Loctite 222 is a purple, low-strength anaerobic threadlocker formulated for small fasteners up to 6.35 mm (1/4 inch). It locks threads, prevents loosening from vibration, and is deliberately engineered to break free with standard hand tools — no heat, no impact wrench, no drama. That removability is not a weakness; it is the specification. If you need to service, adjust, or disassemble the joint regularly, 222 is the correct grade.
The "anaerobic" part matters. Loctite 222 cures only when it is trapped between close-fitting metal surfaces and deprived of oxygen. Leave it in the bottle with the cap off and it stays liquid. Apply it to threads, assemble the fastener, and the absence of air triggers the cure. The process requires metal ions to proceed — which is why stainless steel and aluminium need a primer (Activator 7471) while steel and iron do not.
This guide covers everything that determines whether 222 is the right choice for your application: specifications, cure times, the 222 vs 243 decision, what happens on inactive metals and plastics, and the 222MS Mil-Spec variant used in defence and precision industries.
What Is Loctite 222?
Loctite 222 is a single-component anaerobic adhesive in Henkel's threadlocker range. It is colour-coded purple — Henkel's universal indicator for low strength — and is part of a graded system designed so that the correct product can be selected by fastener size and required removal torque:
| Colour | Grade | Product | Typical use |
|---|---|---|---|
| Purple | Low | Loctite 222 | Fasteners ≤M6 (6.35 mm); instrument and adjustment screws |
| Blue | Medium | Loctite 243 | Fasteners M6–M20; general engineering |
| Red | High | Loctite 271/277 | Fasteners M20+; permanent or structural |
| Green | Retaining | Loctite 620/641 | Cylindrical fits; bearings, bushings, shafts |
The colour system applies across the entire Loctite range, not just threadlockers. Purple always means low strength and small fastener application. If you pick up a purple Loctite product, you can be confident it is designed for removable, light-duty thread locking.
Chemically, Loctite 222 is a dimethacrylate ester — it polymerises in the presence of metal ions and the absence of oxygen. Once cured, it forms a thermoset plastic film that fills thread voids, dampens vibration, and prevents the micro-movements that cause self-loosening. The low-strength formulation produces enough cure to hold the fastener against vibration, but a low enough breakaway torque (3 Nm on M10 steel) that the joint can be undone with a standard screwdriver or allen key.
For a broader overview of the full Loctite product range including medium and high-strength options, see our Loctite Application Guide.
Loctite 222 Specifications
| Property | Value |
|---|---|
| Product name | Loctite 222 / Loctite 222 Low Strength Threadlocker |
| Colour | Purple |
| Strength grade | Low |
| Chemical base | Dimethacrylate ester (anaerobic) |
| Breakaway torque (M10, steel) | 3 Nm |
| Prevail torque (M10, steel) | 2 Nm |
| Fixture time (steel, 22°C) | 10 minutes |
| Functional strength | 1 hour |
| Full cure | 24 hours |
| Service temperature | −55°C to +150°C |
| Maximum fastener size | ≤6.35 mm (1/4 inch) / M6 |
| Pack sizes | 5 mL, 10 mL, 50 mL, 250 mL |
| Mil-Spec variant | Loctite 222MS (MIL-S-46163A Type 1 Grade K) |
All torque values are for steel fasteners at 22°C. Values on stainless steel, aluminium, or at low temperatures will differ — see the sections below on inactive metals and activator use.
What Is Loctite 222 Used For?
Loctite 222 is designed for any small fastener application where the joint needs to resist vibration-induced loosening but must remain removable with hand tools. The defining criterion is fastener size: if the thread is 6.35 mm (M6) or smaller, 222 is the correct Loctite threadlocker grade in most cases.
Instrument and adjustment screws
Set screws, grub screws, limit screws, and fine-adjustment fasteners in instruments, machinery, and precision equipment are the classic 222 application. These fasteners are typically M2–M5, made from steel or stainless, and need to hold their position against vibration without requiring destructive force to move during calibration or service. A drop of 222 is the standard solution across industrial, laboratory, and scientific instrument manufacture.
Optics, scopes, and firearm hardware
Loctite 222 (and its Mil-Spec equivalent 222MS) is widely specified for scope ring screws, base screws, and optic mounting hardware. Scope screws are typically 6–48 UNC or 8–40 UNC — small fasteners that must hold against significant recoil vibration while remaining removable for sight adjustment. The 3 Nm breakaway torque is calibrated specifically for this use case: enough to prevent walking under recoil, low enough that a proper tool can break the joint without deforming the screw head or the mount. Loctite 222MS is the defence-grade equivalent for military and precision applications.
Bicycle and powersports components
Stem bolts, cleat bolts, derailleur limit screws, bottle cage screws, and saddle rail clamps are common bicycle applications for Loctite 222. These fasteners are almost all M4–M6, typically in aluminium components that are serviced regularly. The low strength of 222 is appropriate: it holds against road vibration without preventing the disassembly that every service requires. Loctite 243 (blue) is too aggressive for many of these joints — particularly on anodised aluminium, where higher breakaway torque risks thread damage on repeated removal.
Electronics and precision equipment housings
M2 and M3 machine screws securing PCB mounts, panel hardware, connector surrounds, and instrument housings. 222 prevents self-loosening from vibration without over-stressing small threads that cannot take high removal torques.
Grub screws and set screws in powertrain components
Motor shaft set screws, pulley grub screws, and coupling set screws in light-duty power transmission applications. These are commonly M3–M5 and made from steel — 222 works without activator and holds the set screw in position against rotational vibration. For M6 and above at significant torque, move to Loctite 243.
Loctite 222 vs 243 — Which Should You Choose?
The 222 vs 243 choice comes down to fastener size and the torque required for removal. Both are removable with hand tools. The difference is how much force is needed — and what happens when you apply a medium-strength product to a small fastener.
| Loctite 222 | Loctite 243 | |
|---|---|---|
| Colour | Purple | Blue |
| Strength | Low | Medium |
| Breakaway torque (M10, steel) | 3 Nm | 13 Nm |
| Prevail torque (M10, steel) | 2 Nm | 10 Nm |
| Maximum recommended fastener size | M6 (6.35 mm / 1/4") | M20 |
| Removal method | Standard hand tools, no heat | Standard hand tools, heat helps on large fasteners |
| Inactive metals (SS, Al) | Activator 7471 required | Activator 7471 required |
| Typical applications | Instrument screws, optics, bicycle components, grub screws, M2–M6 | General engineering, automotive, M6–M20 bolts |
| Risk on M2–M4 fasteners | Low — designed for these sizes | High — can seize small fasteners or strip heads on removal |
The rule of thumb: If your fastener is M6 or smaller (or 1/4 inch or smaller in imperial), use Loctite 222. If it is M8 or larger, use Loctite 243. For M6 fasteners specifically — 222 if the joint needs regular service; 243 if the joint is semi-permanent and higher vibration resistance is needed.
The practical risk of using 243 on small fasteners is significant and underappreciated. On an M2 or M3 grub screw, the 13 Nm breakaway torque of 243 can exceed what the screw head can withstand — particularly on soft alloy grub screws — resulting in a rounded or sheared fastener that must be drilled out. 222 is specified for these sizes precisely because its breakaway torque is proportionate to the fastener's strength.
For a full technical comparison and the complete Loctite threadlocker selection table, see our Loctite 243 Guide.
Loctite 222 Cure Time
Loctite 222 cures in stages, and the terms are used loosely in the field. Understanding the difference between fixture time, functional cure, and full cure prevents premature service of treated joints.
| Stage | Time (steel, 22°C) | What it means |
|---|---|---|
| Fixture time | 10 minutes | Joint can be handled without disturbing the curing threadlocker. Do not apply load. |
| Functional cure | 1 hour | Sufficient cure for light service. Not full rated strength. |
| Full cure | 24 hours | Full rated breakaway and prevail torque achieved. |
These values are for steel substrate at 22°C. Several factors slow cure:
- Low temperature: Below 15°C, cure time increases substantially. Below 5°C, anaerobic cure may stall. If working in cold conditions, allow 48 hours before service or warm the assembly.
- Inactive metals: Stainless steel, aluminium, and zinc without Activator 7471 will cure slowly and may not reach full rated torque values. Activator 7471 restores standard cure times on these substrates.
- Large gap between threads: If there is significant clearance between mating threads (worn threads, oversized holes), the thin film of threadlocker at the edges may not cure fully. Loctite 222 is designed for standard thread fits — use thread repair inserts if clearance is excessive.
- Oil or grease contamination: Residual cutting oil or grease on threads will significantly impair cure. Degrease with acetone or isopropyl alcohol before application.
Activator 7471 applied to one surface before threadlocker application will reduce fixture time on inactive metals to approximately 10–15 minutes, matching the standard steel cure profile.
Is Loctite 222 Removable?
Yes — Loctite 222 is specifically engineered to be removable with standard hand tools, and this is its primary advantage over medium and high-strength grades for small fasteners. The 3 Nm breakaway torque (on M10 steel) is low enough that a screwdriver, allen key, or small spanner will break the joint without damaging the fastener or the thread.
No heat is required. No impact tools. No penetrating fluid. For most M2–M6 fasteners treated with 222, normal workshop tools are sufficient to remove the fastener cleanly.
This is why 222 is the threadlocker of choice for components that require periodic adjustment or servicing: scope mounts, bicycle components, instrument panels, and grub screws on machinery that is maintained regularly. The threadlocker does its job — it stops vibration-induced loosening — without committing you to a permanent joint.
If you have applied 222 and genuinely cannot break the fastener with hand tools — which is rare but possible on very small fasteners with very tight threads — gentle heat (80–100°C) will soften the cured polymer and allow removal without damage.
Loctite 222 and Activator 7471
Anaerobic threadlockers require free metal ions to initiate the cure reaction. Steel and iron provide sufficient free ions directly from the metal surface — no primer needed. Stainless steel, aluminium, zinc, titanium, and most non-ferrous metals carry a passive oxide layer that blocks ion transfer and significantly slows or prevents cure.
Loctite Activator 7471 (also sold as Primer N) is the solution. It is a surface treatment applied to one mating surface before threadlocker application. It introduces the metal ions the cure reaction needs, restoring standard cure times and full torque performance on inactive metals.
When Activator 7471 is required with Loctite 222:
- Stainless steel fasteners or substrate
- Aluminium fasteners or substrate (including anodised aluminium)
- Zinc-plated or galvanised fasteners
- Titanium fasteners
- Cadmium-plated fasteners
- Any application where one or both surfaces are non-metallic (with caveats — see the plastics section)
How to apply Activator 7471:
- Clean and degrease all surfaces first. The activator will not work on contaminated threads.
- Apply a thin, uniform coat of 7471 to one mating surface only — typically the female thread or the nut.
- Allow the activator to dry for 30–60 seconds. It should be dry to the touch before proceeding.
- Apply Loctite 222 to the male thread in the normal way.
- Assemble immediately.
Do not flood or pool the activator. A thin, dry film is the target — excess activator can inhibit cure rather than promote it. If the activator appears wet when you apply the threadlocker, wait another 30 seconds.
Loctite 222 on Stainless Steel and Aluminium
These are the two most common substrates where Activator 7471 is required, and the two that cause the most problems when users skip the primer step.
On stainless steel without activator: the passive chromium oxide layer on the surface is an effective barrier to the anaerobic cure mechanism. The threadlocker may appear to have set — it will feel tacky or semi-cured — but will not develop full mechanical strength. Breakaway torque will be well below the rated 3 Nm, and the joint may fail to hold against vibration. Always use 7471 on stainless.
On aluminium without activator: similar outcome. Anodised aluminium compounds the problem — the anodising layer is an intentional oxide barrier and will almost completely prevent cure without activator. On bare machined aluminium, cure is possible but slow and incomplete. On anodised aluminium, treat 7471 as mandatory.
Practical applications where this matters: aluminium bicycle components (stems, handlebars, seatposts), stainless fasteners in marine environments, scope bases mounted on aluminium receiver rails, and stainless machine screws used in precision instruments.
Loctite 222 on Plastics — What You Need to Know
This is one of the most frequently asked questions from the 3D printing and electronics communities, and the answer requires care.
Loctite 222, like all Loctite anaerobic threadlockers, uses a methacrylic ester as its carrier solvent. This solvent can attack certain plastics — particularly ABS (acrylonitrile butadiene styrene), polystyrene, and polycarbonate. The result is crazing (surface cracking), swelling, softening, or in severe cases, dissolution of the plastic substrate. This is not a failure of the threadlocker — it is a materials incompatibility that applies to the entire anaerobic threadlocker chemistry class.
Plastics that are commonly attacked by Loctite anaerobic threadlockers:
- ABS — high risk. Very commonly used in 3D printing, enclosures, and consumer electronics.
- Polystyrene — high risk.
- Polycarbonate — moderate to high risk.
- PETG — lower risk than ABS but not immune. Proceed with caution.
Plastics with better resistance:
- Nylon (PA6, PA66) — generally more resistant. Still not recommended for flooded application.
- PEEK — resistant, but verify with Henkel TDS for your specific application.
- Acetal (POM) — moderate resistance.
If you are using metal fasteners into tapped plastic threads (common in electronics housings and 3D-printed assemblies), the risk is to the plastic threads themselves — the solvent contacts the plastic directly. The practical result is weakened threads or a permanently damaged housing on the first removal attempt.
For plastic applications, use Loctite 401 (cyanoacrylate) with Loctite 770 primer, which is specifically formulated for plastics and rubbers. For thread-locking applications on plastic-bodied components, consult Henkel's compatibility data for your specific plastic grade.
In 3D printing applications specifically: if you are using Loctite 222 on metal fasteners in VORON or similar printer builds that use ABS structural components, minimise contact between the threadlocker and the ABS — apply to the fastener only, avoid overflow, and cure fully before the joint contacts any ABS surface. Many builders use 222 on steel set screws in steel motor shafts (metal-to-metal) without issue; the problem arises when the threadlocker reaches the surrounding plastic.
For thread-locking in mixed-media assemblies, see our Loctite 401 Guide.
Loctite 222MS — The Mil-Spec Version
Loctite 222MS is chemically identical to Loctite 222. The difference is the testing, certification, and packaging regime it has been submitted to.
The "MS" designation indicates compliance with MIL-S-46163A — a United States military specification for anaerobic sealants and threadlockers. The specific type is Type 1 (threadlocker/retaining compound), Grade K (low strength). This certification requires the product to be manufactured, tested, and packaged to defined protocols that allow defence and aerospace procurement systems to specify it by MIL number.
222MS is sold in 6 mL bottles. This packaging format is itself a MIL-SPEC requirement — the volume and labelling must conform to the standard's packaging specification. In commercial practice, the 6 mL size has become the recognisable indicator that a product has MIL-SPEC certification.
Who uses 222MS:
- Defence and military maintenance programmes where all materials must be specified by MIL number
- Aerospace MRO (maintenance, repair, overhaul) facilities
- Firearms manufacturers and gunsmiths, particularly in the US market, where 222MS is the standard specification for scope mounting
- Precision instrument manufacturers with quality systems that require MIL-certified materials
For commercial and trade use: standard Loctite 222 is the correct product. 222MS costs more per mL and the MIL certification adds no functional performance advantage for commercial applications. If your engineering spec, quality system, or customer requirement calls for MIL-S-46163A, use 222MS. Otherwise, use 222.
AIMS stocks both variants. See our Loctite range for current availability.
What Size Fasteners Does Loctite 222 Suit?
The Henkel TDS specifies Loctite 222 for fasteners up to 6.35 mm (1/4 inch) in diameter. In metric terms, this covers M2 through M6. For M8 and above, Loctite 243 (medium strength, blue) is the appropriate grade.
| Thread size | Diameter | Recommended Loctite grade | Notes |
|---|---|---|---|
| M2 | 2 mm | 222 (purple) | 222 designed for this range |
| M2.5 | 2.5 mm | 222 (purple) | 222 designed for this range |
| M3 | 3 mm | 222 (purple) | 222 designed for this range |
| M4 | 4 mm | 222 (purple) | 222 designed for this range |
| M5 | 5 mm | 222 (purple) | 222 designed for this range |
| M6 | 6 mm | 222 (light duty) or 243 (heavier) | 222 for regular service; 243 if higher vibration resistance needed |
| M8 | 8 mm | 243 (blue) | 222 breakaway torque insufficient at this size |
| M10 | 10 mm | 243 (blue) | Standard torque specs referenced in both TDS |
| M12 and above | 12 mm+ | 243 or 271 (red) | Depends on permanence requirement |
Using Loctite 222 on M8 and above will provide insufficient vibration resistance for most engineering applications — the low cure strength that makes it removable on small fasteners means it will not perform adequately on larger fasteners subject to real-world loads. Conversely, applying Loctite 243 to M2–M4 fasteners risks seizing the joint beyond what the fastener can withstand on removal.
For the full threadlocker selection table including high-strength and retaining compound grades, see our Thread Locking & Sealing Guide.
How to Apply Loctite 222 — Step by Step
- Clean and degrease — wipe threads on both the fastener and the mating hole with acetone or isopropyl alcohol. Remove cutting oil, grease, and any existing threadlocker residue. Allow to dry completely.
- If substrate is inactive metal (stainless, aluminium, zinc) — apply a thin, uniform coat of Loctite Activator 7471 to one mating surface (typically the female thread). Allow 30–60 seconds to dry until the surface feels dry to the touch. Do not proceed if wet.
- Apply Loctite 222 to the threads — apply one or two drops to the first few leading threads of the male fastener (the bolt or screw). One drop is sufficient for M4 and below; two drops for M5–M6. Do not apply to the female thread if activator is in place — the threadlocker goes on the male thread.
- Assemble immediately — thread the fastener in and torque to specification. Anaerobic cure begins as soon as the threadlocker is trapped between the surfaces.
- Cap the bottle immediately — leaving the tip open contaminates the nozzle and can cause cure inside the bottle's dispensing tip. If the tip becomes blocked, warm water will clear it.
- Allow fixture time — do not apply load or vibration for at least 10 minutes. Allow 1 hour for functional service and 24 hours for full rated cure before the assembly goes into demanding service.
- Clean up squeeze-out — wipe any threadlocker that squeezes out of the joint with a dry cloth before it cures. Cured Loctite 222 on external surfaces can be removed with a scraper, but is easier to clean before cure.
Loctite 222 in Australia
Loctite 222 is available from AIMS Industrial across multiple pack sizes to suit individual trade use through to production application. The Loctite 222 Low Strength Threadlocker is stocked in the standard 10 mL and larger production sizes. For the full range including activators and other Loctite threadlocker grades, see the AIMS Loctite collection.
Loctite 222 is also available at Bunnings and automotive retailers (Repco, Supercheap Auto) in small consumer packs — typically 5 mL. For trade and production quantities, direct supply through a distributor like AIMS is more cost-effective than retail packaging. The 50 mL and 250 mL bottles are production sizes not typically found at retail.
For guidance on selecting between 222, 243, 271, and the Loctite retaining compounds for specific applications, see our Loctite Application Guide.
FAQ
What is Loctite 222 used for?
Loctite 222 is used to lock small fasteners (M2–M6 / ≤6.35 mm) against vibration-induced loosening, while remaining removable with standard hand tools. Typical applications include instrument screws, optic and scope mounting hardware, bicycle components, grub screws, and small machine screws in electronics housings.
What is the difference between Loctite 222 and 243?
Loctite 222 is purple and low strength (3 Nm breakaway torque, M10 steel), designed for fasteners ≤M6. Loctite 243 is blue and medium strength (13 Nm breakaway torque, M10 steel), designed for fasteners M6–M20. Using 243 on M2–M4 fasteners risks seizing the joint; using 222 on M8+ fasteners provides insufficient vibration resistance. The selection criterion is fastener size.
How long does Loctite 222 take to cure?
Fixture time is 10 minutes on steel at 22°C. Functional cure is reached in 1 hour. Full cure, at which the rated breakaway and prevail torques are achieved, takes 24 hours. Lower temperatures and inactive metal substrates (without Activator 7471) extend these times.
Is Loctite 222 removable after curing?
Yes. Loctite 222 is engineered to be removable with standard hand tools — a screwdriver, allen key, or spanner appropriate to the fastener. The 3 Nm breakaway torque is low enough that no heat is required under normal conditions. If a joint treated with 222 is genuinely seized, gentle heat (80–100°C) will soften the cured polymer and allow clean removal.
Can I use Loctite 222 on stainless steel?
Yes, but Activator 7471 is required. Stainless steel's passive chromium oxide layer prevents the anaerobic cure reaction from proceeding normally. Without activator, the threadlocker will cure slowly and incompletely, resulting in below-spec breakaway torque. Apply 7471 to one surface, allow to dry for 30–60 seconds, then apply 222 in the standard way.
Can I use Loctite 222 on aluminium?
Yes, with Activator 7471. Aluminium — and especially anodised aluminium — has a passive oxide layer that prevents anaerobic cure without a primer. Apply 7471 to the female thread before applying 222 to the male thread. On anodised aluminium (bicycle components, camera equipment), treat the activator as mandatory.
Can Loctite 222 be used on plastics?
Not recommended for most plastics. Loctite anaerobic threadlockers use a methacrylic ester carrier that can attack ABS, polystyrene, and polycarbonate — causing crazing, swelling, or dissolution of the plastic. For plastic-to-plastic or metal-into-plastic thread applications, use Loctite 401 with Loctite 770 primer instead.
What is Loctite 222MS?
Loctite 222MS is the Mil-Spec version of Loctite 222, certified to MIL-S-46163A Type 1 Grade K. It is chemically identical to standard 222 but is tested, packaged, and documented to military procurement specifications. It is sold in 6 mL bottles and used in defence, aerospace, firearms manufacturing, and precision industries where MIL-spec materials are required. For commercial use, standard Loctite 222 is appropriate.
What size fasteners is Loctite 222 designed for?
Loctite 222 is specified for fasteners up to 6.35 mm (1/4 inch) in diameter — metric M2 through M6. For M8 and above, use Loctite 243 (medium strength, blue). Using 243 on fasteners below M6 risks over-torque failure on removal; using 222 on M8+ provides insufficient vibration resistance.
Do I need Activator 7471 with Loctite 222?
Only when the substrate is an inactive metal — stainless steel, aluminium, zinc, titanium, or cadmium-plated fasteners. On steel and iron, Loctite 222 cures without activator. On inactive metals, omitting 7471 will produce incomplete cure and below-spec performance. Apply 7471 to one surface, allow to dry, then apply 222 normally.
What is the breakaway torque of Loctite 222?
3 Nm on M10 steel at full cure (24 hours, 22°C). Prevail torque is 2 Nm. These values are for steel substrate — stainless steel and aluminium without Activator 7471 will produce lower values. By comparison, Loctite 243 (medium strength) produces 13 Nm breakaway on the same test.
Can I use Loctite 222 on bicycle components?
Yes — 222 is widely used and recommended for bicycle fasteners including stem bolts, cleat bolts, derailleur limit screws, and saddle rail clamps. Most bicycle fasteners are M4–M6 aluminium, and 222 is the correct grade: it holds against road vibration while remaining removable for regular service without damaging anodised aluminium threads. Loctite 243 is too aggressive for most aluminium bicycle fasteners.
Is Loctite 222 the same as purple Loctite?
Yes. "Purple Loctite" refers to Loctite 222. Henkel colour-codes its threadlocker range: purple = low strength (222), blue = medium strength (243), red = high strength (271/277). Any purple Loctite threadlocker is a low-strength, removable product for small fasteners.
What temperature can Loctite 222 withstand?
Loctite 222 has a service temperature range of −55°C to +150°C when fully cured. For sustained service above 120°C, verify performance with Henkel's high-temperature data — elevated temperature over extended periods can reduce prevail torque. For applications above 150°C, consider Loctite 272 (high-temperature anaerobic threadlocker).
Can Loctite 222 be used on firearm and optic screws?
Yes — 222 and its Mil-Spec equivalent 222MS are the standard threadlocker specification for scope ring screws, base screws, and optic mounting hardware. The low breakaway torque (3 Nm) is calibrated for small fasteners that must hold against recoil vibration while remaining removable for adjustment without tools that would damage the mount or receiver. 222MS is the preferred grade for defence and precision applications requiring MIL-S-46163A certification.
What is the shelf life of Loctite 222?
Unopened Loctite 222 has a shelf life of 24 months from the date of manufacture when stored at 8–21°C in its original, sealed container. Once opened, use within 12 months and ensure the cap is replaced immediately after each use. Store away from heat, direct sunlight, and metal tools — contact with metal can initiate cure in the bottle tip. Do not refrigerate.