Powder Coating Over Bondo – Is It A Good Idea?

We all know Bondo putty to be a very versatile and strong filler product that is used for repairing exterior and interior surfaces. It is a very fast curing filler that comes in two parts. You can use this product to make all kinds of long-lasting, high-quality repairs to materials such as painted wood, plastic, drywall, concrete, and even metal.

It is also used quite significantly in the automotive industry. It works great as an automotive body filler. But, a lot of the time, when we use this incredibly useful product, a question comes to mind- can you powder coat over Bondo?

Well, there is a short and clear answer to this question. Let’s get into it.

What Is Bondo and How Does It Work?


Bondo is a body filler and putty that’s used to patch small holes and defects in cars, trucks, boats and airplanes. It fills imperfections while eliminating unsightly scratches, dings and other blemishes. Bondo comes in different types and cures to create varying degrees of hardness. When bonded together with special adhesive, it can be shaped by you like clay to fill large areas or held together with epoxy or fiberglass for strength.

Can You Powder Coat Over Bondo?

To answer this in short- no. You should not powder coat over Bondo. Not only over Bondo but also any kind of putty product that you use on automobiles.

The main reason why this is not recommended is that- powder coating over a layer of Bondo causes outgassing. This, in return, causes a lot of trouble in the final finish of the product. This is why you will find that many custom coaters reject metal fabrication that has a layer of Bondo on it.

Most of the putties that are used in automotive cannot withstand the high temperature of a powder coating. A lot of the time, even if you have added a very thin layer of Bondo, the extreme heat during the powder coating process will melt the putty and give you a very irregular finish.

Rather than powder coating over a layer of Bondo- you can get expensive versions of the product that have a high heat withstanding power. If the high temp body filler for powder coat is capable of withstanding about 350° F plus or 500° F plus temperatures, then you are good to go.

Does Powder Coating Require A Primer?

A lot of the time, powder coating finishes come out quite rough. One of the prime reasons for this is an uneven layer application or the absence of a primer.

The main objective of a primer is to prepare the metal for exposure to aquatic environments and exterior installations. Adding primer makes sure that the powder coating is better capable of bonding to materials such as aluminum, iron, and steel.

Moreover, if you put on a layer of primer before the powder coating, there is a higher possibility of the underlying material getting protection from corrosion and rust.

If you are working with steel products, you should keep an eye out for zinc-rich primers. These primers have similarities with galvanizing. Therefore, if after installation the exterior powder coating gets scratched, the zinc acts as a protective sacrificial layer. Even if the powder coating is scratched, the steel underneath still has protection from corrosion and rust.

For aluminum, it is better if you use a primer that has an epoxy base. Epoxy-based primers work wonders for protecting aluminum against rusting.

While you can go on with the powder coating procedure without using a primer, it is advisable to use it.

How Do You Fill Holes Before Powder Coating?

Before one goes on with their powder coating procedure, they must make sure that the surface has no rough areas or small holes.

A great way to do this is to use a product that will fill in the holes and smooth out the rough surface.

The easiest solution is to find a lab-metal filler That is capable of withstanding high temperature and can be powder coated over.

A product that will work wonders for this is the thermobond-3 powder coating filler. This has high-temperature resistance and is very easy to apply. Not to mention that it is also a cost-effective product that can give you the perfect powder coating finish. The filler is such a good product that it is often recommended by professional coaters.

How Do You Smooth Out Powder Coating?

There are a few ways in which you can smooth out a powder coating. Here are the most effective ones-

1. Reapplying

If you want a smooth finish of powder coating, it is better to start with a very thin layer. If the layer is not smooth, you can recoat the powder coating to get a smoother finish.

The recoating process can only be done if you have nothing over the powder coating and it is a freshly applied layer. You cannot use this procedure for powder coatings that are more than a week old.

2. Sanding And Buffing

If you have already applied a very sick layer of powder coating and reapplying is not an option for you- you can try sanding and buffing.

This is one of the most effective ways to smooth out the exterior.

The sanding procedure will smooth out any orange peel-like texture over the powder coating. The buffing will give it a mirror-like finish. People often prefer this method over reapplication because it is much faster and gives more effective results.

Related Post : Can You Paint Over Bondo Without Primer? – Is it a Safe Shortcut or Disaster

Frequently Asked Questions

Here are some very common question about the topic-

1. What Is The Need For Powder Coating?

If you want a metal exterior to appear well maintained and clean, powder coating is a necessary step. It is a procedure that keeps the metal from looking degraded, especially when it is often exposed to dirt, grime, and other outdoor elements.

Powder coating helps block out salt, oils, and moisture from interfering with the metal surface. That is why, if you want an automotive to look its best, powder coating is the way to go.

2. Why Would Powder Coating Be Rough?

Powder coating often results in an uneven finish because the film thickness is either too high or too low. If the coating is not spread evenly, the finish will be rough.

3. Is Bondo Putty A Permanent Fix?

This material is capable of giving a very fast cure. Depending on how it’s maintained, Bondo can give you a permanent and non-shrinking solution.

4. How Can You Remove Bondo?

Bondo can be removed by sanding. Or, you can also get Bondo removed professionally by using a chemical stripping procedure.


You often hear people using a metal filler for powder coating. But, you might have had a very bad experience when you tried it out on your own. Why is this so?

A lot of the fillers that are available in the market cannot be applied before a powder coating application. This is because the putty does not have very high-temperature resistance and can melt easily when exposed to the powder coating procedure.

So, can you powder coat over Bondo? The short answer to this is no. You can only powder coat over fillers that have a very high-temperature resistance. There are different kinds of fillers made specifically to be used under a layer of powder coating. You can use those instead of experimenting with Bondo and ending up with an uneven exterior.

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