Application of Powder Coatings

The most common application method is by electro-static spray normally using the so called “Corona” high voltage application gun.

The powder coating is put into a fluidising hopper where dry clean air is fed through the powder making the particles behave like a fluid.  Powder in fluidised form can now be delivered through feed pipes to the spray guns.

The air around the nozzle of the spray gun is electrostatically charged.  This ionises the powder particles giving the powder a negative charge.  A small amount of air pushes the powder towards the metal substrate, which is electrically grounded.

A charged particle will always travel towards a grounded object.  And so, the powder is held onto its surface by a strong electrostatic bond.

There are many types and shapes of Corona spray guns.  And there are variations on the theme of Corona charging using bells and disks.

There are also variations on the way in which electrostatic charge is created.  The so-called Tribo charging gun uses friction charging to achieve the same effect as the corona gun but without generating an electric field.  The benefits of Tribo application can be used to give good access into deep recessed spaces.

Another way of applying powder coating is by fluid bed dipping, which is used by a number of specialist industries.

Electrostatic Application

In this method of application, a high voltage generator is used to charge an electrode at the tip of the powder gun. This creates an electrostatic field (or corona) between the gun and the substrate. Gas molecules in the air pick up electrons emitted from the corona. This negative charge is, in turn, transferred to the powder particles as they are propelled from the gun head towards the substrate. The charged powder particles are deposited on the earthed substrate.

Tribostatic Application

In this method of application, powder particles are charged by causing them to move along a specially designed and shaped surface. The frictionally charged particles will then be attracted to, and deposited onto the substrate. The extent of frictional charging is governed by the volume of powder delivered onto the charging surface and the speed it moves across the surface, both of which can be controlled by the tribostatic gun operator.