2K primer is a high-quality acrylic urethane primer that adheres exceptionally well to recommended substrates. It is well known for its rust-inhibiting properties and ease of sanding. It is pretty durable.
If applied correctly, 2K primer can last for years. 2K primer is also considered a filler primer. If you need to fill holes, you can apply some and level it by sanding.
There are a lot of benefits associated with 2K primer, but one of the things most people are unsure about is if it can be used on bare metal. If you are considering using 2K primer on bare metal, here is everything you need to know.
Can 2K Primer Be Used on Bare Metal?
2k primer should not be used on bare metal. Epoxy primer is the best type of primer that should be used directly on metal.
2K primer does not adhere firmly to bare metal. Therefore, if you go ahead and use it, there is a good chance it will peel and flake off prematurely.
It can be tempting to use 2K primer on bare metal. However, once it cures, you will notice poor adhesion. If this is a project that you would like to last for years, it’s not worth the risk of using 2K primer, knowing that it will not last.
Nearly all brands of 2K primer will advise against using it on bare metal. I understand that, as a DIY enthusiast, you may have successfully hacked several products in the past. Unfortunately, 2K primer isn’t one of them.
Applying 2K primer on bare metal is a huge gamble. And the odds are against your side. Suppose you have some bare metal that you would like to prime. Start with some epoxy.
Some people prefer self-etch primer. I have no problem with that. However, going directly with 2K primer over bare metal is a considerable risk.
Flaking and peeling isn’t the only thing you should be worried about when using 2K primer on bare metal. Due to the poor adhesion, there is a good chance that rust will develop and spread quickly beneath the primer.
Therefore, you won’t be getting any of the excellent rust-inhibiting properties of 2K primer.
Can I Use 2K Primer on Small Bare Metal Cuts?
If you visit most collision shops, you will notice that they use 2K primer on minor bare metal cuts. Most of the time, they usually get away with it. It’s not the right thing to do. But 2K primer will stick to minor bare metal cuts.
The assumption here is that if the cuts to the bare metal are tiny, the 2K primer will bond to the surroundings, and the tiny cuts will be covered in the process. However, there is always an element of risk because the adhesion in that particular area is weak.
If you have small cuts leading directly to bare metal, the best thing to do is apply some self-etch primer and then proceed to 2K primer. If there are many cuts, it would be better to first spread a thin layer of epoxy.
Will 2K Primer Stick to Bare Metal Without Epoxy?
The recommended method of laying primer on bare metal is epoxy first and then 2K primer after. If you are in a hurry to get the job done or don’t want to buy epoxy primer, you may consider skipping it and going directly to 2K primer. But the question is – will it stick?
Yes, 2K primer will stick to bare metal, but the adhesion will weaken. It may last longer if you add more top coats of paint. But it won’t last as long as it would have if you had applied epoxy primer first.
The bottom line is that 2K primer will stick to bare metal without epoxy. But as mentioned earlier, the project will be a huge gamble.
Using an epoxy primer is very important when dealing with bare metal. Not only will it give you peace of mind knowing that the adhesion is strong. But you will get better protection against rust.
If you live in a rust-prone area or your car spends a lot of time outside, epoxy is a must before you can apply 2K primer.
✔ Professional Build & Fill – This urethane primer lays down thick for serious filling power, ideal for block sanding within 3–4 hours. Perfect for smoothing out patch panels, repairs, and full resprays.
✔ Fast Dry & Easy Sanding – Dries quickly and sands clean without clogging, giving you a smooth, feathered surface ready for topcoat.
✔ Exceptional Holdout – Offers excellent color holdout, helping your paint look richer and more uniform. Works over epoxy, filler, or old finishes.
✔ Mixes 4:1 (Activator Sold Separately) – Requires Eastwood 2K Urethane Activator 50241ZP for proper curing.
✔ Versatile Use – Great for bare metal, filler, or previously painted panels. Whether you're doing spot repair or a full resto, this primer is up for the job.
Will 2K Primer Chip When Used on Bare Metal?
Yes, 2K primer will start to chip prematurely when used on bare metal. The chipping will most likely occur on the edges because of poor adhesion.
This is one of the main drawbacks of using 2K primer on bare metal. It will chip even when you apply top coats. To be safe, you should use epoxy first and then proceed to 2K primer.
Are There 2K Primers That Can Be Used Directly Over Bare Metal?
Yes—and not just in theory. A few 2K primer systems are specifically designed to go straight over bare metal, and Custom Shop’s KEP Series Gray Epoxy Primer/Sealer is one of the most trusted in that category.
This isn’t just some urethane primer claiming to do it all. It’s a true DTM epoxy system that bonds tightly to steel, aluminum, fiberglass, and even body filler. It also doubles as a sealer, which makes it a go-to for both restorers and DIYers trying to lock out moisture and rust before laying down paint.
But don’t get lazy—surface prep still matters. Degrease thoroughly. Scuff the metal. Blow off every bit of dust. That primer’s only as good as the surface you lay it on.
Some folks still insist on spraying urethane primer over bare metal. And sure, some of those newer DTM urethanes are impressive. But if you want something proven, versatile, and ready to play nice with whatever you’re painting next, epoxy’s still the safer move. Custom Shop’s KEP Series makes that call easy.
✔ Direct-to-Metal Performance – Designed for DTM use with excellent adhesion to bare metal, aluminum, fiberglass, gelcoat, body filler, and more.
✔ Anti-Corrosive Protection – Lead- and chromate-free formula fortified with rust-inhibiting additives and superior salt spray resistance.
✔ Dual Purpose – Primer or Sealer – Can be used as a high-build epoxy primer or reduced for sealing under basecoat or single-stage paint systems.
✔ Smooth Application, No Induction Time – Mixes 1:1 with no waiting; sprays smooth with a 4-hour pot life for longer working time.
✔ Works with Major Paint Brands – Compatible with Custom Shop, PPG, House of Kolor, Valspar, and other top automotive finishes.
What are the Recommended Substrates for 2K Primers?
If you buy any 2K primer, you will see a list of recommended substrates. It’s advisable to use 2K primer on a substrate that the manufacturer recommends. Otherwise, it may not bond, and you may run into problems in the future.
Some of the substrates 2K primer is recommended for use include;
• Fiberglass
• Etch primer
• Polyester putty
• OEM primer
• Epoxy primer surfaces
• Existing finishes, provided they are in excellent condition
What are the Best Primers for Bare Metal?
Having ruled out that the 2K primer shouldn’t be used over bare metal, you may be wondering what options I have.
If you were keen when reading the above article, you have noticed our top recommendation, which is epoxy primer. Out of the many types of primers in the market, epoxy is the best option to use on bare metal.
It doesn’t matter which brand you go with, as long as it’s epoxy. It will bond well with metal and promote rust protection. There is only one problem people don’t like about epoxy primer, and that’s the fact that it is non-sandable. But that’s why people apply 2K primer on top of the epoxy.
✔ Durable, Rust-Resistant Finish – Designed to go directly over bare steel, aluminum, body filler, or fiberglass, this 2K epoxy primer lays down a tough, corrosion-blocking base that sets the stage for long-lasting paintwork.
✔ No HVLP Needed – Get professional spray results without a gun. The German-made nozzle delivers a smooth, wide fan pattern, mimicking pro paint equipment.
✔ Built-In 2K Catalyst – Features an internal hardener system for enhanced adhesion and chemical resistance. Activates with a simple button press, offering up to 48 hours of pot life once triggered.
✔ Coverage & Shelf Life – Each 12 oz can covers up to 16 square feet, with an impressive 3-year shelf life unopened.
✔ Trusted by Pros – Backed by Eastwood’s reputation for high-performance restoration tools, with lifetime tech support and a 60-day limited warranty.
The other type of primer that can be used over bare metal is the etch primer. This type of primer etches itself to bare metal. It’s a suitable option if you are in a hurry to get the job done.
✔ Etch & Prime in One Step – Formulated to bond directly to bare, rust-free metal surfaces including steel, aluminum, stainless, and chrome.
✔ Lacquer-Based Convenience – Single-stage primer requires no catalyst, saving time and simplifying application.
✔ Improves Topcoat Performance – Boosts adhesion and durability of most non-epoxy paint systems.
✔ High-Temperature Resistance – Withstands heat up to 170°F, making it ideal for automotive and industrial applications.
✔ Covers Up to 120 Sq Ft – Provides excellent coverage with a smooth, even spray pattern for larger jobs.
Also, it offers some form of rust protection thanks to the presence of Zinc Phosphate. You can confidently use these two types of primers over bare metal and be assured of maximum adhesion and rust protection.
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Rami Hasan is the founder of CherishYourCar.com, where he combines his web publishing experience with a passion for the automotive world. He’s committed to creating clear, practical guides that help drivers take better care of their vehicles and get more out of every mile.