What is 'flow out' in powder coating?

Flow out in powder coating is a critical part of the powder coating process.

As a form of dry finishing, powder coating goes onto surfaces in powder form, but it requires heat to transform it into an even, uniform and durable coating.

Flow out describes when the powder melts and takes on liquid form.

What is the Powder Coating Process?

The main application of powder coating is in coating metals and this occurs as a three-part process.

First you clean, pre-treat and condition the surface you wish to powder coat

Then you apply the powder coating using an electrostatically-charged spray gun

Finally, you cure the powder coating under heat.

How Does Powder Coating Work?

There are two broad types of powder coating: thermoplastics and thermosets.

All powder coatings melt and merge together when subjected to heat.

But because thermoset powder coatings are polymer resin-based, the ingredients they contain also merge together in a chemical reaction.

The difference between the two types of powder coating is that thermoset coatings will not soften or melt if you re-apply heat to them once they have hardened.

Powder coatings first adhere to the metal substrate to which they are applied through the electrostatic charge of a spray gun.

Because you apply them in dry powder form, they provide a uniformity of covering, enabling you to cover otherwise difficult-to-reach or upside down surfaces, as well as sharp angles and tight corners.

This process is known as electrostatic spray deposition (ESD).

Once you have sprayed the substrate, you must then apply heat to it to cure the powder coating.

This happens in a special oven.

There are several factors to consider here, to ensure the best possible finish:

• The substrate material you are coating
• Its end purpose
• The type of powder coating you intend to apply

The preparation stage is also critical. You must first ensure the substrate is thoroughly clean, and, where necessary, pre-treated ready for the powder coating application.

You need to remove any dust, dirt or particles, and any traces of grease, solvents or other residues.

It may also be necessary to use a dry-off oven, to ensure any remaining water or treatments materials completely evaporate before applying the powder coating.

Why is Flow Out Important for Powder Coating?

Once you put the sprayed part in the oven, it must reach the optimum temperature for flow out to occur.

Flow out in powder coating takes place when the powder particles melt and flow together as they make contact with the heated surface.

Flow out is a vital part of the powder coating process because it ensures that the dry powder transforms into an even film to coat and protect the surface it is applied to.

Most powder coatings will cure at temperatures of 200°C and take between 10 and 15 minutes to do this.

Once cured, they provide hardwearing, functional surfaces which can also be decorative.

For more information about our powder coating range and its many uses, please contact us.