Aluminum veneer spraying process

Abstract

The invention relates to the technical field of aluminum product processing, in particular to an aluminum veneer spraying process. According to the scheme, the regularly-arranged grids and the concave parts are machined on the surfaces of the aluminum veneers, the micro-convex structures are formed on the edges of the concave parts, the micron-sized porous structures are formed at the bottoms of the concave parts, and a multi-stage attachment system combining a surface layer rough structure and a fine anchoring structure is constructed. The micro protrusions can form a mechanical locking effect on the coating, the micron-sized porous structure can adsorb primer through the capillary effect, the contact area of the coating and the substrate is greatly increased in cooperation with the rough surface of the concave part, and the problem that the coating is prone to stripping due to the fact that a traditional technology only depends on physical adsorption is solved. The coating can still keep stable combination under the environments of long-term vibration, temperature difference change and the like, and the service life of a product is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to the field of aluminum product processing technology, specifically to an aluminum single-panel spraying process. Background Technology

[0002] Aluminum single-layer panels, as a lightweight, high-strength, and easily processed metal material, are widely used in architectural decoration, rail transportation, aerospace, and other fields. Their surface properties (such as corrosion resistance, wear resistance, and decorative properties) are crucial to the overall product quality. With the expansion of application scenarios, the requirements for the adhesion, weather resistance, and functionality of aluminum single-layer panel surface coatings are increasing, and traditional processing techniques are gradually revealing their key shortcomings.

[0003] In existing technologies, aluminum single-panel surface treatment often involves simple sandblasting to create a rough surface followed by direct overall spraying. This relies solely on the macroscopic roughness to enhance coating adhesion, lacking microscopic anchoring structures. Consequently, under long-term vibration and temperature variations, the coating struggles to maintain stable adhesion through physical adsorption alone, leading to peeling and severely impacting product lifespan and safety performance.

[0004] Therefore, developing an aluminum single-panel spraying process that can enhance the coating anchoring effect and significantly improve the adhesion strength through precise structural design has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To address the above problems, this invention discloses an aluminum single-panel spraying process, comprising the following steps:

[0006] S1: A regularly arranged grid is formed on the surface of the aluminum panel, with recesses inside the grid and a rough surface on the outer surface of the recesses;

[0007] S2: The depth of the recessed portion gradually changes from the edge to the center, with the edge forming a micro-protrusion structure and the bottom forming a micron-level porous structure by laser etching.

[0008] S3: Apply primer, functional intermediate layer and topcoat in sequence. The primer is used for the recessed parts, and the functional intermediate layer and topcoat cover the entire aluminum panel.

[0009] S4: Apply primer to the recessed area in a directional manner. After the primer is surface dry, apply the functional intermediate layer and topcoat to the entire aluminum panel in sequence.

[0010] S5: Grind and smooth the surface of the sprayed aluminum panel.

[0011] In step 2, the depth of the recess gradually decreases from the edge to the center.

[0012] In step 2, the micro-protrusion is a hook-shaped structure inclined toward the center of the recess, with a height of 50-100μm.

[0013] In step 2, the pore size of the micron-scale porous structure is 5-20 μm, and the roughness Ra of the outer surface of the recess is controlled between 3.2-6.3 μm.

[0014] In step 3, the primer is a modified epoxy primer, and 5-8% aluminum powder is added thereto.

[0015] In step 3, the functional intermediate layer is filled with functional fillers according to the application scenario. When used for exterior walls, 20% hollow glass microspheres are added; when used indoors, 5% antibacterial zeolite powder is added.

[0016] In step 3, the topcoat is a fluorocarbon resin, wherein the PVDF content is ≥70%, and it forms an interpenetrating network structure with the primer, and the elongation at break of the coating is ≥200%.

[0017] In step 4, a high-pressure airless spray gun is used when directional spraying the primer, with a spray gun pressure of 15-20 MPa.

[0018] In step 4, the primer surface drying condition is to be placed at 25℃ for 2 hours, and the total thickness of the intermediate layer and topcoat of the overall spraying is controlled at 80-120μm, and the actual coating thickness of the recessed area is 30% higher than that of the non-recessed area.

[0019] This application's solution constructs a multi-level adhesion system combining a rough surface structure and a fine anchoring structure by processing regularly arranged grids and recesses (millimeter-level visible structures) on the surface of an aluminum panel, forming micro-protrusions (micrometer-level) at the edges of the recesses and micrometer-level porous structures at the bottom. The micro-protrusions provide mechanical locking for the coating, while the micrometer-level porous structures adsorb the primer through capillary action. Combined with the rough surface of the recesses, this significantly increases the contact area between the coating and the substrate, solving the problem of easy coating peeling caused by traditional processes relying solely on physical adsorption. This allows the coating to maintain stable adhesion even under long-term vibration and temperature variations, significantly extending product lifespan. Attached Figure Description

[0020] Figure 1 This is a flowchart of an aluminum single-panel spraying process in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of a grid structure on another aluminum single-layer panel in an embodiment of this application. Detailed Implementation

[0022] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The principles and features of this invention are described below with reference to the accompanying drawings. The examples given are only for explaining this invention and are not intended to limit the scope of this invention.

[0023] The term "comprising" and other similar expressions used in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, or apparatus that includes a series of steps or units but is not limited to the steps or units listed.

[0024] Example 1: As Figure 1 As shown, an aluminum single-panel spraying process includes the following steps:

[0025] S1: A regularly arranged grid is formed on the surface of the aluminum panel, with recesses inside the grid and a rough surface on the outer surface of the recesses;

[0026] S2: The depth of the recessed portion gradually changes from the edge to the center, with the edge forming a micro-protrusion structure and the bottom forming a micron-level porous structure by laser etching.

[0027] S3: Apply primer, functional intermediate layer and topcoat in sequence. The primer is used for the recessed parts, and the functional intermediate layer and topcoat cover the entire aluminum panel.

[0028] S4: Apply primer to the recessed area in a directional manner. After the primer is surface dry, apply the functional intermediate layer and topcoat to the entire aluminum panel in sequence.

[0029] S5: Grind and smooth the surface of the sprayed aluminum panel.

[0030] By processing regularly arranged grids (such as...) on the surface of aluminum panels Figure 2 As shown, the coating consists of a surface roughness layer and a recessed area (millimeter-level visible structure). Micro-protrusions (micrometer-level) are formed at the edges of the recessed area, and a micrometer-level porous structure is formed at the bottom, creating a multi-level adhesion system that combines a rough surface structure with a fine anchoring structure. The micro-protrusions provide mechanical locking to the coating, while the micrometer-level porous structure adsorbs the primer through capillary action. Combined with the rough surface of the recessed area, this significantly increases the contact area between the coating and the substrate, solving the problem of easy peeling caused by relying solely on physical adsorption. This allows the coating to maintain stable adhesion even under long-term vibration and temperature changes.

[0031] Example 2: This example is for aluminum single panels used in high-cleanliness indoor environments (such as medical and food processing workshops), which need to balance antibacterial properties and surface smoothness. The specific processing technology is as follows:

[0032] S101: Utilizing aluminum panels, a 3mm diameter circular grid with a 1mm mesh spacing is formed through laser processing. The circular grid reduces stress concentration, making it suitable for lightweight installation in dry indoor environments. The smaller grid spacing increases the overall coating adhesion area. Recesses within the grid are formed using laser engraving with multi-segment power gradient engraving, avoiding edge burrs caused by single-power processing. Simultaneously, laser scanning parameters are adjusted to create a rough surface on the outer surface of the recesses, achieving initial roughness standards. This rough surface increases the contact area with the primer, laying the foundation for subsequent coating adhesion.

[0033] S102: The laser power is controlled to make the depth of the recess gradually change from the edge to the center, with an edge depth of 0.2mm and a center depth of 0.05mm. This gradient design guides the paint during filling, as the deeper edge recess creates a larger "accommodation space," allowing the paint to preferentially fill the edge area sufficiently. The shallower center recess, on the other hand, limits excessive accumulation due to the paint's own fluidity, preventing the paint film from becoming too thin and cracking at the edges due to insufficient filling. It also reduces the problem of excessive edge load caused by paint accumulation in the center spilling over to the edges. The laser-processed edge micro-protrusions are hook-shaped structures tilted towards the center at a 35° angle. This angle provides mechanical locking to the paint without being too large, which would hinder paint filling during spraying. With a height of 60μm and a bottom width of 90μm, the dimensions are designed to meet the coating thickness requirements of indoor scenarios (this size is suitable for a general scenario coating thickness of 70μm (primer + intermediate layer + topcoat). The 75μm height ensures coverage by the 60μm coating while allowing for sufficient allowance for polishing to prevent over-polishing and exposure of the protrusions). This prevents the substrate from being exposed after polishing due to excessive protrusion height. The bottom is laser-etched to form a micron-sized porous structure with a 6μm pore size. This pore size matches the aluminum powder particle size (4μm) in the primer, allowing for primer adsorption through capillary effect. The resulting roughness Ra is 3.5μm, further enhancing primer adhesion strength.

[0034] S103: The primer is a modified epoxy primer (E-51 epoxy resin and polyamide mixed in a 1:1 ratio). This ratio ensures adhesion while improving curing speed, making it suitable for rapid indoor application. It contains 5% aluminum powder (4μm particle size). The aluminum powder is similar in material to the aluminum veneer substrate, enhancing interlayer compatibility. Its smaller particle size compared to the porous structure allows for thorough filling of pores. The functional intermediate layer contains 6% antibacterial zeolite powder (12μm particle size, 99.8% antibacterial rate). This high proportion of antibacterial filler meets the antibacterial requirements of high-cleanliness environments. The particle size is matched to the intermediate layer thickness (25μm), preventing uneven coating due to excessively large particles. The topcoat uses fluorocarbon resin with 71% PVDF content, balancing scrub resistance and gloss. Its 205% elongation at break helps withstand micro-deformation caused by changes in indoor temperature.

[0035] S104: The directional primer is applied using a high-pressure airless spray gun at 16 MPa, with a nozzle diameter of 0.45 mm and a spraying distance of 260 mm. This pressure and nozzle combination produces a finely atomized primer that precisely fills the tiny porous structures. The closer spraying distance reduces paint mist diffusion, making it suitable for fine processing in small indoor areas. After surface drying for 2 hours at 25°C, the entire surface is sprayed with a functional intermediate layer (25 μm thick) and a topcoat (45 μm thick), for a total thickness of 70 μm. The thinner total thickness reduces the risk of coating peeling in indoor environments. The coating thickness in recessed areas is 30% higher than in non-recessed areas, ensuring full coating coverage in recesses and enhancing overall adhesion.

[0036] S105: After the topcoat has cured (25℃ / 22h), hand-polish with 600-grit silicon carbide sandpaper until the surface roughness Ra≤0.5μm. High-grit sandpaper can produce a smooth surface, meeting the easy-to-clean requirements of high-cleanliness scenarios. Hand-polishing allows for precise control of the force, avoiding damage to the thin coating.

[0037] Example 3: This example is applicable to aluminum single panels used in exterior wall applications requiring strong weather resistance (such as high-rise building exterior walls), which need to withstand harsh environments such as wind, rain, and ultraviolet radiation. The process steps are as follows:

[0038] S201: Utilizes aluminum single-panel aluminum, laser-processed to form a 5mm side-length hexagonal grid with a 2.5mm grid spacing. The hexagonal structure offers excellent mechanical properties, effectively dispersing stress generated by wind pressure on the exterior wall. The larger grid size and spacing are suitable for large-area exterior wall processing, improving production efficiency. Laser engraving creates recesses, which are shaped by adjusting power and scan count. Simultaneously adjusting scanning parameters creates a rough surface for the recesses. Exterior wall applications require a higher surface roughness to resist coating peeling caused by strong winds.

[0039] S202: The laser power gradient results in a recessed area with an edge depth of 0.3mm and a center depth of 0.1mm, creating a smooth transition. The deeper edge depth enhances the anchoring effect on the thick coating, mitigating the weight of the thick exterior wall coating. The micro-protrusions at the edges are hook-shaped structures tilted towards the center at a 50° angle, with the steeper angle creating stronger mechanical locking force; the height is 90μm and the bottom width is 110μm, dimensions adapted to thick exterior wall coatings (this size is suitable for a general scenario with a total coating thickness of 110μm (primer + intermediate layer + topcoat), the 90μm height ensures it can be covered by the 110μm coating, while reserving a certain amount of grinding allowance to avoid over-grinding and exposing the protrusion), ensuring the protrusion is completely covered. The bottom laser etching forms a micron-level porous structure with a pore size of 15μm. The larger pore size can accommodate more exterior wall primer (containing 7% aluminum powder), with a roughness Ra of 5.8μm, significantly increasing the bonding area with the thick coating.

[0040] S203: The primer is a modified epoxy primer (E-44 and polyamide in a 1:0.8 ratio). The lower curing agent ratio improves the primer's flexibility, enabling it to withstand drastic temperature changes on exterior walls. It contains 7% aluminum powder (6μm particle size), and the higher aluminum powder content enhances UV reflection, protecting the substrate. The particle size is suitable for a 15μm porous structure. The functional intermediate layer contains 18% hollow glass microspheres (70μm particle size, 0.35g / cm³). 3 The high proportion of lightweight microspheres reduces the coating's weight while enhancing thermal insulation through a hollow structure, minimizing deformation of the exterior wall due to temperature differences. The particle size is matched to the intermediate layer thickness (45μm) to prevent protrusion from the coating surface. The topcoat contains 73% PVDF, a high PVDF content that significantly improves weather resistance and UV aging resistance, with an elongation at break of 215%, allowing it to adapt to a wide range of temperature deformation on the exterior wall.

[0041] S204: The directional primer is applied using a high-pressure airless spray gun at 19 MPa, with a nozzle diameter of 0.55 mm and a spraying distance of 320 mm. The higher pressure is suitable for filling deeper depressions and larger porous structures; the wider nozzle and longer distance improve the efficiency of large-area exterior wall spraying. After surface drying for 2 hours at 25°C, the entire surface is sprayed with a functional intermediate layer (45 μm thick) and a topcoat (65 μm thick), for a total thickness of 110 μm. The thicker coating enhances the barrier effect against external erosion; the coating thickness in depressions is 30% higher than in non-depression areas, ensuring the coating integrity remains even under wind and rain.

[0042] S205: After curing (25℃ / 26h), mechanically sand with 300-grit alumina sandpaper until the surface roughness Ra≤0.9μm. Sanding with lower grit sandpaper can retain some surface texture, enhance rainwater flow, and reduce stain adhesion; mechanical sanding is suitable for large-area processing of exterior walls and improves efficiency.

[0043] Example 4: This example demonstrates a general-purpose aluminum single-panel spraying process, suitable for common indoor and outdoor scenarios (such as office building corridors and commercial exterior walls), balancing performance and cost. The steps are as follows:

[0044] S301: Made of aluminum single sheet, laser-processed to form a square grid with sides of 4mm and a grid spacing of 2mm. The square grid is easy to process and has a low cost; the medium-sized grid and spacing balance the adhesion area and processing efficiency, making it suitable for mass production in general scenarios. The laser engraving forms the recesses, and the shaping is achieved through power variation, simultaneously creating a rough surface for the recesses. The roughness is set to an intermediate value to meet the adhesion requirements of general scenarios.

[0045] S302: The recessed area has an edge depth of 0.25mm and a center depth of 0.08mm, achieved through gradual laser power variation. The edge micro-protrusion has a 40° tilt angle, a height of 75μm, and a bottom width of 100μm. The central dimension is adapted to a general coating thickness (this dimension is adapted to a general scene coating thickness of 90μm; the 75μm height ensures that it can be covered by the 90μm coating, while reserving a certain amount of grinding allowance to avoid over-grinding and exposing the protrusion), balancing adhesion strength and processing difficulty. The bottom laser etching forms a micron-level porous structure with a pore size of 10μm. The medium pore size is compatible with various coating systems, and the roughness Ra4.2μm meets the adhesion requirements of general scenes. S303: The primer is a modified epoxy primer (E-44 and polyamide in a 1:0.85 ratio). The intermediate ratio of curing agent gives the primer both a certain degree of hardness and flexibility, adapting to various environments; 6% aluminum powder (particle size 5μm) is added, and the medium proportion of aluminum powder balances cost and adhesion effect. The functional intermediate layer can be optionally supplemented with 10% hollow glass microspheres or 3% antibacterial zeolite powder, depending on the requirements. The low filler ratio controls costs while meeting basic functions (light heat insulation or antibacterial properties). The topcoat has a PVDF content of 72%, and the intermediate PVDF content strikes a balance between weather resistance and cost. With an elongation at break of 210%, it can withstand deformation in normal environments.

[0046] S304: The directional spraying primer pressure is 17MPa, nozzle diameter is 0.5mm, and the distance is 300mm. These parameters are set to suit general spraying needs, balancing precision and efficiency. After surface drying, a 35μm intermediate layer and a 55μm topcoat are applied, resulting in a total thickness of 90μm. This moderate coating thickness balances protective effect and material cost. The coating thickness in recessed areas is 30% thicker to ensure basic adhesion enhancement.

[0047] S305: After curing, sand with 400-grit sandpaper until Ra≤0.7μm. Sanding with medium-grit sandpaper will give a surface that balances smoothness and slight texture, suitable for the appearance requirements of most general scenarios.

[0048] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. An aluminum single-panel spraying process, characterized in that, Includes the following steps: S1: A regularly arranged grid is formed on the surface of the aluminum panel, with recesses inside the grid and a rough surface on the outer surface of the recesses; S2: The depth of the recessed portion gradually changes from the edge to the center, with the edge forming a micro-protrusion structure and the bottom forming a micron-level porous structure by laser etching. S3: Apply primer, functional intermediate layer and topcoat in sequence. The primer is used for the recessed parts, and the functional intermediate layer and topcoat cover the entire aluminum panel. S4: Apply primer to the recessed area in a directional manner. After the primer is surface dry, apply the functional intermediate layer and topcoat to the entire aluminum panel in sequence. S5: Grind and smooth the surface of the sprayed aluminum panel.

2. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (2), the depth of the recess gradually decreases from the edge to the center.

3. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (2), the micro-protrusion is a hook-shaped structure that is inclined toward the center of the recess and has a height of 50-100μm.

4. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (2), the pore size of the micron-sized porous structure is 5-20 μm, and the roughness Ra of the outer surface of the recess is controlled at 3.2-6.3 μm.

5. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (3), the primer is a modified epoxy primer, and 5-8% aluminum powder is added thereto.

6. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (3), the functional intermediate layer is filled with functional fillers according to the application scenario. When used for exterior walls, 20% hollow glass microspheres are added; when used indoors, 5% antibacterial zeolite powder is added.

7. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (3), the topcoat is a fluorocarbon resin, wherein the PVDF content is ≥70%, and it forms an interpenetrating network structure with the primer, and the elongation at break of the coating is ≥200%.

8. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (4), a high-pressure airless spray gun is used when directional spraying the primer, and the spray gun pressure is 15-20MPa.

9. The aluminum single-panel spraying process according to claim 1, characterized in that, In step (4), the primer surface drying condition is to be placed at 25℃ for 2 hours, the total thickness of the intermediate layer and topcoat of the overall spraying is controlled at 80-120μm, and the actual coating thickness of the recessed area is 30% higher than that of the non-recessed area.

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