Technological method for coating stainless steel with high-gloss enamel paint

Abstract

The invention discloses a process method for coating stainless steel with high-gloss enamel, which comprises the following steps: S1, mechanically polishing the surface of a stainless steel sub-control box to remove a passivation layer; s2, a degreasing process is conducted, specifically, spraying treatment is conducted through an alkaline degreasing agent, and surface oil stains are removed; s2, spraying a phosphating primer to form a transition layer of 5-10 [mu] m; s3, zinc-rich primer is coated, and the thickness of a dry film is 20-30 microns; s4, coating epoxy intermediate coat, wherein the thickness of a dry film is 30-40 microns; and S5, acrylic polyurethane finish paint is coated, the thickness of a dry film is 40-50 microns, the adhesive force of the coating is remarkably improved, the adhesive force of the coating is improved to 0-1 grade from 3-4 grade of a traditional technology through mechanical polishing for removing a passivation layer, phosphating primer transition and the synergistic effect of multiple layers of coatings, the problem of paint film stripping is effectively avoided, and a multi-layer coating system has good adhesive force and also has the advantages of being good in corrosion resistance, good in corrosion resistance and the like. And the stainless steel sub-control box for the air cooler also has excellent corrosion resistance, high decoration performance and weather resistance, and can meet the use requirements of the stainless steel sub-control box for the air cooler in different environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal surface coating, in particular to a process method for coating stainless steel with high-gloss enamel paint, a process method for improving the adhesion of the surface coating of a stainless steel distribution control box through pretreatment, and is suitable for the coating of industrial equipment that requires high decorative and weather-resistant properties. BACKGROUND

[0002] Stainless steel distribution control boxes are widely used in the fields of power and communication. A distribution control box, also known as a distribution controller box, is an electrical control device used to control and manage multiple devices or systems. Its main function is to centrally manage multiple control modules to achieve automatic control of equipment, and its surface often needs to be coated with high-gloss enamel paint to meet the aesthetic and identification requirements. However, the stainless steel surface has a dense passivation layer (Cr2O3), which can easily lead to insufficient adhesion (test results of 3-4 levels) of zinc-rich primer, mid-coat paint, and topcoat when directly coated, resulting in paint film peeling problems. Traditional solutions (such as pickling or sandblasting) may damage the stainless steel substrate or increase costs. Therefore, there is an urgent need for an improved process that balances efficiency and cost, and thus a process method for coating stainless steel with high-gloss enamel paint is provided. SUMMARY

[0003] To overcome the deficiencies of the prior art, the present application provides a process method for coating stainless steel with high-gloss enamel paint, which can solve the following technical problems: the stainless steel surface has a dense passivation layer (Cr2O3), which can easily lead to insufficient adhesion (test results of 3-4 levels) of zinc-rich primer, mid-coat paint, and topcoat when directly coated, resulting in paint film peeling problems. Traditional solutions (such as pickling or sandblasting) may damage the stainless steel substrate or increase costs.

[0004] To solve the above technical problems, the present application provides the following technical solution: a process method for coating stainless steel with high-gloss enamel paint, comprising: S1, mechanically polishing the surface of the stainless steel distribution control box to remove the passivation layer; S2, degreasing process, using an alkaline degreasing agent to spray and treat to remove surface dirt; S2, spraying a phosphating primer to form a 5-10 μm transition layer; S3, coating a zinc-rich primer with a dry film thickness of 20-30 μm; S4, coating an epoxy mid-coat paint with a dry film thickness of 30-40 μm; S5, coating an acrylic polyurethane topcoat with a dry film thickness of 40-50 μm.

[0005] As a preferred technical solution of the present application, the mechanical polishing uses 180-240 mesh sandpaper or a steel wire brush, with a roughness controlled at Ra 1.5-2.5 μm.

[0006] As a preferred technical solution of the present application, for complex curved surfaces, a φ50 mm steel wire wheel is used, and for flat areas, a sanding machine is used.

[0007] As a preferred technical scheme of the present application, the concentration of the alkaline degreasing agent is 3-5%, the spraying temperature is 50-60℃, and the spraying time is 3-5 minutes.

[0008] As a preferred technical scheme of the present application, the phosphating primer is a two-component epoxy zinc phosphate primer, the spraying temperature is 15-30℃, the spraying environment humidity is ≤75%, and the coating method is air spraying.

[0009] As a preferred technical scheme of the present application, the zinc powder content of the zinc-rich primer is ≥80%, the zinc powder particle size is 5-10μm, the spraying temperature is 10-40℃, the spraying environment humidity is ≤80%, and the coating method is airless spraying (pressure 15-20MPa).

[0010] As a preferred technical scheme of the present application, the epoxy intermediate coating is a gray epoxy mica iron paint, the spraying temperature is 5-35℃, the spraying environment humidity is ≤85%, and the coating method is air-assisted airless spraying.

[0011] As a preferred technical scheme of the present application, the acrylic polyurethane topcoat is a high-gloss ceramic paint (glossiness ≥90%), the spraying temperature is 15-30℃, the spraying environment humidity is ≤70%, and the coating method is electrostatic spraying.

[0012] Compared with the prior art, the present application has the following beneficial effects: (1) The coating adhesion is significantly improved: through mechanical polishing to remove the passivation layer, phosphating primer transition, and the synergistic effect of multi-layer coating, the coating adhesion is improved from 3-4 levels in traditional process to 0-1 level, effectively avoiding the problem of paint film peeling.

[0013] (2) Mechanical polishing is used instead of pickling, avoiding the pollution of pollutants generated in the pickling process to the environment.

[0014] (3) Compared with traditional processes such as sand blasting, the process steps of the present application are simple, convenient to operate, and the process cost is reduced.

[0015] (4) The multi-layer coating system not only has good adhesion, but also has excellent corrosion resistance, high decorative property, and weather resistance, which can meet the use requirements of the stainless steel control box for air coolers in different environments. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a process flow chart of the present application; Figure 2 is a schematic diagram of the adhesion of the traditional process; Figure 3 is a schematic diagram of the adhesion of the process of the present application; DETAILED DESCRIPTION

[0017] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments. However, the following embodiments are only preferred embodiments of the present application, not all. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative labor also belong to the protection scope of the present application. EMBODIMENT

[0018] Referring to Figure 1 The present application provides a process for coating high-gloss porcelain paint on stainless steel, which comprises substrate treatment. The substrate treatment comprises mechanical polishing: uniform polishing with 220-grit sandpaper, for complex curved surfaces, a steel wire wheel with a diameter of φ50mm is preferred (rotating speed 1500-2000r / min), and a sand belt machine is used for flat areas (feeding speed 2-3m / min) to remove the passivation layer and form appropriate roughness (Ra 1.5-2.5μm); The substrate treatment further comprises a degreasing process: after mechanical polishing, the surface is treated with a 50℃ alkaline degreasing agent (concentration 4%) for 4 minutes to remove surface oil, and then rinsed with deionized water until pH=7; After polishing, 316 stainless steel needs to be additionally sprayed with a layer of silane treatment agent (thickness 1-2μm) to enhance the adhesion of the phosphating primer to the high-nickel material; Phosphating primer transition: spray epoxy zinc phosphate primer (ratio: main agent: curing agent = 4:1), film thickness 8μm, the phosphate ions react with the surface of the stainless steel to form a complex, enhancing the adhesion, forming a 5-10μm transition layer, and then spraying the epoxy zinc phosphate primer; wherein the spraying temperature is 15-30℃, the spraying environment humidity is ≤75%, the coating method is air spraying, and after spraying, the next process is entered after standing for 10-15 minutes, and in actual production, standing for 15 minutes is the best, ensuring that the primer fully reacts with the substrate to form a complex. After the phosphating primer is dried, the adhesion is tested by the pull-off method (≥5MPa); The zinc-rich primer has a dry film thickness of 20-30μm, the zinc powder content of the zinc-rich primer is ≥80%, the zinc powder particle size is 5-10μm, and the best is 6μm, the spraying temperature is 10-40℃, the spraying environment humidity is ≤80%, the coating method is airless spraying (pressure 15-20MPa), and after drying at 80℃ for 30 minutes, the epoxy intermediate coating is coated at least 24 hours apart to ensure that the primer is fully cured and plays a role in corrosion protection; for high-humidity environments (such as coastal areas): 2% nano-alumina (particle size 20nm) is added to the zinc-rich primer to improve the water resistance of the coating.

[0019] Epoxy midcoat painting, spraying gray epoxy cloud iron paint, dry film thickness is 35pm, spraying temperature is 5-35℃, spraying environment humidity is less than or equal to 85%, coating method adopts air-assisted airless spraying, leveling 10 minutes and drying, detecting surface flatness (less than or equal to 3pm), and at least 12 hours apart before coating acrylic topcoat, ensuring that the midcoat is fully dried to provide a smooth substrate; Acrylic polyurethane topcoat painting, dry film thickness is 40-50pm, acrylic polyurethane topcoat is high-gloss ceramic paint (glossiness is greater than or equal to 90%), spraying temperature is 15-30℃, spraying environment humidity is less than or equal to 70%, coating method adopts electrostatic spraying; adding 0.8% of nano-silicon dioxide (particle size is 75nm) in acrylic high-gloss topcoat, uniformly mixing through high-speed dispersion (3000r / min, 30min), improving the scratch resistance (pencil hardness is improved from 2H to 3H) and weather resistance (QUV aging test 1000h without powdering) of the topcoat, then spraying the topcoat (glossiness is 92%), film thickness is 45pm, detecting the adhesion after curing is 0 level.

[0020] Among them, to improve spraying efficiency, the spraying temperature can be regulated at 25℃, the dry film thickness is determined according to actual production needs, and the dry film thickness is detected after each coating by eddy current thickness gauge (if the error is more than ±5%, rework), and the grid method test (GB / T 9286) + impact test (GB / T 20624.2, 50cm impact without cracks) is carried out after the topcoat is cured.

[0021] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A process for painting high gloss porcelain enamel on stainless steel, characterized by: Comprise: S1, mechanical polishing on the surface of stainless steel control box, remove the passivation layer; S2, degreasing process, using alkaline degreasing agent spray treatment, remove the surface dirt; S2, spray phosphating primer, form a 5-10um transition layer; S3, coating zinc-rich primer, dry film thickness of 20-30um; S4, coating epoxy mid-coat, dry film thickness of 30-40um; S5, coating acrylic polyurethane topcoat, dry film thickness of 40-50um.

2. A process for coating a stainless steel with a high gloss porcelain enamel according to claim 1, characterized in that: The mechanical polishing uses 180-240 mesh sandpaper or steel wire brush, roughness control in Ra 1.5-2.5um.

3. A process for coating a stainless steel with a high gloss porcelain enamel according to claim 2, characterized in that: For complex curved surface, use φ50mm steel wire wheel, plane area using sand belt machine.

4. The process for coating high gloss porcelain enamel on stainless steel as claimed in claim 1 wherein: The concentration of the alkaline degreasing agent is 3-5%, the spraying temperature is 50-60℃, and the spraying time is 3-5 minutes.

5. A process for coating stainless steel with high gloss porcelain enamel as claimed in claim 1 wherein: The phosphating primer is a two-component epoxy zinc phosphate primer, the spraying temperature is 15-30℃, the spraying environment humidity is ≤75%, the coating method adopts air spraying, and the next process is entered after standing for 10-15 minutes after spraying.

6. A process for coating stainless steel with high gloss porcelain enamel according to claim 1, characterized in that: The zinc powder content of the zinc-rich primer is ≥80%, the zinc powder particle size is 5-10um, the spraying temperature is 10-40℃, the spraying environment humidity is ≤80%, and the coating method adopts airless spraying (pressure 15-20MPa).

7. The process for coating high gloss porcelain enamel on stainless steel as claimed in claim 1 wherein: The epoxy mid-coat is gray epoxy cloud iron paint, the spraying temperature is 5-35℃, the spraying environment humidity is ≤85%, and the coating method adopts air-assisted airless spraying.

8. The process for coating high gloss porcelain enamel on stainless steel as claimed in claim 1 wherein: The acrylic polyurethane topcoat is high-gloss ceramic paint (glossiness ≥90%), the spraying temperature is 15-30℃, the spraying environment humidity is ≤70%, and the coating method adopts electrostatic spraying.

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