Faraday cage effect: what is this and how to avoid it
Powder paint is applied to products with an electric field. This allows the surfaces to be created evenly and with perfect quality. However, as soon as the powder is to be applied to things of a more complex shape, with corners, various defects in powder coating can occur. One of the most common is the Faraday cage effect. What is it and how to avoid such a defect, so that the coating is of high quality, we tell further.
What is a Faraday cage
The Faraday cage effect is named after Michael Faraday. He is the scientist, the founder of the doctrine of the electromagnetic field. He conducted experiments with static electricity.
Products with this defect have the so-called Faraday zone. It includes angles and hollows where powder paint does not settle. This is due to the fact that, within these zones, the resistance to electrical forces is much greater than on all other surfaces. Therefore, the powder accumulates at their edges, but much less inside.
And in the Faraday zone itself, vortices can form. It can also cause reverse ionization.
Because of the Faraday cage effect in powder coating one of the most difficult tasks is to apply to the depressions.
How to avoid the Faraday effect
Longer spraying time will not solve the problem. Even when a thick layer of coating is formed at the edges and the powder can no longer settle there, the particles are still not directed into the recesses. And reverse ionization takes place.
The only thing that can help the powder to settle in the troughs is the field, which is created by the spatial charge of the powder brought by the air into the troughs.
So, how to cover a corner with powder paint? First, you need to check the grounding of the product, equipment and a painter. This, in general, should be a daily task for the painter. The powder particles are attracted to the grounded surface.
There should be a good charge of powder.
The velocity of the air flow should be sufficient to transfer the powder inside the recess. But it should not be very big, otherwise it will interfere with the settling of powder particles.
It is necessary to control the electrostatic field so that it does not “push” the powder to the edges of the Faraday cage.
You should reduce the voltage, try to reduce or increase the distance from the sprayer to the product.
Through the study of powder coatings, defects and the analysis of their possible causes, specialists have come to the conclusion that in some cases to avoid the Faraday effect, it is necessary to use triboelectric equipment. It does not generate ion flux and strong electric charge. Due to this, the powder easily penetrates the recesses and settles on the corners. The coating is high-quality, uniform, without defects.
Following our tips, you can avoid the Faraday cage effect and easily apply powder coatings on products of any shape and configuration.