• Threadlocker Facts, References & Resources

    For some, threadlockers are a mystery. For others, they are an everyday tool. Often known by simply their color and the generic (but trademarked brand) name "Loctite," they provide a way of keeping threaded fasteners from vibrating loose. This article attempts to explain (without going into excruciating detail) how threadlockers work, discusses the three basic types of threadlockers and their respective uses, and also provides information on what brands are available for retail purchase. Links to manufacturer's websites are included.

    Definition:

    • Threadlockers are generally used to keep threaded fasteners from loosening due to vibration.
    • They are usually based on a methacrylate compound which is an anaerobic compound. It polymerizes (cures, or hardens) in an oxygen-free environment free of oxygen, such as between the threads of tightened machine screws and bolts.
    • Threadlockers provide increased corrosion resistance where applied.
    • The breakaway strength of threadlockers decreases with an increase of temperature.
    • Generally speaking, threadlockers use the electrochemical properties of the metal with which they are in contact to help form the molecular bonds that cause them to polymerize. In some cases, when used exclusively with inactive metals, the cure time increases and the end strength decreases. When used with inactive metals, a primer is helpful to fully activate the appropriate molecular activity needed for complete polymerization.
    • Active metals include:
      • Brass
      • Steel
      • Bronze
      • Commercial aluminum
      • Copper
      • Iron
      • Kovar®
      • Manganese
      • Monel®
      • Nickel



    • Inactive metals include:
      • Anodized aluminum
      • Cadmium
      • Chemical black oxide
      • Galvanized steel
      • Gold
      • Inconel®
      • Magnesium
      • Magnetite steel
      • Brightly plated parts
      • Pure aluminum
      • Silver
      • Stainless steel
      • Titanium
      • Zinc


    Scope:
    This article will address the three main types of threadlockers designed for threaded metal fasteners.
    The following types of threadlockers will not be discussed in this article:
    1. Threadlockers designed for plastic threaded fasteners,
    2. Penetrating threadlockers that can be applied to an already tightened fastener
    3. Threadlockers designed for extremely limited and specialized applications, such as some types used only in military and aerospace applications.


    Manufacturers
    :
    There are several primary brands of threadlockers available in the USA:
    • Turbo-Lock® (Palm Labs, Inc., an independent company in South Carolina)
    • Loctite® (a division of Henkel AG & Co.)
    • Permatex® (owned by Illinois Tool Works, Inc.)
    • Devcon® (ITW Devcon, Inc. A division of Illinois Tool Works, Inc.) (Note: Devcon markets Permatex threadlockers)
    • 3MTM Scotch-WeldTM (3M Company) (Note: formerly marketed under the "Rite-Lok" brand name)
    • There are likely other brands, especially in countries outside the USA.

    Types of threadlockers:
    1. Low Strength Threadlocker: Generally this is a PURPLE liquid or gel that is designed for small fasteners up to approximately 1/4". When using this type of threadlocker, parts are easily removable with hand tools. The breakaway torque strength for this type of threadlocker at room temperature is generally between 10 and 80 inch pounds, depending on the size and type of fastener.

    This type of threadlocker is available as
    Turbo-Lock® Threadlocker Purple Removable



    Permatex® Low Strength Threadlocker PURPLE



    Loctite® 222 threadlocker is no longer marketed by their consumer products division, so it is not available in retail stores such as Lowe's or Home Depot. However the product is still manufactured, but it is now marketed exclusively through the industrial division of Loctite. It is available at industrial supply companies such as McMaster Carr, Fastenal, and Grainger. It is also available at mail order and internet firearms parts suppliers such as Brownells and MidwayUSA.


    3M Scotch-Weld thread locker TL-22

    2. Medium Strength Threadlocker: Generally this is a BLUE liquid or gel that is designed for fasteners from 1/4" up to approximately 3/4" (approximately 6-19 mm). When using this type of threadlocker, parts are still removable with hand tools. This type of threadlocker is also suited for less reactive metals such as stainless steel. The breakaway torque strength for this type of threadlocker at room temperature is generally between 10 and 180 inch pounds, depending on the size and type of fastener.
    This type of threadlocker is available as
    Turbo-Lock® Threadlocker Blue Removable



    Permatex® Medium Strength Threadlocker Blue



    Loctite® Threadlocker Blue 242


    3M Scotch-Weld thread locker TL-42


    3. High Strength Threadlocker: Generally this is a RED liquid or gel that is designed for either large fasteners (up to ~1" or 25 mm) or for permanent installations which do not normally need to be disassembled. Generally breakaway torque for this type of threadlocker decreases with a rise of temperature. Disassembly of a fastener on which high strength threadlocker is used usually requires a generous application of heat, usually with a torch or heat gun. The breakaway torque strength for this type of threadlocker at room temperature is generally between 150-400 inch pounds, depending on the size and type of fastener.

    There are special variations of this high strength threadlocker designated for the following uses:


    1. High strength situations
    2. High temperature environments
    3. Large diameter fasteners (greater than 1" or 25 mm)
    4. Permanent fastener installations

    This type of threadlocker is available as
    Turbo-Lock® Threadlocker Red Permanent


    Permatex® High Strength Threadlocker Red

    Loctite® Threadlocker Red 271


    3M Scotch-Weld thread locker TL-71

    Conclusions:
    • This author has used low strength purple threadlocker on his firearms for many years and has never had a threadlocked fastener work itself loose. Purple threadlocker is recommended for most firearms-related applications.
    • Some individuals prefer the medium strength blue threadlocker, however in this author's opinion, the extra strength afforded by the blue theadlocker is not normally necessary.
    • Red threadlocker is not recommended for use with firearms due to the inherent desire/requirement for periodic disassembly.
    • In comparing retail pricing, Palm Labs Turbo-Lock® Threadlocker is significantly less expensive than the other brands mentioned in this article. Palm Labs Turbo-Lock® Threadlocker is not sold through as many retail locations as many of the other brands, but is also available directly from the manufacturer either in small amounts, or case quantities with an additional discount.


    Acknowledgements:


    Disclaimers:
    • The author has obtained no remuneration, financial or otherwise, and no "free samples" from any organizations mentioned.
    • All brands and company names, logos, and images are copyrighted and trademarked by their respective owners.
    Comments 4 Comments
    1. Ed Carey's Avatar
      Ed Carey -
      Excellent write up, I've been looking for this type of info for a while thank you

      Ed
    1. lew42's Avatar
      lew42 -
      I too have been looking for this type of information and I appreciate the effort that you put into the research. Thank you.
    1. Ravenhurst's Avatar
      Ravenhurst -
      There's also a green 290. Aptly known as mean green, if you use too much of it.
    1. thomae's Avatar
      thomae -
      Quote Originally Posted by Ravenhurst View Post
      There's also a green 290. Aptly known as mean green, if you use too much of it.
      Right you are, but that is for bolt/nut assemblies that are already put together. It is a penetrating adhesive, and as such I didn't cover it in my article. I was concentrating only on the threadlockers that are applied prior to assembly.