Guides & Selectors
Loctite Threadlocker Guide
Pick the right threadlocker by strength, thread size, temperature, and whether you need to remove the fastener later — a quick comparison of the common Loctite grades (purple 222, blue 242/243, red 262/271/272, green 290 wicking) with color, strength, size range, and removal.
Last verified: 2026-07-09
Anaerobic threadlockers cure in the absence of air between engaged threads to stop vibration loosening and seal against leaks. Choose by four things: how much strength/removability you need, the thread (bolt) size, the service temperature, and whether the joint is oily or already assembled. Color is the quick field cue — purple = low, blue = medium (removable), red = high (heat to remove), green = wicking for pre-assembled parts.
Threadlocker selection at a glance
| Product | Color | Strength | Max thread | Service temp | Removal | Typical use |
|---|---|---|---|---|---|---|
| 222 | Purple | Low | Up to 3/8" (M10) | -55 to 150°C | Hand tools | Adjustment & set screws, small fasteners you'll re-adjust |
| 242 | Blue | Medium | Up to 3/4" (M20) | -55 to 150°C | Hand tools | General-purpose; removable for service |
| 243 | Blue | Medium | Up to 3/4" (M20) | -55 to 150°C | Hand tools | Like 242 but oil-tolerant (light oils, minimal cleaning) |
| 262 | Red | High/Medium-high | Up to 3/4" (M20) | -55 to 150°C | Heat + hand tools | Studs/heavy fasteners needing controlled disassembly |
| 271 | Red | High | Up to 1" (M25) | -55 to 150°C | Localized heat (~250°C) | Permanent studs & fasteners, high vibration |
| 272 | Red | High | Up to 1-1/2" (M36) | -55 to 232°C | Localized heat (~250°C) | High-temperature high-strength assemblies |
| 290 | Green | Medium-high (wicking) | Up to 1/2" (M12) | -55 to 150°C | Heat + hand tools | Wicks into already-assembled/pre-torqued fasteners |
How to choose
- Will you remove it later? Low (222) and medium (blue 242/243) come apart with hand tools. High-strength red (271/272) needs localized heat (~250°C / ~500°F) before it will release.
- Thread size: match the grade's size range — small screws use 222; general fasteners use 242/243; large or high-vibration studs use 271; very large or hot joints use 272.
- Temperature: standard grades run to ~150°C; for hotter service (to ~232°C) choose 272.
- Oily or hard-to-clean threads: 243 tolerates light oils with minimal cleaning. Otherwise clean and dry the threads first.
- Already assembled? Green 290 wicks into the threads of a torqued fastener by capillary action.
Application & curing
- Clean and dry both threads (a solvent cleaner removes oils). Contamination is the most common cause of a weak lock.
- Apply to the engaged thread area — for a through-hole, apply to the bolt where the nut will engage; for a blind hole, apply down the hole and onto the bolt.
- Handling/fixture strength develops in minutes on steel; full cure is typically ~24 hours.
- Inactive metals (stainless, zinc-plated, aluminum, anodized) and larger gaps cure slower — use an activator/primer (e.g. 7649 / 7471) to restore cure speed.
Frequently asked
- Blue vs red Loctite — what's the difference?
- Blue (242/243) is medium strength and removable with normal hand tools, so it's the default for fasteners you may service. Red (271/272) is high strength and effectively permanent — you usually have to apply localized heat (~250°C) to break it loose.
- Can I use threadlocker on oily bolts?
- Best practice is clean, dry threads. If you can't fully clean them, 243 is formulated to tolerate light oils. Heavy oil or grease will still weaken any threadlocker.
- How do I remove red threadlocker?
- Apply localized heat to the fastener/joint (roughly 250°C / 500°F, e.g. with a heat gun or torch as appropriate for the assembly), then remove the fastener while it's still warm with hand tools.
- How long until it's fully cured?
- Fixture (handling) strength usually develops within minutes on steel, but plan on about 24 hours for full cure — and longer on inactive metals or with larger gaps unless you use a primer/activator.
Sources
- Henkel Loctite — product technical data sheets (222, 242, 243, 262, 271, 272, 290)
- Anaerobic threadlocker application & curing guidance (Henkel Loctite)