Back-To-Basics: Weldable Seam Sealer

Sometimes going back-to-basics can make the difference between a quality repair and a failed repair. When researching some OEM body repair manuals (BRM) you may find call outs for the use of weldable seam sealer. What exactly is a weldable seam sealer?

Weldable seam sealers are utilized to provide corrosion protection between panel flanges during squeeze-type resistance spot welding (STRSW) repairs. The use of weldable seam sealers is limited to a few OEMs and does not replace weld bonding with 2-part adhesives.

Per the Subaru 2024 Crosstrek BRM: "Apply a conductive rust preventive sealer to the mating surfaces targeted for spot welding."

Per the Nissan Body Repair Manual Fundamentals - 2015 Edition: "When spot welding panels, spot sealer must be applied to the mating surfaces to prevent rust formation."

Weldable seam sealer products include 1-part urethane or modified silane polymer (MSP) seam sealers. Make sure to review the technical data sheet (TDS) to confirm the product can be used on bare metal and in conjunction with STRSW.

Examples of commercially available products include:

• 3M Urethane Seam Sealer 08360, 08361, and 08364
• 3M MSP Seam Sealer 08368 and 08370
• Lord Fusor Direct-To-Metal Sealer 800DTM, 801DTM, and 803DTM
• SEM 1K Seam Sealer 29362, 29372, 29382, and 29392
• SEM 2-In-1 Seam Sealer 29462, 29472, 29482, and 29492

Lord Fusor provides information on how to identify the material within a pinchweld in their Weld Sealing Standard Operating Procedures document.

3M, Lord Fusor, and SEM all state not to apply any of the above-listed seam sealers over acid-based self-etching primer. All three only recommend the use of their seam sealers in a weld-through application with STRSW.

Always follow OEM repair information and product maker TDS for proper usage of weldable seam sealer. Following OEM corrosion protection guidelines, that may include the use of weldable seam sealer, ensures a complete, safe, and quality repair.

Additional I-CAR Collision Repair News you may find helpful:

• Back-To-Basics: Seam Sealer
• Corrosion Protection Guidelines: Nissan/INFINITI
• Corrosion Protection Guidelines: Subaru
• Welding And MIG Brazing Hotspot

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Related I-CAR Courses

Course Corrosion Protection

Course Seam Sealer