Low-temperature curing process for preparing weather-resistant coating of metal protective net

Abstract

This application relates to the field of surface protection treatment technology for metal mesh components, and in particular to a low-temperature curing preparation process for a weather-resistant coating on metal protective mesh. The process includes: cleaning the surface of the metal protective mesh to be treated and dividing it into main wire areas, node areas, end areas, and mesh edge areas; applying a high-thixotropic sealing slurry to the end areas and performing low-temperature pre-gelling; applying an overall weather-resistant coating; removing liquid bridges in the mesh holes using directional liquid spraying and pulse air knife; performing film thickness compensation in the node areas; and finally performing low-temperature segmented curing, including leveling and drainage, low-temperature gelling, and low-temperature complete curing. This application can effectively solve the problems of uneven coating in the node areas of metal protective mesh, exposed corrosion of the end area cross-section, and clogging of mesh edges, achieving uniform coating coverage and synergistic weather resistance and corrosion protection in complex structural areas.

Description

Technical Field

[0001] This application relates to the field of surface protection treatment technology for metal mesh components, and in particular to a low-temperature curing preparation process for a weather-resistant coating of metal protective mesh. Background Technology

[0002] Metal protective netting, as a critical infrastructure in outdoor scenarios such as highways, railway slopes, municipal fences, and building protection, is typically made of low-carbon steel wire, galvanized steel wire, or alloy-coated steel wire through processes such as welding, weaving, stranding, and cutting. Existing surface treatment technologies commonly employ hot-dip galvanizing, powder coating, dip coating, or ordinary water-based anti-corrosion coating to protect the metal netting. These existing technologies generally treat the metal protective netting as a homogeneous metal component, applying coating to the wire surface through dip coating, spray coating, or dip-coating. Subsequent heating and baking or natural drying then form a continuous anti-corrosion coating, isolating the netting from moisture and corrosive media in the environment and extending the service life of the metal product.

[0003] However, in the existing technology, due to the complex mesh structure and numerous nodes, ends and mesh edges of the metal protective mesh, the overall coating process is prone to liquid accumulation and blistering or local exposure of the coating at the welding nodes, preferential corrosion at the cut surface due to inadequate sealing, and blockage and nodules at the mesh junctions due to the liquid bridge effect. It is difficult to achieve uniform coverage of complex structural areas and efficient curing under low temperature conditions at the same time. Summary of the Invention

[0004] This application provides a low-temperature curing process for preparing a weather-resistant coating on a metal protective mesh to solve the above-mentioned problems. The method includes:

[0005] S1. Clean the surface of the metal protective mesh to be processed and divide the metal protective mesh into the main wire area, node area, end area and mesh edge area. The node area includes welded nodes, cross-over nodes, twisted nodes or bending intersection areas. The end area includes cut ends, broken wire ends, bent and damaged ends or frame welded ends.

[0006] S2. Apply a high-thixotropic, low-temperature curing sealing slurry to the end area to form an end sealing layer in the end area. The coverage length of the end sealing layer along the wire axis is 1 to 5 times the wire diameter.

[0007] S3. Perform low-temperature pregelation treatment on the metal protective mesh with the end sealing layer formed thereon, so that the end sealing layer is in a surface-dry or semi-gel state.

[0008] S4. Apply an overall weather-resistant coating to the metal protective mesh after low-temperature pregelation to form a continuous wet film in the main mesh area, node area, end area and mesh edge area.

[0009] S5. After the overall weather-resistant coating is applied, the metal protective mesh is subjected to directional liquid spraying treatment to remove the liquid bridges and suspended droplets in the mesh edge area, while retaining the continuous wet film on the surface of the main mesh wire area.

[0010] S6. Perform pulse air knife film treatment on the metal protective net after directional liquid ejection to break the continuous liquid film remaining in the edge area of ​​the mesh and reduce mesh clogging.

[0011] S7. After pulse air knife film preparation, the node area is subjected to film thickness compensation treatment so that the dry film thickness of the cured node area is 1.15 to 1.80 times the dry film thickness of the main mesh area.

[0012] S8. The metal protective mesh after film thickness compensation treatment is subjected to low-temperature segmented curing. The low-temperature segmented curing includes a leveling and drainage stage, a low-temperature gel stage, and a low-temperature complete curing stage, so that the end area forms an end-sealed anti-corrosion layer, the node area forms a film thickness compensation protective layer, and the mesh edge area remains in a non-blocked state, thereby obtaining a weather-resistant coating for the metal protective mesh.

[0013] By dividing the metal protective mesh into different risk areas and implementing differentiated coating strategies, a high-thixotropic slurry is used to form an anti-flowing sealed cap layer at the ends. This is combined with pre-gelling to lock the position. Then, directional liquid spraying and pulse air knife are used to precisely remove residual liquid from the mesh without damaging the main wet film. Finally, node compensation and segmented curing balance the curing kinetic differences between thick and thin films. This solves the technical problems of easy exposure and blistering at nodes, easy corrosion and expansion at the ends, and easy clogging of mesh in the existing technology. Its beneficial effects are that it significantly reduces the exposure rate at the ends and the clogging rate of mesh, while improving the weather resistance and corrosion protection life of the overall coating.

[0014] Optionally, the metal protective netting may be welded wire mesh, woven metal protective netting, diamond-shaped protective netting, flexible slope protective netting, metal fence netting, or municipal isolation netting.

[0015] The diameter of the wires in the metal protective mesh is 1.0 to 8.0 mm, and the equivalent aperture of the mesh is 10 to 150 mm. In step S1, the surface cleaning includes degreasing, washing, surface activation and drying treatment, so that the main wire area, node area, end area and mesh edge area are free of visible oil and water film before coating.

[0016] By defining the applicable mesh types and size ranges and combining them with strict surface cleaning standards of "no visible oil stains and no visible water film", the bonding strength between the coating and the substrate interface is ensured, avoiding early peeling caused by substrate contamination. At the same time, this parameter range covers mainstream engineering application scenarios, making this process universally applicable and feasible for protective meshes of different specifications.

[0017] Optionally, in step S2, the high thixotropic low-temperature curing sealing slurry comprises the following components in parts by weight:

[0018] The mixture contains 45-70 parts of waterborne epoxy-modified acrylic resin or waterborne polyurethane-modified acrylic resin, 3-12 parts of low-temperature crosslinking agent, 5-20 parts of anti-corrosion filler, 2-10 parts of sheet-like shielding filler, 0.5-3 parts of silane coupling agent, 0.3-2 parts of thixotropic agent, 0.2-2 parts of additives, and deionized water.

[0019] The high thixotropic low-temperature curing sealing slurry has a construction viscosity of 1500–8000 mPa·s and a thixotropic index of 2.0–6.0.

[0020] By introducing a high thixotropic index (2.0-6.0) sealing slurry, and utilizing its shear thinning and restorative rheological properties, the slurry is easy to apply during construction. After shearing stops, it can quickly restore its structural strength to resist gravity flow. Combined with the physical barrier effect of the sheet-like shielding filler and the electrochemical passivation effect of the anti-corrosion filler, a dense and controllable thickness anti-corrosion barrier is formed at the end section, effectively blocking the path of moisture and corrosive media to penetrate from the cut surface.

[0021] Optionally, in step S2, the end area is coated with the end sealing layer by dot coating, roller coating, short-path dip coating, end-oriented spray coating or capillary adsorption coating.

[0022] The wet film thickness of the end sealing layer is 80–250 μm, and the dry film thickness of the cured end sealing layer is 40–120 μm; in step S3, the temperature of the low-temperature pre-gel treatment is 40–75 °C, and the time is 3–15 min.

[0023] By controlling the wet film thickness within the range of 80–250 μm and subjecting it to low-temperature pre-gelling treatment at 40–75 °C, the end sealing layer reaches a surface-dry or semi-gel state. This prevents the sealing layer from being washed away during subsequent overall dip coating and retains sufficient active groups to chemically cross-link with subsequent coatings. Thus, while ensuring the integrity of the end sealing, good interlayer bonding is achieved, avoiding delamination failure.

[0024] Optionally, in step S4, the overall weather-resistant coating is formed using a water-based low-temperature curing weather-resistant and anti-corrosion coating, which comprises the following components in parts by weight:

[0025] The mixture contains 50-75 parts of waterborne acrylic-modified epoxy resin, waterborne fluorosilicone-modified acrylic resin, or waterborne polyurethane-modified acrylic resin; 4-15 parts of low-temperature crosslinking agent; 5-18 parts of anti-corrosion pigments and fillers; 1-6 parts of weather-resistant additives; 2-12 parts of sheet-like shielding fillers; 0.2-1.5 parts of wetting and leveling agent; 0.1-1.0 parts of defoamer; 0.2-2.0 parts of thickening thixotropic agent; and deionized water.

[0026] Through the above technical solution, by selecting a resin system containing fluorosilicone or epoxy modified groups and compounding weather-resistant additives and sheet-like shielding fillers, a coating skeleton with excellent UV resistance, hydrolysis resistance and physical barrier function is constructed. With the synergistic effect of wetting and leveling agents and defoamers, a continuous, uniform and defect-free wet film base is formed on the complex network structure, providing a reliable carrier for subsequent processes.

[0027] Optionally, in step S4, the overall weather-resistant coating is applied by dip coating, spray coating, or a combination of spray coating and dip coating.

[0028] When applying the overall weather-resistant coating, the coating solid content is 35-65%, the application viscosity is 300-2500 mPa·s, the immersion time is 10-120 s, and the lifting speed is 0.05-0.50 m / s, so that the main mesh area forms a wet film thickness of 60-200 μm.

[0029] By precisely controlling the dipping time, lifting speed, and the solid content and viscosity of the coating, the adhesion of the coating to the wire mesh surface and the effect of gravity loss are dynamically balanced, ensuring that the main wire mesh area obtains a suitable wet film thickness of 60-200μm. This thickness range can meet the final dry film corrosion protection requirements and also leave a reasonable margin for subsequent liquid removal and air knife treatment, avoiding sagging caused by excessive initial film thickness or exposure caused by excessively thin film thickness.

[0030] Optionally, in step S5, the directional liquid ejection process is carried out by rotating liquid ejection, swinging liquid ejection, tilting conveying liquid ejection, or vibrating liquid ejection.

[0031] When directional liquid ejection is performed, the tilt angle of the metal protective net relative to the horizontal plane is 15-75°, the rotation speed is 60-450 r / min, and the liquid ejection time is 5-60 s; when vibration liquid ejection is used, the vibration frequency is 5-40 Hz and the amplitude is 1-10 mm.

[0032] By setting an inclination angle of 15 to 75° and utilizing the centrifugal force and inertial force generated by rotation or vibration, the liquid bridges and suspended droplets at the edge of the mesh are guided to flow and detach along the axial direction of the mesh wire. This parameter combination effectively removes excess coating that is prone to clogging without damaging the continuous wet film of the main mesh wire. It cuts off the path of liquid bridge curing from a physical mechanism and significantly reduces the mesh clogging rate.

[0033] Optionally, in step S6, the angle between the air outlet direction of the pulse air knife in the film-forming process and the surface of the metal protective mesh is 20-70°, the distance between the air knife and the surface of the metal protective mesh is 50-300mm, the air pressure is 0.02-0.20MPa, the pulse frequency is 0.5-5Hz, and the single pulse time is 0.2-2s.

[0034] By employing the above technical solution, using an oblique air outlet angle of 20-70° and a pulsed airflow mode, the continuous liquid film remaining at the mesh opening is broken by instantaneous high-energy impact. At the same time, the stress relaxation during the intermittent period avoids excessive reduction of the wet film on the main body by continuous high-pressure purging. This non-contact film-forming method accurately breaks the residual liquid bridge, further ensuring the permeability of the mesh opening, while maintaining the uniformity of the main coating thickness.

[0035] Optionally, in step S7, the film thickness compensation treatment is performed using micro-spraying, spot-drop coating, fine atomization repair coating, roller contact repair coating, or pitch template guided repair coating.

[0036] The application viscosity of the node compensation coating used for film thickness compensation is 1.2 to 3.0 times that of the coating used for the overall weather-resistant coating, so that the node area forms a dry film thickness of 60 to 180 μm after curing.

[0037] By using the above technical solution, a high-viscosity compensating coating with a viscosity 1.2 to 3.0 times that of the overall coating is used, and a fixed-point recoating method is employed, the coating can remain in the geometrically complex node depressions without flowing to the surrounding area. This forms a reinforced protective layer in the node area with a thickness 1.15 to 1.80 times that of the main mesh area, effectively compensating for the thin coating caused by electric field distribution or hydrodynamic effects at the node, and improving the local corrosion resistance redundancy.

[0038] Optionally, in step S8, the temperature of the leveling and drainage stage is 25-45°C and the time is 3-15 min; the temperature of the low-temperature gel stage is 50-75°C and the time is 10-30 min; and the temperature of the low-temperature complete curing stage is 80-120°C and the time is 15-60 min.

[0039] After low-temperature segmented curing, the dry film thickness of the main mesh area is 40-120 μm, the dry film thickness of the end area is 70-220 μm, the mesh clogging rate of the metal protective mesh is not higher than 2%, and the end exposed bottom rate is not higher than 1%.

[0040] Through the above technical solution, a three-stage low-temperature segmented curing process is adopted. First, in the low-temperature stage, residual microdroplets are promoted to migrate and be discharged to avoid pinholes. Second, in the medium-temperature stage, the coating gels and sets to prevent sagging. Finally, in the high-temperature stage, deep cross-linking is completed. This gradient heating strategy matches the differences in heat conduction and reaction kinetics of different regions (end thick film, node compensation layer, and main film), thereby achieving the comprehensive technical effect of simultaneously achieving dense end sealing, enhanced node protection, no mesh blockage, and no exposed substrate at the end under low-temperature conditions. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flow chart of a low-temperature curing process for preparing a weather-resistant coating for a metal protective mesh, provided as an embodiment of this application. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0044] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0045] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0046] Example 1

[0047] This embodiment provides a low-temperature curing preparation process for a weather-resistant coating of a metal protective mesh suitable for welded steel wire mesh, and verifies the comprehensive protective effect under the synergistic effect of zoned coating and low-temperature segmented curing.

[0048] Galvanized welded steel wire mesh with a wire diameter of 3.0 mm and a mesh size of 50 mm × 50 mm was selected as the base material.

[0049] S1. Surface Cleaning and Zoning: Immerse the protective mesh in a weakly alkaline degreasing solution at 45℃ for 5 minutes, rinse with clean water, and then treat with a silane activating solution with a pH of 5.0 for 60 seconds. Finally, dry with hot air until no visible oil or water film remains on the surface. Divide the mesh into the main wire area, welding node area, cutting end area, and mesh edge area.

[0050] S2. End Sealing: Prepare a high-thixotropic, low-temperature curing sealing slurry, composed of: 60 parts water-based epoxy-modified acrylic resin, 8 parts carbodiimide crosslinking agent, 12 parts zinc phosphate, 6 parts flake mica powder, 1.5 parts silane coupling agent, 1.0 part fumed silica, 1.0 part additives, and deionized water for adjustment. Adjust the application viscosity to 3500 mPa·s, with a thixotropic index of 3.5. Apply the slurry to the cut ends and the welded ends of the frame using a short-path dipping method, controlling the end sealing layer to cover a length of 9 mm (approximately 3 times the wire diameter) along the wire axis, with a wet film thickness of approximately 150 μm.

[0051] S3. Low-temperature pre-gelling: Place the sealed protective net in a 60℃ drying tunnel for 8 minutes to allow the sealed layer to reach a surface-dry state (not sticky to the touch, and without obvious stringiness).

[0052] S4. Overall Coating: Prepare a water-based low-temperature curing weather-resistant and anti-corrosion coating, composed of: 65 parts water-based fluorosilicone modified acrylic resin, 10 parts blocked isocyanate crosslinking agent, 10 parts anti-corrosion pigments and fillers, 3 parts weather-resistant additives, 8 parts glass flakes, 0.8 parts wetting and leveling agent, 0.5 parts defoamer, 1.0 part thickening thixotropic agent, and deionized water for conditioning. The coating has a solid content of 48% and an application viscosity of 900 mPa·s. Immerse the entire protective net in the coating for 30 seconds, then pull it up at a uniform speed of 0.15 m / s to form a wet film of approximately 120 μm in the main mesh area.

[0053] S5. Directional liquid removal: Place the coated protective net at a 45° angle on a rotary spin dryer and spin it at 180 r / min for 20 seconds to remove liquid bridges and suspended droplets from the edge of the mesh using centrifugal force.

[0054] S6. Pulse air knife film treatment: The protective net is treated with a pulse air knife. The air knife outlet direction is at an angle of 45° to the net surface, the distance is 150mm, the air pressure is 0.08MPa, the pulse frequency is 2Hz, the single pulse time is 1.0s, and the total treatment time is 15s, in order to break the residual continuous liquid film.

[0055] S7. Node compensation: The welded node area is repaired by micro-spraying. The viscosity of the node compensation coating is adjusted to 1800 mPa·s (about 2.0 times that of the overall coating). The amount of coating is controlled so that the dry film thickness of the node area after curing is 1.35 times that of the main wire mesh area.

[0056] S8. Low-temperature segmented curing: The treated protective net is sent into a segmented curing oven. The first stage is 35℃ for leveling and drainage for 8 minutes; the second stage is 65℃ for low-temperature gelation for 20 minutes; and the third stage is 95℃ for complete curing for 35 minutes.

[0057] The resulting metal protective mesh has a smooth appearance, free from sagging and shrinkage cavities. Testing revealed that the dry film thickness in the main mesh area was 65 μm, the dry film thickness in the node area was 88 μm, and the dry film thickness of the end sealing layer was 115 μm. There were no continuous liquid bridges at the mesh edges, and the mesh clogging rate was 0.5%; the end cross-section had no exposed metal, and the end exposure rate was 0%.

[0058] This embodiment successfully achieved differentiated and precise coating of each functional area of ​​the protective net under low-temperature conditions through a synergistic process of end pre-sealing, directional liquid spraying, pulse air knife, and node compensation. This effectively solved the problems of end corrosion and mesh clogging, and verified the feasibility of the technical solution.

[0059] Example 2

[0060] This embodiment aims to verify the impact of the lower limit of the end-capping layer coverage length parameter on the technical effect.

[0061] With all other preparation conditions the same as in Example 1, only the coverage length of the end sealing layer along the wire axis in step S2 was adjusted from 9 mm to 3.5 mm (approximately 1.2 times the wire diameter), while the other process parameters remained unchanged.

[0062] The dry film thickness of the end-sealing layer of the prepared product was 110 μm. Testing showed that the end-surface exposure rate was 0.5%, and the mesh clogging rate was 0.6%. The results indicate that even with a coverage length close to the lower limit (1 times the wire diameter), the high-thixotropic slurry can still form an effective sealing cap layer, and the end-sealing corrosion resistance still meets the standards, proving that the technical solution within this parameter range has good feasibility.

[0063] The end-sealing process of this invention can still effectively block corrosion paths near the lower limit of the coverage length being 1 to 5 times the wire diameter, demonstrating the robustness of the process.

[0064] Example 3

[0065] This embodiment aims to verify the impact of the upper limit of the low-temperature pregelation treatment temperature on the technical effect.

[0066] With all other preparation conditions the same as in Example 1, only the temperature of the low-temperature pregelation treatment in step S3 was adjusted from 60°C to 75°C, and the time was kept at 8 min, while the other process parameters remained unchanged.

[0067] The end-sealing layer of the prepared product showed good adhesion to the overall coating without delamination. Testing revealed a dry film thickness of 64 μm in the main mesh area and 87 μm in the node area, with a 0% end-surface exposure rate. These results demonstrate that, under the upper limit of the pre-gelling temperature, the end-sealing layer rapidly reaches a semi-gel state without excessive cross-linking, and still forms a good bond with the subsequent coating, proving the effectiveness of the temperature range.

[0068] The low-temperature pregelation process provided by this invention can achieve stable locking of the end layer and interlayer bonding within the temperature range of 40 to 75°C, and has strong adaptability.

[0069] Example 4

[0070] This embodiment aims to verify the effect of the lower limit of the tilt angle parameter on the anti-clogging effect in directional liquid ejection treatment.

[0071] With all other preparation conditions the same as in Example 1, only the tilt angle of the metal protective mesh relative to the horizontal plane in step S5 was adjusted from 45° to 15°, while the rotation speed and time remained unchanged, and the remaining process parameters remained unchanged.

[0072] The mesh clogging rate of the obtained product was 1.8%. Although slightly higher than that of Example 1, it was still below the control target of 2%. The results show that even with a small tilt angle, centrifugal force can effectively remove most of the liquid bridges, proving the feasibility of the lower limit of this parameter.

[0073] The directional liquid-spraying process of the present invention can effectively control the mesh clogging rate within the tilt angle range of 15 to 75°, meeting the needs of different production line layouts.

[0074] Example 5

[0075] This embodiment aims to verify the influence of the upper limit of the wind pressure parameter on the thickness of the main film during pulse air knife film forming.

[0076] With all other preparation conditions the same as in Example 1, only the air pressure of the air knife in step S6 was adjusted from 0.08MPa to 0.20MPa, while the other process parameters remained unchanged.

[0077] The dry film thickness of the main mesh area of ​​the obtained product was 62 μm, slightly lower than that in Example 1, but still within the range of 40–120 μm. The mesh clogging rate was 0.4%. The results show that under the upper limit of wind pressure, the pulse mode effectively avoids excessive purging of the main wet film, while still ensuring film thickness uniformity and mesh permeability.

[0078] The pulse air knife film-forming process of the present invention can achieve a balance between film forming and film preservation within an air pressure range of 0.02 to 0.20 MPa, with a wide process window.

[0079] Example 6

[0080] This embodiment aims to verify the effect of the upper limit of the film thickness compensation factor parameter in the node region on the appearance and performance of the coating.

[0081] With all other preparation conditions the same as in Example 1, the only difference was that the goal of the node compensation treatment in step S7 was adjusted to make the dry film thickness of the cured node area 1.80 times (i.e., about 117 μm) of the dry film thickness of the main mesh area. This was achieved by increasing the amount of micro-spraying, while the other process parameters remained unchanged.

[0082] The dry film thickness in the node region of the prepared product was 116 μm, with no obvious sagging or nodules. Bending tests showed no continuous cracks in the coating in the node region. The results indicate that even under the upper limit of the compensation factor, the high-viscosity compensation coating can still remain stably without inducing thick film defects, demonstrating the reliability of this parameter range.

[0083] The node film thickness compensation process of the present invention can form a high-quality reinforced protective layer in the range of 1.15 to 1.80 times, effectively improving the node corrosion resistance.

[0084] Example 7

[0085] This embodiment aims to verify the effect of the lower limit of the temperature during the fully cured stage in low-temperature segmented curing on the coating performance.

[0086] With all other preparation conditions the same as in Example 1, only the temperature of the low-temperature complete curing stage in step S8 was adjusted from 95°C to 80°C and the time was extended to 50 min, while the other process parameters remained unchanged.

[0087] The dry film hardness, adhesion, and salt spray resistance of the main mesh area of ​​the obtained product were comparable to those of Example 1. The end exposure rate was 0%, and the mesh clogging rate was 0.5%. The results show that, under the lower limit of the fully curing temperature, by appropriately extending the curing time, the coating can still achieve full cross-linking and the expected weather resistance and corrosion protection effect.

[0088] The low-temperature segmented curing process of the present invention can obtain coatings with excellent performance in the range of 80 to 120°C, and is particularly suitable for heat-sensitive substrates.

[0089] Example 8

[0090] This embodiment aims to comprehensively evaluate the significant technical effects of the preparation process of the present invention in solving end corrosion, node protection, and mesh hole plugging by setting a comparative example.

[0091] 1. Scale settings

[0092] Comparative Example 1: Traditional one-time dip coating process was used. No end pre-sealing, no liquid spraying air knife treatment, no node compensation, direct dip coating and one-time curing at 140℃ for 20 minutes.

[0093] Comparative Example 2: The end pre-sealing step is missing. Other steps are the same as in Example 1, but end sealing is not performed in S2; the entire coating is applied directly.

[0094] Comparative Example 3: The pulse air knife film-forming step is missing. Other steps are the same as in Example 1, but pulse air knife treatment is not performed in S6; natural drainage is relied upon instead.

[0095] Comparative Example 4: Lacks the node thickness compensation step. Other steps are the same as in Example 1, but node recoating is not performed in S7.

[0096] Comparative Example 5: Single-stage high-temperature curing was used. Other steps were the same as in Example 1, but the segmented curing was omitted, and the curing was carried out directly at 120°C for 30 minutes.

[0097] 2. Test Items and Results

[0098] The performance of the samples prepared in Examples 1 to 7 and the comparative samples were tested respectively, and the test results are summarized in Table 1.

[0099] Table 1 Comparison of performance test results between the examples and the comparative examples.

[0100] Example 1 65 88 115 0.5 0 0 1.2 No cracks Example 2 64 87 110 0.6 0.5 0 1.5 No cracks Example 3 64 87 112 0.5 0 0 1.3 No cracks Example 4 65 89 114 1.8 0 0 1.4 No cracks Example 5 62 85 113 0.4 0 0 1.3 No cracks Example 6 65 116 115 0.5 0 0 1.1 No cracks Example 7 66 89 116 0.5 0 0 1.4 No cracks Comparative Example 1 58 45 30 15.5 25.0 1 8.5 minor cracks Comparative Example 2 60 82 25 0.8 18.0 0 7.2 No cracks Comparative Example 3 64 86 114 12.3 0 0 1.5 No cracks Comparative Example 4 65 66 115 0.6 0 0 3.8 Obvious cracks Comparative Example 5 63 80 105 1.2 2.0 1 2.5 minor cracks

[0101] 3. Effect Analysis

[0102] As shown in Table 1, the performance indicators of Examples 1 to 7 are all superior to those of the comparative examples.

[0103] Specifically, compared with Comparative Example 2, Example 1 reduced the exposed end rate from 18.0% to 0% through end pre-sealing treatment, and the rust expansion width of the end after salt spray test was significantly reduced from 7.2mm to 1.2mm, which confirmed the key role of the "high thixotropic sealing + pre-gel" strategy in steps S2-S3 in blocking the end corrosion path.

[0104] Compared with Comparative Example 3, Example 1 significantly reduced the mesh clogging rate from 12.3% to 0.5% by introducing pulse air knife film treatment, indicating that step S6 can effectively remove residual liquid from the mesh and solve the clogging problem.

[0105] Compared with Comparative Example 4, Example 1 increased the dry film thickness in the node area to 1.35 times that of the main body through node film thickness compensation. After the salt spray test, the corrosion expansion of the node was significantly reduced, and no cracks were found in the bending test. This proved the effectiveness of step S7 in improving the corrosion resistance redundancy of the node and avoided early failure caused by the node coating being too thin.

[0106] Compared with Comparative Examples 1 and 5, the partitioned coating combined with low-temperature segmented curing process used in Example 1 not only significantly reduced the pore blockage rate and substrate exposure rate, but also improved the adhesion and flexibility of the coating in complex structures, avoiding the problems of uneven internal and external curing and thick film blistering caused by single-segment high-temperature curing.

[0107] In summary, through the coordinated operation of each step, this invention achieves comprehensive and high-quality protection of metal protective netting under low-temperature conditions, resulting in unexpected technical effects.

[0108] In this application embodiment, the test samples include the products prepared according to each embodiment in Examples 1 to 7. Experimental results show that the weather-resistant coating for metal protective mesh prepared by this invention exhibits excellent corrosion resistance, aging resistance, and damage resistance in harsh outdoor environments such as highway guardrails, railway slope protection nets, and municipal isolation nets. In particular, after 240 hours of neutral salt spray testing and artificial accelerated aging testing, the coating remained intact, with no rust expansion at the ends, no mesh blockage, and the adhesion level remained between 0 and 1. Therefore, the weather-resistant coating for metal protective mesh prepared by this invention can be used to prepare protective materials for preventing and / or treating structural failures of metal protective mesh caused by environmental corrosion, and is widely applicable to metal mesh component protection projects in transportation, construction, water conservancy, and other fields.

[0109] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A low-temperature curing preparation process for a weather-resistant coating on a metal protective mesh, characterized in that, include: S1. Clean the surface of the metal protective mesh to be processed and divide the metal protective mesh into the main wire area, node area, end area and mesh edge area. The node area includes welded nodes, cross-over nodes, twisted nodes or bending intersection areas. The end area includes cut ends, broken wire ends, bent and damaged ends or frame welded ends. S2. Apply a high-thixotropic, low-temperature curing sealing slurry to the end area to form an end sealing layer in the end area. The coverage length of the end sealing layer along the wire axis is 1 to 5 times the wire diameter. S3. Perform low-temperature pregelation treatment on the metal protective mesh with the end sealing layer formed thereon, so that the end sealing layer is in a surface-dry or semi-gel state. S4. Apply an overall weather-resistant coating to the metal protective mesh after low-temperature pregelation to form a continuous wet film in the main mesh area, node area, end area and mesh edge area. S5. After the overall weather-resistant coating is applied, the metal protective mesh is subjected to directional liquid spraying treatment to remove the liquid bridges and suspended droplets in the mesh edge area, while retaining the continuous wet film on the surface of the main mesh wire area. S6. Perform pulse air knife film treatment on the metal protective net after directional liquid ejection to break the continuous liquid film remaining in the edge area of ​​the mesh and reduce mesh clogging. S7. After pulse air knife film preparation, the node area is subjected to film thickness compensation treatment so that the dry film thickness of the cured node area is 1.15 to 1.80 times the dry film thickness of the main mesh area. S8. The metal protective mesh after film thickness compensation treatment is subjected to low-temperature segmented curing. The low-temperature segmented curing includes a leveling and drainage stage, a low-temperature gel stage, and a low-temperature complete curing stage, so that the end area forms an end-sealed anti-corrosion layer, the node area forms a film thickness compensation protective layer, and the mesh edge area remains in a non-blocked state, thereby obtaining a weather-resistant coating for the metal protective mesh.

2. The preparation process according to claim 1, characterized in that, The metal protective netting may be welded wire mesh, woven metal protective netting, diamond-shaped protective netting, flexible slope protection netting, metal fence netting, or municipal isolation netting. The diameter of the wires in the metal protective mesh is 1.0 to 8.0 mm, and the equivalent aperture of the mesh is 10 to 150 mm. In step S1, the surface cleaning includes degreasing, washing, surface activation and drying treatment, so that the main wire area, node area, end area and mesh edge area are free of visible oil and water film before coating.

3. The preparation process according to claim 1, characterized in that, In step S2, the high thixotropic low-temperature curing sealing slurry comprises the following components in parts by weight: The mixture contains 45-70 parts of waterborne epoxy-modified acrylic resin or waterborne polyurethane-modified acrylic resin, 3-12 parts of low-temperature crosslinking agent, 5-20 parts of anti-corrosion filler, 2-10 parts of sheet-like shielding filler, 0.5-3 parts of silane coupling agent, 0.3-2 parts of thixotropic agent, 0.2-2 parts of additives, and deionized water. The high thixotropic low-temperature curing sealing slurry has a construction viscosity of 1500–8000 mPa·s and a thixotropic index of 2.0–6.

0.

4. The preparation process according to claim 1, characterized in that, In step S2, the end area is coated with a sealing layer by dot coating, roller coating, short-path dipping coating, end-oriented spraying or capillary adsorption coating. The wet film thickness of the end sealing layer is 80–250 μm, and the dry film thickness of the cured end sealing layer is 40–120 μm; in step S3, the temperature of the low-temperature pre-gel treatment is 40–75 °C, and the time is 3–15 min.

5. The preparation process according to claim 1, characterized in that, In step S4, the overall weather-resistant coating is formed using a water-based low-temperature curing weather-resistant and anti-corrosion coating, which comprises the following components in parts by weight: The mixture contains 50-75 parts of waterborne acrylic-modified epoxy resin, waterborne fluorosilicone-modified acrylic resin, or waterborne polyurethane-modified acrylic resin; 4-15 parts of low-temperature crosslinking agent; 5-18 parts of anti-corrosion pigments and fillers; 1-6 parts of weather-resistant additives; 2-12 parts of sheet-like shielding fillers; 0.2-1.5 parts of wetting and leveling agent; 0.1-1.0 parts of defoamer; 0.2-2.0 parts of thickening thixotropic agent; and deionized water.

6. The preparation process according to claim 1, characterized in that, In step S4, the overall weather-resistant coating is applied by dip coating, spray coating, or a combination of spray coating and dip coating. When applying the overall weather-resistant coating, the coating solid content is 35-65%, the application viscosity is 300-2500 mPa·s, the immersion time is 10-120 s, and the lifting speed is 0.05-0.50 m / s, so that the main mesh area forms a wet film thickness of 60-200 μm.

7. The preparation process according to claim 1, characterized in that, In step S5, the directional liquid ejection process is carried out by rotating liquid ejection, swinging liquid ejection, tilting conveying liquid ejection, or vibrating liquid ejection. When directional liquid ejection is performed, the tilt angle of the metal protective net relative to the horizontal plane is 15-75°, the rotation speed is 60-450 r / min, and the liquid ejection time is 5-60 s; when vibration liquid ejection is used, the vibration frequency is 5-40 Hz and the amplitude is 1-10 mm.

8. The preparation process according to claim 1, characterized in that, In step S6, the angle between the air outlet direction of the pulse air knife in the film-forming process and the surface of the metal protective mesh is 20-70°, the distance between the air knife and the surface of the metal protective mesh is 50-300mm, the air pressure is 0.02-0.20MPa, the pulse frequency is 0.5-5Hz, and the single pulse time is 0.2-2s.

9. The preparation process according to claim 1, characterized in that, In step S7, the film thickness compensation process is carried out by micro-spraying, fixed-point dripping, fine atomization repair coating, roller contact repair coating, or pitch template guided repair coating. The application viscosity of the node compensation coating used for film thickness compensation is 1.2 to 3.0 times that of the coating used for the overall weather-resistant coating, so that the node area forms a dry film thickness of 60 to 180 μm after curing.

10. The preparation process according to claim 1, characterized in that, In step S8, the temperature of the leveling and drainage stage is 25-45℃ and the time is 3-15 min; the temperature of the low-temperature gel stage is 50-75℃ and the time is 10-30 min; and the temperature of the low-temperature complete curing stage is 80-120℃ and the time is 15-60 min. After low-temperature segmented curing, the dry film thickness of the main mesh area is 40-120 μm, the dry film thickness of the end area is 70-220 μm, the mesh clogging rate of the metal protective mesh is not higher than 2%, and the end exposed bottom rate is not higher than 1%.

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