Pre-Coated vs. Liquid Thread Locking Agents: Which Is Right for Your Application?
Reading Time: 5 minutesLiquid Thread Locking Agents come in two main formats: liquid anaerobic adhesives applied at the point of assembly, and pre-applied coatings already cured onto the fastener at the factory. Liquid Thread Locking Agents, like ThreeBond’s 1300-series, suit flexible, in-house assembly, while pre-applied coatings, like Sealock or ThreeLock, suit high-volume, consistent production lines.
What Is a Liquid Thread Locking Agent?
A Liquid Thread locking Agent is exactly what it sounds like — something applied to a screw, bolt, or nut thread to stop it loosening under vibration, and often to seal the joint against leaks at the same time.
The two main formats differ in one key way: who applies it, and when.
- Liquid Thread Locking Agents are applied by the person or robot doing final assembly, right before the fastener goes in.
- Pre-applied coatings arrive on the fastener already cured, straight from the supplier, ready to install with no extra step on the line.
How Liquid (Anaerobic) Thread Locking Agents Work
Most Liquid Thread Locking Agents, including ThreeBond’s 1300-series, are anaerobic — meaning they only cure in the absence of air.
That’s actually the clever part. The liquid stays uncured as long as it’s exposed to oxygen so that it won’t harden in the bottle or on the tip of the applicator. The moment it’s squeezed into the confined gap between a bolt and a nut — shut away from air — it reacts and hardens.
In our experience, this is what makes Liquid Thread Locking Agents so flexible to work with:
- Strength is chosen at the point of use — low, medium, or high strength, picked for that specific joint
- No pre-planning required — a technician can grab whichever grade fits the repair in front of them
- Works on a wide range of fastener sizes without needing matched, pre-coated parts
How Pre-Applied Thread Coatings Work
Pre-applied coatings work completely differently. Instead of a liquid reacting at assembly, the fastener supplier coats the screw or bolt threads with a dry, non-tacky film before it ever reaches your line.
- No liquid handling on the assembly line — nothing to dispense, mix, or clean up
- Color-coded by grade for fast visual identification during assembly and inspection
- Ready to install straight out of the box, with locking and sealing already built into the fastener itself
That said, pre-applied coatings aren’t automatically the “better” choice — they require sourcing fasteners that already carry the coating, which means less flexibility if your design changes mid-production.
A Real-World Example: Where the Format Actually Matters
Here’s a scenario we see often.
On a high-volume automotive line — say, thousands of identical engine fasteners a day — stopping to dispense liquid thread locker at every station adds a small amount of time, every single cycle. Multiply that across a full shift, and it becomes a meaningful bottleneck. This is exactly the kind of line where pre-applied coatings, like Sealock or ThreeLock, tend to make more sense — the locking agent is already on the part before it reaches the operator.
Compare that to a maintenance or repair shop, where every job is a little different. A technician might need high strength on one bolt and a removable medium strength on the next, often on fasteners they didn’t choose and can’t pre-order coated. That’s where a liquid thread locker earns its keep — one bottle covers a wide range of jobs without needing matched, pre-coated parts for each one.
We mention this because the “right” format usually isn’t about which product is stronger — it’s about which one fits how your fasteners actually reach the assembly point.
ThreeBond’s Liquid Thread Locking Agents Range at a Glance
| Product | Format | Key Trait | Best For |
| ThreeBond 1303 | Liquid, anaerobic | Low viscosity; reacts on inert plated surfaces without an accelerator | General screw/bolt/shaft fixing and sealing |
| ThreeBond 1305 | Liquid, anaerobic | High strength, permanent; no volume reduction on cure | Permanent fastener locking |
| ThreeBond 1322D | Liquid, anaerobic | Medium strength; phthalate-free | Standard-duty locking and sealing |
| ThreeBond 1324 | Liquid, anaerobic | Medium strength, removable | Fasteners needing occasional disassembly |
| 1360 | Liquid, anaerobic | High strength; heat resistant to 200°C | High-temperature fastener locking |
| 1386D | Liquid, anaerobic (specialty) | Thixotropic — resists sagging into gaps during long assembly waits | Welch plug (cap) sealing |
| Sealock | Pre-applied (factory coating) | Combined sealing + locking; low install torque | Fasteners needing both sealing and locking from the factory |
| ThreeLock | Pre-applied (factory coating) | Nylon-based; rated -50°C to 120°C; allows repeated reuse | Fasteners serviced or removed repeatedly |
| MEC | Pre-applied (micro-encapsulation) | Ranges from temporary to permanent strength | High-vibration environments |
Worth noting separately: ThreeBond also makes 1401B and 1401C, brush-on removable locking agents. These sit in a middle category — applied manually like a liquid thread locker, but working as a dry coating rather than an anaerobic cure, and designed specifically for fasteners that need to come off with a known, controlled amount of extra torque.
Choosing the Right Liquid Thread Locking Agents: What to Consider
A few questions tend to settle the choice quickly:
- Is this a high-volume production line, or variable repair work? Pre-applied coatings favor consistent, repeated assembly; Liquid Thread Locking Agents favor flexibility.
- How much strength do you actually need? Permanent high-strength joints and serviceable medium-strength joints call for different products within the same format.
- Will this fastener face high heat? 1360‘s 200°C rating and ThreeLock’s -50°C to 120°C range aren’t interchangeable — check your actual operating temperature
- Does the joint need to come apart again? Some products, like 1324 and ThreeLock-TB2365B, are specifically built with controlled removability in mind.
None of these questions has a one-size-fits-all answer — the right product depends on your fastener size, material, and how the assembly is actually built.
Frequently Asked Questions
Can pre-applied thread coatings be reapplied after a fastener is removed?
It depends on the product. ThreeLock is specifically designed to allow repeated use of the same coated screw, but this isn’t true of every pre-applied coating — always check the specific product’s rating before reusing a fastener.
Are anaerobic Liquid Thread Locking Agents always permanent?
No. Anaerobic liquid thread locking agents come in a range of strengths, and several, like ThreeBond 1324, are formulated to be removable with the right amount of torque. High-strength grades like 1305 are intended for permanent fixing, but “anaerobic” describes the cure mechanism, not automatically the strength.
Do pre-applied coatings need to react with metal the way anaerobic adhesives do?
No — that’s actually the core difference. Pre-applied coatings are already cured before the fastener is installed, so there’s no air-exclusion reaction happening at assembly. Anaerobic Liquid Thread Locking Agents specifically depend on that reaction, which is why they only harden once confined in the joint.
Final Thoughts
Choosing between a pre-applied coating and a liquid thread locking agents usually comes down to one practical question: does your fastener arrive pre-coated and ready to install, or does locking strength need to be decided at the point of assembly?
High-volume, consistent production lines tend to favor pre-applied coatings like Sealock or ThreeLock, while flexible or variable assembly and repair work tends to favor liquid anaerobic options from the 1300-series.
As with any fastener decision, checking the specific product’s data sheet — particularly for temperature range and removability — remains the most reliable way to confirm the right fit before committing to full-scale use.
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