Can you Bondo aluminum siding?

In this blog post, we will answer the following question: Can you Bondo aluminum siding? We will explain what Bondo is, how much it costs and where to buy it. We will also briefly discuss how you can repair RV aluminium siding. 

Can you Bondo aluminum siding?

Yes, you can use Bondo (or any other body filler) to fix your RV aluminium siding. Bondo is a two-part resin originally formulated for auto-body repairs, including damaged aluminium.

To apply Bondo on the aluminium siding follow these steps:

  1. Mix the putty according to the manufacturer’s instructions.
  2. Apply, mold and wait the time necessary for drying.
  3. Sand the putty with P150 – P220 abrasive products.
  4. Apply a thin coat of Washprimer before the filler, as it alone does not ensure good adhesion and optimal results on aluminum surfaces.
  5. Add primer once the Washprimer has evaporated.
  6. Sand the filler with P400 / P500 discs.
  7. Clean and degrease.
  8. Apply finish paint.

Are there additional products to add to the Bondo?

Yes, the use of a hardener with the Bondo is necessary. Most often sold with the fillers pot, the mixing proportions must be strictly observed for a nickel result.

The hardener is a reaction catalyst, i.e. it will accelerate the drying process of the fillers.

In general, the proportion of hardeners is about 2%. This is about the size of a small weight of hardener for a golf ball of putty.

What exactly is Bondo?

Bondo is a body filler made from polyester resins, also known as putty in the automotive industry. Bondo is a composition of wax, resin and brick powder from which one can be used for different purposes:  It is used in various sectors of industry to repair, join parts together, caulk, but also when combined with colored pigments, it provides camouflage (natural defects in wood, scratches on bodywork).

Particularly used in the automotive body sector it is often the result of a complex mixture depending on whether it is intended for the sealing of the vehicle, the reinforcement bodywork, soundproofing … Multifunctional material, it allows the repair but also the shaping of elements.

What other types of body fillers for aluminium siding exist?

Besides Bondo, for an RV’s bodywork, there are eight different types of body fillers: universal fillers, cellulosic fillers, aluminum fillers, plastic fillers, metal fillers, fibreglass fillers and tin fillers.

Most often, “polyester” type sealants, like Bondo, are used for cars & motorcycles. Here are the best sealants you can use for your RV aluminium siding:

  1. Universal Sealant: Universal polyester putty is the most widely used putty. It is mainly used on sheet metal/steel bodywork. These fillers can be more or less filling. Low-density sealants are less filling than traditional polyester sealants but allow a better finish. It also effectively protects the worked parts from humidity.
  1. Cellulose putty: Cellulose finishing putty, which can also be used on all kinds of materials, is above all an excellent way to polish up a job, or to carry out a light touch-up on the RV bodywork. This sealant is usually in the form of a tube and does not need a hardener. It is the only putty that can be painted without having to be primer coated. It is used for filling micro-cracks or scratches too deep to be filled with paint.
  1. Steel & aluminum putty: Metal sealant, composed of components with a high aluminum content, which is specifically recommended for bodywork. Indeed, having anti-corrosion properties ensures good protection against humidity for your bodywork under your repairs. Aluminum fillers, anti-corrosive and very resistant, are composed of aluminum powder and have good adhesion on steel surfaces treated with zinc and aluminum. It is used to fill crevices and cracks.
  1. Plastic putty: Plastic sealant is only used for all plastic parts on your vehicle. Side sills, bumpers or roof bars can be repaired with this sealant. It has very good adhesion and makes sanding easier.
  1. Fibreglass putty: Polyester fibreglass or “sauerkraut” putty, which repairs cracks in bodywork. The fibreglass gives this resin excellent resistance and robustness and makes it possible to work on surfaces of greater depth (between 0.5 cm and 1 cm). New fibreglass sealants have appeared on the market for some time. They are more flexible and thinner.
  1. Anti Rust Putty: Still little known to the general public and democratized by the ECAR brand (reference EP 400), there are today anti-rust sealants. Yes, you read that right! Even if the treatment of rust is essential (rust converter, epoxy primer …), this new type of sealant makes it possible to strengthen the part against corrosion, which is not negligible when restoring a vehicle.
  1. Acrylic Putty: Even though a large majority of bodybuilders use polyester sealants, it is noted that there are also acrylic sealants. This is the case for example with 3M sealant reference 05096. It is a one-component sealant (without hardener) to fill small scratches. This type of putty is comparable to nitro-cellulosic putty.

The various sealants can be in the form of cartridges that can be sprayed using a silicone gun, or in the form of a resealable pot supplied with the hardener. Gun cartridges are sealants and sealants (often elastic acrylic sealants) that are used to repair or change windshield gaskets or to ensure the seal between two sheets. It adheres to different surfaces such as glass, metal, plastic … and can be painted using classic car paint.

Silicone sealants are also used for waterproofing, but cannot be painted. However, manufacturers strive to make silicone sealants available in different colors to overcome this lack. Sealants presented in the form of pots accompanied by their tube of hardener are sealants for repair, surfacing or finishing. There are also sealants that can be applied with a paint gun. They usually come with a liquid hardener.

Do not forget, after each use, close the pot or the tube of hardener in an airtight manner so that you can use it again.

How much does a can of Bondo cost?

A can of Bondo will cost you between $18.99 and $22,99 depending on where you will buy it! Keep in mind that aluminum and fibreglass sealants cost more than a universal sealant.

To buy a can on Bondo, you can go to DIY stores or you can turn to product dealers for bodywork professionals. You can also find Bondo on Amazon

How do you fix a hole in an RV aluminium siding?

Aluminum is a flexible metal in the field of transport. Its characteristics, especially low density and corrosion resistance make it a popular and useful material. Aluminum is also 100% recyclable and can easily be repaired. If you want to fix your aluminum siding or repair your aluminum RV, you may know how to fix the holes in the aluminum.

  1. Clean the area around the hole in the aluminum with a sponge dipped in water mixed with liquid detergent. Rinse thoroughly with water to remove detergent, dirt and debris. If the hole has pieces of aluminum lifted around it, like the shutters, press them down to cover part of the hole to minimize damage; if the shutters are badly damaged or uneven, it is best to remove them with tin snips or a similar tool.
  1. Mix the epoxy according to package directions. Here’s where our star, Bondo, comes to the game. Stir the mixture with a putty knife. Apply the epoxy mixture to the hole, precisely covering it as transparently as possible. Allow the epoxy to dry, harden, and cure thoroughly for at least an hour.
  1. Apply the epoxy mixture to the hole, precisely covering it as transparent as possible. Use the putty knife to pry the epoxy off the surface of the aluminum. Allow the epoxy to dry, harden, and cure thoroughly for at least an hour.
  1. Treat the damaged area and surrounding area with fine-grit sandpaper.

The bottom line

Fixing your RV aluminum siding is not the easiest job to do, but if you follow our instructions step-by-step you have a great chance of succeeding! The most important thing is to act as quickly as possible. A hole in the motorhome will cause you more issues, such as water leaks and mold. 

Please feel free to get in contact should you have any questions, comments, or suggestions on the topic.

FAQ on Can you Bondo aluminum siding?

Do I have to replace the entire sheet to repair an aluminium siding?

It depends on whether it is a scratch or a strong blow or a “break”. In most cases, however, you will have to replace the whole sheet. This is why people prefer polyester since it is easier to repair, as it is chemically bonded.

Can you patch holes in aluminum siding?

Yes, you can patch holes in aluminium siding. Depending on the size of the hole, you can sand and paint over it, or you may need to replace the whole thing!

Does aluminium siding oxidize?

Unprotected aluminum oxide, leaving an unsightly chalky appearance. Severely damaged aluminum may require professional replacement. You can do small repairs and generally restore aluminum surfaces with a few heavy-duty cleaning.