What to Use – Rust Converter or Rust Encapsulator?

Not every rust repair allows for stripping back to bare metal and refinishing like new. Think about frame maintenance, trailers, and shop equipment. For these situations, the question that often comes up is whether it’s better to use a chemical rust converter product or simply bury the rust in an encapsulator paint. The decision will typically come down to how rusty the part is and what you plan to with it once you address the rust. But before we get into that, let’s explain what these two different products are and how they work.

Rust Converter

Rust converter is a chemical emulsion that reacts with rusty iron or steel to stop the corrosion process in its place. A phosphoric acid emulsion, it reacts with the iron oxide (rust) to convert it to a more stable polymeric compound. The reaction eventually turns the former rusty metal black, after which it can be painted. In fact, the converted metal will eventually begin to rust again if it is not painted or otherwise sealed, as the coating is not considered permanent.

Rust converter works only on rusty metal, however, and therefore will not react with non-oxidized metal, paint, or other materials. This means it requires a minimum of surface preparation before use. Simply remove any loose material (rusty scale, paint flakes, dirt) with a wire brush and then clean and degrease the area to be treated. Once the rust has fully converted (about 48 hours in total), simply wipe it clean before painting.

Rust Encapsulator

The name is pretty self-explanatory, but to be clear, there is no chemical reaction taking place with this product. Rust encapsulator is a specialized impermeable paint. It simply seals off the oxygen supply that causes rust to continue forming, whether airborne or from direct contact with moisture. The rust that already exists remains in place, but isn’t allowed to spread.

Because it’s a paint and doesn’t create a chemical reaction, it can be applied just about anywhere you would normally apply paint, making it especially versatile for chassis parts and machinery uses. Prep involves removing loose material with a wire brush and preparing the area to be treated just as you would normally would for paint. No heavy sanding is required, and there is no need to get down to bare metal.

When to use each one

Rust converter can be the right solution when you have severely rusted metal, especially deeply pitted rust, that may need to be finished in a specific color. Once the rust has been converted, the metal can be primed and painted like any other metal part. This solution works well for many types of machinery, particularly cast parts that have rough surfaces anyway. It’s a great way to stop heavy oxidation on cart parts before painting them.

The beauty of rust encapsulator is its versatility as a finish paint that requires very little in the way of preparation. It can be applied on top of most other finishes, allowing it to blend with existing paint such as chassis and underhood components. It can also be brushed, rolled, or sprayed on, making it convenient for field repairs and maintenance without any specialized equipment. Available in a variety of colors and textures, including rubberized, it stops rust permanently while providing an attractive finish. Rust encapsulator is a go-to spot repair finish for projects that don’t require a full refinish but where appearance still matters to some extent.