Threadlocker on oily threads
In practice, threads are rarely grease-free: cutting, lubricating, and corrosion-inhibiting oils remain on the component. Anaerobic threadlockers can tolerate light oil films – but only the right type, applied correctly, provides reliable locking. This article shows which product adheres to oily threads and what you need to pay attention to.
To the point
Choose an oil-tolerant, medium-strength threadlocker such as LOCTITE 243 or a medium-strength Permabond product. Light industrial oils are tolerated; however, heavy soiling and grease must still be removed. On passive metals (stainless steel, galvanized steel), an activator will accelerate curing.
How anaerobic threadlocker works
Anaerobic adhesives cure in the absence of air and in the presence of metal ions as a catalyst – precisely between the tightly fitting thread flanks. Any adhesive that oozes beyond the threads remains liquid. Oil-tolerant types are formulated to absorb or displace small amounts of cutting, lubricating, and corrosion-inhibiting oil. However, the limit is clear: thick layers of grease or standing oil prevent curing – these must be removed (see Surface Preparation Before Bonding).
Passive metals often need an activator
Stainless steel, galvanized, or zinc flake-coated screws are "passive"—they provide few catalyst ions, resulting in slow curing. An activator (e.g., LOCTITE SF 7649 or 7471) helps in this case. It is applied to one side while the adhesive is applied to the other. This also applies at temperatures below approximately 10 °C or with larger gaps. We supply the appropriate activator (more information under Primers and Adhesion Promoters).
Choose the right strength
| Requirement | Loctite | Permabond |
|---|---|---|
| Low strength, easily removable (adjusting screws) | 222 | A1042 |
| Medium strength, oil-tolerant (standard) | 243 | A126 |
| High strength, durable | 270 | A131 |
| High strength + high temperature | 272 | HH 131 |
Low-strength adhesives can be loosened with hand tools, while high-strength adhesives usually require local heating to around 300 °C. A brand comparison can be found under Permabond & Loctite Overview, and their classification within the adhesive spectrum under Industrial Adhesives Comparison.
Application
Remove coarse dirt and grease; apply activator to passive metals; apply threadlocker to the lower third of the internal thread or onto the screw, screw it in, and tighten to the specified torque. Wait for the hand and final strength to be determined according to the data sheet (background: understanding adhesive curing). For general selection, see Selecting & Using Threadlockers Correctly.
Frequently Asked Questions
Will threadlocker adhere to an oily thread? With an oil-tolerant type like Loctite 243, yes, as long as there is only a light film of oil. Thick grease or standing oil must be removed.
Do I still need to degrease? For full strength, yes – oil-tolerant means "tolerates small residues", not "replaces cleaning".
Which type of stainless steel? Stainless steel is passive; use the appropriate strength plus an activator for safe, fast curing.
Consultation and samples
Tell us the thread size, material, oil type, and desired strength – we will recommend a product and, if necessary, an activator, and provide a sample. Contact us or write to info@silitech.ch.
