What is the powder coating process?

If you’re looking for a way to protect metal surfaces, parts or products, then powder coating provides a versatile and durable solution. It’s a popular, dry-coating alternative to liquid paint finishes and it offers several major benefits, including:

• Resistance to scratches, chips and other wear and tear
• Weather resilience
• UV protection
• Even finish and hardened shell
• Improved matte and gloss retention.

Powder coating is both functional and decorative and offers a range of surface finishes, along with excellent colour-matching.

Another big advantage that powder coating has is the efficiency of its application process.

What Happens During the Powder Coating Process?

There are three steps to the powder coating process:

• Preparation
• Application
• Curing.

Of these, preparation is likely to be the most labour-intensive, depending on the type of surface you’re applying powder coating to and its condition.

The actual application and curing parts of the powder coating process are fast, enabling rapid finishing as part of the overall production process.

1. Preparing Surfaces for Powder Coating?

On whichever surface you apply powder coating, typically a metal substrate, you'll need to prepare it first. You must remove any grease, oil or oxides from the surface to ensure that the powder coating will stick to it properly.

Degreasing is the most important part of preparing metals for powder coating application. A basic method is to apply a solvent, but there these are more effective methods:

• Vapour degreasing – applying a hot vapour from heated chlorinated hydrocarbon solution, which condenses on the metal parts
• Aqueous washing – washing the metal parts using a detergent and hot water jets
• Immersion washing – passing the metal through a sequence of tanks containing a cleaning solution followed by hot and cold rinses.

There are also various pre-treatment options for metal surfaces that also clean and prepare them for powder coating:

• Phosphating, and 
• Chromating.

These processes improve the bond between the substrate and its powder coating and create a barrier against corrosion.

The other crucial part of preparing metal surfaces for powder coating is the removal of inclusions. These are dust and particles that can remain on surfaces after degreasing. You simply wipe them off with a clean rag or cloth.

2. Applying the Dry Powder Coating

Although powder coating is dry, it’s still a form of paint but it has no liquid carrier.

Instead, it consists of various resins and pigments ground down into a powder, melted to combine them, then re-ground.

To apply this powder coating to surfaces, you use an electrostatic spray gun.

Compressed air forces the paint through the end of the spray gun, atomising it into a fine spray, creating small droplets.

The gun gives the powder a positive charge before it leaves the nozzle. This makes it stick to the negatively charged surface of the substrate, countering the effects of gravity and aerodynamics. This reduces paint drift, making the application process extremely efficient and thorough.

Along with the spray gun is a powder feeder that controls the flow of powder to the gun, enabling the person using it to control dilution ratios.

The spraying takes place in a powder booth, which has a recovery system, which means any over-sprayed powder is easily recoverable for re-use.

3. Curing the Coated Surface

Once the application of the powder coating is complete, and you’ve checked the surface, it now requires curing.

Curing involves the application of heat to the coated surface, inside a convection oven. This part of the process is energy-intensive because achieving the right metal temperature is critical to the successful coating.

Each component you powder-coat must reach its optimum curing temperature to ensure the coating hardens properly.

When curing takes place, the resins in the applied powder melt and fuse together, forming an even surface.

Larger and heavier materials requiring coating will require larger volumes of heated air to cure and dry them.

The minimum temperature for curing is 160°C, but many modern coating powders such as thermoset powders are resilient at higher temperatures. This can cut curing times. 

For example, thermoset powders will cure at 200°C in as little as 15 minutes.

After curing comes the cooling of the coated and cured parts. Once cooled, these parts should be extremely hardwearing. There are various guarantees available for durability, of between 30 and 40 years.

Why Choose the Powder Coating Process?

The powder coating process is highly efficient, cutting down on waste and providing aesthetic, durable and resilient finishes rapidly when compared to liquid paint applications.

With multiple uses, from industrial steel fabrications to garden furniture, powder coating presents a customisable and highly professional finishing solution.

For more information about the powder coating process, please contact us.