Electrophoresis finishing surface treatment process for aluminum profile

Abstract

The invention provides an aluminum profile electrophoresis finishing surface treatment process which comprises the steps that S1, an aluminum profile is sequentially pretreated, and pretreatment comprises degreasing, acid pickling, alkali etching, neutralizing and water washing treatment; s2, the pretreated aluminum profile is immersed in electrophoresis tank liquid, and direct-current voltage is applied; wherein the electrophoresis tank liquid is composed of acrylic resin, epoxy resin, deionized water and a curing agent, the solid content is 10%-15%, the pH value is 5.5-6.5, the direct-current voltage is 80-120 V, the electrophoresis time is 2-4 minutes, the temperature of the electrophoresis tank liquid is controlled to be 25-30 DEG C, and the thickness of an electrophoresis film is 15-25 microns; and S3, the aluminum profile subjected to electrophoresis is sequentially subjected to liquid draining, water washing, baking and curing treatment. Electrophoretic coating is carried out after pretreatment, the adhesive force of a coating reaches 4B or above by using a composite resin system in the electrophoretic coating, the thickness uniformity of an electrophoretic film is improved during electrophoresis, and the cracking resistance and the hardness of the coating are improved through subsequent baking treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum profile processing, and particularly relates to an electrophoretic finishing surface treatment process for aluminum profiles. Background Art

[0002] In the field of aluminum profile surface treatment, electrophoretic coating technology is widely used due to its high uniformity, high corrosion resistance and environmental friendliness. However, the existing aluminum profile electrophoretic process still has defects, such as imperfect pretreatment process, single electrophoretic bath solution formula, contradiction between energy consumption and efficiency, insufficient environmental compliance, etc. The above defects seriously restrict the application of aluminum profiles in high-end buildings, automotive parts and other fields. Therefore, there is an urgent need to develop an electrophoretic finishing process for aluminum profiles with high adhesion, low energy consumption and environmental compliance, and to achieve the coordinated improvement of coating performance and production efficiency through the optimization of the whole process parameters. Summary of the Invention

[0003] The main purpose of the present invention is to provide an electrophoretic finishing surface treatment process for aluminum profiles, which is used to improve the energy consumption efficiency of aluminum profile electrophoresis and improve the surface treatment effect.

[0004] To achieve the above object, the present invention provides an electrophoretic finishing surface treatment process for aluminum profiles. The electrophoretic finishing surface treatment process for aluminum profiles includes step S1: sequentially pretreating the aluminum profiles, and the pretreatment includes degreasing, pickling, alkali etching, neutralization and water washing treatments; step S2: immersing the pretreated aluminum profiles in an electrophoretic bath solution and applying a DC voltage; wherein, the electrophoretic bath solution is composed of acrylic resin, epoxy resin, deionized water and a curing agent, the solid content is 10%-15%, the pH value is 5.5-6.5, the DC voltage is 80-120V, the electrophoresis time is 2-4 minutes, the temperature of the electrophoretic bath solution is controlled at 25-30°C, and the electrophoretic film thickness is 15-25μm; step S3: sequentially performing draining, water washing and baking and curing treatments on the electrophoresed aluminum profiles.

[0005] For the electrophoretic finishing surface treatment process for aluminum profiles provided by the present invention, after pretreatment, electrophoretic coating is carried out. In the electrophoretic coating, a composite resin system (acrylic + epoxy) is used to make the adhesion of the coating reach above 4B. During electrophoresis, a low voltage of 80-120V saves 30% energy compared with the traditional process, and the uniformity of the electrophoretic film thickness is improved at this voltage. Subsequent baking treatment improves the anti-cracking property of the coating and improves the coating hardness.

[0006] As a further preferred technical solution of the above technical solution, in the step S1, the degreasing is carried out with an alkaline degreasing solution with a pH value of 10 - 12, a temperature of 40 - 50 °C, and an immersion time of 8 - 12 minutes. The pickling is carried out with a sulfuric acid solution with a concentration of 10% - 15%, and the treatment is carried out at room temperature for 3 - 5 minutes. The alkali etching is carried out with a mixed solution containing 50 - 80 g / L of NaOH and 20 - 30 g / L of Na2CO3, a temperature of 50 - 60 °C, and the treatment is carried out for 6 - 10 minutes. The neutralization is carried out by adjusting the pH of the aluminum profile surface to 6 - 7 with a nitric acid solution. In the pretreatment, the surface of the aluminum profile is cleaned, and Na2CO3 is used to buffer the alkali etching rate to avoid over-corrosion. In the neutralization treatment, nitric acid is used to neutralize the residual alkali solution, and the surface pH is stable, improving the electrophoretic deposition uniformity.

[0007] As a further preferred technical solution of the above technical solution, in the step S1, the surface roughness Ra of the aluminum profile during alkali etching is controlled at 0.8 - 1.2 μm. The optimization of the Ra value improves the coating adhesion to 4B - 5B.

[0008] As a further preferred technical solution of the above technical solution, in the electrophoretic bath solution, the mass ratio of acrylic resin to epoxy resin is 3:1 - 5:1, and the addition amount of the curing agent is 2% - 5% of the total resin amount.

[0009] As a further preferred technical solution of the above technical solution, in the step S2, the circulating filtration accuracy of the electrophoretic bath solution is ≤5 μm, and the conductivity of the electrophoretic bath solution is controlled at 800 - 1200 μS / cm. Filtering the electrophoretic bath solution reduces the possibility of pinhole defects on the surface of the aluminum profile.

[0010] As a further preferred technical solution of the above technical solution, in the step S1, after the neutralization treatment, the surface of the aluminum profile is passivated. The passivation solution is a solution containing 0.5 - 1 g / L of chromate and 1 - 2 g / L of sodium fluoride, and the passivation time is 30 - 60 seconds. Description of the Drawings

[0011] Figure 1 is a schematic diagram of the surface treatment process flow of electrophoretic finishing of an aluminum profile provided by this application. Detailed Embodiments

[0012] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles defined in the following description can be applied to other embodiments, variants, improvements, equivalent solutions, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0013] See the drawings Figure 1 , Figure 1It is a schematic diagram of the surface treatment process for electrophoretic finishing of aluminum profiles provided by this application. As Figure 1 shown, the present invention provides a surface treatment process for electrophoretic finishing of aluminum profiles, including step S1: pretreating the aluminum profiles in sequence, and the pretreatment includes degreasing, pickling, alkaline etching, neutralization, and water washing; step S2: immersing the pretreated aluminum profiles in the electrophoretic bath solution and applying a direct current voltage; wherein, the electrophoretic bath solution is composed of acrylic resin, epoxy resin, deionized water, and curing agent, with a solid content of 10%-15%, a pH value of 5.5-6.5, a direct current voltage of 80-120V, an electrophoretic time of 2-4 minutes, the temperature of the electrophoretic bath solution is controlled at 25-30°C, and the electrophoretic film thickness is 15-25μm; step S3: subjecting the electrophoresed aluminum profiles to draining, water washing, and baking and curing treatments in sequence.

[0014] For the surface treatment process for electrophoretic finishing of aluminum profiles provided by the present invention, after pretreatment, electrophoretic coating is carried out. In the electrophoretic coating, a composite resin system (acrylic + epoxy) is used to make the adhesion of the coating reach above 4B. During electrophoresis, a low voltage of 80-120V is 30% more energy-saving than the traditional process, and the uniformity of the electrophoretic film thickness is improved at this voltage. Subsequent baking treatment improves the anti-cracking property of the coating and increases the hardness of the coating.

[0015] As a further preferred technical solution of the above technical solution, in step S1, for degreasing, an alkaline degreasing solution with a pH value of 10-12 and a temperature of 40-50°C is used, and the immersion time is 8-12 minutes. For pickling, a sulfuric acid solution with a concentration of 10%-15% is used, and the treatment is carried out at room temperature for 3-5 minutes. For alkaline etching, a mixed solution containing 50-80g / L of NaOH and 20-30g / L of Na2CO3 is used, and the temperature is 50-60°C, and the treatment time is 6-10 minutes. For neutralization, a nitric acid solution is used to adjust the surface pH of the aluminum profiles to 6-7. In the pretreatment, the surface of the aluminum profiles is cleaned, and Na2CO3 is used to buffer the alkaline etching rate to avoid over-corrosion. In the neutralization treatment, nitric acid is used to neutralize the residual alkaline solution, and the surface pH is stable, improving the uniformity of electrophoretic deposition.

[0016] As a further preferred technical solution of the above technical solution, in step S1, the surface roughness Ra of the aluminum profiles during alkaline etching is controlled at 0.8-1.2μm. Optimizing the Ra value improves the adhesion of the coating to 4B-5B.

[0017] As a further preferred technical solution of the above technical solution, in the electrophoretic bath solution, the mass ratio of acrylic resin to epoxy resin is 3:1-5:1, and the addition amount of the curing agent is 2%-5% of the total amount of the resin.

[0018] As a further preferred technical solution of the above technical solution, in the step S2, the circulating filtration accuracy of the electrophoretic bath solution is ≤5 μm, and the conductivity of the electrophoretic bath solution is controlled at 800-1200 μS / cm. Filtering the electrophoretic bath solution reduces the possibility of pinhole defects on the surface of the aluminum profile.

[0019] As a further preferred technical solution of the above technical solution, in the step S1, after the neutralization treatment, the surface of the aluminum profile is passivated. The passivation solution is a solution containing 0.5-1 g / L of chromate and 1-2 g / L of sodium fluoride, and the passivation time is 30-60 seconds.

[0020] In practical applications, when treating architectural aluminum profiles, pretreatment is carried out in step S1, specifically including:

[0021] Degreasing: Alkaline degreasing solution with pH = 11, soaked at 45°C for 10 minutes;

[0022] Pickling: 12% H2SO4 solution, treated at room temperature for 4 minutes;

[0023] Alkaline etching: NaOH 60 g / L + Na2CO3 25 g / L, treated at 55°C for 8 minutes (Ra = 1.0 μm);

[0024] Neutralization: Adjust the pH to 6.5 with nitric acid;

[0025] Passivation: Chromate 0.8 g / L + sodium fluoride 1.5 g / L, passivated for 45 seconds.

[0026] In step S2, electrophoretic coating is carried out. Specifically, the electrophoretic bath solution uses acrylic resin: epoxy resin = 4:1, 3% curing agent, solid content 12%, pH = 6.0; the voltage is 100 V, the time is 3 minutes, the bath solution temperature is 28°C, the film thickness is 20 μm, the accuracy of circulating filtration is μm, and the conductivity is 1000 μS / cm.

[0027] In step S3, the draining is carried out by natural dripping for 5 minutes, the water washing is carried out by deionized water spraying, the first stage of baking is preheated at 90°C for 12 minutes, and the second stage is baked at 170°C for 25 minutes (heating rate 4°C / min).

[0028] It is worth mentioning that for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some of the technical features can be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrophoretic finishing surface treatment process for aluminum profiles, characterized in that, Including: Step S1: Pretreat the aluminum profile successively. The pretreatment includes degreasing, pickling, alkali etching, neutralization and water washing. Step S2: Immerse the pretreated aluminum profile into the electrophoretic bath solution and apply a DC voltage. Among them, the electrophoretic bath solution is composed of acrylic resin, epoxy resin, deionized water and curing agent, with a solid content of 10%-15%, a pH value of 5.5-6.5, a DC voltage of 80-120V, an electrophoresis time of 2-4 minutes, the temperature of the electrophoretic bath solution is controlled at 25-30°C, and the electrophoretic film thickness is 15-25μm. Step S3: Subject the electrophoresed aluminum profile to draining, water washing and baking curing treatment successively.

2. The electrophoretic finishing surface treatment process for aluminum profiles according to claim 1, wherein, In the step S1, for degreasing, use an alkaline degreasing solution with a pH value of 10-12, a temperature of 40-50°C, and soak for 8-12 minutes; for pickling, use a sulfuric acid solution with a concentration of 10%-15% and treat at room temperature for 3-5 minutes; for alkali etching, use a mixed solution containing 50-80g / L of NaOH and 20-30g / L of Na2CO3, a temperature of 50-60°C, and treat for 6-10 minutes; for neutralization, use a nitric acid solution to adjust the surface pH of the aluminum profile to 6-7.

3. The electrophoretic finishing surface treatment process for aluminum profiles according to claim 2, characterized in that, In the step S1, during alkali etching, the surface roughness Ra of the aluminum profile is controlled at 0.8-1.2μm.

4. The electrophoretic finishing surface treatment process for aluminum profiles according to claim 3, characterized in that, In the electrophoretic bath solution, the mass ratio of acrylic resin to epoxy resin is 3:1-5:1, and the addition amount of the curing agent is 2%-5% of the total amount of the resin.

5. The electrophoretic finishing surface treatment process for aluminum profiles according to claim 4, characterized in that, In the step S2, the circulating filtration accuracy of the electrophoretic bath solution is ≤5μm, and the conductivity of the electrophoretic bath solution is controlled at 800-1200μS / cm.

6. The electrophoretic finishing surface treatment process for aluminum profiles according to claim 5, characterized in that, In the step S1, after neutralization treatment, passivation treatment is carried out on the surface of the aluminum profile. The passivation solution is a solution containing 0.5-1g / L of chromate and 1-2g / L of sodium fluoride, and the passivation time is 30-60 seconds.

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