Aluminum surface coating technology and detailed process

Everyone knows that the adhesion of the aluminum alloy surface is poor. It is difficult to directly spray the paint with good adhesion to the surface of the aluminum. Even if it is barely applied, it will fall off quickly. So how do you increase adhesion?

Then you need to apply a primer on the aluminum alloy substrate to increase the adhesion of the paint, and then spray the finish. The main three steps:

First, preparation and conditions before spraying:

1. Weather conditions: Paints must be selected to be constructed under fine weather conditions. Construction is prohibited under conditions of rain, fog, snow and heavy dust. The optimum temperature for spraying is about 25 ° C and the humidity is below 80% RH. .

2. Substrate treatment: The aluminum alloy substrate should be polished, oxidized, etc. The surface should be derusted, degreased, and cleaned and dry without dirt. Remove the dust and fill it before painting, and ensure the drying of the substrate before spraying.

3. Spray gun standard: Spray gun with a diameter of 1.5-2.0mm can be used for spraying. The pressure of the spray gun should be adjusted to 3-4kg/cm2. The fog is adjusted to medium pressure to 3-4kg/cm

2, spray the surface of the workpiece as much as possible, spray 2-3 times evenly. Appropriate adjustment of the amount of oil, when the amount of oil is too small, the surface of the paint film is prone to particles.

4. Air compressor: Before construction, the air compressor and filter should be dehydrated to avoid pinholes in the paint film.

Second, the spraying of the primer:

1. After obtaining a good surface treatment effect on the surface of the aluminum alloy (no oil, no dust, a certain roughness on the surface), it can be sprayed with an epoxy-rich zinc-rich primer for aluminum alloy. The primer has good adhesion to the surface of the aluminum alloy, especially a two-component epoxy zinc yellow primer. The paint has the high adhesion, unique toughness and hardness of the epoxy paint, and the matching performance is good.

2. Mixing ratio: Primer: Primer curing agent: Thinner = 4:1: Appropriate amount. Stir the paint for 5 minutes until it is homogeneous before mixing. Weigh the mixture with a more accurate electronic scale to ensure accurate ratio. After mixing the paint, stir it with a clean aluminum strip or iron bar until it is completely homogeneous. Be careful not to mix other types of paints, solvents, etc. during construction. Keep the spray environment clean. Use it within 2H after mixing. After the ambient temperature is greater than 30 °C, the use time after mixing should be shortened.

3. For best results when spraying, you can spray twice:

First spray - fog spray:

1. Viscosity - 14-16 seconds (20 °)

2. Discharge amount - 1/2-2/3

3. Painting pressure - 4.0-5.0 bar

4. Distance of spraying tool - 25-30cm

5. Standard spray - full open

6. When spraying - slightly faster

The whole body is sprayed in a thin and thin manner, and is initially integrated with the underlying coating film. At the same time, confirm whether there is a shrinkage hole, if any, slightly increase the air pressure (6.5 bar) for the part, and concentrate the spray.

Painted to fill the shrinkage cavity.

Second spray - primer spray

1. Viscosity - 14-16 seconds (20 °)

2. Spray volume - 2/3-3/4

3. Painting pressure - 4.0 bar

4. Distance of spraying tool - 25-30cm

5. Standard spray - full open

6. When spraying - slightly faster

Third, the topcoat spray:

1. The topcoat is directly selected from aluminum alloy paint. The paint is composed of imported hydroxy acrylic resin, pigments, additives and the like. The paint has strong adhesion on the surface of the aluminum alloy, fast drying, self-drying or baking at room temperature, and has strong protection and decorative effect.

2. Spraying method:

First spray - fixed color spray

1. Viscosity - 14-16 seconds (20 °)

2. Spray volume - 2/3-3/4

3. Painting pressure - 4.0 bar

4. Distance of spraying tool - 25-30cm

5. Standard spray - full open

6. When spraying - slightly faster

The first time the spray is applied to fix the color. Don't care too much about the spray marks and metallic spots, just spray a layer and set the color. It is better to move the spray tool a little faster, repeat the spray once.

It can solve the problem. If the color is not enough, you can spray it again according to the secondary spraying method.

Second spray - correct spray

1. Viscosity - 11-13 seconds (20 °)

2. Discharge amount - 1/2-2/3

3. Painting pressure - 4.5-5.0 bar

4. Distance of spraying tool - 25-30cm

5. Standard spray - full open

6. When spraying - slightly faster

This spraying is to repair the paint stains and spray marks left after the fixed color spraying, and to make the mechanical texture better.

4. Safety and environmental protection regulations: This product contains flammable organic solvents. When used, it should comply with the safety regulations and process operation specifications of the coating operation. The construction site should be protected from fire sources, ventilation, fire protection, anti-static, anti-poisoning and other protective measures. .