Powder paint charging process in a corona discharge field

In order to charge the powder paint in a corona-charged field, a high electric field between the spray gun and the painted item is must, and latter it should be grounded.

Thanks to this, the space between the gun and the item charges with ions (charged air molecules) which attach to the powder, charging it.

At the same time, part of the air molecules remains free and does not attach to the powder particles. These free particles will follow the line of the electric field and flow towards the colored product at a speed that exceeds the speed of particles with powder.

But if the surface of the part has a negative dielectric susceptibility, then the charge of air molecules simply flows down to the ground without taking part in the painting process.

The free flowing properties of the ions are reduced during the powder coating process. So, a shaped charge is formed on the coating.

Reverse ionization often occurs due to charge accumulation. As a result, this leads to a deterioration of powder particles desublimation and to a deterioration in the quality of the coating.

The dielectric susceptibility reduces If the product has dirt or old layers of paint.

Also, it is important to mention the peculiarity of the “corona charge”, that is the Faraday cage. A Faraday cage is a defect that appears when powder coating is applied to arduous places: grooves, corners, recess, ledges – everywhere where the external electric field does not penetrate.

It makes applying a uniformal paint layer difficult and sometimes impossible.

Therefore, in order to apply powder paint correctly and successfully to arduous areas, you need to use the following:

• well charged powder;
• optimal flow rate for the powder to fly into the cavity;
• the external electric field must be controlled to reduce the pushing of powder particles towards the edges of the Faraday cage.

And also use the right technique to make this whole process easier.