Is Bondo Waterproof? Here Is The Answer

Bondo is a familiar name to numerous drivers, widely used as an automotive body filler. Yet is Bondo waterproof? If you cannot find a feasible answer, our article may come in handy. Keep scrolling down! 

What Is Bondo?

Bondo is an automobile’s putty, including two primary components: aluminum powder and polyester. They combine together and solidify when making contact with the air. 

What is Bondo made of? Aluminum, polyester, and plastic resin are three fundamental components of a Bondo product. These are water-repellant; therefore, it commonly offers interior and exterior repairs to metal, masonry, painted wood or drywall.  

So how strong is Bondo? Well, Bondo, which has just been applied, is quite fragile since the solidification process takes a lot of time to complete. After a few hours, the body filler will become harder and stand a less chance of cracking. 

Is Bondo Waterproof

Is Bondo Waterproof?

Although many assume that Bondo is water resistant, it is not 100% waterproof. Indeed, when it gets constantly exposed to water, it will likely absorb a little portion of water and become wet. 

That explains why Bondo is water-repellent during a short period of time, particularly car wash rain because its exposure ratings are not continuous. However, as mentioned earlier, once the exposure time has prolonged, it is unable to hold up the water well. 

What Type Of Bondo Is 100% Waterproof?

The answer is the fiberglass resin product.

Generally speaking, it cannot resist water fully, but its capacity is most optimal. Thanks to this wonderful function, coupled with its strength and duration, the Bondo fiberglass resin is good at sealing cracks, repairing breaks, or filling holes. 

Why Doesn’t Bondo Get Wet Easily?

The answer lies in Bondo’s main components. Most Bondo products are made of aluminum and polyester, two agents good at preventing the water from getting in. 

Plastic resin is another important constituent famous for its excellent water-resistance capacity. When it interacts with droplets, it will soak in water like a sponge. After that, it might squeeze, release water, and become dry. Thanks to its ideal operation, Bondo gains optimal protection from water. 

What Are The Impacts When Bondo Wets Out?

Below are some notable impacts exerted on the Bondo and your car when it gets wet. 

Damage To Your Bondo

Bondo is more prone to wear when it gets soaked in water. Although it is designed to resist water, an excessive amount will undoubtedly ruin its internal components and even form dents, cracks, or scratches on its surface. 

Rusting Or Corrosion

When water finds its way into this putty, a moisture level will escalate. Consequently, the metal underneath falls victim to rusting or gets corroded over time. 

This is a familiar phenomenon, mainly attributed to the contact between materials derived from metal and air moisture. 

Your Vehicle Is Susceptible To Breakdown

Once your Bondo ultimate filler is worn out, it cannot provide the best protection for your automobile. Hence, your car would be more affected by external factors, such as rocks, potholes or weather. 

Rusting is a possible scenario, as most car bodywork is made of metal or non-stainless steel. Among different brands, Toyota, especially the 12th gen Corolla, is most susceptible.

It is even more dangerous when Bondo falls off. If you are lucky, only damage to your car’s wheels or other parts is rendered. Unfortunately, an accident might arise in many situations, jeopardizing drivers’ safety. 

Can I Paint Over Bondo?


Painting is a great method to cover the rough Bondo surface and show off your smooth sand work. You should remember to put on the primer first before layering the polyester putty. 

This is because the primer will act as a base coat, preventing the polyester material from absorbing the paint. So, you might find it easier to remove if needed.  

How To Prevent My Bondo From Getting Wet

When you have just applied Bondo on the external bodywork of your car, it is advisable to avoid washing it or driving your vehicle in the downpour. Newly applied textures of Bondo are pretty vulnerable. 

Most importantly, ensure that you mix the Bondo with the accurate ratio. If it is too soft, it can sweep away under the effect of water. Yet, suppose it is too hardened; you may encounter trouble applying it on your automobile. 

Other methods are strongly recommended, advising you to seal it or use the printer before painting the Bondo on your car.  

Frequently Asked Questions

What Happens If Bondo Gets Caught Under The Rain Droplets? 

The rain is inclined to wash off your Bondo’s surface when it is not hardened enough. In this case, you should start applying Bondo from scratch instead of placing a new one on the ruined putty.

If you do so, Bondo cannot completely cover the dent and scratch. During the procedure, you could park your car in the shade to avert a sudden downpour. Water, which has invaded inside the Bondo, would also evaporate when some arrays of sunshine appear. 

Should You Use An Unfinished Bondo In The Rain?

The answer varies greatly, depending on numerous factors. Temperature is a notable one. As presented above, if Bondo is still soft and does not fully solidify, it easily gets damaged when exposed to rain. 

But on some hot days, your Bondo becomes dry more quickly, so you don’t need to worry whether you should keep your automobile away from water or not. 

A protective measure you could take to handle your unfinished Bondo is using a primer spray, which facilitates the solidifying process. 

Is It Advisable To Wash Over Bondo?

You can wash over Bondo if it has been cured for a while. Nevertheless, you are not advised to do so once your Bondo is still fresh or newly applied. 

The reason is that Bondo needs time to become dry and solid like other fillers. Washing off the Bondo immediately wreaks havoc on its components and degrades its water-resistance ability. 

Suppose you have to perform this act; you can prime and cover it with a special paint as a protective layer. 

The Bottom Line

Hopefully, our post will offer a satisfying answer to the question: Is Bondo waterproof? You can also learn more about the damage triggered if your Bondo contacts the rain, followed by numerous solutions to this issue. 

Thank you for being so supportive, and have a good day!

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