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Truck bed with rust and body filler
Auto Body Rust Repair & Prevention Technical

Can You Use Body Filler on Top of Rust Encapsulator?

A reader recently asked a great question about rust repair in response to our recent article on body fillers. In fact, it’s a common one that often pops up when discussing body fillers. This reader asked whether he can use body filler after he’s treated rusty pickup truck cab corners with Eastwood Rust Encapsulator.

The short answer to his question is yes, though it’s not generally our preferred method. We typically recommend eliminating all rust and then treating the bare metal with epoxy primer before filling. However, certain circumstances can prevent the ideal from becoming the reality. These might include:

  • Non-Structural Areas – If the rust is on non-structural areas where complete metal replacement isn’t critical to the vehicle’s safety or performance, using Rust Encapsulator and body filler might be acceptable.
  • Minor Surface Rust – When the rust is minor and limited to surface corrosion without deep pitting or structural damage, applying Rust Encapsulator can effectively seal and stop the rust from spreading. In this case, applying body filler on top of the encapsulator is acceptable as long as the surface is well-prepared.
  • Budget or Time Constraints – In situations where time or budget is limited, and the rust is not severe, using Rust Encapsulator followed by body filler can be a practical solution. This approach is common in situations where a temporary or quick repair is needed.
  • Prepping for Temporary Repairs – If the goal is to prepare a vehicle for temporary use or sale, and the rust is not in a critical area, using this method can provide an aesthetically pleasing finish without the extensive work required for metal replacement.

Body filler on car fender

How To Properly Apply Filler After Rust Encapsulator Treatment

  1. Remove all loose, flaky rust first using a wire brush, sandpaper, or grinder.
  2. Clean the entire repair area with a degreasing prep solvent, such as Eastwood Pre Paint Prep.
  3. Apply either Rust Encapsutaor or Rust Encapsulator Plus to the entire repair surface and allow to fully cure.
  4. Apply polyester- or epoxy-based body filler over the area to be filled.
  5. To reduce the chance of air bubbles that might lead to future rust from moisture intrusion, use a short-strand fiberglass-reinforced polyester filler. The glass strands help evacuate any air bubble that may have formed. The short-strand variety will also be easier to sand than the long-strand type.

For restoration-quality finishes or for structurally-critical repairs, we still recommend the right way. This involves cutting or grinding out the rusted area and welding in new metal when necessary before priming and filling. However, if time and budget are bigger priority than perfection, at least you can still stop the rust in place.

4 Comments

  1. The comment “If the goal is to prepare a vehicle for temporary use or sale ” is disturbing to see here. Having someone hide rust with filler for resale is an all too common but unsavory practice.

  2. Darwin, I would recommend you call our technical assistance line at 1-800-343-9353. They can ask you some more specific questions and give you direct answers as you speak with them. I suspect there’s no need to use body filler if the rust hasn’t really attacked the sheet metal too badly. I’m sure your grandson will be thrilled to get your old truck regardless of condition. Thanks for reaching out and good luck.

  3. I have surface rust on the roof of my 2003 Silverado. Just a couple sq feet. The rust isn’t invading the sheet metal. After sanding off the paint I can slightly feel the rust areas. I’m 70 yrs old and I’m giving this truck to my 16 yr old grandson. I’m just trying to make it look presentable for him. I’m debating to applying body filler over the rust or maybe just painting over the rust. Since it’s the roof most people can’t the top of the truck. Should I continue to sand, which I’m afraid of warping the metal, use body filler then paint or just paint the roof?

  4. Located in New England this is a topic that I deal with several times a year. While we can’t all drive a collector car/hot rod oven a daily basis , I do drive my truck and it shows. My 2013 Silverado is my daily driver and while it gets used as a truck ( dump runs, firewood, compost and towing) I still like it to look presentable. I under coat it yearly but it still has the usual spots. for several years I treated the wheel house and box with encapsulater, last year I replaced the sheet metal as there was nothing left. The rocker panels started showing signs and I applied the same “stuff”. I have several holes and rust is migrating toward the cab corners. I guess my finding is that rust never sleeps. Being a old mopar guy, I’m used to rust. Things are much better , but rust never sleeps.