Threadlocker
Threadlocker turns up in 2 fields: adhesives, fasteners. Here is what it means to the people in each one.
Threadlocker in adhesives
An anaerobic adhesive applied to fastener threads to stop them loosening from vibration.
Threadlockers fill the gaps between mating threads and cure into a solid plastic that blocks loosening and seals out moisture. Strengths are color-coded by common convention: purple for low strength on small screws, blue for medium strength removable with hand tools, red for high strength that usually needs heat around 250 C to break, and green for thin wicking grades applied after assembly. They come as liquids, sticks and pre-applied coatings.
"Threadlocker on all the motor mount bolts, blue only, maintenance has to get these out."
Threadlocker in fasteners
An anaerobic adhesive applied to threads that hardens between metal surfaces to stop loosening and seal.
A liquid or gel that stays fluid in air but cures into a hard plastic when confined between metal threads without oxygen. Strength follows a common color code: purple low strength for small screws, blue medium strength removable with hand tools, red high strength that needs heat of about 250 C to release, and green wicking grade that seeps into already assembled threads. Inactive surfaces such as stainless and zinc plating cure slowly unless a primer is used.
"Blue threadlocker on the caliper bracket bolts, red stays on the shelf unless you want to bring the torch next time."