Can You Fiberglass Over Bare Metal? (Explained)

Fiberglass is one of the most versatile products in the market. As a result, it can bond to nearly all types of surfaces, metal included.

However, when bonding fiberglass to metal, you have to consider a couple of things. This article will shed more light on how you can fiberglass over bare metal and ensure it lasts for a long.


How to Fiberglass Over Bare Metal

Step 1 – Gather Essential Materials

We have already established that fiberglass will stick to metal. But before attempting such a project, you must assemble the correct materials. Fiberglass is available in different forms.

The best form that will stick to metal is using both the fiberglass mat and resin. This is a sticky substance that comprises woven fiberglass mats. It is often mixed with a hardener before it is applied to a surface.

Therefore, the first thing you will need is a fiberglass mat and resin. You can find it at a local auto parts store. The other thing you will need is an orbital sander. Make sure that you have a strong cleaner such as acetone.

Step 2 – Scuff Up the Surface

A crucial part of sticking fiberglass over bare metal is scuffing the latter’s surface. By scuffing it up, you give the metal a rough finish, promoting better adhesion. You can use two things to scuff up metal; a grinder or sandpaper.

For relatively smaller projects, sandpaper should get the job done. For bigger projects, you should scuff up the metal using an air sander. It’s faster and more effective.

Step 3 – Clean the Metal Surface

The presence of contaminants can affect fiberglass adhesion to bare metal. Therefore, it is crucial to clean the metal surface with a strong solvent before application. Acetone is highly effective. Clean and wipe with a microfiber cloth.

Step 4 – Lay the Fiberglass Mats

What goes first is the fiberglass mat. You will need to cut the mat to fit the affected area. A razor knife should come in handy during such. You may also need several layers if you are filling a deeper area.

Please note that the more fiberglass mats are used, the shorter their lifespan. It’s best to keep the number of layers to a minimum.

Step 5 – Mix Resin with Hardener and Pour It

When buying fiberglass resin, make sure that you get the hardener as well. The manufacturer should provide instructions on how to mix the fiberglass resin with a hardener.

Follow these instructions and stir thoroughly until all contents are mixed. Pour the resin over the fiberglass mat. Spread it evenly with a roller.

If you must add more mats, do so but ensure that you spread the resin evenly. Remove any air bubbles on the mat and resin mixture.

Remember, once you add the hardener, you only have at most thirty minutes to work with the mixture. Please don’t waste any time; otherwise, it will start to harden even before you can pour it.

That’s how you can fiberglass over bare metal. After application, you should give the fiberglass some time to dry. At least two hours should be enough.

Then you can sand it until you get a smooth finish. You can paint over the metal or do whatever you want.

Should You Paint Epoxy Primer Before Using Fiberglass Over Metal?

There are many ways you can approach fiberglass installation over bare metal. One of the most common methods is to apply an epoxy primer over bare metal first.

Whether to apply primer or not depends on your preferences. As long as you follow the method prescribed above, you are assured that the fiberglass will adhere to bare metal.

However, we also can’t dispute the fact that primer will improve adhesion between fiberglass and metal. If you have some primer lying around, you can apply it over the bare metal first before adding the fiberglass.

Will Fiberglass Delaminate from Bare Metal?

If you are considering using fiberglass over metal, you have to understand that this isn’t a long-term solution. It won’t last forever but can hold for a considerable period.

Fiberglass and metal are two different materials. That’s why it’s difficult for them to bond permanently. But that doesn’t mean fiberglass will delaminate from bare metal after a day or two.

It can last for years as long as you follow the instructions shared above. How long fiberglass lasts over bare metal depends on how correctly it has been applied.

Besides the delamination, which is inevitable, fiberglass can crack shortly. Therefore, this is expected.

Fiberglass vs. Welding Sheet Metal

Fiberglass and welding sheet metal are two excellent choices when repairing metallic components in your car. Fiberglass is the easiest and quickest solution.

However, welding metal sheets is the most durable solution. Welding a metal sheet lasts longer because metal and fiberglass are two different materials. It’s expected that their bond won’t be strong, and neither will it last long.

As you plan on using fiberglass over bare metal, you need to understand the durability concerns.

Can Grease Interfere with Fiberglass Adhesion to Bare Metal?

For fiberglass to stick to bare metal, it has to be 100% free of contaminants. Many of us love shortcuts. But in such a scenario, it’s best not to skip any step. Cleaning bare metal is a crucial step in the installation of fiberglass.

After sanding, you should look for a clean solvent that will strip off grease, dirt, and any contaminants on the surface. Grease will indeed affect the adhesion of fiberglass to bare metal.

What is the Role of Scuffing Bare Metal Before Adding Fiberglass?

If you have been doing some painting over metal in the past. You are aware that paint requires a rough surface to adhere to. That’s the same case with fiberglass.

When you scuff up the surface, you create a suitable environment for fiberglass to stick to. As tempting as it may be to stick fiberglass directly to bare metal, ensure that you sand the surface first. That will guarantee the fiberglass has got something to grab.

How Long Can Fiberglass Last Over Bare Metal?

Would you believe it when we tell you that fiberglass can last over bare metal for more than five years? Fiberglass is a highly durable material. As long as you can get it to stick to bare metal by using the techniques shared above, it can last for years.

There are also scenarios where the fiberglass patch can last only a few months. The longevity of this project narrows down to the method of application.

Do Temperature Changes Affect the Longevity of Fiberglass on Bare Metal?

This is an area where fiberglass can’t outshine its alternative, welding sheet metal. Fiberglass and metal have varying expansion and contraction rates.

When you install fiberglass over bare metal, which will be exposed to high heat, expect the fiberglass to crack after some time. As the two expand and contract at different rates, more pressure will be applied to the fiberglass, leading to cracking.

Should You Remove Rust Before Patching Bare Metal with Fiberglass?

The importance of removing rust before doing anything to bare metal can’t be overemphasized. Rust isn’t one of the things you should want to see on metal.

Before bringing in fiberglass, you need to sand and remove the rust with etching acid. Always make sure that the metal is rust-free before patching it with fiberglass.

Even though fiberglass will stick for a considerable period, it isn’t a solution for stopping the spread of rust. You will have to deal with the rust first.

Is Fiberglass Sandable?

When patching fiberglass over bare metal, it’s important to ensure the final finish is aesthetically pleasing. With fiberglass, it’s very easy to protrude higher than the surface of the metal.

To prevent this, always keep the fiberglass patches thinner. But if you need to smoothen the fiberglass surface over bare metal, don’t hesitate to sand it.

An orbital sander is the best solution for this project since it’s more powerful. Fiberglass is a durable material that will need a lot of power to be sanded over. Ensure you wear protective gear as fiberglass particles can be pretty harmful.

Do I Need Adhesives to Stick Fiberglass to Bare Metal?

As long as you use the fiberglass resin with a hardener to hold the fiberglass mat, there is no need for an adhesive. But if you must use an adhesive, go for epoxies. This is the only type of adhesive that will withstand the expansion and contraction of metal and fiberglass.

Can I Use Fiberglass Over Painted Metal?

Yes, you can. But because fiberglass requires metal to be sanded before its applied, any paint on the metal will be removed as the surface is scuffed up.

You can apply fiberglass over any metal, whether bare or painted. You only need to follow the instructions shared above.

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  1. Good info !!

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