why does powder coating flake off

Powder Coating Flakes Off? 5 Common Causes And What To Do

Powder coating is a great way of protecting metal surfaces. Sometimes, though, you’ll see it flake off. This can be disappointing since it doesn’t look good and leaves the metal exposed to corrosion. So why does that happen?

Powder coating flakes off often because of poor surface preparation before the powder coating process. But the powder coating will also flake off if any oils or contaminants on the metal aren’t cleaned off thoroughly.

In this article, I’ll explain exactly how this happens, how you can prevent it from happening to your parts, and what else you need to watch out for when powder coating.

5 Most Common Reasons Why Powder Coating Flakes Off

#1. Improper Powder Coat Substrate

The substrate is the material that’s being powder coated. For example, steel or aluminum are common candidates for powder coating.



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However, some substrates don’t do well with powder coating. For example, some plastics like LDPE and PCL simply can’t take the heat. Others are so soft that the coating will crack and flake off later.

Another thing that might not work is aluminum, which has been anodized and dyed. Sometimes, the inorganic dye will react poorly with the coating and prevent adhesion, resulting in a powder coating that flakes.

Aluminum that’s been anodized and dyed will likely take longer to properly prepare for powder coating since a fair bit of the anodized layer must be removed through sanding or blasting.

Rust and corrosion are also major problems. The powder coat won’t stick and will most definitely flake if this isn’t completely removed.

Conversely, it could also flake off if the metal is too smooth and the coating isn’t able to “bite in” to the substrate.

#2. Improper Powder Coating Equipment

Another reason why your powder coating might be flaking off is that you might not be using the proper equipment for the job. This is something that I personally noticed after I used some very old equipment for a job.

I eventually had to change the equipment and get something more fit for the job.

So what I did is I got this Chicago Electric Portable Powder Coating System. It did a great job of applying the powder coating, and it was super easy to use, too.

Also, something that I really appreciated about it is the fact that it’s significantly cheaper than most other powder-coating guns on the market, perfect for folks performing DIY projects and on a budget.

#3. Improper Technique When Applying Product

Another reason your powder coating might be flaking off or chipping off is that you are not applying the product properly. This is actually much more common than most people realize.

The best thing to do regarding this is to talk to a professional with some experience about applying powder coating.

However, there are some of you who won’t have the luxury to actually have access to the type of person, at least not without paying them first.

If that’s the case, then I have good news for you. Several books can actually help you apply the powder coating properly. If you are interested in learning on your own time, the book is called A Guide to High-performance Powder Coating.

#4. Improper Cleaning

It’s good practice to bead blast or sandblast parts before powder coating. This will help rough up the surface for better adhesion and remove any corrosion, grease, or grime.

When sandblasting, it’s important to process the part evenly.

Any areas that are blasted too lightly or missed entirely will likely be a problem area for flaking.

Any areas that are blasted too heavily might give a different surface texture or shape, especially if a very smooth or glossy powder-coated surface is desired. It might be that bead blasting would be a better option.

For textured coatings, rougher sandblasting is less of an issue. This process still requires a certain amount of skill to ensure it’s done thoroughly.

Speaking of sandblasting, you might also want to check out how much sandblasting costs. This guide will help you learn about the proper cost estimates and how you should plan your project accordingly.

Sanding The Part

An alternative to sandblasting is to sand the part. This can be tricky, though, for parts that have small inside corners or detailed geometry.

Since it’s difficult to reach these areas with sandpaper, this could result in a surface with poor adhesion, where the powder coating will likely flake off.

Cleaning with a solvent will remove any kinds of oils or other contaminants on the part.

The powder coating won’t adhere to any surfaces with oil on them, and a powder coating is guaranteed to yield poor results if this step is done improperly.

After abrasive cleaning, the part needs to be rinsed off. This is because media blasting and sanding will leave a dust coating on the part, preventing adhesion. The rinsing media also needs to be very pure, like distilled water. Otherwise, contaminants will be left on the surface.

One common issue is insufficient rinsing. If the distilled water isn’t applied generously enough, the dust particulates might collect along the bottom of the part instead of being washed away. This will almost guarantee to flake later on since the powder coating will adhere to the dust film instead of the metal substrate.

#5. Improper Powder

There are many different kinds of powder coating. Some are made of thermoplastic. Some are thermoset plastic.

Within these categories, many specific types are more suited for some substrate materials than others. You’ll likely get flaking if you use the wrong powder type that doesn’t match the substrate.

For example, aluminum can be difficult to adhere to. That means that the powder used for aluminum is often different from that used for steel. There are also different kinds of powder based on application.

For example, parts that will need to be able to flex might need a softer powder. Springs can be powder coated, but the coating could flake off if the spring is put under extreme compression and the coating is too hard and brittle. A slightly softer, more flexible coating may be more appropriate.

Realistic Expectations – Why It’s Important?

At the end of the day, you need to be reasonable with what you expect to get out of a powder coating. It’s absolutely a great way of protecting surfaces, and it’s a very durable coating, but it’s also not impervious to wear and tear over time.

For example, powder coats can chip off or flake over time if the area is exposed to impact.

One possible scenario is for springs under a car; rocks hitting the spring when driving over a gravel road at high speed will chip off the coating.

Eventually, rust can form under the surface of the coating. Once this develops, the coating is no longer able to adhere to the surface of the metal, and it will flake off.

UV lighting can also break down powder coats. It will degrade the coating, making it lose its color and weaken. Once this happens, it can flake or rub off.

It’s a good idea to not leave anything powder-coated in intense sunlight for very extended time. However, some kinds of powder are more resistant to UV damage than others.

Speaking coating and paints, have you ever wondered if you can use exterior paint inside? Check out the guide to get more insights about the topic.

What to Do When Powder Coats Flake

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Usually the best approach to repairing damaged coatings to redo it simply. This can be a fair amount of work.

The Proper Way To Redo A Coating

Disassemble the component that needs to be recoated if necessary. Sand it down or media blast it until the part surface is totally even and clean of any contaminants.

The old powder coating likely won’t need to be completely removed unless it has a major issue. Just blast off anything loose.

If you want it to look good cosmetically, it’s a good idea to “feather” the areas that flaked off. Use sandpaper to work down the edges where the coating broke off until it’s smooth. This works great if you plan on using a non-glossy or textured coating.

For glossy surfaces, you’ll likely see any imperfections, bumps, or waves in the substrate. If you want it to be perfect, your best bet is to blast it down to the bare metal.

Once the previous coating is dealt with, continue the cleaning process the same way you would the initial coating. Wipe it with solvent, rinse it off, and ensure it’s thoroughly clean and dry before redoing the coating.

If you don’t want to go through this much effort, you could also simply do a paint touch-up. Sand down the problem area, feather the coating edges, and try etching the bare metal with acid to provide a good grip.

Clean with solvent and let dry. Then, touch up the area with the closest matching paint that suits the substrate material.

The fix will likely be visible, but it will be coated and more corrosion-resistant. It will likely look better than the flaked-off powder coat.

While speaking of powder coating, you might also want to know how to remove it properly. So we highly recommend you checking out this detailed guide on removing powder coating.

Related Questions:

Does powder coating scratch easily?

Powder coating is generally tough and scratch-resistant when properly applied and cured. It is often much tougher than typical paint coatings, and it can be applied thicker. However, some types of powder coats are more scratch-resistant than others. Overall, it can perform better than many other coatings in abrasive applications.

Why is my powder coating chipping easily?

If your powder coating is chipping easily, it’s most likely a problem with improper curing. If the powder didn’t get baked for long enough it will be much weaker. During the baking process, the powdered plastic has time to interlink and do science stuff which gives the coating its famous strength. If the problem persists, try etching the substrate before powder coating. This will ensure a much stronger bond and will help it to resist chipping.

If you do a lot of powder coating jobs and are interested in different methods for removal check out our article how to remove powder coating here.

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