Product details
| Grade | Loctite 518 |
| Strength | Low strength |
| Colour | Red |
| Family | Flange & gasket sealants |
| Brand | Loctite (Henkel) |
| Stock | Held in Dubai — buy one or bulk |
Pack sizes
Prices on request. Tell us the quantity you need.
Check stockWhat Loctite 518 is for
A form-in-place gasket rather than a thread sealant. Applied as a bead to one flange face, it cures in the absence of air to a flexible seal that fills the machining marks and takes up gaps to 0.25 mm — so a gearbox or engine casing can be sealed without cutting a gasket. It resists low pressure immediately after assembly, before it has cured, and it tolerates the oils and surfactant cleaners left on flange faces in real workshops.
Key features
- Form-in-place gasket — no gasket to cut, store or misalign
- Seals low pressure immediately on assembly, before curing
- Gap performance to 0.25 mm
- Cures on mild steel and on passive substrates such as low-copper aluminium
- Tolerates cutting, lubricating and anti-corrosion oils and surfactant cleaners
- 64% elongation at break — flexible, so it survives flange movement
- Cold strength tested to −75°C; glass transition 100°C
Typical applications
- Engine covers
- Cast flanges
Technical data
Uncured material
| Technology | Acrylic |
| Chemical type | Dimethacrylate ester |
| Appearance | Red gel-like material |
| Fluorescence | Positive under UV light |
| Components | One component — no mixing |
| Cure | Anaerobic; secondary cure by activator |
| Viscosity, Brookfield HBT 25°C | Spindle TC at 0.5 rpm, Helipath: 4,000,000 mPa·s |
| Specific gravity at 23°C | 1.1 |
| Maximum gap | 0.25 mm (0.01 in) |
Instant sealing — pressure resistance before cure
Uncured product, tested immediately after assembly on a 50/70 mm annular steel face. Pen-roller application limits instant sealing to 0.125 mm by film thickness.
| Induced gap | Pressure resistance |
|---|
| 0.05 mm | 1.35 MPa |
| 0.125 mm | 0.14 MPa |
| 0.25 mm | 0.1 MPa |
Lap shear strength (ISO 4587)
Cured at 23°C. Values N/mm² (psi).
| Substrate | 24 hours | 72 hours |
|---|
| Mild steel, grit blasted | 8.4 (1,220) | 11 (1,530) |
| Mild steel | 5.5 (800) | 5.5 (800) |
| Aluminium | 5.4 (780) | 5.8 (840) |
| Aluminium (Alclad) | 2.2 (320) | 1.6 (230) |
| Grit-blasted steel to aluminium | 6.7 (970) | 6.7 (970) |
Further strength data
| Compressive shear strength after 1 h (ISO 10123) | 5 N/mm² (730 psi) |
| Compressive shear strength after 24 h | 5 N/mm² (730 psi) |
| Tensile strength, grit-blasted mild steel pin (ISO 6922) | 10 N/mm² (1,450 psi) |
| Tensile strength, aluminium pins | 13 N/mm² (1,930 psi) |
| Tensile strength (ISO 527-2) | 7.3 N/mm² (1,060 psi) |
| Tensile modulus (ISO 527-2) | 54 N/mm² (7,850 psi) |
| Elongation at break (ISO 527-2) | 64% |
| Glass transition temperature | 100°C |
| Sealing capability, mild steel and aluminium | Sealed to 0.25 mm induced gap at 1.3 MPa |
| Cold strength | Tested to −75°C |
Chemical resistance
Effect of environment on strength, not a measure of sealing performance. Note the poor petrol figures — 518 is not the grade for a fuel flange.
| Environment | °C | 500 h | 1,000 h | 3,000 h | 5,000 h |
|---|
| Motor oil (5W30 synthetic) | 120 | 175% | 115% | 110% | 145% |
| Motor oil (5W30 synthetic) | 150 | 55% | 50% | 50% | 50% |
| ATF | 120 | 175% | 100% | 105% | 140% |
| ATF | 150 | 60% | 40% | 40% | 40% |
| Water / glycol 50:50 | 87 | 80% | 65% | 65% | 65% |
| DEF (AdBlue®) | 23 | 95% | 65% | 70% | 85% |
| Unleaded petrol | 23 | 15% | 10% | 10% | 5% |
How to use it
- Flange faces must be clean and free from grease and other contaminants.
- Designed for close-fitting flanges with gaps up to 0.25 mm.
- Apply as a continuous bead, a rolled film, or by screen printing to one flange face.
- For gaps over 0.125 mm using a pen roller, apply a rolled film to both faces.
- Low pressure (under 0.05 MPa) may be applied to confirm the seal immediately after assembly, before curing.
- Tighten the flanges as soon as possible after assembly to avoid shimming.
Handling and storage
- Not recommended for pure oxygen or oxygen-rich systems.
- Not a sealant for chlorine or other strong oxidising materials.
- Not normally recommended on plastics — thermoplastics can stress-crack.
- Not suitable for petrol/fuel flanges — strength falls to 5% of initial after 5,000 hours in unleaded petrol at 23°C.
- Store unopened and dry, ideally 8°C to 21°C; outside 8–28°C the properties can be affected.
- Do not return decanted product to the original container.
518 against the other flange sealants
518 is the general-purpose anaerobic form-in-place gasket for rigid metal flanges with gaps to 0.25 mm. 510 is the high-temperature grade to 200°C. 573 is slow-cure, giving longer assembly time; 574 is fast-cure for production work. SI 5927 is a silicone rather than an anaerobic — flexible, and the right choice where flanges flex or the gap is larger than an anaerobic can bridge.
Always read the current technical and safety data before use —
ask us and we'll send it with your quotation.
