Surface treatment process for metal product
By forming a composite structure of phosphate or passivation layer-transition layer-topcoat layer on the surface of metal products, the problem of insufficient adhesion of functional layers on the surface of metal products is solved, achieving good scratch resistance and simplifying the production process, while improving the adhesion and protective performance of the topcoat layer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-10
AI Technical Summary
In existing technologies, the functional layer on the surface of metal products has insufficient adhesion to the underlying layer, which makes the topcoat layer easy to scratch and damage, resulting in weak protection. In particular, there are problems such as interlayer peeling and unsatisfactory dyeing effects in the surface treatment of aluminum and iron products.
Phosphating or passivation layers are used as pretreatment, followed by spraying powder coating to form a transition layer, which is then cured at high temperature under normal pressure. Finally, a topcoat layer is sprayed and cured to form a composite structure of phosphate or passivation layer-transition layer-topcoat layer, which enhances adhesion.
It improves the scratch resistance of metal products, simplifies the dyeing process, reduces the stringent requirements for pretreatment steps, improves production efficiency, and enhances the adhesion and protective performance of the topcoat layer.
Smart Images
Figure CN121820143A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of surface treatment and protection of metal products, and particularly relates to a surface treatment process for metal products. BACKGROUND
[0002] Metals or alloys with iron or aluminum as main materials are widely used. In order to improve the corrosion resistance, decoration and prolong the service life, it is usually necessary to apply a protective coating on the surface. However, due to the different properties of the materials, the existing mainstream processing technologies for iron and aluminum have their own problems, and the effects are not ideal.
[0003] For aluminum products, the current mainstream anodic oxidation or electrophoresis process can form a basic protective film, but in order to achieve better corrosion resistance and rich decorative color, it is necessary to rely on multiple subsequent processes such as sealing and coloring. This not only makes the process complex and increases energy consumption, but more importantly, the interface between these functional layers (such as coloring layer, sealing layer) and the bottom layer of the oxidation film or electrophoretic paint film mainly relies on physical adsorption or weak chemical action to combine, and there is an inherent shortcoming in the interlayer adhesion. Even if the pretreatment is strict, the fragile interface is easily affected by environmental or mechanical stress during use, which can cause interlayer peeling, resulting in failure of protection and deterioration of appearance, and long-term reliability of the product is difficult to guarantee.
[0004] For iron products, the focus in the pretreatment step is rust prevention. Blackening is a widely used traditional process. The process generates a dense black magnetite layer on the surface by reacting in an alkaline high-temperature or room-temperature solution, which can effectively isolate air and moisture and achieve basic rust prevention. However, there are obvious shortcomings: the film layer formed by the blackening process is relatively thin and has poor wear resistance, and a slight scratch can easily expose the bottom layer. If a topcoat layer is directly applied on the film layer, the topcoat layer can easily peel off together with the film layer; the surface of the metal after blackening is monotonous black, and if other colors are desired, dyeing is needed after blackening. However, the effect of dyeing is even less ideal because the blackening film itself is not strong enough, and the dyeing layer can easily peel off. Once the outer color layer is peeled off, not only the appearance is affected, but also the internal metal is corroded more quickly, leading to early scrapping of the product.
[0005] For example, in the field of strollers, the stroller frame is usually made of lightweight aluminum alloy. In order to meet the needs of consumers for appearance and scratch resistance, the metal surface is usually treated by coloring and painting using the above conventional method during manufacturing, which makes the adhesion between the functional layer formed on the metal surface and the metal surface not strong enough, and scratches can easily occur during packaging, transportation and use due to accidental scratches, which affects the complete coverage and protection function of the functional layer to different degrees.
[0006] Therefore, in view of the above technical problems, the present application is proposed. SUMMARY
[0007] The present application provides a surface treatment process for metal products, which at least solves one of the above technical problems. In the present application, the metal product can be an iron product or an aluminum product. According to the different material properties of the metal product, a pretreatment step is performed to form a phosphating layer or a passivation layer on the surface thereof. Then, a powder coating is sprayed on the surface of the phosphating layer or the passivation layer of the metal product, and after high-temperature curing, a transition layer is formed attached to the surface of the metal product. Finally, a paint is coated and cured on the transition layer to form a topcoat layer. The present application firmly attaches the transition layer to the surface of the metal product and enhances the adhesion of the topcoat layer, so that the metal product treated by the process of the present application has good scratch-resistant protective performance, solving the problem of insufficient adhesion of the topcoat layer and weak protection of the metal product surface from scratching in the prior art.
[0008] The present application increases the adhesion of the topcoat layer to the metal surface through the transition layer, and the metal product treated by powder spraying and paint spraying has better scratch-resistant protective performance, solving the problem of insufficient adhesion and weak protection of the metal surface from scratching in the prior art.
[0009] To solve the above technical problems, the present application provides a surface treatment process for metal products, comprising the following steps:
[0010] S1, pretreatment: performing corresponding surface treatment on the metal product;
[0011] S2, powder spraying and curing: uniformly spraying powder coating on the surface of the metal product after pretreatment, and then baking at normal pressure and 190-210°C for 10-15 min to cure the powder coating on the surface of the metal product to form a transition layer;
[0012] S3, topcoat spraying: uniformly spraying paint on the surface of the transition layer of the metal product;
[0013] S4, topcoat curing: baking at normal pressure and 170-190°C for 10-15 min to cure the paint on the surface of the metal product to form a topcoat layer;
[0014] The powder coating comprises the following components by weight percentage: polyester resin 23-25%, epoxy resin 34-36%, calcium carbonate 30-33%, and flatting curing agent 3.5-3.7%.
[0015] The surface treatment process for metal products as described above further comprises a functional additive accounting for 3-5% of the total weight of the powder coating; the functional additive can be at least one of ultraviolet protection agent, leveling agent, and defoaming agent.
[0016] A surface treatment process for metal products as described above, the powder coating further comprises pigments for toning, the pigments accounting for 1.5-1.8% of the total weight of the powder coating.
[0017] A surface treatment process for metal products as described above, the metal products are iron products, and the pre-treatment step S1 comprises a surface conditioning treatment to generate crystal nuclei on the surface of the iron products for depositing phosphate coating crystals.
[0018] A surface treatment process for metal products as described above, the iron products are completely immersed in a surface conditioning treatment chemical bath for 30-90 seconds, and the surface-treated iron products are transferred to a phosphating bath to form a phosphating layer on the surface of the iron products; the iron products sequentially undergo oil removal treatment, rust removal treatment and neutralization treatment before the phosphating treatment process, and the iron products are cleaned after each treatment process and then transferred to the next treatment process.
[0019] A surface treatment process for metal products as described above, the metal products are aluminum products, and the pre-treatment step S1 comprises a passivation treatment to remove the natural oxide layer on the surface of the aluminum products and form a passivation layer; the aluminum products sequentially undergo oil removal treatment and pickling treatment before the passivation treatment process, and the aluminum products are cleaned after each treatment process and then transferred to the next treatment process.
[0020] A surface treatment process for metal products as described above, the transition layer on the surface of the metal products after the powder spraying and curing of step S2 has a matte effect.
[0021] A surface treatment process for metal products as described above, the powder coating comprises the following components by weight percentage: polyester resin 24%, epoxy resin 35%, calcium carbonate 32%, matt curing agent 3.6%, functional additives 4%, pigments 1.6%.
[0022] A surface treatment process for metal products as described above, the thickness of the transition layer ranges between 40-100 μm.
[0023] Compared with the prior art, the surface treatment process for metal products has the following advantages:
[0024] 1、The metal product surface in the application adopts the composite layer structure of phosphating film or passivation film-transition layer-topcoat layer, is firmly attached to the metal product surface through the transition layer, so that the adhesion of the topcoat layer to the metal product surface is strengthened, and the metal product has good scratch-resistant protective performance, solving the problems of insufficient adhesion of the topcoat layer and weak protection of the metal product topcoat layer vulnerable to scratch damage in the prior art.
[0025] 2、In the application, the powder is sprayed on the surface of the iron or aluminum product, the powder can be smoothly absorbed and filled into the micropore structure on the surface of the film layer, and a film-shaped transition layer can be formed in the subsequent solidification process, which not only plays a role in closing the micropores, but also provides a strong adhesion surface foundation, facilitating the firm attachment of the subsequent topcoat layer.
[0026] 3、In the application, the powder coating has color, simplifying the dyeing process. The powder spraying process is versatile and suitable for both iron and aluminum metal products, improving the flexibility of the production line.
[0027] 4、In the application, the transition layer formed by the powder can effectively cover the micro defects on the surface of the metal product, reducing the harsh requirements for the surface finish of the metal pretreatment step, and saving the production process and improving the production efficiency without the need for processes such as sand blasting.
[0028] 5、In the surface treatment process of the application, the treated metal product, especially the aluminum product used to make a stroller frame, has a transition layer on the metal surface, which allows the topcoat layer to adhere firmly. The application improves the protective ability and topcoat adhesion of the metal surface during packaging, transportation and use, thereby playing a key role in the overall protective performance and aesthetics of the product. BRIEF DESCRIPTION OF DRAWINGS
[0029] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings, in which:
[0030] Figure 1 is a surface treatment process flowchart of the iron product in the application;
[0031] Figure 2 is a surface treatment process flowchart of the aluminum product in the application. DETAILED DESCRIPTION
[0032] The embodiments of the application will be described in detail below with reference to the accompanying drawings.
[0033] As shown in Figures 1-2 , the application includes a surface treatment process for metal products, comprising the following steps:
[0034] S1, pretreatment: performing corresponding surface treatment on the metal product;
[0035] S2, powder spraying and curing: uniformly spray the powder coating on the surface of the pretreated metal product, and then bake at 190-210°C for 10-15 min under normal pressure to cure the powder coating on the surface of the metal product to form a transition layer;
[0036] S3, topcoat spraying: uniformly spray paint on the surface of the transition layer of the metal product;
[0037] S4, topcoat curing: bake at 170-190°C for 10-15 min under normal pressure to cure the paint on the surface of the metal product to form a topcoat layer;
[0038] The powder coating comprises the following components by weight percentage: polyester resin 23-25%, epoxy resin 34-36%, calcium carbonate 30-33%, and matting curing agent 3.5-3.7%.
[0039] Further, the powder coating further comprises functional additives accounting for 3-5% of the total weight of the powder coating.
[0040] Further, the powder coating further comprises pigments accounting for 1.5-1.8% of the total weight of the powder coating, which are used for color matching.
[0041] Further, after the powder spraying and curing S1 step, the transition layer on the surface of the metal product has a matte effect.
[0042] The pretreatment is intended to provide a clean, highly chemically active surface with an excellent adhesion base for the subsequent coating. The treatment paths for iron products and aluminum products are different, as follows:
[0043] As shown in Figure 1 , the pretreatment process for iron products aims to remove contaminants and form a porous phosphate film layer, i.e., a phosphating layer, through phosphating. The specific pretreatment procedures include:
[0044] a. degreasing treatment: completely immerse the iron product in an alkaline or neutral chemical degreasing tank and soak at a suitable temperature (e.g., 50-60°C) for about 10 min, aiming to remove surface dirt such as rolling oil, machining grease, etc.
[0045] b. primary cleaning: clean the surface of the iron product to remove residual degreasing agents. Conventional operations can use spraying or up-and-down movement in the cleaning tank for at least 5 times to ensure thorough cleaning.
[0046] c. derusting treatment: also an acid pickling process; completely immerse the iron product in a derusting chemical tank for 5-10 min to completely remove the surface scale and rust (mainly 、 Rust removal tank can be selected with 15%-25% of hydrochloric acid, which has the advantages of strong rust removal ability and fast speed at room temperature; or 10%-25% of sulfuric acid, which has the advantages of low cost and less volatility under the condition of 50-70°C. In the conventional operation, a special corrosion inhibitor is also added to prevent over-corrosion and hydrogen embrittlement of iron products.
[0047] d. Secondary cleaning: cleaning the surface of the iron product to remove residual acid and reaction products, preventing pollution of the subsequent tank solution.
[0048] e. Neutralization treatment: immerse the iron product in a sodium carbonate solution with a concentration of about 3% at room temperature for 1-3 min to neutralize the trace amount of acidic substances that may remain on the surface and gaps of the iron product.
[0049] f. Third cleaning: clean again to ensure that the surface of the iron product is neutral, avoiding the pollution of the residual chemical solution to the next process.
[0050] g. Surface adjustment: after sufficient water washing, immerse the iron product in a colloidal titanium phosphate surface conditioner with a pH value of 8.0-9.5 at room temperature for 30-90s. Preferably, the pH value is 9.0 and the soaking time is 60s. This step aims to form a large number of uniformly distributed titanium phosphate crystal nuclei on the clean steel surface, providing an attachment basis for the subsequent phosphating reaction. After the surface adjustment treatment step, the iron product is directly subjected to the phosphating treatment step without cleaning, ensuring that the crystal nuclei formed by the surface adjustment treatment directly constitute the attachment surface of the phosphating treatment.
[0051] h. Phosphating treatment: transfer the surface-adjusted iron product to a phosphating tank (such as a zinc-based phosphating solution) to generate a phosphating layer on the surface of the iron product, which is crystalline, uniform, dense, and has a micro-porous structure. The film layer has a certain rust prevention ability, and at the same time, the film layer serves as the surface basis for powder adhesion, providing mechanical anchoring for the transition layer. Preferably, the reaction is carried out at 35-45°C for 5-10 min. The phosphating layer generated after phosphating treatment has a thickness of about 1-5μm, is micro-porous and rough, which helps to form a firm physical bond during the subsequent powder heat curing process and helps to increase the surface roughness.
[0052] As shown in Figure 2 , the pretreatment process of aluminum products aims to remove the natural oxide film and form a dense and stable passivation layer through passivation. The specific pretreatment process includes:
[0053] a. Degreasing treatment: completely immerse the aluminum product in an alkaline or neutral chemical degreasing tank at an appropriate temperature (such as 50-60°C) for about 10 min, aiming to remove surface dirt such as rolling oil, processing grease, etc.
[0054] b. First cleaning: cleaning the surface of the aluminum product to remove residual degreasing agent. Conventional operations can use spraying or washing in a cleaning tank to achieve the effect of washing, for example, operating the aluminum product up and down at least 5 times to ensure cleaning.
[0055] c. Pickling treatment: immersing the aluminum product in an acidic solution for about 4-5 min, aiming to remove the uneven oxide film naturally formed on the surface of the aluminum product and dissolve residual partial alloy elements, mainly obtaining a surface with high chemical activity. For example, the composition of the acidic solution is a mixture of 15%-25% nitric acid and 0.5-1.52% hydrofluoric acid by weight.
[0056] d. Second cleaning: removing residual acidic solution by cleaning.
[0057] e. Passivation treatment: immersing the aluminum product in a passivation solution to remove trace impurities on the surface through chemical reaction and form a uniform, dense, and chemically stable aluminum oxide composite film, i.e., a passivation layer. This passivation layer can improve the corrosion resistance of the metal product and provide a good bonding interface for subsequent coating. For example, an environmentally friendly approach, the passivation treatment is a chromium-free passivation process, the passivation solution contains fluorozirconate, fluorotitanate, fluoride, and pH adjuster, under the conditions of pH value of 3.8-4.5 and temperature of 25-35°C, immersion treatment for 2-3 min to form a composite passivation layer containing zirconium and titanium oxides on the surface of the aluminum. Thus, after the passivation treatment, the flowing powder composition will penetrate into the micropores and defects of the passivation layer during the subsequent powder spraying and curing process, providing an ideal attachment surface for the subsequent topcoat layer to complete the pretreatment process of the metal product. Then, the phosphated iron product or the passivated aluminum product is dried and enters the next processing procedure.
[0058] Powder spraying, curing, and painting process:
[0059] The iron product or aluminum product after the above-mentioned pretreatment has a layer of film with high chemical activity and microporosity on its surface. It should be noted that the film referred to here refers to the phosphating layer generated on the surface of the iron product and the passivation layer generated on the surface of the aluminum product, and the coating refers to the transition layer and the topcoat layer.
[0060] Powder spraying and curing: the powder coating of a specific formula is evenly attached to the surface of the metal product by electrostatic spraying. Then, bake at 190-210°C for 10-15 minutes under standard atmospheric pressure. Preferably, bake at 200°C for 10 minutes to complete the curing of the transition layer, which is efficient and energy-saving. At high temperature, the powder coating is in a molten state and has fluidity, which can fully wet and penetrate into the micro-pores of the film layer formed by the pre-treatment. After the powder coating is cured, its components can be firmly combined with the surface of the film layer formed by the pre-treatment, thereby forming a transition layer on the metal product. The transition layer provides an excellent adhesion base for the topcoat layer coated thereafter. The transition layer not only makes up for the micro-defects of the film layer formed on the surface of the metal product by pre-treatment, but also generates a uniform and fine micro-rough or porous surface itself, which is the key to the powder spraying process. The present application uses electrostatic spraying to ensure that the powder can fully and evenly cover the surface of the phosphating layer or passivation layer formed by pre-treatment. During the operation, the powder adhesion amount can be accurately controlled by controlling the electrostatic voltage, the movement speed of the spray gun and the spraying time.
[0061] If only relying on the direct combination of the topcoat layer and the film layer formed by pre-treatment, the requirement for the perfection of pre-treatment is extremely high, which requires the film layer to be uniform, continuous and defect-free. However, this will lead to an increase in process cost. In the present application, a transition layer is attached between the topcoat layer and the metal product, one side of the transition layer is firmly combined with the metal product, and the other side is firmly combined with the topcoat layer. The powder melts and flows during curing, levels on the surface of the metal product, and can well wet and anchor on the surface of the metal product, and effectively cover the micro-pores and defects. The surface of the transition layer formed after curing has uniform micro-roughness, which provides an ideal anchoring point for the topcoat layer.
[0062] Topcoat spraying and curing steps:
[0063] The metal product after the powder spraying and curing steps is transferred to a high-temperature curing oven, and the topcoat material is evenly sprayed on the surface of the powder transition layer. Bake at 170-190°C for 10-15 minutes under normal pressure to cure the paint layer and form a topcoat layer. The topcoat material and the transition layer can interpenetrate at the interface to achieve firm adhesion, forming a final protective layer with excellent adhesion, high weather resistance and protective performance. Preferably, bake at 180°C for 10 minutes to cure and form a topcoat layer, which balances energy consumption and efficiency while ensuring that the topcoat layer is completely cured and a stable interface is formed.
[0064] Preferably, the thickness of the topcoat layer is 20-40 μm, and more preferably 20-30 μm.
[0065] The thickness of the transition layer can be controlled in the range of 40-100 μm, preferably 40-60 μm. The transition layer serves as a protective layer of the metal product, and on top of it there is a topcoat layer with protective effect. Under the double-layer protection, even if the topcoat layer is worn out, the transition layer can still play a protective barrier role, which can delay the corrosion speed of the metal product and help to prolong the service life.
[0066] In the present application, the powder spraying superposition painting process is used to form a double-layer protection, and the surface treatment grade requirement of the metal product is reduced. Even if the surface has slight oxidation, B-level plate defects such as pinholes and color difference will be completely covered by the powder, and the performance and appearance of the final product will not be affected. The powder has leveling property during the curing process, which can fill the micro-unevenness of the metal product surface, cover the small scratches and the rough surface of the raw material itself. The production method integrates the pretreatment + powder spraying + painting process steps to form a standardized process with strong universality, which can be applied to both iron and aluminum substrates. Manufacturers can use the same integrated production line to process iron or aluminum products, which helps to save production resources and reduce equipment operation, site occupation and subsequent maintenance costs.
[0067] The present application is particularly suitable for application fields with high requirements for coating adhesion, mechanical scratch resistance and outdoor durability, typically including metal frames of baby strollers. By providing a transition layer on the metal surface, the topcoat layer can be firmly attached, and the protection ability of the metal surface and the adhesion of the topcoat during packaging, transportation and use. The application scenario usually selects iron or aluminum products, especially aluminum products, to fully utilize the light weight characteristics, thereby significantly reducing the overall weight of the stroller and improving the portability and use convenience of the product. The stroller made by the surface treatment process has better protection performance in outdoor use scenarios and the like to ensure long-lasting durability and the aesthetic appearance of color and complete topcoat coverage.
[0068] The powder coating composition and function in the present application are as follows:
[0069] Preferably, 23-25% of polyester resin and 34-36% of epoxy resin by weight are used as the main film-forming material. The polyester resin can provide flexibility, weather resistance and leveling property; the epoxy resin provides excellent adhesion and chemical resistance, which is beneficial to increase the adhesion of the transition layer on the film layer.
[0070] Preferably, calcium carbonate is used as the skeleton material, and the weight percentage is 30-33%. It can significantly improve the hardness and wear resistance of the transition layer, and at the same time improve the leveling performance during powder melting and promote leveling. The addition of calcium carbonate helps to cover the color and small defects of the metal product surface; while optimizing the comprehensive performance, it can also effectively reduce the cost of powder raw materials.
[0071] Preferably, 3.5-3.7% of matting curing agent is added to participate in the cross-linking reaction. The principle of matting is to produce microscopic irregular rough surface inside the transition layer, thereby scattering light, achieving the effect of matte or matting, and presenting a matte appearance on the surface of the metal product.
[0072] Preferably, 3-5% of functional additives is added to improve the construction and film forming performance. The type of functional additives is not limited to at least one of leveling agent, defoaming agent, ultraviolet protection agent, electric enhancer, and hardening agent. The leveling agent ensures uniform flow of the powder during heat curing, forming a smooth transition layer. The defoaming agent helps to discharge gas and avoid defects in the transition layer. The ultraviolet absorber can absorb ultraviolet energy, delay the aging phenomena such as chalking, yellowing, loss of luster, cracking, etc. caused by sunlight (mainly UV) irradiation, and improve the weather resistance of the metal product. The hardening agent helps to improve the scratch resistance and wear resistance of the coating. The electric enhancer can increase the amount of charge carried by the powder particles during electrostatic spraying, making them more firmly adsorbed on the phosphating layer or passivation layer on the surface of the metal product, improving the powder application rate and spraying efficiency. The consistency of the coating quality is ensured by various additives in this application.
[0073] Preferably, the powder coating contains 1.5-1.8% of pigments by weight. The pigments provide the desired color and hiding power for the transition layer, so that the transition layer completes coloring while forming the structural layer. Compared with the traditional coloring process of soaking dye or electrolytic deposition of metal salt on the conversion film (such as anodic oxidation film), the color range is limited due to the limitation of the number of special tanks and site layout. However, this process realizes uniform dispersion of pigments during the curing and leveling of the transition layer by adding pigments in the powder coating, which not only ensures the consistency of the thickness and color of the transition layer, provides a uniform and stable base color for the topcoat layer, but also makes the color and gloss of the final coating more stable, avoiding the problem of uneven appearance caused by differences in the base material. In addition, this integrated design eliminates the need for an independent coloring process, which not only eliminates the risk of peeling of the traditional colored layer, but also simplifies the process and improves production efficiency. The transition layer serves as an intermediate layer to tightly combine the phosphating layer or passivation layer and the topcoat layer.
[0074] Example 1
[0075] A powder coating, comprising the following components by weight percentage: polyester resin 24%, epoxy resin 35%, calcium carbonate 32%, matting curing agent 3.6%, functional additives 4%, pigments 1.6%.
[0076] The following introduces a preparation method of powder coating: preparation method: first, according to the formula component composition accurate weighing of raw materials, in the premix tank through high speed rotation mixing uniform, premix time 5-10 min. Then put the mixed uniform raw material into the twin screw extruder at a constant speed, melt extrusion under the condition of 100-130 ℃, after cooling roll into a piece, cooling, then the piece is crushed (including coarse crushing and fine crushing), grinding, screening, obtain the final powder coating.
[0077] In the process of melt blending, not only the micro-uniform dispersion of each component is realized, but more importantly, the extinction curing agent and polyester resin, epoxy resin are preliminarily crosslinked under controlled conditions, so as to ensure that the powder can realize complete curing and stable extinction effect at the same time during the subsequent coating and final curing.
[0078] Among them, the particle size range of the powder is 30-80 um, which is helpful to the surface flatness of the transition layer.
[0079] The matte effect presented by the metal product after the powder spraying and curing steps has a surface roughness Ra value range of 0.8-2.5 μm. The micro-relief of this scale can effectively scatter visible light, thereby achieving the ideal extinction effect, and also providing a good mechanical anchoring effect for the topcoat layer adhesion.
[0080] The above is a detailed description of the process, and the specific process parameters can be appropriately adjusted within the scope of the idea of the present application.
Claims
1. A surface treatment process for metal products, characterized in that... Includes the following steps: S1. Pretreatment: Perform appropriate surface treatment on metal products; S2. Powder coating and curing: Powder coating is uniformly sprayed onto the surface of the pretreated metal product, and then baked at normal pressure and 190-210°C for 10-15 minutes to cure the powder coating on the surface of the metal product and form a transition layer. S3. Topcoat spraying: Applying paint evenly to the transition layer surface of metal products; S4. Topcoat curing: Bake at normal pressure and 170-190°C for 10-15 minutes to cure the paint on the surface of the metal product and form a topcoat layer. The powder coating comprises the following components by weight percentage: 23-25% polyester resin, 34-36% epoxy resin, 30-33% calcium carbonate, and 3.5-3.7% matting curing agent.
2. The surface treatment process for metal products according to claim 1, characterized in that... The powder coating also includes functional additives accounting for 3-5% of the total weight of the powder coating; the functional additives can be at least one of ultraviolet protectants, leveling agents, and defoamers.
3. A surface treatment process for metal products according to claim 1 or 2, characterized in that... The powder coating also includes pigments for color adjustment, wherein the pigments account for 1.5-1.8% of the total weight of the powder coating.
4. The surface treatment process for metal products according to claim 1, characterized in that... The metal product is an iron product. The pretreatment in step S1 includes a surface conditioning treatment to generate crystal nuclei on the surface of the iron product for depositing phosphate coating crystals.
5. A surface treatment process for metal products according to claim 4, characterized in that... The iron products are completely immersed in a surface conditioning chemical bath for 30-90 seconds. The surface-treated iron products are then transferred to a phosphating bath to form a phosphating layer on the surface of the iron products. Before the phosphating process, the iron products undergo degreasing, rust removal, and neutralization treatments in sequence. During each of the degreasing, rust removal, neutralization, and phosphating processes, the iron products are cleaned accordingly before proceeding to the next processing step.
6. A surface treatment process for metal products according to claim 1, characterized in that... The metal product is an aluminum product. The pretreatment in step S1 includes passivation treatment to remove the natural oxide layer on the surface of the aluminum product and form a passivation layer. Before the passivation treatment, the aluminum product undergoes degreasing treatment and pickling treatment in sequence. The aluminum product is cleaned accordingly before entering the next treatment process after the degreasing treatment, pickling treatment and passivation treatment processes.
7. A surface treatment process for metal products according to claim 1, characterized in that... After powder coating and curing in step S2, the transition layer on the surface of the metal product has a matte finish.
8. A surface treatment process for metal products according to claim 1, characterized in that... The powder coating comprises the following components by weight percentage: 24% polyester resin, 35% epoxy resin, 32% calcium carbonate, 3.6% matting curing agent, 4% functional additives, and 1.6% pigment.
9. A surface treatment process for metal products according to claim 1 or 9, characterized in that... The thickness of the transition layer ranges from 40 to 100 μm.