Aluminium profiles are produced by electrostatic spray coating

With the wide application of aluminum profiles in the decorative industry, aluminum surface treatment technology has also developed rapidly. Electrostatic spraying and electrophoretic painting are among the aluminum profile processing technologies with rapid development and advanced technology in recent years. The advantages of electrostatic spraying: energy saving, environmental protection, pollution-free, high production efficiency, easy automation production, a wide range of products, to meet the different needs of different customers color personality. The advantages of electrophoretic painting: high surface finish, bright color and crystal clear, the product surface covered with a layer of lacquer solvent, more resistant to corrosion than ordinary aluminum alloy profiles. According to the project budget, the amount of investment in electrostatic spraying and electrophoretic painting production lines is almost the same. Generally medium-sized aluminum extrusion companies have: furnace-recovery-oxidation production lines, but few companies can simultaneously apply two production lines: electrostatic spraying and electrophoretic painting. If we can produce electrophoretic paint products through electrostatic spraying and oxidative coloring, we will reduce investment and increase equipment utilization, which is also a new technological innovation. After one year of process testing, this product can be realized and industrial production can be formed.

1, production process requirements

1.1 Equipment requirements a. Aluminium alloy profile furnace - extrusion - oxidation coloring production line b. electrostatic spraying production line c. aluminum alloy profile products, surface film thickness and coating adhesion and other testing equipment

1.2 Covered Crystal Aluminum Production Process

Formed aluminum alloy profile loading → degreasing → washing → caustic washing → light removal → oxidation → coloring → semi-sealing → electrostatic spraying → drying → packaging in the production process Each process must be washed with water to prevent pollution, improve the slot Liquid use time, the key process is: coloring → semi-sealed → electrostatic spraying, each process strictly in accordance with the process control operation.

1.3 Process Requirements

a. Degreasing: 100-150g/L (mass concentration) H2SO2: time 3-5 minutes

b. Caustic wash: 45-85 g/L (mass concentration): time 5-15 minutes. If the surface profile of the profile is slight, alkali cleaning time can be reduced.

c. Light output: 200-250g/LH2SO2 (mass concentration), 3-5 g/LH2NO3, playing a role in neutralizing and improving the surface smoothness of the profiles.

d. Oxidation coloring: 150-180 g/L H2SO2 (mass concentration) is an oxidizing conductivity liquid, the coloring liquid is a stannous salt and a nickel salt, and the colorant is a gold champagne color.

e. Semi-sealing: the key process. The process requires that the hole is sealed at room temperature, the oxide film is 1 μm, and the hole is sealed for 1 minute. However, after the film is not completely closed, half of the film hole must be left to adsorb the electrostatically sprayed powder.

f. Electrostatic spraying: automatic spray booth, dusting agent for high-gloss transparent polyester powder, milky white, covered in the profile surface after drying into a crystal clear color, bright and clean crystal, the oxidation of colored golden pinnacle profile background, set off Beautiful color, crystal clear, no less than electrophoretic paint aluminum products.

g. Drying package: drying room temperature 180 degrees, drying time is 2 minutes, aluminum products from the drying room, cooled with cold air to 40-50 degrees, artificial visual inspection product quality, qualified after packaging, under The material must be handled with care and lightness to prevent scratches.

2. Product inspection

2.1 Test methods

The test of film properties shall be conducted after the coating is cured for 24 hours.

a. Coating thickness monitoring method:
The film thickness of the coating was monitored with a film meter.

b. Coating impact resistance test method:

Using a punch diameter of 16mm, the weight is placed at a suitable height to fall freely, and the coating surface is directly impacted so that a pit having a depth of 2.5 0.03mm is generated, and the coating change is observed.

c. Coating adhesion test method:

In the coating surface, the spacing is 2mm, and then it is peeled off with adhesive tape to observe whether the coating falls off.

d. Cupping test method

With the spherical tip of the punch, the sample is advanced at a constant speed of 0.2-0.1 mm per second until a specified 0.75 0.05 mm is observed, and it is observed whether the coating has fallen off or separated from the profile.

2.2 Inspection equipment

a.ED-200 Eddy Current Thickness Tester b. Impact Tester c. Cupping Tester d.4 times magnifying glass (for observation)
2.3 Test results

According to the national inspection standard for aluminum powder coating profiles, the crystal-covered aluminum profiles can fully meet the requirements for use.

There was no quality problem during the use of the product. After one year of testing, the profile was left for one year and the surface was still clear and transparent, with a level of 0. No fading, peeling phenomenon, the film thickness is higher than the electrophoretic coating film, the cost is basically the same, and the organic oxidation-spraying production line together to avoid the equipment isolated production.

3 General quality issues

Most of the quality problems are caused by lax production controls. The main problems are as follows:

Matte 1, profile light does not shine; 2, high-light transparent powder quality problems; 3, oven temperature is too high

Film thickness is low 1. The powder from the spray gun is low; 2. Check the powder supply device and air pressure

Surface skin 1, film thickness is too high; 2, powder moisture; 3, paint particle size is too coarse, coating poor level of poor adhesion

1, coating quality problems; 2, spraying on the hanging oxide film before the hole is completely closed; 3, the profile surface is contaminated; 4, drying temperature is too low, the time is too short oxidation coloring

1. Poor conductivity; 2. Low temperature of the coloring bath solution, failure of bath solution; 3. Problems with the coloring machine; 4. Oxide film thickness is too low

4 Conclusion

The production process of crystal-covered aluminum profiles is more complex and runs through the oxidation-colored spots; it must be strictly controlled in order to produce high-standard products and be accepted by customers.