Powder Coating Particle Generation and How to Reduce Particle Occurrence

Generally, the powder coating workpiece needs to go through the following process: after degreasing and rust removal, degreasing, water washing, phosphating, water washing, (passivation), deionized water washing, and drying; among them, the rust removal in the surface treatment process , phosphating residues and other impurities may adhere to the workpiece, resulting in the existence of particles after film formation

So how can we mitigate this phenomenon?

1 Coating working environment:

A clean production environment has a good effect on product quality

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The oil pollution in the oil tank on the coating line is combined with the dust in the air, and particles will also be formed when falling on the workpiece through vibration and other factors.
Regular cleaning of the oil tank and other places where dirt and scale are easy to accumulate is one of the effective means to reduce the generation of particles.
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2 Thickness control of coating film:

Appropriately increasing the thickness of the coating film can effectively reduce the formation of particles.
The coating film should not be too thick.
Generally, too thick will affect the size of the coated workpiece, and the impact, flexibility, adhesion and other properties will decrease.
Generally, the thickness of the coating film Control at 60-80um is normal
.

For coating enterprises, the thickness of the coating film can be controlled in the following ways:

a: The number and arrangement of spray guns in the booth;

b: Powder output and air pressure of spray gun (powder output, atomization, fluidization parameters);

c: The running speed of the conveyor chain, that is, the chain speed;

d: The hanging method and arrangement of the coated workpiece
.

3 Processing of recovered powder:

For the recovered powder that has not been screened or the mesh size of the screen is too small, some infusible particles (including spreaders, foreign impurities, etc.
) will become particles of the coating film
.

For most coating companies, recycled powder generally has the following treatments:

a.
In the automatic powder coating system recovered by the conveyor belt, after the sprayed powder is automatically recovered and sieved, it is mixed with the new powder coating and continues to be supplied to the powder spray gun.
The quality of the recovered powder is relatively stable, and it is not easy to produce particles;

b.
In the two-stage recovery system of cyclone separator and bag filter, when the powder recovered in the first stage of the cyclone separator is sieved by the vibrating screen and circulated with the powder supply system, it basically has little effect on the coating, and it is not easy to generate particles;

c.
For the powder recovered by the manual spray coating recovery system, because the dust and impurities in the environment are easily brought into the recovered powder, it must pass through a vibrating screen of 150 mesh or more after recovery
.

In the above three commonly used recycling systems, due to the influence of the environment and the influence of the attachments on the chain, it is easy to bring some impurities into the recycled powder, especially small solid particles, which are easy to accumulate in the powder supply bucket gradually.
A considerable part of them are solidified powder particles that fall from hanging chains or spreaders.
For high-demand and high-end products, the recycled powder must be sieved and then used in a certain proportion
.

Both powder coating companies and powder manufacturing companies are eager to have an effective method to control the appearance of powder particles
.
Because once the particles on the coating surface are obvious after coating, the waste of material resources and manpower is bound to be huge
.
Therefore, it is very practical to treat the particle problem correctly
.