Name: Tec-Bond® 251
Brand: Tectorius

Tec-Bond® 251 is a high-temperature resistant, microencapsulated pre-applied thread adhesive designed for fastener applications where elevated operating temperatures are a primary design constraint. It can be applied to male or female threaded fasteners of virtually all sizes, configurations, compositions, and finishes. Its microencapsulated reactive elements remain dormant in a quick-curing resin until fastener installation, requiring no heat or primers for cure activation.

The shearing forces generated during fastener installation rupture the microcapsules, releasing reactive compounds that cure into a tough, well-bonded polymer matrix. This matrix rapidly bonds mating surfaces, semi-permanently locking the joint and sealing leak paths.

Engineered for sustained performance in high-temperature environments such as engine compartments.
Compatible with virtually all fastener sizes, finishes, and substrate types.
No heat or primers required for cure activation.
Available in Industrial Grade (251-IN) and Precision Grade (251-PR).
Available in standard solvent-based formula and DPC (Dry Concentrate) variant with solvent removed for transport efficiency.
Pre-applied coating available for bulk fasteners at Tectorius licensed service centers and partners.

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Tec-Bond® 251 may be used as a direct replacement for 3M™Fastener Adhesive 2510, which has been discontinued. Read more here.

For a water-based, REACH and RoHS compliant alternative, see Tec-Bond®261.

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Automotive Powertrain: Engine compartment fasteners, exhaust system components, transmission assemblies.
High-Temperature Industrial: Fluid power systems and equipment operating under sustained thermal loads.
Industrial Maintenance & Repair: Remanufacturing and field service of high-temperature assemblies.
Production Coating: Compatible with a broad range of automated and semi-automated production coating equipment.

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Installation Torque: <10 in/lbs.

Break/Prevail Torque After Full Cure: 225/250 in/lbs. 25/28 Nm

Temperature Range: -65/350 °F -54/175°C

Fixture Time: >90 min

Standard Color: Orange

Specialty Colors: Neutral, Yellow, Red, Green

On-Part Life: 4 years

Air Dry: 24 hours

Full Cure Time At Room Temperature: 72 hours required before testing or removal

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Performance,Advantages and Benefits

High-Temperature Resistance: Tec-Bond® 251 is specifically formulated to maintain locking performance under sustained elevated temperatures, including in engine compartments and other high-thermal-load assemblies, with a service temperature range of -65°F to 350°F (-54°C to 175°C).
Room-Temperature Cure: Despite its high-temperature service capability, Tec-Bond® 251 cures fully at ambient temperature without requiring heat activation or primer pre-treatment, simplifying integration into existing assembly processes.
MicroencapsulationTechnology: Reactive elements remain dormant until fastener installation. This enables long on-part shelf life, dry-to-the-touch handling, and consistent activation at the point of assembly.
Automotive Fluid Resistance: Once fully cured, Tec-Bond® 251 resists and seals against most automotive fluids, including oil, water, antifreeze, and gasoline, and is designed to maintain this resistance in high-temperature service environments such as engine compartments.
Variety of Strengths, Colors, and Viscosities: Available in multiple colors for easy part inspection and in formulas suited to a wide range of production coating equipment, supporting quality control and manufacturing flexibility.
Production Coating Compatible: Available in viscosities suitable for use on automated production coating lines, supporting high-volume manufacturing requirements.
Cost-Effective Thread Locking: Pre-applied at the point of manufacture, Tec-Bond® 251 eliminates the need for bottled threadlocking compounds applied at the point of assembly, reducing labor time and per-unit cost.

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What is the difference between Tec-Bond® 251-IN and 251-PR?

‍The Industrial Grade (251-IN) is suited for general-purpose fastener locking on standard metal substrates in high-temperature environments. The Precision Grade (251-PR) was developed for precision assemblies where physical properties are tightly controlled and microcapsule character is specifically engineered.

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What is the difference between Tec-Bond 251 solvent-based and Tec-Bond 251 DPC?

Tec-Bond 251 is the standard solvent-based formula. Tec-Bond 251 DPC (Dry Concentrate) has the solvent removed, improving transport efficiency and extending bulk shelf life from 1 year to 3 years, while delivering equivalent on-part performance.

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How does Tec-Bond® 251 differ from Tec-Bond® 235?

‍Tec-Bond® 251 is the high-temperature grade of the solvent-based Tec-Bond® pre-applied adhesive family. Its formulation is engineered for sustained performance in elevated-temperature service environments such as engine compartments, with a maximum service temperature of 350°F (175°C), compared to 300°F (150°C) for Tec-Bond® 235.

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Does Tec-Bond® 251 require primer or heat to cure?

No. Tec-Bond® 251 is a room-temperature curing adhesive that requires neither heat nor primers for activation. Cure is initiated by the shearing forces generated during fastener installation.

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Is there a water-based alternative to Tec-Bond® 251?

Yes. Tec-Bond® 261 is the direct water-based, REACH and RoHS compliant alternative to Tec-Bond® 251, delivering equivalent high-temperature locking performance with solvent-free chemistry.

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