted (to fit the contour of the hidden parts), and a "slow scan + reciprocating" scanning method is adopted to ensure that the high voltage electrostatic can fully act on the hidden areas. Combined with directional blowing of compressed air, dust is avoided from remaining in dead corners.

[0041] Meanwhile, a dust concentration sensor is installed next to the electrostatic dust removal gun to detect the dust content on the profile surface in real time. When the dust content in a local area exceeds 5mg / m³, the sensor will detect the dust concentration. 2 When the standard is met, the system automatically fine-tunes the air pressure and scanning speed of the dust removal gun in that area until the dust content meets the standard.

[0042] To address the potential presence of fine phosphate residue on the surface of phosphated profiles, a "low-pressure air pre-purging" step (0.2-0.3 MPa) is added before electrostatic dust removal. This first removes larger particulate impurities before high-voltage electrostatic dust removal, further improving surface cleanliness. This solves the problems of incomplete dust removal and unstable cleanliness in complex cross-sections found in existing technologies, ultimately ensuring that the dust content on the entire surface of the profile (including concealed areas) is consistently controlled at 5 mg / m³. 2 Inside, it provides a more reliable clean substrate for subsequent preheating and spraying processes.

[0043] III. Preheating Treatment

[0044] The profiles that have undergone electrostatic dust removal are preheated in a preheating furnace. The furnace temperature is raised from room temperature to 120-140℃ at a heating rate of 5-8℃ / min, and then held at this temperature for 20-30 minutes.

[0045] At least three temperature sensors (located at the front, middle, and rear of the furnace body) are installed in the preheating furnace to monitor the temperature in real time, thereby ensuring that the surface temperature of the profile is uniform and the surface temperature difference after preheating is ±5℃. At the same time, residual moisture on the surface of the profile is removed, so that the moisture content is ≤0.1%, avoiding problems such as sagging and coating bubbles during subsequent spraying.

[0046] IV. Primer Spraying

[0047] The preheated profiles are conveyed using a conveying device, and an epoxy primer is sprayed onto the preheated profiles using an electrostatic spraying machine (nozzle diameter 1.2-1.5mm). Before spraying, the epoxy primer is preheated at a temperature of 50-60℃ for 10-15 minutes to remove air bubbles from the paint.

[0048] During spraying, control the spraying pressure to 0.4-0.6MPa and the spraying distance to 200-300mm, and match the profile conveying speed with the spraying speed to ensure that the epoxy primer coating thickness is controlled at 30-40μm.

[0049] The primer has a solids content of ≥60% and a pigment volume concentration of 30-35% to ensure that the zinc powder in the primer is evenly dispersed, plays a sacrificial anode protection role, and avoids uneven coating thickness.

[0050] V. Flash-drying treatment

[0051] When flash-drying profiles with primer coating completed using a flash-drying oven, a segmented temperature control program is set up in the flash-drying oven, taking into account the solvent evaporation pattern of the primer coating on recycled aluminum profiles and the temperature conduction differences of complex cross-sections (multi-cavity, irregular curved surfaces, etc.): First, the profiles are initially kept at a slightly lower temperature range to accelerate the stable evaporation of solvent on the coating surface and avoid pinholes caused by excessively rapid temperature rise leading to film formation on the coating surface and the inability of internal solvent to be discharged; then, the temperature is transitioned to the process-specified temperature range of 80-100℃ for 10-15 minutes to ensure that 30-40% of the solvent in the primer is fully removed.

[0052] Meanwhile, for areas prone to solvent residue, such as the interior of cavities and corners of complex cross-section profiles, a directional airflow auxiliary device is added to the corresponding area in the flash drying oven. This device promotes solvent evaporation in concealed areas through gentle airflow circulation, preventing localized solvent residue from causing sagging or reduced interlayer adhesion during subsequent topcoat application.

[0053] By optimizing segmented temperature control and directional airflow, the problems of uneven solvent removal and coating defects in complex cross-section profiles caused by traditional constant temperature flash drying are solved, further ensuring the uniformity of the primer in the semi-cured state and strengthening the interlayer bonding effect with the topcoat.

[0054] VI. Topcoat Spraying

[0055] Within 30 minutes after the primer flash-off, the profile is coated with fluorocarbon topcoat using an electrostatic spraying machine (nozzle diameter 1.0-1.2mm). Spraying must be carried out under the conditions of relative humidity ≤70% and temperature 15-30℃.

[0056] Control the spraying pressure to 0.3-0.5MPa and the spraying distance to 250-350mm to ensure that the fluorocarbon topcoat coating thickness is 20-30μm, the fluorine content of the topcoat is ≥18%, and the gloss (60°) reaches 50-70GU. Reduce the production cycle through wet-on-wet process to ensure the weather resistance and appearance quality of the topcoat.

[0057] The wet-on-wet process refers to the process of spraying fluorocarbon topcoat onto the surface within a specified 30 minutes after the primer has completed flash-drying (not fully cured, in a semi-cured state) without waiting for the primer to fully cure.

[0058] This process eliminates the need for topcoat spraying after the primer has fully cured, saving the extra time and energy required for complete primer curing. At the same time, the semi-cured primer surface still retains a certain degree of activity, allowing for better wetting and bonding with the newly sprayed fluorocarbon topcoat. This reduces the interlayer interface between the primer and topcoat, enhances the interlayer adhesion between the two, and avoids the problem of poor interlayer bonding caused by the reduced surface activity after the primer has fully cured.

[0059] This wet-on-wet process effectively reduces the overall production cycle of the spraying process and improves industrial production efficiency. It also leverages the good interlayer bonding between the primer and topcoat, combined with the high fluorine content of the fluorocarbon topcoat, to further ensure the weather resistance and appearance quality of the topcoat. This results in a coating system that is superior in terms of aging resistance, corrosion resistance, and surface gloss consistency.

[0060] VII. Curing Treatment

[0061] The profiles with the topcoat applied are cured in a curing oven. After the profiles are placed in the curing oven, the temperature is first raised to 120-140℃ at a rate of 3-5℃ / min, and then held at this temperature for 5-8 minutes to allow the surface and internal temperatures of the profiles to approach each other synchronously, avoiding local temperature differences caused by uneven heat conduction of the recycled aluminum profiles. Then, the temperature is raised to 160-180℃ at the same rate and then held for 40-60 minutes. At the end of the holding period (when there are 10-15 minutes left), the temperature in the curing oven is slowly reduced to 150-160℃ at a rate of 2-3℃ / min, and then held for 5 minutes before heating is stopped. This avoids excessive thermal expansion and contraction differences between the coating and the substrate caused by directly removing the profiles from the high temperature, further reducing the risk of profile deformation, ensuring the dimensional accuracy of the complex cross-section recycled aluminum profiles, and ensuring that the coating cross-linking degree is stable and meets the standards.

[0062] At least three temperature sensors (located at the top, middle, and bottom of the profile, respectively) are installed inside the curing oven to monitor the temperature in real time. The temperature fluctuation is controlled within ±3℃ by a PID temperature control system. When the temperature fluctuation in a certain area exceeds ±3℃, the temperature control system automatically adjusts the heating power of that area to achieve dynamic heat preservation. This ensures that the temperature of the entire profile area is stable within the process requirements range, avoiding the differences in coating crosslinking caused by local overheating or insufficient temperature under the traditional fixed heat preservation mode.

[0063] After curing, the profile is transferred to a room temperature environment of 20-25℃ to cool to room temperature (cooling rate ≤10℃ / min) to avoid excessive thermal expansion and contraction difference between the coating and the substrate due to rapid cooling, which would affect the adhesion. Ultimately, the degree of crosslinking of the cured coating is ≥90% (differential scanning calorimetry test).

[0064] This invention revolves around the core process logic of "substrate purification - coating adhesion - performance enhancement," specifically optimizing each stage of the spraying process for recycled aluminum profiles, effectively solving many pain points of traditional processes. In the substrate pretreatment stage, through the synergistic combination of chemical degreasing, acid pickling and rust removal, and phosphating, along with the precise addition of surfactants and corrosion inhibitors, oil, rust, and impurities on the profile surface are thoroughly removed. Simultaneously, a dense phosphating film is formed on the profile surface, creating a stable base for subsequent coating adhesion. This significantly improves the bonding ability between the coating and the substrate, avoiding the coating peeling problem caused by incomplete pretreatment in traditional methods.

[0065] The electrostatic dust removal process employs a low-pressure air pre-purging and zoned dust removal strategy to first remove large particles of phosphating slag and floating dust. Then, the scanning method and parameters are adjusted for hidden areas of complex cross-sections. Simultaneously, a real-time dust monitoring and compensation mechanism is implemented to ensure uniform and stable cleanliness across the entire surface of the profile. This addresses the shortcomings of existing technologies in thoroughly removing dust from complex cross-sections such as multi-cavity and irregular curved surfaces, which can easily lead to defects such as pinholes and shrinkage cavities in the coating. This provides high-quality surface conditions for the spraying process.

[0066] The preheating process employs segmented heating and multi-point temperature monitoring to ensure uniform surface temperature of the profiles, effectively removing residual moisture and preventing spray sagging and coating bubbles caused by uneven temperature. It also adapts to the relatively weak thermal stability of recycled aluminum profiles, reducing the impact of thermal stress on the profiles. During primer spraying, preheating and defoaming of the paint are performed, while the profile conveying speed is precisely matched with the spraying parameters. Combined with optimized primer formulation, this ensures a uniform primer coating and sufficient zinc powder dispersion, fully leveraging the sacrificial anode protection of zinc powder to enhance the coating's rust-proof performance. The flash-drying process features segmented temperature control and directional airflow, optimizing the solvent evaporation process for complex cross-sections to prevent localized solvent residue from affecting interlayer adhesion and further strengthening the bond between the primer and topcoat.

[0067] The topcoat spraying adopts a wet-on-wet process, which shortens the production cycle while ensuring the weather resistance and appearance quality of the topcoat. The curing process uses a stepped heating, dynamic heat preservation and low-temperature transition cooling design to ensure that the coating cross-links evenly and fully, meeting the requirements of corrosion resistance and mechanical properties. It can also effectively reduce the risk of deformation of recycled aluminum profiles caused by high temperature, and is especially suitable for the dimensional accuracy requirements of complex cross-section profiles.

[0068] Through the coordinated efforts of each stage, the overall process ultimately forms a uniform and dense coating system on the surface of recycled aluminum profiles, significantly improving coating adhesion, corrosion resistance, and appearance consistency. It solves the problems of easy coating sagging and uneven spraying on complex cross-sections in traditional processes. Moreover, the process is adapted to the needs of industrial production, taking into account both environmental protection and economy, and provides strong support for the application of recycled aluminum profiles in high-end fields.

[0069] In addition, the coating process for recycled aluminum profiles includes the following examples:

[0070] Example 1

[0071] This embodiment uses the following spraying process for multi-cavity reclaimed aluminum profiles (50mm×50mm cross-section, 3mm wall thickness) for building curtain walls:

[0072] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profile is immersed in an 8% sodium hydroxide solution with 0.5% sodium dodecyl sulfate added as a surfactant. The solution temperature is controlled at 50℃, and the immersion time is 20 minutes. This removes oil and oxide film from the profile surface. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The second step is acid pickling to remove rust. The degreased profile is immersed in a 10% hydrochloric acid solution with 0.3% hexamethylenetetramine added as a corrosion inhibitor. The solution temperature is maintained at 25℃, and the immersion time is 15 minutes to remove surface rust and impurities. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The third step is phosphating treatment. The rust-removed profiles are immersed in a 5% zinc-based phosphating solution (total acidity 20 points, free acidity 1.5 points) with a mass concentration of 40℃ and soaked for 20 minutes to form a phosphating film on the surface of the profiles. Then, the profiles are dried in a drying oven at 80℃ for 30 minutes to form a phosphating film with a thickness of 2μm. This phosphating film can withstand salt water immersion time ≥24h.

[0073] Next, electrostatic dust removal is performed using an electrostatic dust gun (60kV, 0.4MPa) to remove dust from the surface of the phosphated and dried profiles. The dust removal distance is controlled at 150mm. Dust is removed from the profile surface through a combination of electrostatic adsorption and compressed air blowing, ultimately ensuring that the dust content on the profile surface is 4mg / m³. 2 .

[0074] Then, a preheating treatment is carried out. The profiles that have undergone electrostatic dust removal are sent into a preheating furnace. The preheating furnace raises the temperature from room temperature to 120°C at a heating rate of 5°C / min. Then, it is held at this temperature for 30 minutes. The temperature difference on the surface of the profiles is controlled within ±3°C by temperature monitoring in the preheating furnace, while removing residual moisture from the surface of the profiles.

[0075] After preheating, the primer is applied. The profile is conveyed at a speed of 1 m / min using a conveyor, while an electrostatic sprayer (1.2 mm nozzle diameter) is used to apply the epoxy primer to the preheated profile. Before spraying, the epoxy primer is preheated at 50℃ for 15 minutes to remove air bubbles. During spraying, the spraying pressure is controlled at 0.4 MPa and the spraying distance is 200 mm. The epoxy primer has a solids content of 60% and a pigment volume concentration (PVC) of 30%, ensuring that the epoxy primer coating thickness reaches 30 μm.

[0076] After the primer is applied, a flash-drying process is performed. The profile is sent into a flash-drying oven and kept at 80°C for 15 minutes. This process removes 30% of the solvent from the primer, leaving it in a semi-cured state.

[0077] Next, the topcoat is applied. Within 30 minutes after the primer flash-dry, the profile is coated with fluorocarbon topcoat using an electrostatic sprayer (1.0mm nozzle diameter). The relative humidity of the spraying environment is controlled at 60%, the spraying pressure is controlled at 0.3MPa, the spraying distance is 250mm, the fluorine content of the fluorocarbon topcoat is 18%, the gloss (60°) is 50GU, and the thickness of the fluorocarbon topcoat coating is ensured to be 20μm.

[0078] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature inside the curing oven is raised to 160°C at a heating rate of 3°C / min. Then, it is held at this temperature for 60 minutes. After curing, the profile is transferred to a room temperature environment of 20°C to cool to room temperature, so that the crosslinking degree of the coating reaches 90%.

[0079] Testing showed that the coating of the recycled aluminum profile treated in this embodiment had an adhesion of 5 MPa, an impact resistance of 50 kg·cm, and a neutral salt spray test duration of 1000 hours. It can meet the usage requirements of multi-cavity recycled aluminum profiles for building curtain walls. The coating performance is stable and can effectively resist outdoor environmental corrosion.

[0080] Example 2

[0081] This embodiment uses the following spraying process for irregular curved recycled aluminum profiles (cross-section R40mm, wall thickness 4mm) used in transportation:

[0082] First, substrate pretreatment is performed. The first step is chemical degreasing, where the recycled aluminum profile is immersed in a 10% sodium hydroxide solution with a surfactant added at 0.8% by mass. The solution temperature is controlled at 55℃, and the immersion time is 18 minutes to remove oil and oxide film from the profile surface. Afterward, it is rinsed with deionized water until the pH of the residual water on the profile surface is 7. The second step is acid pickling to remove rust, where the degreased profile is immersed in a 12% hydrochloric acid solution with a corrosion inhibitor added at 0.4% by mass. The solution temperature is maintained at 30℃, and the immersion time is 12 minutes to remove surface rust and impurities. Then, it is rinsed with deionized water until the pH of the residual water on the profile surface is 7. The third step is phosphating treatment. The rust-removed profiles are immersed in a 6% zinc-based phosphating solution (total acidity 25 points, free acidity 2.0 points) with a mass concentration of 45℃ for 18 minutes to form a phosphating film on the profile surface. Then, they are dried in a drying oven at 90℃ for 25 minutes to form a phosphating film with a thickness of 2.5μm. This phosphating film can withstand salt water immersion for up to 26 hours.

[0083] Next, electrostatic dust removal was performed using an electrostatic dust gun (70kV, 0.5MPa) to remove dust from the surface of the phosphated and dried profiles. The dust removal distance was controlled at 180mm. For the concave areas of irregular curved surfaces, the angle of the dust gun was adjusted. A "slow sweep + reciprocating" scanning method was used to ensure that the dust was completely removed. The final dust content on the profile surface was 3mg / m³. 2 .

[0084] Then, a preheating treatment is performed. The profiles after electrostatic dust removal are sent into a preheating furnace. The preheating furnace raises the temperature to 130°C at a heating rate of 7°C / min. Then, it is held at this temperature for 25 minutes. The temperature difference on the surface of the profiles is controlled within ±4°C by monitoring the temperature sensor in the preheating furnace, while removing residual moisture from the surface of the profiles.

[0085] After preheating, primer spraying is carried out. The profiles are conveyed at a speed of 1.5 m / min using a conveyor, and an electrostatic sprayer (1.4 mm nozzle diameter) is used to spray the epoxy primer onto the profiles. Before spraying, the epoxy primer is preheated at 55℃ for 12 minutes to remove air bubbles. During spraying, the spraying pressure is controlled at 0.5 MPa, the spraying distance is 250 mm, and the epoxy primer used has a solids content of 62%, ensuring that the primer coating thickness reaches 35 μm.

[0086] After the primer is applied, a flash-drying process is performed. The profile is sent into a flash-drying oven and kept at 90°C for 12 minutes to remove 35% of the solvent in the primer and prevent sagging during subsequent topcoat application.

[0087] Then, the topcoat is applied. Within 25 minutes after the primer flash-dry, the fluorocarbon topcoat is applied to the profile using an electrostatic sprayer (1.1mm nozzle diameter). The relative humidity of the spraying environment is controlled at 65%, the spraying pressure is controlled at 0.4MPa, the spraying distance is 300mm, the fluorocarbon topcoat used has a fluorine content of 20%, and the gloss (60°) is 60GU, ensuring that the topcoat coating thickness is 25μm.

[0088] Finally, a curing process is carried out. The profile after the topcoat is sprayed is sent into a curing oven, which is heated to 170°C at a rate of 4°C / min and held for 50 minutes. After curing, the profile is transferred to a 22°C room temperature environment to cool to room temperature, so that the crosslinking degree of the coating reaches 92%.

[0089] According to the test results, the recycled aluminum profile with irregular curved surface for transportation after treatment in this embodiment has a coating adhesion of 5.2MPa, an impact resistance of 52kg·cm, and a neutral salt spray test duration of 1050h. The coating is evenly distributed on the irregular curved surface and can adapt to the complex operating environment of vibration and temperature difference in the transportation field, and has excellent weather resistance and structural stability.

[0090] Example 3

[0091] This embodiment uses the following spraying process for recycled aluminum profiles with grooves (groove depth 5mm, wall thickness 2.5mm) for electronic and electrical applications:

[0092] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profile is immersed in a 12% sodium hydroxide solution with 1% sodium dodecyl sulfate added as a surfactant. The solution temperature is controlled at 60℃, and the immersion time is 15 minutes. This removes oil and oxide film from the profile surface. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The second step is acid pickling to remove rust. The degreased profile is immersed in a 15% hydrochloric acid solution with 0.5% hexamethylenetetramine added as a corrosion inhibitor. The solution temperature is maintained at 35℃, and the immersion time is 10 minutes to remove surface rust and impurities. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The third step is phosphating treatment. The rust-removed profiles are immersed in a zinc-based phosphating solution with a mass concentration of 8% (total acidity 30 points, free acidity 2.5 points). The solution temperature is controlled at 50℃, and the profiles are soaked for 15 minutes to form a phosphating film on the surface of the profiles. Then, the profiles are dried in a drying oven at 100℃ for 20 minutes to form a phosphating film with a thickness of 3μm. This phosphating film can withstand salt water immersion time ≥24h.

[0093] Next, electrostatic dust removal is performed using an electrostatic dust gun (80kV, 0.6MPa) to remove dust from the surface of the phosphated and dried profiles. The dust removal distance is controlled at 200mm. The angle of the dust gun is adjusted for areas such as the bottom of the grooves. A "slow sweep + reciprocating" scanning method is used to ensure thorough dust removal. By combining electrostatic adsorption with compressed air blowing, dust is removed from the profile surface, ultimately ensuring that the dust content on the profile surface is 2mg / m³. 2 .

[0094] Then, a preheating treatment is carried out. The profiles that have undergone electrostatic dust removal are sent into a preheating furnace. The preheating furnace raises the temperature from room temperature to 140°C at a heating rate of 8°C / min. Then, it is held at this temperature for 20 minutes. The temperature difference on the surface of the profiles is controlled within ±5°C by temperature monitoring in the preheating furnace, while removing residual moisture from the surface of the profiles.

[0095] After preheating, the primer is applied. The profiles are conveyed at a speed of 2 m / min using a conveyor system, while an electrostatic sprayer (1.5 mm nozzle diameter) is used to apply the epoxy primer to the preheated profiles. Before spraying, the epoxy primer is preheated at 60℃ for 10 minutes to remove air bubbles. During spraying, the spraying pressure is controlled at 0.6 MPa, and the spraying distance is 300 mm. The epoxy primer has a solids content of 65% and a pigment volume concentration (PVC) of 35%, ensuring that the epoxy primer coating thickness reaches 40 μm.

[0096] After the primer is applied, a flash-drying process is performed. The profile is sent into a flash-drying oven and kept at 100°C for 10 minutes. This process removes 40% of the solvent from the primer, leaving it in a semi-cured state.

[0097] Next, the topcoat is applied. Within 30 minutes after the primer flash-drys, the profile is coated with fluorocarbon topcoat using an electrostatic sprayer (1.2mm nozzle diameter). The relative humidity of the spraying environment is controlled at 70%, the spraying pressure is controlled at 0.5MPa, the spraying distance is 350mm, the fluorine content of the fluorocarbon topcoat is 22%, the gloss (60°) is 70GU, and the thickness of the fluorocarbon topcoat coating is ensured to be 30μm.

[0098] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature inside the curing oven is raised to 180°C at a heating rate of 5°C / min. Then, it is kept at this temperature for 40 minutes. After curing, the profile is transferred to a room temperature environment of 25°C to cool to room temperature, so that the crosslinking degree of the coating reaches 95%.

[0099] Testing showed that the coating of the recycled aluminum profile treated in this embodiment had an adhesion of 5.5 MPa, an impact resistance of 55 kg·cm, and a neutral salt spray test duration of 1100 h, which meets the usage requirements of recycled aluminum profiles with grooves for electronic and electrical applications. The coating performance is stable and can effectively adapt to the complex environment in the field of electronic and electrical applications.

[0100] Example 4

[0101] This embodiment is for a multi-cavity profile (55mm×45mm), with optimized chemical degreasing parameters and the following spraying process:

[0102] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profile is immersed in a 9% sodium hydroxide solution with 0.6% sodium dodecyl sulfate added as a surfactant. The solution temperature is controlled at 52℃, and the immersion time is 19 minutes to enhance the oil removal effect. Immersion removes oil and oxide film from the profile surface. The profile is then rinsed with deionized water until the pH of the residual water on the profile surface reaches 7. The second step is acid pickling for rust removal. The degreased profile is immersed in an 11% hydrochloric acid solution with 0.35% hexamethylenetetramine added as a corrosion inhibitor. The solution temperature is maintained at 28℃, and the immersion time is 14 minutes to remove surface rust and impurities. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The third step is phosphating treatment. The rust-removed profiles are immersed in a 5.5% zinc-based phosphating solution (total acidity 22 points, free acidity 1.7 points) with a mass concentration of 42℃ and soaked for 19 minutes to form a phosphating film on the surface of the profiles. Then, the profiles are dried in a drying oven at 85℃ for 28 minutes to form a phosphating film. This phosphating film can withstand salt water immersion time ≥24h.

[0103] Next, electrostatic dust removal is performed using an electrostatic dust gun (65kV, 0.45MPa) to remove dust from the surface of the phosphated and dried profiles. The dust removal distance is controlled at 160mm. Dust is removed from the profile surface through a combination of electrostatic adsorption and compressed air blowing. The dust removal method is adjusted for the multi-cavity structure to ultimately ensure that the dust content on the profile surface is 4.5mg / m³. 2 .

[0104] Then, a preheating treatment is carried out. The profiles that have undergone electrostatic dust removal are sent into a preheating furnace. The preheating furnace raises the temperature from room temperature to 125°C at a heating rate of 6°C / min. Then, it is held at this temperature for 28 minutes. The temperature difference on the surface of the profiles is controlled within ±3°C by temperature monitoring in the preheating furnace, while removing residual moisture from the surface of the profiles.

[0105] After preheating, the primer is applied. The profiles are conveyed at a speed of 1.2 m / min using a conveyor system, while an electrostatic sprayer (1.3 mm nozzle diameter) applies the epoxy primer to the preheated profiles. Before spraying, the epoxy primer is preheated at 52℃ for 14 minutes to remove air bubbles. During spraying, the spraying pressure is controlled at 0.45 MPa, and the spraying distance is 220 mm. The epoxy primer has a solids content of 61% and a suitable pigment volume concentration (PVC) to ensure a 32 μm epoxy primer coating thickness.

[0106] After the primer is applied, a flash-drying process is performed. The profile is sent into a flash-drying oven and kept at 85°C for 14 minutes. This process removes 32% of the solvent from the primer, leaving it in a semi-cured state to prevent problems in subsequent processes.

[0107] Next, the topcoat is applied. Within 30 minutes after the primer flash-dry, the profile is coated with fluorocarbon topcoat using an electrostatic sprayer (1.0mm nozzle diameter). The relative humidity of the spraying environment is controlled at 62%, the spraying pressure is controlled at 0.35MPa, the spraying distance is 280mm, the fluorine content of the fluorocarbon topcoat is 19%, the gloss (60°) is 55GU, and the thickness of the fluorocarbon topcoat is ensured to be 22μm.

[0108] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature inside the curing oven is raised to 165°C at a heating rate of 3.5°C / min. Then, it is held at this temperature for 55 minutes. After curing, the profile is transferred to a room temperature environment of 21°C to cool to room temperature, so that the crosslinking degree of the coating reaches 91%.

[0109] Testing showed that the coating adhesion of the multi-cavity regenerated aluminum profile treated in this embodiment was 5.1 MPa, the impact resistance was 51 kg·cm, and the neutral salt spray test duration reached 1020 h. After optimizing the chemical degreasing parameters, the oil stains were removed more thoroughly, the coating performance was better, and it could meet the usage requirements of multi-cavity profiles.

[0110] Example 5

[0111] This embodiment optimizes the pickling and rust removal parameters for irregular curved profiles (R35mm) and adopts the following spraying process:

[0112] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profile is immersed in an 11% sodium hydroxide solution with 0.9% sodium dodecyl sulfate added as a surfactant. The solution temperature is controlled at 58℃, and the immersion time is 16 minutes. This process removes oil and oxide film from the profile surface. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The second step is acid pickling and rust removal. The degreased profile is immersed in a 14% hydrochloric acid solution with 0.45% hexamethylenetetramine added as a corrosion inhibitor. The solution temperature is maintained at 33℃, and the immersion time is 11 minutes to reduce surface corrosion and remove rust and impurities. The profile is then rinsed with deionized water until the pH of the residual water on the surface reaches 7. The third step is phosphating treatment. The rust-removed profiles are immersed in a 7.5% zinc-based phosphating solution (total acidity 28 points, free acidity 2.3 points) with a mass concentration of 48℃ and soaked for 16 minutes to form a phosphating film on the surface of the profiles. Then, the profiles are dried in a drying oven at 95℃ for 22 minutes to form a phosphating film. This phosphating film can withstand salt water immersion time ≥24h.

[0113] Next, electrostatic dust removal is performed using an electrostatic dust gun (75kV, 0.55MPa) to remove dust from the surface of the phosphated and dried profiles. The dust removal distance is controlled at 190mm. Considering the structural characteristics of the irregular curved surface, the angle and scanning method of the dust gun are adjusted. Dust is removed from the profile surface through a combination of electrostatic adsorption and compressed air blowing, ultimately ensuring that the dust content on the profile surface is 3.5mg / m³. 2 .

[0114] Then, a preheating treatment is carried out. The profiles that have undergone electrostatic dust removal are sent into a preheating furnace. The preheating furnace raises the temperature from room temperature to 135°C at a heating rate of 7.5°C / min. Then, it is held at this temperature for 22 minutes. The temperature difference on the surface of the profiles is controlled within ±4°C by temperature monitoring in the preheating furnace, while removing residual moisture from the surface of the profiles.

[0115] After preheating, the primer is applied. The profiles are conveyed at a speed of 1.8 m / min using a conveyor system, while an electrostatic sprayer (1.4 mm nozzle diameter) applies the epoxy primer to the preheated profiles. Before spraying, the epoxy primer is preheated at 58°C for 11 minutes to remove air bubbles. During spraying, the spraying pressure is controlled at 0.55 MPa, and the spraying distance is 260 mm. The epoxy primer has a solids content of 64% and the pigment volume concentration (PVC) is matched to ensure that the epoxy primer coating thickness reaches 38 μm.

[0116] After the primer is applied, a flash-drying process is performed. The profile is sent into a flash-drying oven and kept at 95°C for 11 minutes. This process removes 38% of the solvent from the primer, leaving it in a semi-cured state.

[0117] Next, the topcoat is applied. Within 30 minutes after the primer flash-dry, the profile is coated with fluorocarbon topcoat using an electrostatic sprayer (1.1mm nozzle diameter). The relative humidity of the spraying environment is controlled at 68%, the spraying pressure is controlled at 0.45MPa, the spraying distance is 320mm, the fluorine content of the fluorocarbon topcoat is 21%, the gloss (60°) is 65GU, and the thickness of the fluorocarbon topcoat is ensured to be 28μm.

[0118] Finally, a curing process is carried out. The profile with the topcoat sprayed is sent into a curing oven. The temperature inside the curing oven is raised to 175°C at a heating rate of 4.5°C / min. Then, it is held at this temperature for 45 minutes. After curing, the profile is transferred to a room temperature environment of 24°C to cool to room temperature, so that the crosslinking degree of the coating reaches 93%.

[0119] Testing showed that the coating adhesion of the irregular curved recycled aluminum profile treated in this embodiment was 5.4 MPa, the impact resistance was 54 kg·cm, and the neutral salt spray test duration reached 1080 h. After optimizing the pickling and rust removal parameters, the corrosion of the curved surface was effectively reduced, and the coating was more evenly distributed on the irregular curved surface, which can meet the application requirements of related fields.

[0120] Example 6

[0121] This embodiment optimizes the phosphating treatment parameters for grooved profiles (groove width 4mm) and adopts the following spraying process:

[0122] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profiles are immersed in a 10% sodium hydroxide solution containing 0.7% sodium dodecyl sulfate (surfactant) at 56°C for 17 minutes. This removes oil and oxide film from the profile surface through saponification. Afterward, the profiles are rinsed with deionized water until the residual pH is 7. The solution is changed after treating every 50 profiles. The second step is acid pickling to remove rust. The degreased profiles are immersed in a 13% hydrochloric acid solution containing 0.4% hexamethylenetetramine (corrosion inhibitor) at 32°C for 13 minutes to remove rust and impurities. Afterward, the profiles are rinsed with deionized water until the residual pH is 7, ensuring a corrosion rate ≤0.02 g / (m³). 2 The third step is phosphating treatment (optimized parameters). After rust removal, the profile is immersed in a zinc-based phosphating solution with a mass concentration of 6.5%, a total acidity of 26 points, and a free acidity of 2.1 points. It is soaked at 46°C for 17 minutes to ensure uniform phosphating in the grooves and form a phosphating film on the profile surface. Then it is dried in a drying oven at 92°C for 24 minutes. The formed phosphating film can withstand salt water immersion time ≥24 hours (5% sodium chloride solution, 25°C).

[0123] Next, electrostatic dust removal is performed, including "pre-blowing" and "electrostatic treatment": First, the surface of the phosphated and dried profile is blown with low-pressure compressed air at 0.2-0.3MPa, focusing on cleaning large particles of phosphate residue and floating dust remaining in the grooves to avoid damaging the phosphate film; then, an electrostatic dust removal gun (70kV, 0.5MPa) is used, controlling the dust removal distance at 170mm. The angle of the dust removal gun is adjusted for the bottom of the grooves, and a "slow sweep + reciprocating" scanning method is adopted, combined with real-time monitoring by a dust concentration sensor, to ultimately ensure that the dust content on the entire surface of the profile (including inside the grooves) is 3mg / m³. 2 .

[0124] Then, a preheating treatment is carried out. The profile after electrostatic dust removal is sent into the preheating furnace. The preheating furnace is heated from room temperature to 130°C at a heating rate of 7°C / min, and then held at that temperature for 24 minutes. At least 3 temperature sensors (including detection points in the tank) are installed in the furnace to monitor the temperature in real time, ensuring that the surface temperature difference of the profile after preheating is ±3.5°C and the surface moisture content is ≤0.1%, so as to remove residual moisture and avoid defects in subsequent spraying.

[0125] After preheating, the primer is sprayed. The profile is conveyed at a speed of 1.6 m / min using a conveying equipment, and the epoxy primer is sprayed using an electrostatic sprayer (1.3 mm nozzle diameter). Before spraying, the primer is preheated at 56℃ for 13 min to remove air bubbles. During spraying, the pressure is controlled at 0.5 MPa and the distance is 240 mm. The primer solids content is 63% and the pigment volume concentration is 35%, ensuring a coating thickness of 36 μm and uniform dispersion of zinc powder in the tank.

[0126] After the primer is sprayed, a flash-drying treatment is performed. The profile is sent into the flash-drying oven and kept at a temperature of 13 minutes through a segmented temperature control program (first preheating at a low temperature and then transitioning to 92℃). At the same time, a directional airflow auxiliary device is added to the corresponding area of ​​the groove to promote the evaporation of solvent in the tank. Finally, 36% of the solvent in the primer is removed, and the primer is in a semi-cured state.

[0127] Next, the topcoat is sprayed. Within 24 minutes after the primer flash-dry (wet-on-wet process), the fluorocarbon topcoat is sprayed using an electrostatic sprayer (1.1mm nozzle diameter). The spraying environment has a humidity of 66% and a temperature of 15-30℃. The pressure is controlled at 0.4MPa and the distance is 310mm. The fluorine content of the topcoat is 20%, and the gloss (60°) is 62GU. The coating thickness is 26μm, and the topcoat coverage in the tank is uniform.

[0128] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature is first increased to 120-140℃ at 4℃ / min and held for 5-8 minutes. Then, the temperature is increased to 170℃ and held for 50 minutes. At the end of the holding period, the temperature is reduced to 150-160℃ at 2-3℃ / min and held for 5 minutes. The oven temperature sensor (including the detection point in the tank) works in conjunction with the PID temperature control system to ensure that the temperature fluctuation is ±3℃. After curing, the material is transferred to a 23℃ ambient temperature environment to cool to room temperature. The cross-linking degree of the coating reaches 92%.

[0129] Testing showed that the recycled aluminum profile with grooved grooves treated in this embodiment had a coating adhesion of 5.3 MPa, an impact resistance of 53 kg·cm, and passed a neutral salt spray test for 1060 hours. After optimizing the phosphating parameters, the coating in the groove was more firmly bonded and could meet the needs of related fields.

[0130] Example 7

[0131] This embodiment targets thin-walled multi-cavity profiles (48mm×36mm, wall thickness 1.8mm). To control the acid pickling corrosion rate, the following spraying process is adopted:

[0132] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profiles are immersed in an 8.5% sodium hydroxide solution containing 0.55% sodium dodecyl sulfate (surfactant) at 51°C for 18.5 minutes to saponify and remove oil and oxide film. Afterwards, they are rinsed with deionized water until the residual water pH is 7. The solution is changed after treating every 50 profiles. The second step is acid pickling (to control the corrosion rate), where the degreased profiles are immersed in a 10.5% hydrochloric acid solution containing 0.32% hexamethylenetetramine (corrosion inhibitor) at 27°C for 14.5 minutes. The corrosion rate is precisely controlled to 0.015 g / (m²) using the corrosion inhibitor. 2 •h), to avoid excessive corrosion of thin walls; then rinse with deionized water until the residual water on the surface has a pH of 7. The third step is phosphating treatment, in which the rust-removed profile is immersed in a zinc-based phosphating solution with a mass concentration of 5.2%, a total acidity of 21 points, and a free acidity of 1.6 points, at 41℃ for 19.5 minutes to form a phosphating film; then dry in a drying oven at 83℃ for 27 minutes, and the phosphating film can withstand salt water immersion time ≥24 hours (5% sodium chloride solution, 25℃).

[0133] Next, electrostatic dust removal is performed, including "pre-purging" and "electrostatic treatment": First, the surface of the phosphated and dried profile is purged with low-pressure compressed air (0.2-0.3 MPa), focusing on cleaning large particles of impurities in the gaps of the thin-walled cavities; then, an electrostatic dust removal gun (62kV, 0.42MPa) is used, controlling the dust removal distance at 155mm, adjusting the scanning speed for the thin-walled cavities, and monitoring with a dust concentration sensor to ultimately ensure that the dust content on the entire surface of the profile is 4.2mg / m³. 2 .

[0134] Then, a preheating treatment is carried out. The profiles after electrostatic dust removal are sent into a preheating furnace. The preheating furnace is heated slowly at 5.5℃ / min (to avoid deformation of thin walls). After the temperature rises from room temperature to 122℃, it is held for 29 minutes. At least 3 temperature sensors (including detection points inside the cavity) are installed in the furnace to monitor the temperature in real time, ensuring that the surface temperature difference of the profiles after preheating is ±3℃ and the surface moisture content is ≤0.1%.

[0135] After preheating, the primer is sprayed. The profile is conveyed at a speed of 1.1 m / min using a conveying device (to avoid deformation of thin-walled materials). The epoxy primer is sprayed using an electrostatic sprayer (1.2 mm nozzle diameter). Before spraying, the primer is preheated at 51℃ for 14.5 min to remove air bubbles. During spraying, the pressure is controlled at 0.42 MPa and the distance is 210 mm. The primer has a solid content of 60.5% and a pigment volume concentration of 30%, ensuring a coating thickness of 31 μm.

[0136] After the primer is sprayed, a flash-drying treatment is performed. The profile is sent into the flash-drying oven and kept at a temperature of 14.5 minutes through a segmented temperature control program (first pre-heating at a low temperature and then transitioning to 82℃). At the same time, a directional airflow auxiliary device is added to the corresponding area of ​​the thin-walled cavity to promote the evaporation of solvent in the cavity, remove 31% of the solvent in the primer, and make the primer in a semi-cured state.

[0137] Next, the topcoat is applied. Within 29 minutes after the primer flash-dry (wet-on-wet process), the fluorocarbon topcoat is applied using an electrostatic sprayer (1.0mm nozzle diameter). The spraying environment is 61% humidity, 15-30℃ temperature, controlled pressure 0.32MPa, distance 260mm, topcoat fluorine content 18.5%, gloss (60°) 52GU, ensuring a coating thickness of 21μm, and avoiding paint accumulation that could lead to thin-wall deformation.

[0138] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature is first slowly increased at 3.2℃ / min (to avoid thermal deformation of thin walls) to 120-140℃ and held for 5-8 minutes. Then, the temperature is increased to 162℃ and held for 58 minutes. At the end of the holding period, the temperature is reduced to 150-160℃ at 2-3℃ / min and held for 5 minutes. The oven temperature sensor, in conjunction with the PID temperature control system, ensures that the temperature fluctuation is ±3℃. After curing, the profile is transferred to a room temperature environment of 20.5℃ and cooled to room temperature at a cooling rate of ≤10℃ / min. The cross-linking degree of the coating reaches 90.5%.

[0139] Testing revealed that the thin-walled multi-cavity regenerated aluminum profile treated in this embodiment exhibits a coating adhesion of 5.05 MPa, an impact resistance of 50.5 kg·cm, and a neutral salt spray test duration of 1010 h. The acid pickling corrosion rate is precisely controlled, and the thin-walled profile shows no deformation, thus meeting the requirements for use in the electronics and electrical appliance fields.

[0140] Example 8

[0141] This embodiment is for large-size multi-cavity remanufactured aluminum profiles (80mm×60mm, 6 cavities). The preheating treatment parameters are optimized, and the following spraying process is adopted:

[0142] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profiles are immersed in a 9.8% sodium hydroxide solution containing 0.85% sodium dodecyl sulfate (surfactant) at 57°C for 16.5 minutes to saponify and remove oil and oxide film. Afterwards, they are rinsed with deionized water until the residual surface water pH is 7. The solution is changed after treating every 50 profiles. The second step is acid pickling to remove rust, where the degreased profiles are immersed in a 12.8% hydrochloric acid solution containing 0.48% hexamethylenetetramine (corrosion inhibitor) at 34°C for 10.5 minutes to remove rust and impurities. Afterwards, they are rinsed with deionized water until the residual surface water pH is 7, ensuring the profile corrosion rate is ≤0.02 g / (m³). 2 The third step is phosphating treatment. After rust removal, the profile is immersed in a zinc-based phosphating solution with a mass concentration of 7.2%, a total acidity of 27 points, and a free acidity of 2.2 points. It is immersed at 49°C for 16.5 minutes to form a phosphating film. Then it is dried in a drying oven at 98°C for 21 minutes to form a 2.8μm phosphating film, which can withstand salt water immersion time ≥27h (5% sodium chloride solution, 25°C).

[0143] Next, electrostatic dust removal is performed, including "pre-blowing" and "electrostatic treatment": First, the surface of the phosphated and dried profile is blown with low-pressure compressed air (0.2-0.3 MPa), focusing on cleaning large particles of phosphate slag inside the large-size cavities; then, an electrostatic dust removal gun (78kV, 0.58MPa) is used, controlling the dust removal distance at 195mm. The angle and scanning path of the dust removal gun are adjusted for each of the six cavities, using a "slow sweep + reciprocating" method, combined with real-time monitoring by a dust concentration sensor, ultimately ensuring that the dust content on the entire surface of the profile (including each cavity) is 2.5mg / m³. 2 .

[0144] Subsequently, preheating treatment (parameter optimization) is carried out. The profiles after electrostatic dust removal are sent into the preheating furnace. The preheating furnace heats the profiles from room temperature to 138°C at a rate of 7.8°C / min (adapted to the thermal conductivity of large-sized profiles), and then holds the temperature for 21 minutes. At least three temperature sensors are installed in the furnace (each cavity has a detection point) to monitor and control the temperature in real time, ensuring that the temperature inside and outside of the large-sized profiles is consistent. After preheating, the surface temperature difference is ±4.5°C and the surface moisture content is ≤0.1%, avoiding uneven temperature due to the large size.

[0145] After preheating, the primer is sprayed. The profile is conveyed at a speed of 1.9 m / min using a conveying device, and the epoxy primer is sprayed using an electrostatic sprayer (nozzle diameter 1.45 mm). Before spraying, the primer is preheated at 57℃ for 10.5 min to remove air bubbles. During spraying, the pressure is controlled at 0.58 MPa and the distance is 285 mm. The primer solids content is 64.5% and the pigment volume concentration is 34.5%, ensuring a coating thickness of 39 μm and uniform coating inside each cavity.

[0146] After the primer is sprayed, a flash-drying treatment is performed. The profile is sent into the flash-drying oven and kept at a temperature of 10.5 minutes through a segmented temperature control program (first pre-heating at a low temperature and then transitioning to 98℃). At the same time, directional airflow auxiliary devices are added to the corresponding areas of the 6 chambers to promote the synchronous evaporation of solvents in each chamber, removing 39% of the solvent in the primer and making the primer semi-cured.

[0147] Next, the topcoat is applied. Within 21 minutes after the primer flash-dry (wet-on-wet process), the fluorocarbon topcoat is applied using an electrostatic sprayer (1.15mm nozzle diameter). The spraying environment is 69% humidity, 15-30℃ temperature, controlled pressure 0.48MPa, distance 345mm, topcoat fluorine content 21.8%, gloss (60°) 68GU, ensuring a coating thickness of 29μm and complete topcoat coverage inside each cavity.

[0148] Finally, a curing process is performed. The profiles after topcoat spraying are placed in a curing oven. The temperature is first increased to 120-140℃ at 4.8℃ / min and held for 5-8 minutes (to synchronize the internal and external temperatures of large-sized profiles). Then, the temperature is increased to 178℃ and held for 41 minutes. At the end of the holding period, the temperature is reduced to 150-160℃ at 2-3℃ / min and maintained for 5 minutes. The oven temperature sensor, in conjunction with the PID temperature control system, ensures that the temperature fluctuation is ±3℃. After curing, the profiles are transferred to a 24.8℃ ambient temperature environment to cool to room temperature, and the coating crosslinking degree reaches 94.5%.

[0149] Testing showed that the large-size multi-cavity regenerated aluminum profiles treated in this embodiment had a coating adhesion of 5.45 MPa, an impact resistance of 54.5 kg·cm, and passed a neutral salt spray test for 1090 hours. After optimizing the preheating parameters, the performance of the inner and outer coatings of the profiles was consistent, which can meet the needs of large-size profiles in the fields of construction and transportation.

[0150] Example 9

[0151] This embodiment optimizes the primer spraying parameters for irregular curved profiles (R50mm, wall thickness 3.8mm) and adopts the following spraying process:

[0152] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profiles are immersed in a 9.5% sodium hydroxide solution containing 0.78% sodium dodecyl sulfate (surfactant) at 54.5℃ for 17.2 minutes. This removes oil and oxide film from the curved surface through saponification. Afterwards, the profiles are rinsed with deionized water until the residual pH is 7. The solution is changed after treating every 50 profiles. The second step is acid pickling to remove rust. The degreased profiles are immersed in a 12.5% ​​hydrochloric acid solution containing 0.44% hexamethylenetetramine (corrosion inhibitor) at 31.5℃ for 12.3 minutes to remove rust and impurities. Afterwards, the profiles are rinsed with deionized water until the residual pH is 7, ensuring a corrosion rate ≤0.02g / (m³). 2 The third step is phosphating treatment. After rust removal, the profile is immersed in a zinc-based phosphating solution with a mass concentration of 6.9%, a total acidity of 26.5 points, and a free acidity of 2.15 points. The immersion is carried out at 47.5℃ for 17.2 minutes to form a phosphating film. Then, it is dried in a drying oven at 94.5℃ for 23.2 minutes. The phosphating film can withstand salt water immersion time ≥24 hours (5% sodium chloride solution, 25℃).

[0153] Next, electrostatic dust removal is performed, including "pre-blowing" and "electrostatic treatment": First, the surface of the phosphated and dried profile is blown with low-pressure compressed air at 0.2-0.3MPa, focusing on cleaning large particles of phosphate residue and floating dust remaining in the concave areas of irregular curved surfaces to avoid damaging the phosphate film; then, an electrostatic dust removal gun (75kV, 0.55MPa) is used, controlling the dust removal distance at 185mm. The angle of the dust removal gun is adjusted according to the curvature of the curved surface, and a "slow sweep + reciprocating" scanning method is adopted, combined with real-time monitoring by a dust concentration sensor, ultimately ensuring that the dust content on the entire surface of the profile (including curved concave areas) is 3.2mg / m². 2 .

[0154] Then, a preheating treatment is carried out. The profile after electrostatic dust removal is sent into the preheating furnace. The preheating furnace is heated from room temperature to 135℃ at a heating rate of 7.2℃ / min, and then held at that temperature for 22.5min. At least 3 temperature sensors (including detection points in key curved areas) are installed in the furnace to monitor the temperature in real time, ensuring that the surface temperature difference of the profile after preheating is ±4℃ and the surface moisture content is ≤0.1%, removing residual moisture to avoid defects in subsequent spraying.

[0155] After preheating, the primer is sprayed (optimized parameters). The profile is conveyed at a speed of 1.7 m / min using a conveyor, and the epoxy primer is sprayed using an electrostatic sprayer (1.42 mm nozzle diameter). Before spraying, the primer is preheated at 54.5℃ for 12.2 min to remove air bubbles. To address the issue of easy sagging on irregular curved surfaces, the spraying pressure is precisely controlled at 0.53 MPa and the spraying distance at 265 mm. At the same time, the movement trajectory of the sprayer is adjusted to adapt to the curvature of the curved surface to ensure uniform coverage of the paint without accumulation. The primer has a solid content of 62.8% and a pigment volume concentration of 35%, ultimately forming a primer coating with a thickness of 37.2 μm. Zinc powder is evenly dispersed on the curved surface.

[0156] After the primer is sprayed, a flash-drying treatment is performed. The profile is sent into the flash-drying oven and kept at a temperature of 11.2 minutes through a segmented temperature control program (first pre-heating at a low temperature and then transitioning to 94.5℃). At the same time, a directional airflow auxiliary device is added to the corresponding area of ​​the curved surface depression to promote local solvent evaporation and remove 37% of the solvent in the primer, so that the primer is in a semi-cured state.

[0157] Next, the topcoat is applied. Within 22.5 minutes after the primer flash-off (wet-on-wet process), the fluorocarbon topcoat is applied using an electrostatic sprayer (1.12mm nozzle diameter). The spraying environment is 67% humidity and 15-30℃, with a controlled pressure of 0.43MPa and a distance of 325mm. The spraying trajectory is adapted to the curved surface. The fluorine content of the topcoat is 20.6%, and the gloss (60°) is 65GU. The coating thickness is 27.2μm, and there are no missed sprays or runs on the curved surface.

[0158] Finally, a curing process is performed. The profile with the topcoat sprayed is sent to a curing oven. The temperature is first increased to 120-140℃ at 4.5℃ / min and held for 5-8 minutes. Then, the temperature is increased to 174℃ and held for 45.5 minutes. At the end of the holding period, the temperature is reduced to 150-160℃ at 2-3℃ / min and held for 5 minutes. Temperature sensors (including curved surface detection points) in the oven, in conjunction with a PID temperature control system, ensure that the temperature fluctuation is ±3℃. After curing, the profile is transferred to a room temperature environment of 22.8℃ to cool to room temperature. The cross-linking degree of the coating reaches 93.2%.

[0159] Testing showed that the shaped curved recycled aluminum profiles processed in this embodiment had a coating adhesion of 5.38 MPa, an impact resistance of 53.2 kg·cm, and passed a neutral salt spray test for 1075 hours. After optimizing the primer spraying parameters, the uniformity of the curved coating was significantly improved, which can meet the needs of transportation and other fields for shaped curved profiles.

[0160] Example 10

[0161] This embodiment is for grooved profiles (groove depth 7mm, wall thickness 2.6mm), with optimized flash-drying parameters and the following spraying process:

[0162] The first step is substrate pretreatment. The first step is chemical degreasing, where the recycled aluminum profiles are immersed in a 10.8% sodium hydroxide solution containing 0.82% sodium dodecyl sulfate (surfactant) at 56.5℃ for 16.2 minutes to saponify and remove oil and oxide film from the profile surface (including the tank). Then, they are rinsed with deionized water until the residual pH of the surface water is 7. The solution is changed after treating every 50 profiles. The second step is acid pickling to remove rust, where the degreased profiles are immersed in a 13.8% hydrochloric acid solution containing 0.43% hexamethylenetetramine (corrosion inhibitor) at 32.5℃ for 12.2 minutes to remove rust and impurities. Then, they are rinsed with deionized water until the residual pH of the surface water is 7, ensuring the profile corrosion rate is ≤0.02g / (m³). 2 The third step is phosphating treatment. After rust removal, the profile is immersed in a zinc-based phosphating solution with a mass concentration of 7.1%, a total acidity of 26.8 points, and a free acidity of 2.18 points. The solution is soaked at 46.5℃ for 17.2 minutes to form a phosphating film. Then, it is dried in a drying oven at 93.5℃ for 23.8 minutes to form a 2.6μm phosphating film. The solution can withstand salt water immersion time ≥26.5h (5% sodium chloride solution, 25℃).

[0163] Next, electrostatic dust removal is performed, including "pre-blowing" and "electrostatic treatment": First, the surface of the phosphated and dried profile is blown with low-pressure compressed air at 0.2-0.3MPa, focusing on the groove openings and bottoms to remove residual large particles of phosphate slag; then, an electrostatic dust removal gun (72kV, 0.52MPa) is used, controlling the dust removal distance at 175mm. For 7mm deep grooves, the insertion depth and angle of the dust removal gun are adjusted, using a "slow sweep + reciprocating" scanning method, combined with real-time monitoring by a dust concentration sensor, ultimately ensuring that the dust content on the entire surface of the profile (including the bottom of the groove) is 3.1mg / m³. 2 .

[0164] Then, a preheating treatment is carried out. The profile after electrostatic dust removal is sent into the preheating furnace. The preheating furnace is heated from room temperature to 132℃ at a heating rate of 7.2℃ / min, and then held at that temperature for 23.8min. At least 3 temperature sensors (including detection points in the tank) are installed in the furnace to monitor the temperature in real time, ensuring that the surface temperature difference of the profile after preheating is ±4.2℃ and the surface moisture content is ≤0.1%, so as to avoid residual moisture in the tank from affecting subsequent spraying.

[0165] After preheating, the primer is sprayed. The profile is conveyed at a speed of 1.65 m / min using a conveyor. The epoxy primer is sprayed using an electrostatic sprayer (nozzle diameter 1.35 mm). Before spraying, the primer is preheated at 56.5℃ for 12.2 min to remove air bubbles. The spraying pressure is controlled at 0.52 MPa and the distance is 255 mm. For deep grooves, the spraying angle is adjusted to ensure that the paint fills in. The primer has a solid content of 63.8% and a pigment volume concentration of 35%, forming a primer coating with a thickness of 36.8 μm.

[0166] After the primer is sprayed, a flash-drying treatment is performed (optimized parameters). The profile is sent into the flash-drying oven. To address the issue of solvent evaporation difficulties in the 7mm deep tank, a segmented temperature control program is set: first, a pre-heating at 85℃ for 5 minutes is used to allow the solvent in the tank and on the surface to evaporate simultaneously; then, the temperature is transitioned to 93.5℃ for 7.2 minutes, with a total flash-drying time of 12.2 minutes. At the same time, a directional airflow auxiliary device is added directly above the tank opening to remove the evaporated solvent in the tank through gentle airflow circulation, ensuring that 37.5% of the solvent in the primer is fully removed, leaving no solvent residue in the tank, and the primer is in a semi-cured state.

[0167] Next, the topcoat is applied. Within 23.8 minutes after the primer flash-dry (wet-on-wet process), the fluorocarbon topcoat is applied using an electrostatic sprayer (1.12mm nozzle diameter). The spraying environment is 66.5% humidity, 15-30℃ temperature, controlled pressure of 0.43MPa and distance of 315mm. The spraying angle is adjusted to ensure that the topcoat covers the bottom of the tank. The fluorine content of the topcoat is 20.8%, and the gloss (60°) is 66GU, forming a topcoat coating with a thickness of 26.8μm.

[0168] Finally, a curing process is performed. The profile with the topcoat sprayed is sent into a curing oven. The temperature is first increased to 120-140℃ at 4.2℃ / min and held for 5-8 minutes. Then, the temperature is increased to 172℃ and held for 46.5 minutes. At the end of the holding period, the temperature is reduced to 150-160℃ at 2-3℃ / min and maintained for 5 minutes. Temperature sensors (including detection points in the tank) in the oven, in conjunction with a PID temperature control system, ensure that the temperature fluctuation is ±3℃. After curing, the material is transferred to a room temperature environment of 23.5℃ to cool to room temperature. The cross-linking degree of the coating reaches 92.8%.

[0169] Testing showed that the recycled aluminum profile with grooved grooves processed in this embodiment had a coating adhesion of 5.32 MPa, an impact resistance of 53.8 kg·cm, and passed a neutral salt spray test for 1065 hours. After optimizing the flash-drying parameters, there were no solvent residue defects in the coating inside the groove, and the interlayer adhesion was significantly improved, which can meet the needs of the electronics and electrical appliance industry for deep groove profiles.

Claims

1. A coating process for recycled aluminum profiles, characterized in that: The following steps are included: S1. Substrate pretreatment: First, the profile is immersed in a sodium hydroxide solution containing surfactant for chemical degreasing. Then, the profile is immersed in a hydrochloric acid solution containing corrosion inhibitor for pickling and rust removal. Finally, the profile is immersed in a zinc phosphating solution for phosphating treatment and then dried after phosphating treatment. S2. Electrostatic dust removal: First, low-pressure compressed air with a pressure of 0.2-0.3MPa is used to pre-purge the surface of the profile. Then, a zone adaptation strategy is adopted to perform electrostatic dust removal on different cross-sectional structures of the profile. At the same time, the dust content on the surface of the profile is detected in real time by a dust concentration sensor. S3. Preheating treatment: The profiles that have undergone electrostatic dust removal are preheated using a preheating furnace. The preheating furnace is heated from room temperature to 120-140℃ at a heating rate of 5-8℃ / min, and then held at 120-140℃ for 20-30min. S4. Primer spraying: Apply epoxy primer to the preheated profile using an electrostatic spraying machine with a nozzle diameter of 1.2-1.5mm. The spraying pressure is 0.4-0.6MPa, the spraying distance is 200-300mm, and the epoxy primer has a solid content of ≥60% and a pigment volume concentration of 30-35%. Preheat the epoxy primer before spraying at a temperature of 50-60℃ for 10-15 minutes. S5. Flash-drying treatment: Use a flash-drying oven to flash-dry the profiles after the primer has been sprayed. First, keep the profiles at a low temperature for initial heat preservation, and then transition to the heat preservation temperature. The heat preservation temperature is 80-100℃ and the heat preservation time is 10-15 minutes. S6. Topcoat spraying: Within 30 minutes after the primer flash-off, apply fluorocarbon topcoat to the profile using a wet-on-wet process. The relative humidity of the spraying environment is ≤70%, the temperature is 15-30℃, the spraying pressure is 0.3-0.5MPa, and the spraying distance is 250-350mm. S7. Curing treatment: Use a curing oven to cure the profile after the topcoat has been sprayed. During the curing process, first raise the temperature to 120-140℃ at a rate of 3-5℃ / min and keep it at that temperature for 5-8 minutes. Then raise the temperature to 160-180℃ at the same rate and keep it at that temperature for 40-60 minutes. At the end of the holding period, lower the temperature to 150-160℃ at a rate of 2-3℃ / min and maintain it for 5 minutes.

2. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S1, the sodium hydroxide solution has a mass concentration of 8-12%, the temperature is maintained at 50-60℃, the soaking time is 15-20 minutes, and the surfactant is sodium dodecyl sulfate with a mass concentration of 0.5-1%; the hydrochloric acid solution has a mass concentration of 10-15%, the temperature is maintained at 25-35℃, the soaking time is 10-15 minutes, the corrosion inhibitor is hexamethylenetetramine with a mass concentration of 0.3-0.5%; the zinc phosphating solution has a mass concentration of 5-8%, a total acidity of 20-30 points, a free acidity of 1.5-2.5 points, the solution temperature is maintained at 40-50℃, and the soaking time is 15-20 minutes.

3. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S1, the phosphated profiles are dried in a drying oven at a temperature of 80-100℃ for 20-30 minutes.

4. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S2, an electrostatic dust removal gun is used for electrostatic treatment. For the planar area of ​​the profile, the electrostatic dust removal gun scans along the length of the profile with a voltage of 60-80kV, an air pressure of 0.4-0.6MPa, and a dust removal distance of 150-200mm. For the interior of the multi-cavity parts of the profile, the recessed areas of irregular curved surfaces, and the bottom of grooves, the angle between the electrostatic dust removal gun and the surface of the profile is adjusted to fit the contour of the concealed parts.

5. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In S3, at least three temperature sensors are installed in the preheating furnace, located at the front, middle and rear of the furnace body, respectively, to monitor the temperature of different areas in the furnace in real time. The surface temperature difference of different areas of the preheated profile is controlled within ±5℃, and the surface moisture content of the profile is ≤0.1%.

6. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S4, the preheated profile is conveyed using a conveying device, and the conveying speed of the profile is matched with the spraying speed of the electrostatic spraying machine, while the epoxy primer coating thickness is maintained at 30-40μm.

7. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In S5, the initial heat preservation time is 3-5 minutes, and a directional airflow auxiliary device is set in the flash drying oven to make the airflow circulate in the multi-cavity interior of the profile, the concave part of the irregular curved surface, and the bottom area of ​​the groove.

8. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S6, an electrostatic spraying machine with a nozzle diameter of 1.0-1.2mm is used to spray fluorocarbon topcoat.

9. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In S6, the thickness of the fluorocarbon topcoat coating is 20-30 μm.

10. The coating process for recycled aluminum profiles according to claim 1, characterized in that: In step S7, after the constant temperature and heat preservation process is completed, the profile is removed from the curing oven by a conveying device and transferred to a normal temperature environment of 20-25℃ to cool naturally to room temperature.

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