Primer is not an uncommon word in most painting processes, including automotive paint. Here we look at the epoxy primer, including its types, where and when to use it, how to apply it to get proper adhesion,  among other critical things.

What is an Epoxy Primer?

Have you ever seen a paint-like substance that’s applied to freshly sanded surfaces before the topcoat? Well, that’s the primer. So, what is an epoxy primer?

In simple terms, epoxy primer is a sealer with a non-porous finish. Its primary purpose is to prepare bare metal surfaces for painting or coating. You can also use it over plastic, steel, fiberglass, and black iron phosphate coating.

Although it is ideal for dents and cracks, an epoxy primer might not be the best option to use as a primer-sealer. Epoxy primers have excellent mechanical ability, superior adhesion, and durable chemical resistance in various environments, ideal for various materials.

Although it doesn’t provide superior adhesion to metals, it’s an ideal proper base for extra undercoats and topcoats.

Besides, epoxy primer is non-porous, meaning it will not soak up moisture. Since it is waterproof, it has excellent corrosion-resistant characteristics. Epoxy primers can also be used in power plants, tank exteriors, water treatment, and marine applications. Besides, they can be used in waterproof surfaces usually exposed to oxidation.

Materials used to make epoxy primer include carbon chains and other elements, including oxygen, hydrogen, and nitrogen, classified as organic compounds.

Benefits of Epoxy Primer?

The main purpose of using an automotive primer is to help the paint adhere to metal surfaces. After all, a shiny metal surface (whether new or old) will not bond to the paint properly. This can result in flaking, peeling, and rust, which can turn your car into junk in no time. Th

at being the case, here are the benefits of using epoxy primer.

Seal Bare Metal

Are you looking to seal up bare metal and prevent moisture or corrosion? An epoxy primer will come in handy. It prevents corrosion or rust from forming on the surface by keeping out oxygen. Unlike other standard primers, an epoxy primer is non-porous and won’t soak up moisture.

Prevents Rust and Corrosion

Protecting materials against rust and corrosion is the main reason for using primers. Luckily, the epoxy primer does this job perfectly. A two-part epoxy primer has zinc phosphate that improves corrosion-inhibiting properties. As earlier stated, epoxy primers contain binding elements that prevent oxygen from getting in, thus preventing corrosion. They are ideal for waterproof materials and do an excellent job in protecting bare metal from oxidation. Besides, they provide excellent salt spray resistance.

Bonds with a Variety of Materials

Due to its chemical resistance in high-humidity environments, strong adhesion, and excellent mechanical ability, epoxy primer is ideal for various materials. This includes aluminum, steel, galvanized steel, concrete, wood, fiberglass, and asphalt.

Is Epoxy Primer Really Necessary?

Like most people, you might wonder whether it is necessary to use epoxy primer in your car project. The truth is, epoxy primers work just like other primers, but it gives more excellent results. So, why wouldn’t you use it?

It bonds better, doesn’t shrink, fills imperfections better, and seals water. Although you will pay more for the best epoxy primer, the results are worth it. To that end, let’s look at where and when to use epoxy primer on your project.

When to Use Epoxy Primer on Your Car Project?

Unlike in the past when the self-etch primer was a thing, today, epoxy primers have increased in popularity. Epoxy primer is a non-porous and high-bonding sealer that you can use in a variety of materials. This section looks at when and where to use the epoxy primer to get the most out of it.

Over Bare and Clean Metal

Epoxy primers will do an excellent job at sealing up metal surfaces and prevent moisture and corrosion from getting in. It achieves this by sealing oxygen from the metal, ensuring no rust or corrosion forms on the surface. That means you don’t expect rust on your vehicle when you leave it outside after using this primer.

In fact, the two-part primer includes zinc phosphate that helps boost its corrosion-inhibiting properties.

Stacking Coatings

Best epoxy primers adhere mechanically, meaning they will bond with most surfaces with a good texture. As such, it is ideal for stacking, especially when correcting an area that didn’t get perfectly flat and needs more filler.

Scrape the surface with sandpaper and then apply your filler. After that, sand flat, feather the edges and then add epoxy primer over the top until you achieve the desired results.

Mixed surfaces

Many standard primers and coatings will bond with a uniform or a surface with the same material. The case is entirely different for epoxy primers. They have excellent adhesion properties and stick to various materials, including bare metals, paints, body fillers, and primers.

Whether a surface has been sanded down, feathered into the original pain, or repaired with body filler, an epoxy primer will work perfectly. However, ensure to blend these areas properly before you spray epoxy primer to correct any imperfections. Alternatively, consider applying primer surfacer or filler over the epoxy to block flat and fill any imperfections before your paint.

Use Epoxy as a Final Sealer

You can also use epoxy primer as a final sealer before the base coat. In this case, you need to reduce your epoxy to 50% and seal up your work with a coat or two to have an excellent surface to lay your base coat. The primer has stronger adhesion properties than most topcoats and will help keep your paint together, safe from peeling and flaking and give a lasting paint job.

Protect a Long-Term Project

Imagine leaving your paint job for some time only to come to a surface-rusted mess? This happens more often to projects that don’t have climate-controlled shops to protect vehicles during a painting job. Fortunately, you can use an epoxy primer to seal your work till the following working day. This way, you won’t need to spend much of your time mixing up the primer, getting the spray gun, and cleaning everything.

Types of Epoxy Primers

Before we look at how to choose the best epoxy primer, let’s discuss the types of epoxy primers.

One-Part Epoxy Primer

This epoxy primer contains only a sealer. It’s an excellent choice if you are looking for a smooth finish on your topcoats. Besides, it gives a non-porous finish, which is the first base coat on bare steel. As earlier stated, you can also use epoxy primer on phosphate coatings, black iron, plastic, and fiberglass.

It works wonders on metal and is ideal for newly fabricated or fully stripped metal parts. You can also eliminate imperfections and create a flat surface by applying filler over epoxy or primer surfacer before you paint. One-part epoxy primer works as a starter coat for steel and a final sealant before painting.

Two-part Epoxy Primer

A two-part epoxy primer consists of a sealer and zinc phosphate. Ideally, zinc phosphate gives the primer corrosion-inhibiting properties. The two-component primer is a structural steel primer. The two components (sealer and zinc phosphate) cure chemically through cross-linking. The result is a film that is resistant to chemicals, moisture, and abrasion.

Usually, two-part epoxy primers are used in concrete, steel, and industrial applications like water treatment plants, tank exteriors, power plants, and marine equipment.

Choosing the Best Epoxy Primer

Before choosing the best epoxy primer for your project, you should consider many factors, including ease of use, application, and corrosion resistance. After all, with the many epoxy primers on the market, it’s essential to do due diligence to ensure you get excellent results. To that end, here are some factors to consider when choosing the best epoxy primer:

Primer Usage

The first thing to consider when choosing the best epoxy primer is the usage of the primer. After all, every paint won’t work with every primer. Some can only be used as base coats, while other epoxy primers can work as base coats and protective coating on top.

Also, some come in multiple colors depending on the top paint color. While most non-aerosol primers are ideal for both brush/roller and spray application, you will need to reduce some before using them with a spray system.

Ease of Use

You don’t need unnecessary or complex instructions when using an epoxy primer. Depending on why you are using an epoxy primer, you might need to choose a primer that comes with a spray or has its contents mixed.

Corrosion Resistance

The main function of an epoxy primer is to protect against rust and corrosion. As such, it’s a critical component to consider when shopping for the best primer. Ensure your epoxy primer can offer much-needed protection against corrosion, deterioration, and damage. Also, ensure that the primer can block humidity, especially if you live in areas with high humidity levels.

Volatile Organic Compounds (VOCs)

It is not uncommon to find volatile organic compounds in many building materials. Besides being the cause of the new paint smell, VOCs emit harmful gases that can hurt human health. Choose an epoxy primer with a low VOC or none if possible.

Other Supplies You Need

Another crucial factor to consider when selecting the best epoxy primer is the supplies for the job. Depending on your epoxy primer, sandblasting and other manual abrasions will work well. Otherwise, you might need to use a chemical self-etching primer to enhance adhesion. The method you will use will determine the best epoxy primer for your project.

Curing Time

Lastly, you will need to consider the curing time of an epoxy primer. While the epoxy primer usually takes between two and five days to heal properly, the process will take much longer in areas with high humidity levels.

The best way to tell if your epoxy primer is cured is to check whether it has a tacky touch. Heat lamps or electric heaters can help fasten the curing time.

What is the Difference Between Epoxy Primer and Urethane Prime?

By now, you know that epoxy primer is used on a freshly sandblasted or bare metal for rust prevention and maximum adhesion. But what about urethane primer?

Well, you will need to use urethane primer after you’re done with your bodywork as a filler primer. In other words, epoxy is a primer, whereas urethane primer is a prime surfacer.

So, What is a Urethane Primer?

Urethane prime is designed to provide a fast-drying and high-build film. It has excellent adhesion, excellent holdout, and easy sanding properties. It is ideal for properly prepared fiberglass, iron, steel, bare aluminum, and previously painted surfaces.

Epoxy primer ensures that auto paint bonds well in metal and gives a quality paint finish. It is specifically designed to prevent corrosion, meaning it won’t sand like urethane primer.

How to Apply Epoxy Primer

If you are interested in using epoxy primer for corrosion resistance, you might wonder how to apply it to your car. As you’ve seen, epoxy primers will provide quality corrosion resistance, strong adhesion to bare metal, fast build, and exceptional color holdout. In this section, we look at how to apply an epoxy primer to the vehicle.

Surface Preparation

Before you take your paint gun to apply epoxy primer to your vehicle, you must ensure that you blast or strip off all the existing finish and corrosion. You can use wax or grease remover to prepare a metal surface for epoxy primer. This way, you will get rid of all dirt, including road grime. Your metal needs to be slightly abrasive to make the primer coat more adhesive.

You will use the same steps when applying epoxy primer to existing finishes but remember to abrade the surface with grit sandpaper. Also, don’t forget to clean the metal surface using wax and grease remover after abrading it.

Mix one part primer with one part catalyst thoroughly when preparing the epoxy primer. You can use a urethane-grade reducer or an equal solution to reduce any film buildup and improve the flow of the primer mix.

After preparing the primer mix and spray gun, it is time to apply it on the surface.

Applying the Primer

You should apply the epoxy primer in moderate wet coats and allow about 30 minutes between each coat. You can use an epoxy hardener to make your epoxy cure quickly. You’ll get about one-millimeter dry film thickness from one to two coats of this primer, which is relatively enough. Spray each coat evenly across the metal surface.

Topcoat your primer after about 30 if you applied one coat and about an hour if you’ve applied two coats. Suppose you wait for a few days, lightly sand the surface before applying the topcoat after you’ve applied all coats, wet sand the surface after a day or two to three days. As always, remember to wear the proper safety equipment while applying epoxy primer.