3M Urethane Seam Sealer 08367 — Black 310 mL Cartridge, Flexible Paintable Automotive Sealant

3M Urethane Seam Sealer 08367 is a single-component, black urethane sealant in a 310 mL cartridge formulated to bond to metal and painted surfaces while remaining permanently flexible.

Built for automotive and RV bodywork, this high-solids urethane seam sealer fills gaps, resists shrinking and cracking, and cures to a durable, paintable finish. Unlike solvent-based products, the moisture-curing chemistry of 3M 08367 tolerates heat and humidity, adheres to bare or primed metal, and can be tooled to a featheredge or brushed smooth. Typical handling characteristics include a 10-minute working window, tack-free surface in 30–45 minutes, and full cure in 24 hours, making it a practical option for repair shops and DIY restorers.

How will this seam sealer perform on bare or painted metal?

The 3M urethane formula was developed to adhere strongly to a range of automotive substrates, including bare metal, primed panels, and factory paint. Its single-component composition simplifies application without mixing, and the cured material remains flexible to accommodate panel movement.

• Adheres to bare, primed, and painted metal surfaces
• Single-component — no primers or activators required for typical applications
• Permanent flexibility reduces risk of cracks on vibrating panels

What are the working and cure times for practical workshop use?

3M 08367 offers a short working window and fast surface readiness for paint, which helps speed throughput. Expect approximately ten minutes of toolable work time, a tack-free surface after 30–45 minutes, and full cure within about 24 hours under normal shop conditions.

• Work time: ~10 minutes for tooling and smoothing
• Tack-free and paintable: 30–45 minutes
• Full cure: approximately 24 hours depending on temperature and humidity

Can I use this sealer to fill large gaps and finish it to a smooth surface?

Yes — the product's high solids and thick consistency are intended to fill sizable seams and joints without sagging. It can be smoothed to a feathered edge or brushed for a neat transition, then painted over once the tack-free stage is reached.

• Thick, non-sagging formula fills larger voids
• Toolable to featheredge or finished with a brush
• Non-shrinking and non-cracking after cure

Why choose a moisture-curing urethane over solvent-based seam sealers?

Moisture-curing urethanes like 3M 08367 cure from the surface inward using ambient humidity, which improves performance in hot or humid environments and produces a more flexible joint. Compared with older solvent-based products, urethane sealers resist drying-related shrinkage and maintain elasticity over time.

• Moisture-curing for consistent performance in varied climates
• Greater long-term flexibility than solvent-based alternatives
• Reduced risk of cracking or separation on moving panels

Who this product is for: 3M Urethane Seam Sealer 08367 is aimed at professional collision repair shops, custom vehicle builders, RV technicians, and experienced DIYers who need a durable, paintable seam sealer that bonds to metal and painted surfaces. Choose this cartridge when you require a non-shrinking, moisture-curing urethane that can be tooled to a smooth finish, and when predictable working and cure times help keep projects on schedule.