ThreeBond RTV Silicone Gasket Sealant TB1215 — Gray Paste, Oil-Resistant Flexible Seal for Engines & Gearboxes

ThreeBond TB1215 is a gray, paste-like RTV silicone liquid gasket that forms a flexible, oil-resistant seal between metal mating surfaces when exposed to air.

Designed for assemblies where no preformed gasket is used, this room-temperature-vulcanizing (RTV) sealant creates an elastic joint that resists gear oils and prevents leaks in demanding industrial and automotive settings. Its non-sag paste consistency allows application on vertical or inverted faces, making it practical for engine cases, pump housings, gearboxes and other equipment joints.

How does TB1215 form a seal on engine and gearbox casings?

When applied to clean mating metal surfaces, TB1215 cures by reacting with moisture in the air to become an elastic rubber-like bead that fills irregularities and gaps. The cured material bonds to metal and remains flexible to accommodate vibration and thermal expansion without losing adhesion.

• Applies as a non-drip paste for easy placement on vertical joints
• Cures at room temperature to a resilient silicone elastomer
• Seals uneven surfaces and prevents fluid migration through joints
• Gray color helps visibility during inspection and assembly

What equipment and industries is this sealer suitable for?

TB1215 is formulated for heavy-duty uses including marine, construction machinery, automotive repair, agricultural equipment, power generation and general industrial production. It is especially useful where conventional pre-cut gaskets are impractical or where a custom-fit seal is required.

• Engine and transmission casings in vehicles and machinery
• Pumps, gearboxes, and housings subject to gear oil contact
• Shipbuilding and offshore equipment with sealed joints
• Manufacturing lines requiring dependable joint sealing solutions

How should I prepare surfaces and apply the liquid gasket for best results?

Surface preparation is critical: remove old gasket material, oil, and contaminants then dry the surfaces thoroughly. Apply an even bead where the joint mates, assemble within the recommended open time, and allow full cure before introducing fluids or pressure.

• Clean surfaces with solvent and scrape away residue
• Apply continuous bead sized to joint gap and bolt pitch
• Tighten parts per manufacturer torque while sealant is tacky
• Allow complete room-temperature cure before testing or operation

What performance traits and limitations should I expect?

TB1215 provides strong resistance against gear oils and retains elasticity under vibration; however, like all RT V silicones it requires proper curing time and is not intended as a structural adhesive. Its paste-like, non-sag nature improves application control but thickness and joint design affect cure speed.

• Excellent resistance to petroleum-based gear oils
• Non-sag paste allows vertical or overhead application
• Not a substitute for mechanical fasteners or load-bearing joints
• Ambient moisture and temperature influence cure rate

Who is this for? TB1215 is aimed at technicians, mechanics, shipfitters and maintenance engineers who need a reliable, oil-resistant liquid gasket for engine cases, transmissions and industrial housings where a custom, flexible seal is required. It is also suitable for fabrication and repair shops that want a non-drip, easy-to-apply sealant to replace or complement conventional gaskets.