Loctite 5910: Silicone flange sealant (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 and replaces prefabricated flat gaskets. The 5910 is particularly suitable for applications that require flexible sealing at temperatures up to 200 °C – with short-term peaks up to 260 °C.
Technical specifications
| property | value |
|---|---|
| product type | RTV silicone sealant (oxime cross-linking) |
| Application | FIPG – Formed-in-place gasket |
| Color | Black |
| consistency | Thixotropic paste (stable) |
| density | 1.34 g/cm³ at 20 °C |
| Shore hardness (cured) | 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) |
| Temporarily | Up to +260 °C |
| Non-stick time | ≤40 minutes (at 25 °C, 50% relative humidity) |
| full curing | 24 hours at 23 °C / 50% relative humidity |
| 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 air humidity and progresses from the outside inwards.
Why oxime cross-linking?
- Odorless: Unlike acetate silicones (vinegar smell), oxime silicone does not release acetic acid.
- Corrosion-free: No aggressive decomposition products – safe on copper, brass, and other sensitive metals
- Sensor-compatible: No acetic acid that could damage electronic components or sensors
Curing profile:
- Tack-free time: ≤40 minutes (at 25 °C, 50% relative humidity)
- Handling strength: ~4 hours
- Functional tightness: ~24 hours
- Full curing: 24–72 hours (depending on gap depth and humidity)
Applications
Automotive – Engine gaskets
Loctite 5910 was primarily developed for flexible flange seals in the automotive sector:
- Oil pan: FIPG seal between engine block and oil pan (flexible flange movements due to vibrations)
- Timing chain cover: Seal on timing cover with temperature fluctuations
- Valve cover: Flexible sealing for aluminum or plastic-based valve covers
- Transmission housing: Flexible flange seal on automatic and manual transmissions
- Crankcase halves: Sealing the engine housing joint
Not suitable for: Water pumps and water-bearing applications. The 5910 is optimized for permanent oil contact, not for coolants 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 | Note |
|---|---|---|
| Steel, stainless steel | Very good | Clean and degrease the surface |
| aluminum | Very good | No primer required |
| cast iron | Good | Roughen the surface of porous areas |
| Copper, brass | Good | Oxime cross-linking: corrosion-free |
| Plastic (PA, PBT) | Good | Check material compatibility |
| glass | Good | – |
Processing: Step by step
1. Surface preparation
- Completely remove old seal residue (mechanically or with Loctite SF 7200 seal remover).
- Clean and degrease flange surfaces with isopropanol or Loctite SF 7063.
- Surfaces must be dry and free of dust.
2. Application
- Apply sealant evenly in a bead (2–3 mm diameter) to one half of the flange.
- Guide the caterpillar around all screw holes (not through the holes)
- Apply to large flange surfaces with a flat spiral.
- Gap size: Ideally 0.1–0.5 mm, maximum 1 mm
3. Joining together
- Assemble flange halves quickly after application (non-tacky time ≤40 min., ideally within 10 min.)
- Tighten screws by hand—do not apply full load
- Remove excess sealant
4. Curing and commissioning
- After 4 hours: Tighten screws to specified torque
- After 24 hours: Function test possible
- Only load with operating media after 24 hours
Loctite 5910 vs. other Loctite flange sealants
| property | 5910 | 5699 | 5920 | 5970 |
|---|---|---|---|---|
| Color | Black | gray | copper | Black |
| strength | Low | Low | means | 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%) | means | means | Low |
| gap bridging | Up to 1 mm | Up to 1 mm | Up to 0.5 mm | Up to 0.25 mm |
| network type | oxime | oxime | oxime | acetate |
| main use | Flexible flanges, oil | Universal, low odor | High temperature up to 350 °C | High vibration/torque |
When which type?
- Loctite 5910: Flexible flanges with oil contact (oil pan, valve cover, transmission housing). Not for water-carrying applications.
- Loctite 5699: Universal flange sealant, 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 loads, 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 is a FIPG product specially designed to replace prefabricated flat gaskets. For rigid flange connections with high mechanical stress, we recommend Loctite 5970.
How do I remove old Loctite 5910?
Mechanically with a plastic scraper or sealant remover (Loctite SF 7200). The hardened silicone can usually be removed as a continuous strip. Remove any residue with isopropanol.
How soon after sealing can I start the engine?
At the earliest after 24 hours at room temperature. The silicone needs this time to cure sufficiently and become pressure-tight. Premature stress can damage the seal.
Is Loctite 5910 oil resistant?
Yes. The 5910 is resistant to engine oil, transmission oil, coolant (glycol), and fuels. It is specially formulated for use in the automotive sector.
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 (cures with air humidity). The 518 offers higher strength on rigid flange connections, while the 5910 offers higher flexibility and temperature resistance.
Order Loctite 5910 from SILITECH
SILITECH AG stocks the Loctite flange sealant range in Switzerland. We can advise you on choosing the right sealant:
- Loctite 5910 (black, flexible, up to 200 °C)
- Loctite 5699 (gray, universal)
- Loctite 5920 (copper, high temperature)
- Loctite 5970 (black, high strength)
Contact us for samples, technical advice, or a quote.
