Rust converter will stop rust, though the finish quality is rough.

Rust Converter versus Removing Rust and Sealing Metal — Which Protects Metal Longest?

Most everyone knows that once metal starts to rust, it will continue to rust until the metal is completely eaten away. So it's important to stop rust as soon as it's discovered. Here we'll discuss two methods used to stop rust. The first is using rust converter to convert the rust into an inert primed layer that can stand alone or be painted over. The second is to completely remove the rust from the metal, then apply a rust preventive paint or coating to protect it. Both techniques stop rust and seal the metal from moisture and oxygen to keep it from rusting again. However, results vary in how long the metal stays rust-free and in the quality and appearance of the finish.

Method — Using Rust Converter

Rust converter, also known as rust reformer, is a chemical solution or primer applied directly to a metal surface to convert iron oxide (rust) into a protective chemical barrier that resists moisture and further corrosion. Rust converter is made from phosphoric acid, tannic acid, or a blend of both. Phosphoric acid rust converter turns iron oxide into a ferric phosphate inert layer, and it can be used on metal parts exposed to exterior weather conditions if topcoated with a quality paint or coating. Tannic acid produces a protective bluish-black ferric tannate inert primer layer, which can stand alone against exterior weather conditions or be painted over for better appearance — it acts as an excellent primer for both oil and epoxy-based paints. Rust converter works on any rusty iron or steel object, but it will not work on aluminum, copper, stainless steel, or galvanized metal.

Benefits of Using Rust Converter

With rust converter, it's necessary to first remove any loose or flaking rust with a stiff bristle brush, wire wheel, or sandpaper, to provide a stable surface. It's important not to remove all the rust, since that would defeat the purpose of rust converter, which chemically bonds to rust and seals it in. Applying rust converter is a simple, quick procedure compared to eliminating rust and sealing the metal with a rust preventive coating — especially advantageous when project time is limited or the object is large and thorough rust removal would be highly labor-intensive.

Drawbacks of Using Rust Converter

When done properly, eliminating rust and sealing the metal with a rust preventive paint or coating provides a longer-lasting solution than rust converter. While time and labor are reduced up front with rust converter, the procedure has to be repeated before too long. In some cases, a good rust elimination and metal seal job protects against future rust four to five times longer than rust converter.

Finish quality can also be compromised when using rust converter. Eliminating rust typically provides a smoother surface for rust preventive paints and coatings, allowing for a smoother, better-looking final finish. Rust converter is also designed to bond to rust, so it won't work on non-rusty surfaces or surfaces with a mix of rusty and non-rusty areas.

KBS Rust Converter

KBS Coatings offers Rust Converter that easily converts a rusty surface into a black, inert primed surface ready for paint and compatible with most topcoats. It's offered in aerosol form for easy application and dries fast.

Method — Remove Rust and Seal the Metal with a Paint or Coating

Rust removed, and metal sealed with a coating.

For stopping rust, the best and longest-lasting result comes from eliminating rust, using a primer to seal the metal from moisture and oxygen, then applying a topcoat of paint or other coating. It's important that the rust is thoroughly removed and that a strong-bonding, durable paint or coating is applied.

Rust Removal

Rust can be removed with chemicals, solvents, and abrasives. As with rust converter, the first step is to remove loose flaking rust with a stiff bristled brush or sandpaper. Below are common rust removal methods.

Abrasives are a mechanical form of rust removal — sanding by hand or with power tools like an angle grinder, sander, or a drill fitted with a surface finishing disc, cup brush, or wire wheel. Sandblasting is also a popular, easy way to remove rust, and it gives the metal a surface texture that helps paint bond firmly.

Painting/Coating

After rust is removed, the metal needs to be sealed to prevent it from rusting again. A primer is applied and usually topcoated with a paint or coating. Some paints include a primer in their formulation.

Primer — While a metal paint primer isn't always required, it's always recommended, especially if the metal will contact moisture. Depending on the topcoat, the metal may or may not require primer to seal it first. The most popular primer types are self-etching primer and epoxy primer.

Self-etching primer provides a strong bond to the surface and seals metal from air and moisture. It uses an acid to micro-etch the metal for a slightly rough "anchor pattern" surface profile (similar to sandblasting) that gives the primer increased grip and provides a strong base for the topcoat. Some self-etching primers deposit a layer of zinc phosphate for increased adhesion, and they cure quickly, which helps reduce project time.

Epoxy primer provides excellent adhesion when priming metal, but because it doesn't etch the metal like self-etching primer, the proper surface profile must be created manually by sanding with 80 to 180-grit sandpaper or by sandblasting. Epoxy primers also take longer to cure than self-etching primer.

Paint or Coating — When topcoating a primer, the topcoat must be compatible with the primer. No paint will bond to unprepared epoxy paint — epoxy-painted surfaces must be abraded before they'll accept new paint. Sanding old epoxy with 120 to 220-grit sandpaper promotes adhesion; once abraded, any type of paint will bond to it.

Benefits of Removing Rust and Sealing the Metal

As long as the job is done effectively, the best and longest-lasting result for stopping rust comes from eliminating the rust and sealing the metal from moisture and oxygen. Finish quality is also better than with rust converter.

Drawbacks of Removing Rust and Sealing the Metal

The main drawback of removing rust and sealing the metal is that the procedure is more labor-intensive than using rust converter, and material costs are usually higher. In this case, though, you get what you pay for.

KBS Coatings 3-Step System

KBS Coatings offers the user-friendly 3-Step System to stop rust. It performs all the functions necessary to properly remove rust and seal the metal for the best long-term protection.

More information on the KBS 3-Step System is available in the System Sampler Kit.

So, What's Best for Stopping Rust?

Ultimately, it comes down to your goals for protection longevity and visual appeal. KBS Rust Converter does a good job of stopping rust and is a relatively quick process compared to eliminating rust and sealing the metal with a paint or coating. However, it won't protect metal as long, and the finish quality won't be as smooth and attractive.

Frequently Asked Questions