Loctite 5910: Silicone flange gasket (FIPG) in detail
Loctite SI 5910 is a black, low-strength RTV silicone sealant for flexible flange connections. As a FIPG (Formed-In-Place-Gasket) product, the sealant is applied directly to the flange, replacing pre-fabricated flat gaskets. The 5910 is particularly suitable for applications requiring flexible sealing at temperatures up to 200 °C – with short-term peak temperatures up to 260 °C.
Technical data
| Characteristic | Value |
|---|---|
| Product type | RTV silicone sealant (oxime crosslinking) |
| Application | FIPG – Formed-In-Place Gasket |
| Color | Black |
| consistency | Thixotropic paste (non-stable) |
| density | 1.34 g/cm³ at 20 °C |
| Shore hardness (hardened) | 30 Shore A |
| Tensile strength | ≥1.7 N/mm² (ISO 37) |
| Tensile strength at 100% elongation | 0.6–1.0 N/mm² |
| Elongation at break | ≥400 % (ISO 37) |
| Shear strength | 0.9-1.4 N/mm² (130-200 psi) |
| Gap bridging | Up to 1 mm |
| Temperature range | -55 °C to +200 °C (continuous operation) |
| Briefly | Up to +260 °C |
| Sticky time | ≤40 minutes (at 25 °C, 50 % rH) |
| Full curing | 24 hours at 23 °C / 50% RH. |
| Curing depth after 24 hours | ~3 mm |
Networking mechanism
Loctite 5910 is an oxime-curing (neutral-curing) RTV-1 silicone. Curing begins on the surface through contact with atmospheric moisture and progresses from the outside in.
Why oxime crosslinking?
- Odorless: Unlike acetate silicones (vinegar smell), oxime silicone does not release acetic acid.
- Corrosion-free: No aggressive fission products – safe for copper, brass and other sensitive metals.
- Sensor compatible: No acetic acid that could attack electronic components or sensors
Curing profile:
- Tack-free time: ≤40 minutes (at 25 °C, 50% RH)
- Handling resistance: ~4 hours
- Functional sealing: ~24 hours
- Full curing time: 24–72 hours (depending on gap depth and humidity)
Applications
Automotive – Engine seals
Loctite 5910 was primarily developed for flexible flange gaskets in the automotive sector:
- Oil pan: FIPG seal between engine block and oil pan (flexible flange movement due to vibrations)
- Timing chain cover: Gasket on the timing cover affected by temperature fluctuations
- Valve cover: Flexible sealing for aluminum or plastic-based valve covers
- Gearbox housing: Flexible flange gasket on automatic and manual transmissions
- Crankcase halves: Sealing the engine case separation joint
Not suitable for: Water pumps and water-carrying applications. The 5910 is optimized for permanent oil contact , not for coolant or water. For water pumps, we recommend Loctite 5699 or 5920.
Industrial applications
- Housing sealing for compressors and pumps
- Flange gasket for piping systems (non-aggressive media)
- Sealing of inspection covers and maintenance openings
- Flexible seals in the food industry (where permitted)
Suitable substrates
| substrate | Liability | Notice |
|---|---|---|
| Steel, stainless steel | Very good | Clean and degrease the surface |
| aluminum | Very good | No primer required |
| cast iron | Good | Roughen the surface of porous surfaces |
| copper, brass | Good | Oxime crosslinking: corrosion-free |
| Plastic (PA, PBT) | Good | Check material compatibility |
| Glass | Good | – |
Processing: Step by step
1. Surface preparation
- Completely remove old gasket residue (mechanically or with Loctite SF 7200 gasket remover)
- Clean and degrease flange surfaces with isopropanol or Loctite SF 7063
- Surfaces must be dry and dust-free
2. Apply
- Apply the sealant evenly as a bead (2–3 mm diameter) to one flange half
- Guide the bead around all screw holes (not through the holes)
- Apply to large flange surfaces using a flat spiral
- Gap size: Ideally 0.1–0.5 mm, maximum 1 mm
3. Assemble
- Join the flange halves together quickly after application (adhesive-free time ≤40 min, ideally within 10 min)
- Tighten screws by hand – do not fully load the load
- Remove excess sealant
4. Curing and commissioning
- After 4 hours: Tighten screws to the specified torque
- After 24 hours: Function test possible
- Do not load with operating fluids until 24 hours have passed
Loctite 5910 vs. other Loctite flange gaskets
| Characteristic | 5910 | 5699 | 5920 | 5970 |
|---|---|---|---|---|
| Color | Black | Gray | copper | Black |
| strength | Low | Low | Medium | High |
| Temperature range | -55 to +200 °C | -55 to +200 °C | -55 to +350 °C | -50 to +200 °C |
| Tensile strength | 1.2 N/mm² | 1.7 N/mm² | 1.4 N/mm² | 1.5 N/mm² |
| flexibility | High (≥400%) | Medium | Medium | Low |
| Gap bridging | Up to 1 mm | Up to 1 mm | Up to 0.5 mm | Up to 0.25 mm |
| Networking type | Oxime | Oxime | Oxime | acetate |
| Main deployment | Flexible flanges, oil | Universal, low odor | High temperatures up to 350 °C | High vibration/torque |
Which type, and when?
- Loctite 5910: Flexible flanges in contact with oil (oil pan, valve cover, gearbox housing). Not for use in water-bearing applications.
- Loctite 5699: Universal flange gasket, low odor, highest tensile strength (1.7 N/mm²)
- Loctite 5920: High temperature up to +350 °C – exhaust manifold, turbocharger housing, exhaust side
- Loctite 5970: High vibration and torque load, rigid flanges
Frequently Asked Questions (FAQ)
Can Loctite 5910 completely replace a flat gasket?
Yes, for flexible flange connections with a maximum gap of 1 mm. The 5910, as a FIPG product, is specifically designed to replace prefabricated flat gaskets. For rigid flange connections subject to high mechanical stress, we recommend Loctite 5970.
How do I remove old Loctite 5910?
Mechanically remove with a plastic scraper or sealant remover (Loctite SF 7200). The cured silicone can usually be peeled off as a continuous band. Remove residue with isopropyl alcohol.
How soon can I start the engine after sealing it?
Wait at least 24 hours at room temperature. The silicone needs this time to cure sufficiently and become pressure-tight. Premature exposure can damage the seal.
Is Loctite 5910 oil-resistant?
Yes. The 5910 is resistant to engine oil, gear oil, coolant (glycol), and fuels. It is specifically formulated for automotive use.
What is the difference between Loctite 5910 and Loctite 518?
Loctite 518 is an anaerobic flange sealant (cures without air between metal surfaces). Loctite 5910 is a silicone sealant (cures through atmospheric moisture). The 518 offers higher strength on rigid flange connections, while the 5910 offers greater flexibility and temperature resistance.
Further information
- Permabond adhesives: product range, technical data & Loctite comparison
- Bonding metal without welding: 5 high-performance adhesives compared
- Loctite 638: High-strength shaft-hub connection
- Selecting and correctly using screw locking devices
- Industrial adhesives compared: epoxy, cyanoacrylate, anaerobic, UV, MMA. Which adhesive for which application?
- RTV-1 Silicones & Sealants in the Shop
- Request technical advice
)