3M
3M 8308 Black Heavy‑Bodied Seam Sealer 7 oz Cartridge – 6 min Work, 1 hr Cure
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Hazardous material · Paste
This hazardous material ships ground-only. A handling surcharge may be added at checkout.
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Ground freight only (UPS/FedEx). Cannot ship via Air, USPS, or to PO boxes. APO/FPO addresses excluded.
WARNING: Cancer & Reproductive Harm
This product can expose you to chemicals known to the State of California to cause cancer and reproductive harm.Tap for details → P65Warnings.ca.gov
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Overview
Built for the job.
3M™ Heavy-Bodied Seam Sealer is a two-part epoxy seam sealer for all general purpose automotive sealing. It cures quickly to a tough, strong bead for lasting seam sealing protection and is used on door skins, floor pans, trunk floors, roof seams, and many other applications. Our self-mixing system ensures a proper mix…
3M 08308 Heavy Bodied Sealer is a high‑build, paste‑type sealer designed for filling deep imperfections and preparing metal substrates for coating. It is supplied in a 7 fl‑oz cartridge and is formulated for use on aluminum, bare metal, e‑coat, OEM finishes, primers, and steel.
The product offers a 6‑minute work time and a rapid 1‑hour cure, allowing up to 10–13 coats per cartridge for efficient coverage of large repair areas. Its heavy‑bodied consistency provides excellent flash time and fill capability while maintaining compatibility with a wide range of substrates commonly encountered in collision repair.
Due to its hazardous classification (acute toxicity, aspiration hazard, carcinogen, eye damage, organ toxicity, oxidizer, reproductive and respiratory toxicity, skin corrosion), appropriate PPE—including eye protection, chemical‑resistant gloves, protective clothing, and a respirator—must be worn. Apply in a well‑ventilated area and follow the SDS first‑aid procedures for inhalation, skin, eye, and ingestion exposures.
Why Pros Choose 3M Heavy Bodied
- High-performance two-part epoxy seals vertical and horizontal seams to match OEM seals
- Metered mixing with dual syringe cartridge eliminates the difficulty and mess of manual mixing
- Non-flowing, heavy-bodied formula allows easy tooling for matching OEM seam sealer appearances
- Quick cure time and non-sag property aids during vertical applications
- Heavy-bodied, non-sagging, non-flowing, and easy tooling formulation for matching OEM seam sealer appearances
Application Guide
- Clean the substrate (aluminum, steel, bare metal, e‑coat, OEM, or primed surface) to remove dust, oil, and loose material. Ensure the surface is dry.
- Dispense the paste from the 7 fl‑oz cartridge. No mixing ratio is required; the product is ready‑to‑use.
- Apply the sealer with a brush, roller, or spray gun. Work within the 6‑minute work time before the material begins to set.
- Build 10–13 coats as required for the repair, allowing each coat to flash for the remainder of the 6‑minute work window before applying the next.
- After the final coat, allow the sealer to cure for 1 hour before sanding, priming, or applying topcoat.
Compatibility
Compatible paint systems: Epoxy.
Specifications
| Part No. | 8308 |
|---|---|
| Product Line | MMA |
| MFR Model | 8308 |
| Standard/Approvals | OSHA 29 CFR 1910.1200 |
| Manufacturer | 3M Products |
| Alternate Part Number-1 | 60980034908 |
| UPC | 051131168084 |
| Brand | 3M™ |
| Maximum Sale Quantity | 18 |
| Maximum Sale Day | 7 |
| Composition | 40 to 80% Epoxy Resin, 10 to 30% Epoxy Resin, 3 to 7% Dimethyl Siloxane, Reaction Product with Silica, 0.5 to 1.5% Carbon Black |
| Application Time | 6 min |
| Specific Gravity | 1.16 |
| Odor/Scent | Epoxy |
| Color | Black |
| Flash Point | 239 deg F |
| Container Size (oz) | 7 |
| Container Type | Cartridge |
| Form | Paste |
| Temperature Rating (deg F) | -20 to 180 |
| Type | Heavy Bodied |
| Curing Time | 1 hr |
- Cure Time
- 1 hr
- Work Time
- 6 min
- Compatible Substrates
- Aluminum, bare metal, e‑coat, OEM primer, steel
- Number of Coats
- 10–13
About 3M
3M is a global leader in abrasives, masking, and body repair products. Trusted by OEM collision centers for high-performance prep and finishing solutions.
Frequently Asked Questions
What substrates can I apply 3M 08308 Heavy Bodied Sealer to?
The sealer is compatible with aluminum, bare metal, e‑coat, OEM primer, and steel surfaces.
How long is the working (flash) time and when is it fully cured?
The product provides a work (flash) time of 6 minutes. Full cure is achieved in approximately 1 hour at the recommended application temperature.
What personal protective equipment is required when using this sealer?
Use eye protection, chemical‑resistant gloves, protective clothing, and a respirator as specified in the SDS.
Can I sand and paint over the cured sealer?
Yes. After the 1‑hour cure, the sealer can be sanded and subsequently painted. Apply 10–13 coats to achieve the recommended film thickness before finishing.
Documents & Safety
- Safety Data Sheet (SDS)
- 3m_08307_catalog.pdf
- 3m_08308_specification_sheet.pdf
- 3M_05113108307_Catalog.pdf
DANGER: This sealer contains hazardous chemicals that may cause serious health effects including cancer, reproductive harm, and organ damage. Can cause severe eye and skin irritation. Required PPE: safety glasses, chemical-resistant gloves, protective clothing, and respiratory protection in poorly ventilated areas. Avoid skin and eye contact. Use only with adequate ventilation. Keep away from heat and ignition sources. Always refer to the full SDS before use.
Why Buy from autofxmart
- Authorized distributor — authentic, factory-fresh stock.
- Fast US shipping — most orders ship within 1 business day.
- 30-day returns — buy with confidence.
- Pro-shop pricing — bulk discounts available on request.
- Expert support — questions? Email us at support@autofxmart.com.
How to apply
Steps
1Clean both surfaces to bare, dry substrate.
2Load the cartridge and fit the mixing nozzle.
3Apply an even bead (or clamp) where needed.
4Tool or smooth the joint before it skins over.
5Allow to cure fully before stressing or painting.
Specifications
Full data
Frequently asked
Good to know
The curing time for 3M Products MMA is 1 hr. Drying and curing times may vary with temperature, humidity, and film thickness — always consult the Technical Data Sheet (TDS) for exact cycle conditions.
This listing ships 3M Products MMA in a 7 container. Check the autofxmart catalog for other sizes and bulk pricing.
Most in-stock orders for 3M Products MMA ship the same or next business day from our US warehouse. Expedited options are available at checkout. Freight-class items may require an additional 1–2 days for carrier pickup.
Yes. autofxmart is an authorized distributor of 3M Products. Every unit is factory-fresh, sealed, and backed by the manufacturer's standard warranty. If you have a concern, contact support@autofxmart.com and we will make it right.
The MPN for 3M Products MMA is 8308. Use this number when cross-referencing against TDS, SDS, or legacy supplier catalogs.
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