Powder coating finishes are a great option for parts that require a protective layer that also improves their appearance at the same time. Nevertheless, not all powder coats have the same quality, which can sometimes be seen in uneven finishes and other common problems.
What Exactly is Powder Coating Finish?
In manufacturing, powder coating is the process of applying a protective layer to a metal part through a dry finish.
Contrary to traditional paint, powder coats don’t require a solvent. Instead, they use a combination of electrostatics and heat to create a protective layer on the target surface.
Types of Powder Coating
There are two main powder coat finishes types, which are thermoset and thermoplastic. Let’s take a closer look at each one.
Thermosets
Thermoset coats create a hard shell that cannot be melted away by solvent liquids. This stronger coat is due to the chemical properties of this material, so this type of powder coating finish is considered the strongest.
To put it in perspective, this is the same process that many manufacturers use to paint car parts.
Thermoplastics
Thermoplastic finishes, on the other hand, can be removed by liquid solvents.
The reason for this is that thermoplastics don’t experience change at a molecular level when heated, so they can be applied to flexible surfaces or removed completely with specific liquids.
The Powder Coating Finish Process
The powder coating finishing process doesn’t rely on liquid solvents, so it looks completely different from a conventional paint job.
Here are the 4 steps involved in this process.
Step 1 – Preparation
In the first step, the target surface is cleaned with a chemical wash and sometimes additional processes to ensure it’s free of contaminants.
Step 2 – Powder Coating Application
Next, it’s time to apply the powder coat. The target part is placed in a room where the charged coating particles are applied to the grounded surface. Application devices and methods vary based on the part being coated.
Step 3 – Curing
Once the coating is applied, the target part is moved to the curing oven and exposed to high temperatures that help harden the protective layer.
Step 4 – Cooling and Finishing
Finally, the part is cooled, which solidifies the coating. After inspection, the final touch-ups are performed and the part is either assembled or prepped for delivery.
Common Powder Coating Problems and Solutions
Although this type of finish has great applications, there are many powder coating problems and coatings you should keep in mind. These include:
1. Faraday Cage Effect
The Faraday cage effect occurs when the powder coat can’t penetrate small corners and uncommon geometric shapes. This occurs when there are charged particles built up in the confined area, which repels the powder particles.
Solution
It’s possible to adjust the electrostatic settings and modify the spray technique to mitigate this issue. If this occurs consistently in the target area, formulating a special powder to improve circulation in small spaces is also an option.
2. Poor Adhesion
As the name suggests, poor adhesion simply means that the powder coat did not bond to the target surface.
Improper surface preparation, inadequate curing temperatures, and contaminants present on the target part are some of the common reasons why powder coats don’t adhere.
Solution
First off, it’s necessary to clean and prepare the surface properly before any powder coating is applied. This finish may also require a primer depending on the surface and the curing process should be tailored to match the powder’s requirements.
3. Uneven coating
Like paint finishes (but not as frequently), it’s possible for powder coats to be uneven. This causes areas of uneven thickness and thinness, which usually stem from improper application techniques.
Solution
Besides applying proper powder coating techniques, it’s also necessary to maintain and monitor your equipment. Not only this, but all operators must have the same knowledge level and all target parts must be grounded uniformly before any powder application.
4. Orange Peel
This defect makes the coated surface look textured and porous, like an orange peel. Hence the name.
Orange peel is among the most technically complex issues to solve because it occurs when there’s a combination of poor environmental conditions, accelerated curing, and an overly thick layer of powder.
Solution
It’s essential to adjust your curing oven settings based on the powder being used. Not only this, but it’s important to ensure environmental conditions are optical and that the application technique results in an even layer.
5. Fish Eyes
Have you ever noticed powder coats that have small craters or circular marks? This type of imperfection is called a fish eye.
Fish eye formations usually occur when the target surface was not cleaned properly and has contaminants that repel the dry coat.
Solution
The best way to prevent fish eyes from forming is to thoroughly sanitize the target part, remove all impurities, and reduce airborne contaminants in the coating room.
Advantages and Disadvantages Of Choosing Powder Coatings
Here are some of the pros and cons of powder coatings.
Advantages of Powder Coating
- More durable than traditional paint
- Comes in a variety of colors
- More environmentally-friendly than conventional paint
Setbacks of Powder Coating
- Difficult to change colors
- Requires curing oven
- Powder coating finishes are not usually conductive
Frequently Asked Questions (FAQs) – Powder Coating Finish
Let’s go over some of the most frequently asked questions about powder coating finishes.
How Does Powder Coating Metal Work?
The coating particles are electrically charged, so they adhere to the grounded surface upon contact. Then, the coat is finalized in a curing oven to create the protective layer.
How Durable is Powder Coating?
Powder coats are extremely durable and can last decades if cared for properly because they prevent corrosion, require little maintenance, and are impact-resistant.
Conclusion
Powder coatings can create a protective layer that enhances the target surface’s appearance. That said, there are many steps you need to take to prevent issues like the Faraday cage effect, poor adhesion, and the other problems listed above.
Interested in powder coating finishes for your project? Contact us today to learn more about our fabrication services.