Thread Sealants

Thread sealants seal threaded pipe and fitting connections against pressure leaks while still letting the joint be tightened correctly and, on the lower-strength grades, disassembled later for service. AIMS Industrial stocks the Loctite anaerobic thread sealant range in depth — five grades covering fine hydraulic threads through to coarse gas and steam pipework, each with its own strength, temperature range and certification. This is a specific, well-defined chemistry family (anaerobic, cures in the absence of air between close-fitting metal threads) — not to be confused with our gasket sealants range, which seals flat flange faces rather than threaded connections, or our separate pipe sealants range, which covers PTFE-tape alternatives like pipe sealing cord and plastic-safe pipe sealant. If you're weighing up which one to choose, our Thread Locking & Sealing: Loctite, PTFE & Anaerobic Sealant Guide is a good place to start.

Quick Reference — Loctite Thread Sealant Grades

All five grades are anaerobic, methacrylate-based thread sealants that cure when confined between close-fitting metal threads. The right one for your job comes down to breakaway torque (how strong the cured seal is, and whether it can be undone with hand tools), temperature range, and whether your application needs a specific gas or water certification.

Reading the torque numbers: a lower breakaway torque (12 N·m on Loctite 567) means the joint can be broken with ordinary hand tools for future service. A higher figure (33 N·m on Loctite 577) means a firmer, more permanent hold — better vibration resistance, but more effort required to disassemble. Match the grade to whether the joint will ever need to come apart again.

How anaerobic thread sealants work

Every product in this range cures anaerobically — in the absence of air — when squeezed between two closely fitting metal threads. Applied to the male thread, the liquid or paste fills the microscopic gaps between the crests and roots of the thread, then hardens once air is excluded by tightening the joint: an instant low-pressure seal on assembly, followed by a full cure over some hours that locks against vibration and shock. Because the seal forms inside the thread engagement rather than as a wrap around it, anaerobic sealants generally outlast PTFE tape on a joint that stays assembled long-term.

The trade-off is that anaerobic sealants need genuine metal-to-metal thread contact to cure — they won't cure across a gap, on plastic fittings, or on threads heavily contaminated with oil or old sealant residue (Loctite 577 is the exception, formulated to tolerate light contamination). Working on plastic pipe, or over an old, un-degreased joint? That's a different product family — see Companion Ranges below.

Certifications that matter on Australian jobs

• AGA (Australian Gas Association) Approval — Loctite 567 (Approval No. 3207 Class III) and Loctite 569 (Certificate No. 3375 Class III, rated to 2000 kPa working pressure) both carry AGA approval, relevant for gas-service pipework in Australia. Always confirm the approval covers your specific gas type and pressure before specifying.
• DVGW — the German gas and water utility certification (EN 751-1) carried by Loctite 542, and one of the three certifications on Loctite 577. Widely referenced internationally as a benchmark for gas-tight thread sealants.
• WRAS and NSF — water-regulation and public-health certifications carried by Loctite 577, relevant where a sealant needs to be acceptable for water-system use. Check the specific certificate against your water authority's requirements before use on potable water.
• UL listing — Loctite 567 is UL listed, a recognised safety-testing mark relevant to plumbing and industrial fluid systems.

These certifications are exactly what's printed on the product's own technical data sheet — if your job has a specific compliance requirement, check the current TDS or ask our team to confirm before you order.

Choosing the right grade

• High-pressure hydraulic fittings, fine threads: Loctite 542 (medium strength, DVGW approved) or Loctite 569 (hydraulic-grade, AGA gas certified to 2000 kPa) depending on whether gas certification is needed.
• Coarse pipe threads, high temperature, gas or steam service: Loctite 567 — rated to +200°C with AGA and UL approval, and its high lubricity avoids galling on stainless steel.
• Contaminated or lightly oily threads, general industrial use: Loctite 577 — the only grade in this range formulated to cure reliably on threads that haven't been perfectly degreased, and the only one with the DVGW/NSF/WRAS triple certification.
• Instant low-pressure seal for pressure testing: Loctite 565 PST — designed specifically to hold pressure for testing straight after assembly.
• Joint that must come apart again with hand tools: favour the lower-torque grades (565, 567) over 577, which holds at a firmer 33 N·m.

Applying anaerobic thread sealant correctly

Apply a bead to the male thread only, leaving the leading one to two threads bare so sealant doesn't squeeze into the bore and contaminate the system fluid. Assemble and tighten to spec while the joint is still wet — anaerobic sealants need to be confined between the mating metal surfaces to cure, so a joint left open to air too long won't seal properly. Full cure typically takes several hours; the low-pressure "instant seal" on assembly isn't full cure strength, so don't pressure-test to maximum working pressure until the datasheet's cure time has passed.

What to avoid

• Don't mix chemistries on one joint — PTFE tape residue on a thread will stop most anaerobic sealants curing properly (Loctite 577 is more tolerant of light contamination than the others, but a full wrap of tape underneath any anaerobic product is asking for trouble).
• Don't use anaerobic thread sealant on flare or O-ring fittings — those seal on the metal-to-metal flare face or the elastomer itself, not on the threads. Sealant on the threads does nothing useful there and can interfere with correct seating.
• Don't assume gas certification carries across grades — AGA approval is specific to Loctite 567 and 569 in this range; the others aren't gas-certified, so check before using on gas pipework.

Companion ranges at AIMS

This range is Loctite's anaerobic thread sealant line specifically — five grades for metal-to-metal threaded connections. A few related jobs are covered elsewhere in our range:

• Pipe sealants — for plastic-safe pipe sealant (Loctite 5331), pipe sealing cord and insulating/sealing wrap: alternatives to a liquid anaerobic sealant, useful on plastic fittings or where tape-style application suits the job better.
• Gasket sealants — RTV silicone and anaerobic gasket eliminators for flat flange faces (engine covers, gearbox housings, pump casings). Different job entirely — thread sealants seal threads, gasket sealants seal flanges.
• Threadlockers — for securing a fastener (bolt, stud, nut) against vibration loosening, rather than sealing a threaded pipe connection against pressure.
• Retaining compounds — for bearings, bushes and cylindrical parts that need to be locked in place, a different job again from thread sealing.
• Full Loctite range — browse the complete Loctite adhesive, sealant and threadlocking line-up from AIMS.

Order from AIMS

Not sure which grade suits your pressure, temperature and certification requirements? Give our team a call on (02) 9773 0122, reach out through our contact us page, or request a quote for trade or volume pricing. We're a proudly Australian-owned industrial supplies business — Sydney-based with a support team in Manila — and we're happy to talk through the right thread sealant for your job before you order.

People Also Ask

What's the difference between a thread sealant and a threadlocker?

A thread sealant seals a threaded pipe or fitting connection against pressure leaks — it's about stopping fluid or gas escaping through the thread. A threadlocker secures a fastener (bolt, screw, stud) against vibration loosening — it's about keeping the fastener tight, not sealing against pressure. Some anaerobic products do both to a degree, but they're formulated and rated for different jobs, so use the one designed for yours.

Can I use PTFE tape and Loctite thread sealant together?

Generally no. PTFE tape residue on the thread stops most anaerobic sealants curing properly, because the tape breaks the metal-to-metal contact the sealant needs to cure. Loctite 577 is more tolerant of light surface contamination than the other grades in this range, but a full tape wrap underneath any anaerobic sealant risks a joint that neither cures nor seals correctly. Pick one chemistry for the joint, not both.

Which Loctite thread sealant should I use for hydraulic fittings?

Loctite 542 and Loctite 569 are both positioned for hydraulic fine-threaded fittings. Loctite 542 is DVGW approved and rated -55°C to +150°C with a 15 N·m breakaway torque. Loctite 569 is an activator-cure hydraulic-grade sealant with AGA gas certification (Certificate No. 3375, Class III) rated to 2000 kPa working pressure. Choose 569 if you specifically need gas certification alongside hydraulic duty; otherwise 542 covers general hydraulic and pneumatic fine threads.

Are these thread sealants approved for gas pipework in Australia?

Two grades in this range carry Australian Gas Association approval: Loctite 567 (AGA Approval No. 3207, Class III) and Loctite 569 (AGA Certificate No. 3375, Class III, rated to 2000 kPa). The other three grades in the range — 542, 565 and 577 — aren't AGA certified, so check the specific approval against your gas type and pressure before specifying any of these for gas service.

What's the difference between Loctite 567 and Loctite 577?

Loctite 567 is a low-strength, high-temperature paste (12 N·m breakaway torque, -55°C to +200°C) designed for coarse metal pipe threads and rated for hand-tool disassembly — it's UL listed and AGA gas approved. Loctite 577 is a medium-strength gel (33 N·m breakaway torque, -55°C to +150°C) formulated to cure reliably even on lightly contaminated or oily threads, and carries DVGW, NSF and WRAS triple certification. Pick 567 for high-temperature or gas-service coarse threads that may need servicing; pick 577 for general-purpose sealing where the thread condition isn't perfectly clean.

Do I need a primer to use these thread sealants on stainless steel?

Loctite 567 is formulated to cure on stainless steel, galvanised steel and aluminium without a primer, and its high lubricity specifically helps prevent galling on stainless threads during assembly. Loctite 577 is also formulated to cure on both active and passive metals without a primer. If you're working with an unusual or highly passive alloy outside these two, check the current technical data sheet or ask our team before assuming primerless application will work.

How do I remove a cured anaerobic thread sealant to disassemble a joint?

For the lower-strength grades in this range (Loctite 565 and 567, both rated for hand-tool removal), a standard wrench or spanner with normal breakaway force should free the joint. For medium-strength grades (542, 577), expect more resistance — heating the fitting slightly can soften the cured sealant and make disassembly easier, similar to freeing a threadlocked fastener. Always match the sealant's strength grade to whether the joint needs to be serviceable before you apply it.