Technician working on a welding seams treatment

Welding Seams Treatment

Identify efficient and sustainable corrosion proof methods to gain lasting customer satisfaction.

Prevent corrosion and paint lifting issues caused by untreated welding seams.

No matter how professional the welding job is done, any welding seam will have micro pinholes, allowing back side moisture penetration. Any hygroscopic filler such as standard polyester will not seal the surface, but allow this moisture to pass - into the paint film. Long term, this leads to corrosion and paint lifting.

The Epoxy Metal Filler replaces the traditional tin soldering process in terms of modern low temperature welding deformations and deep dent repairs on high strength steel, galvanised steel and aluminum substrates.

  • Technician using maching to fix welding seam
    • Properties:

      • Not hygroscopic like (metal based) styrene fillers due to special developped epoxy resin formulation
      • Sandable after 20 minutes (accelerated drying) or 4 hours (air dry)
      • For steel, zinc and aluminium surfaces


      • Cost reduction - time saving efficient process
      • Reduced risk of longterm corrosion and delamination thanks to special formulation
      • Required amount of material directly applied onto repair area

      Click the play button in the image to watch the video

      Download Welding Seams Treatment Process Brochure (PDF, 478KB)

      Contact a 3M expert

Products to treat welding seams

Discover our range of welding seams treatment products to help achieve high quality, efficient repairs in your bodyshop.

How to treat car panel welding seams

Step-by-step process guide to treating weldings seams

  • Sanding a welding seam between car panels

    Step 1 - Sanding down the job area

  • Cleaning the welding surface

    Step 2 - Cleaning of the surface

  • Calibrating a new filler cartridge

    Calibration of a new cartridge

      • Insert the cartridge into a suitable application gun
      • Before attaching the mixer to the cartridge, squeeze out a small amount of material until both components are equally extruded
      • Attach the mixing nozzle and discard the first 2-4 cm of extruded material, as this might not be fully mixed

      Note: This step is only necessary when using a new cartridge. When reusing a previously used cartridge, this is not necessary.

      Recommended products:

      3M™ FC Epoxy Metal Filler

      3M™ Static Mixing Nozzle

      3M™ High Power Manual Gun 

  • Applying the filler to the welding seam

    Step 3 - Application

      • First apply a “tight” coat of material onto the welded area, in order to to ensure that the material completely covers any pinholes from the previous welding steps. Additional layers of the product can be applied immediately onto the initial later in a "wet on wet" process, in order to build up the repair to the required level
      • Unused material in the nozzle will typically cure after around 15-20 minutes at 22C
      • Recomended settings for applicators: pneumatic max. inlet pressure 5.5 bar / battery driven 3kN, max speed 180mm/min

      Recommended products:

      3M™ Plastic Spreader

  • Drying the filler material

    Step 4 - Drying

      • The curing of 3M™ FC Epoxy Metal Filler can be accelerated using IR drying after the initial gelling period. Wait 10 minutes before using an IR dryer to heat for 10-20 minutes with a panel temperature of 70 °C
      • Airdying: sandable ~ 4 h @ 22 °C ambient temperatures

      Tip for use: warming up the material & surface to ~30°C before material application will help to accelerate curing, particularly at cold ambient temperatures.

  • Pre-sanding process

    Step 5 - Pre sanding of the filler area

      • Pre sanding step can also be done by using traditional body files
  • Sanding the area

    Step 6 - Sanding of the filler area

  • Cleaning the finished welding seam area

    Step 7 - Cleaning of the surface

  • Application of welding seams filler

    Optional - Second layer application

      • Apply a further layer of 3M™ FC Epoxy Metal Filler if nessessary and repeat drying and sanding steps as recomended in the previous steps
      • Maximum finished thickness should not exceed 4-6 mm, maximum layer thickness should not exceed 2-3 mm
      • Follow OEM and paint company recommendations for subsequent steps

      Recommended products:

      3M™ FC Epoxy Metal Filler

      3M™ Static Mixing Nozzle

      3M™ High Power Manual Gun 

Technical tips for cutting off damaged car panels

Here are some valuable insights into specific challenges surrounding cutting off damaged panels, including quick tips on preventing common issues such as....

  • Customer Challenge:
    Previous tin products (sticks) contain high amounts of lead and tin, today the application is no longer allowed due to environmental and health protection reasons enact to the Directives from the European Union guideline II 200/53/EG.

    Technical Tip:
    Use a Lead-free alternative product instead of the process with open flame and hot soldering with tin. 3M recommends using 3M™ FC Epoxy Metal Filler as an easy to use product combined with best corrosion protection properties. 3M also offers the 3M™ High Power Manual Gun for an easy extrusion of filler from the cartridge and a smooth application.

  • Customer Challenge:
    Polyester based materials does not meet industry performance criteria & technical expectations for the longer term quatlity guarantee for vehicle repairs.

    Technical Tip:
    Spot welds and/or beads are not 100% leak-proof / tight . Moisture and salt penetrates from the back side of the repair area, through the welds, causing corrosion & paint lifting issues. Polyester based fillers have hygroscopic properties, which means they absorb water. Hence OEM´s and the manufacturing industry recommend to use the 3M™ FC Epoxy Metal Filler, because its formulation has been specifically developed to support corrosion protection and inhibit water penetration.

  • Customer Challenge:
    Welding seam will have micro pinholes, which needs to be well covered to avoid back side moisture penetration.

    Technical Tip:
    First apply a “tight” coat of 3M™ FC Epoxy Metal Filler onto the welded area, in order to ensure that the material completely covers any pinholes. Additional layers of the product can be applied immediately onto the first layer in a "wet on wet" process, in order to build up the repair to the required level.

Purple banner with computer and electronic devices icon

Watch Webinars Anytime Anywhere

Join the 3M Collision Repair Webinar Hub and hear first hand from our experts:

  • New industry standards, new products and technologies
  • Updated car repair standard operating procedures
  • New design solutions for the collision repair industry

Discover more from 3M

  • Haven't found what you're looking for? Or perhaps you would like to arrange a demonstration? Click here to get in touch!

  • Remember to always select appropriate Personal Protective Equipment - Eyewear, gloves, hearing and respiratory protection for your job and workplace!

  • We don't just have solutions for treating welding seams. See our extensive range of solutions for all your car repair needs!

Ask a Collision Repair Expert

Thank you for your request to 3M. The information you provide on this form will be used to respond to your request through email or telephone by a 3M representative or by one of our authorised business partners with whom we might share your personal information consistent with the 3M privacy policy.