When to use Loctite Activator with your Loctite Threadlocker


All metals are not exactly the same in their characteristics. That is a widely known fact in the engineering world. And hence, they don’t behave the same in how they interact with substances, in how they can be processed and handled etc. When it comes to bonding in general, and threadlocking specifically, there are two main types of metals to distinguish between: active and inactive metals.

Your typical active metals include iron, plain steel, copper, brass, bronze, nickel, manganese, Monel™ and Kovar™. With any one of these, in most of the typical cases, the bonding (threadlocking included) will work just fine without the use of any activator. You might still optionally use it, usually in the cases when you want to speed up the cure and achieve handling strength faster. But it will also work just fine without.

However, there’s also the other group, the inactive metals, such as (and this list is by no means exhaustive) any plated parts, anodised aluminium (i.e. Alodine® or Iridite™), titanium, stainless steel, galvanized steel, zinc, pure aluminium, cadmium, magnesium, natural or chemical black oxide, magnetite steel, Iconel™ or any of your precious metals such as silver or gold.


With these latter, it really is helpful to use the Loctite SF 7649 activatorbefore applying the threadlocker, to activate the surface and enable the adhesive to achieve the full strength quicker.

Loctite SF 7649 has drying time of 30-70 seconds. However, it has on-part life of 30 days, which means you can spray it on your parts ahead of time in a separate phase of your process and have them ready to be built in when the time for that comes.

To summarize what the activator does:

When to use activator_temp_gaps_deep thrds

  • Shortens the cure time on any type of metal
  • Activates the inactive surfaces to promote adhesion
  • Promotes adhesion in cold temperatures
  • Promotes curing / adhesion where there are larger gaps or deep threads

Feel free to visit our website for more information on Loctite Threadlockers (you can select a different language or country in the navigation at the top of the page).

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