How To Prepare Metal Before Body Work To Prevent Future Rust

How To Prepare Metal Before Body Work To Prevent Future Rust

A customer contacted us asking how to avoid future rust when performing auto body work. They were planning to weld in patch panels and apply body filler and wanted to be sure rust wouldn’t start at the site under where the body work was performed. They had a previous experience where rust bubbles appeared under the paint shortly after body work was performed and they didn’t want it to happen again. By taking the proper steps to prepare and seal or prime the metal before body work, future rust can be prevented.

How Does Rust Form in New Body Work?

Rust forms when exposed metal, oxygen, and moisture combine. So, even if body work has been recently performed, if there is any bare metal exposed to moisture, it will soon begin to rust. This doesn’t just apply to metal that’s visible, but in recessed areas where one might think moisture would never reach. Like overlapping joints where capillary action can draw moisture in between the panels. Gaps, nooks, and crevasses need to be thoroughly sealed away from moisture and oxygen.

Properly Prepare Metal Before Body Work

KBS Klean and RustBlast and can be used to thoroughly prepare metal before body work. If patch panels, or new body panels are being put in place, both the existing body panel and the panel to be added need to be prepared.

KBS Klean - Powerful Concentrate Water Based Cleaner

The first step to prepare metal before body work is to use KBS Klean, which is a strong, concentrated cleaner that removes dirt, dust, grime, grease, and other contaminants. KBS Klean is mixed with warm or hot water and used in unison with a bristle brush or scoring pad to clean the metal.

Detailed instructions for use of KBS Klean can be found HERE.

KBS Klean - Powerful Concentrate Water Based Cleaner and Degreaser


The next step to prepare metal before body work is to use RustBlast to dissolve surface rust, etch the metal for adhesion of coatings, and deposit a zinc phosphate to aid in the adhesion of the coating or primer.

Detailed instructions for use of RustBlast can be found HERE.

RustBlast - Powerful Metal Acid Etch - Rust Remover - Pre-Paint Primer

Welding Metal Treated with RustBlast

RustBlast leaves a coating of zinc phosphate. If the body panel is being welded, the coating can be left on the surface for the welding process.

Properly Seal Metal with RustSeal and Cavity Coater

After preparing the metal before body work has been completed, RustSeal, and KBS Cavity Coater are used to seal and protect the surface under the body work from moisture and oxygen.


RustSeal is applied after use of KBS Klean and RustBlast to permanently seal and protect metal. RustSeal is a high-performance, moisture cured, rust preventive paint. RustSeal is a single part (1K) formula that’s ready to use: Just stir and go. RustSeal is impervious to road salts and almost every chemical. RustSeal flows out to a beautiful, rock-hard, tough ceramic-like finish that is tough to chip or scratch and will not crack or peel. RustSeal can be brushed, rolled, or applied with spray equipment

Body Filler Primer

RustSeal Use with Patch Panels

After patch panels have been welded into place, the body work site is again treated with KBS Klean and RustBlast before the application of RustSeal. RustSeal is then applied in a minimum of two thin covering coats, allowing the first or consecutive coat to dry-to-touch and not leave a fingerprint before the next coat of RustSeal is applied which is typically within 2-6 hours depending on temperature and humidity. It is very important to thoroughly coat the repair on both the front and backside to completely seal the metal.

Detailed instructions for use of RustSeal can be found HERE.

Cavity Coater - Cavity Wax and Corrosion Inhibiting Coating

Patch panel before coating with RustSeal

RustSeal Use with Body Filler

When body filler is going to be applied, first prep and coat the area with RustSeal as previously described and allow RustSeal to cure for at least 24 hours. RustSeal then needs to be prepared before the application of body filler. This can be done in one of two ways.

Scuffing Method

  • Scuff the RustSeal with 320 grit sandpaper to provide grip for the body filler. Blow off the dust with clean compressed air.

Self-Etching Primer Method

  • To promote adhesion between the RustSeal and the body filler, KBS Fusion SEP self-etching primer is used.
  • A dusting coat of Fusion SEP is all it takes, and the aerosol version of Fusion SEP works great and conveniently.

Topcoating RustSeal

RustSeal is not intended for use as a final finish when used where the coated surface will be consistently exposed to sunlight. Repeated or prolonged exposure to direct UV light will cause cosmetic alteration to its color and sheen. RustSeal’s guaranteed rust protective properties, however, will not degrade.

There are three ways to topcoat RustSeal with solid color top coat paints or primers so that the coatings bond and fuse together.

  1. Apply the top coat or primer once the second or final coat of RustSeal is dry-to-the-touch (beyond tacky) and does not leave a fingerprint (usually 3-6 hours depending on temperature and humidity).
  2. Let the final coat of RustSeal fully cure (at least 24 hours), scuff the RustSeal with 320 grit sandpaper, then apply your top coat or primer.
  3. Let the second or final coat of RustSeal fully cure (at least 24 hours), dust the RustSeal with Fusion SEPr, let it cure for 30 minutes, then apply the top coat.

Cavity Coater

Cavity Coater is the perfect solution for sealing body work in hard-to-reach areas. Cavity Coater is incredible effective on the back sides of tge surfaces that were sealed with RustSeal on the front side. Cavity Coater is a single step, super-penetrating corrosion inhibiting coating (CIC) designed for long term protection of all metal surfaces. Cavity Coater provides a self-healing film that blocks moisture from reaching areas that can’t be accessed for coating with RustSeal. Cavity Coater wicks into welds and seams and resists road salt, alkaline solutions, and chemicals. For especially hard to-reach-areas the Cavity Wand extends the reach of aerosol Cavity Coater with a reusable 48” hose that features a 360-degree spray tip. The Cavity Wand requires only a 1/8” hole to insert and is easily cleaned.

Cavity Coater - Cavity Wax and Corrosion Inhibiting Coating


Auto body work is a labor-intensive undertaking. By taking the proper steps to prepare the metal and seal the metal before the body work, you can prevent pop off and repairs can last for the life of your vehicle. If you have any questions about using KBS Coatings to protect body work please let us know - Contact KBS Coatings.