Buyers Guide: When to Use Rust Encapsulator VS. Rust Converter

Posted: September 19, 2015 By: MattM

Our tech team answers a lot of technical calls and emails each day, and there are a lot of common questions asked and advice given. Many of them are about when and where to use our different coatings and paints. Rust products might be the most confusing as far as when to use them and which one is correct for your rust situation.

We offer both rust encapsulator and rust converter for DIY automotive restorations. The question isn’t “do rust converters and encapsulators work?” Both are very effective at preventing rust through the task they are designed for. But they are two different products with different uses depending on the rust that is present. I decided to put together this quick Buyer’s Guide to help you decide when you should use rust encapsulator vs. rust converter.


Rust Encapsulator

Rust encapsulator is one of the oldest and most well-known products we sell. We’ve been an innovator in rust treatments, and this “paint over rust” product has stood the test of time. It seals rust in and stops it from spreading while acting as either a primer or base coat. Encapsulator is probably the safest and most universal of our rust products as it doesn’t much matter what it is applied over – it can even be applied to partially rusted surfaces. Below are some examples of situations where rust encapsulator is ideal and where another product may be better.

Best Rust Encapsulator Uses

1. Surface Rust – Encapsulator will easily go over areas of surface rust and stop the rust from spreading. One medium coat usually covers light surface rust.

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2. Medium rust This is rust that is more than just surface or flash rust. It may have started to lightly pit the metal but hasn’t started to affect the rigidity of the metal. Start by wire wheeling or mechanically removing any loose rust and apply 2-3 medium coats to get complete penetration into the rust.

3. Bare metal Rust encapsulator can be used over bare metal, but I wouldn’t suggest it over an epoxy or etch primer if you ONLY have bare metal to deal with. It can be used to quickly seal bare metal in a pinch to avoid flash rusting as well.

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4. Mixed surfaces Rust Encapsulator is the best rust product to apply over surfaces that might vary in grades of rust, have bare metal or old paint present. If you have an area that you cleaned to bare metal or repaired and there’s still rust around that area, I’d suggest Rust Encapsulator.

Poor Uses for Rust Encapsulator

While rust encapsulator can be applied to almost any surface, it isn’t always the best option. Below are instances where we’d suggest a different product for the best results.

1. Over rubberized undercoatings or heavy duty anti-rust Undercoating and Anti-Rust are great products for undercarriage, or hidden areas on a vehicle but using Rust Encapsulator over them is unnecessary and isn’t using the product to its full potential. I absolutely prefer to use it as a base under rubberized undercoating for peace of mind.

2. In hidden, boxed or hard-to-reach areas Rust encapsulator needs some basic prep before application (wire brush loose rust and degrease with PRE™). It also needs complete coverage to properly stop the rust and it can be tough to get it to cover properly on an area that hasn’t been prepared completely. For hidden, boxed and hard-to-reach areas, we suggest our Internal Frame Coating.

Rust Converter

Rust converter is a coating that will convert heavy rusted areas into a protective polymeric coating with little prep. This product works well when used as directed. However, unlike encapsulator, it doesn’t have room for error when it comes to using it on the incorrect surfaces. Rust converter needs 100 percent rust present in order for it to work correctly and to fully cure. The surface also needs to be top coated after it is cured. For the best protection, we suggest applying rust encapsulator over the converter and then applying the top coat.

When Does Rust Converter Work?

1. Medium rust Areas that are completely covered in substantial rust are okay to use rust converter on as long as it isn’t mixed with bare metal or other coatings around it.


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2. Heavy, flaky rust Rust converter works best on rust that is HEAVY. This would be scaly rust that has begun pitting the surface and has covered all of the metal. We still suggest knocking off the loose, flaking rust using a wire brush or wheel before applying the product. The goal is for the entire surface that is rusted to turn a purplish-black once the converter has finished curing. It may take 2-4 coats to fully convert a surface.

Poor Uses for Rust Converter

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1. Bare Metal – Do rust converters work on bare metal? That’s a big, fat no. This product needs 100 percent rust present for it to work. In fact virgin, clean metal could actually flash rust if rust converter is applied and left on it.

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2. Mixed surfaces Again, rust converter needs 100 percent rust present in order for it to fully cure. This means it won’t work completely on areas that are a mix of rust and bare metal, or a mix of original paint and rust. If you’re trying to treat small rust spots that have paint surrounding them (that we assume you don’t want to damage) you can use Fast Etch to saturate the area and get into those small rust spots. Then touch up with paint as needed.

3. Painted or coated surfaces This product won’t work on bare metal areas to protect or prevent them from rusting. If applied to areas that are painted or used to coat for prevention, the rust converter won’t fully cure, and the surface will stay sticky.

If you follow these quick guidelines, you can quickly determine if you need rust encapsulator or rust converter. Feel free to drop us a comment if you’d like to see a Buyer’s Guide for any other product.


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106 thoughts on Buyers Guide: When to Use Rust Encapsulator VS. Rust Converter

  • Applying Rust converter, then rust encapsulator , an then applying Lizardskin ceramic insulation, is there any chemical reaction ?

  • No Chemical reaction issues, but remember that rust converter can ONLY be used on areas that are 100% rusty. That product NEEDS rust present to cure. Otherwise it will never cure. If the surface is a mix of pre-existing paint and or bare metal with rust you would start with Rust Encapsulator first. Hope that helps!

  • Thanks for a good review- I have trouble keeping this straight. If you put bare metal with applied rust converter in the sunlight for a couple weeks, it seems to eventually cure. It may be that it flash rusts underneath as you hinted at above. Definitely not the best approach!

    So, where I have trouble is what to use as a topcoat over these coatings-

    is a primer needed? Can an epoxy primer be used?
    Maybe a dirty word, but what about POR15?
    Urethane based paints/ clears?

    How sandable is the rust converter? am I better off not sanding and then using a high build primer to recover the pit free surface?

    and on a loosely related note, is a primer necessary for engine enamels? what about removal of existing paint with good adherence?

    thanks for your help!

  • Hi Ken, you can apply an epoxy primer over the rust encapsulator and then do your body work from there. Epoxy primer will seal up the surface the best after the rust encapuslator has cured. Primer isn’t necessary for engine enamel. For best results removing all existing paint is best, but if the paint is sold you could sand it to give it a rough surface for the new paint to adhere to.

  • Hi, Im looking to protect the underbody of my 1965 mustang. Im looking at having it media blasted. I want to make do what I can t make sure I dont have to worry about rust again. Would you suggest the Rubberized rust encapsulator to coat the bottom after media blasting?

  • Our rubberized rust encapsulator is a great 1-step product to use. Another option is to apply epoxy primer on the bare metal to seal it up and then add rubberized encapsulator for extra protection on the top. Hope that helps!

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