Loctite 638 Retaining Compound 50ml
Available
Loctite 638 is a green, one-component, high strength anaerobic retaining compound. It is a urethane methacrylate with a high viscosity, and it is fluorescent under UV light.
It is particularly suited to bond gaps that can approach 0.25mm where maximum strength at room temperature is required. Typical uses include locking bushings and sleeves into housings and on shafts, on active metals and on passive surfaces such as stainless steel and plated parts.
Where this product is used
- Locking bushings and sleeves into housings and on shafts
- Cylindrical fitting parts where bond gaps can approach 0.25mm
- Stainless steel and plated parts (passive surfaces)
- Parts with minor surface contamination from cutting, lubrication, anti-corrosion and protection fluids
- Hydrogen applications, where the GASTEC QA AR-214 requirement applies (regional approval)
Features
- High strength class
- One component, no mixing
- Cures on active metals and passive surfaces
- Tolerates minor oil contamination from cutting, lubrication and protection fluids
- 29 N/mm² compressive shear on steel after 72 hours at 23 °C
- 57 N·m breakaway torque on M10 black oxide bolts and mild steel nuts
- Conforms to GASTEC QA Approval requirement 214 (AR-214), a regional approval
Key specifications
| Specification | Detail |
|---|---|
| Brand | Loctite |
| Chemical type | Urethane methacrylate (acrylic) |
| Colour | Green liquid; fluorescent under UV light |
| Cure | Anaerobic, one component; activator as secondary cure |
| Strength class | High |
| Viscosity (Brookfield RVT, 25 °C, spindle 3, 20rpm) | 2,500 mPa·s (class: high) |
| Specific gravity (23 °C) | 1.1 |
| Compressive shear, steel (ISO 10123, 23 °C) | 13.5 N/mm² at 15 min; 29 N/mm² at 72 h |
| Compressive shear, 72 h at 23 °C (stainless steel; aluminium) | 28 N/mm²; 17 N/mm² |
| Breakaway torque (M10 black oxide bolts, mild steel nuts, 72 h at 23 °C, ISO 10964) | 57 N·m |
| Prevail torque (M10, 72 h at 23 °C, ISO 10964) | 22 N·m |
| Disassembly | Standard hand tools; if needed, local heat to about 250 °C and disassemble while hot |
| Approvals | Tested and conforms to GASTEC QA Approval requirement 214 (AR-214), Hydrogen Certified Adhesive; regional approval |
| Storage | Unopened, dry; optimal 8 °C to 21 °C |
Choosing the right option
Loctite 638 suits bond gaps that can approach 0.25mm. For other retaining compounds see Loctite 609 Cylindrical Bonding Retaining Compound, Loctite 635 Retaining Compound, Loctite 680 High Strength Retaining Compound 50ml and Loctite 620 High Temperature Retaining Compound 50ml.
See also: Loctite 609 Cylindrical Bonding Retaining Compound, Loctite 635 Retaining Compound, Loctite 680 High Strength Retaining Compound 50ml, Loctite 620 High Temperature Retaining Compound 50ml.
Using it
Strength is 13.5 N/mm² on steel pins and collars after 15 minutes at 23 °C, and cure rate depends on the bondline gap. Do not disturb the parts until sufficient handling strength is achieved.
To disassemble, use standard hand tools. If needed, apply local heat to about 250 °C and pull apart while hot; otherwise heat as much as practical and use mechanical aids.
Storage and handling
Store unopened in a dry location, with optimal storage at 8 °C to 21 °C. Storage below 8 °C or above 28 °C can adversely affect properties.
Limits and safety
Not normally recommended for plastics. Not recommended for pure oxygen systems, or as a sealant for chlorine or other strong oxidising materials. The AR-214 conformity is a regional approval; confirm it suits your application. Read the safety data sheet before use.
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