Description / Abstract:
This specification describes the test procedures and performance
requirements used to evaluate the locking ability of preapplied
adhesive coatings on threaded fasteners.
Material Description. The adhesive is
mechanically applied in liquid form to the specified threads on the
fastener. After drying, the fastener is clean and dry and can be
handled normally until it is installed. Upon fastener installation,
the adhesive will be activated and begin to cure. The fully cured
properties are expected 72 h after installation. Three (3) grades
of material are covered by this specification.
Grade A: Regular strength grade for use with
fasteners with serviceability requirements with temperatures up to
135 °C. Lower adhesive strength allows for service removal of bolts
with less potential for fastener and/or mating thread
damage.
Grade B: Higher strength grade with
locking/sealing performance up to 135 °C. Use of this material is
not restricted to larger fastener sizes, but potential service
removal concerns should be considered before use with M6 or smaller
fasteners.
Grade C: Higher strength and temperature
resistant grade with locking/sealing performance up to 200 °C. Use
of this material is not restricted to larger fastener sizes, but
potential service removal concerns should be considered before use
with M6 or smaller fasteners.
Symbols. Not applicable.
Applicability. Threaded fasteners that require
a preapplied adhesive for chemical locking and sealing to prevent
self-loosening due to shock, vibration, and thermal
effects.
Remarks. The preapplied thread locking adhesive
compounds are dry to the touch and remain inert on threaded
fasteners until they are engaged into the mating threads. The
shearing action/forces of assembly activate the adhesive. After
proper cure time and temperature, the adhesive hardens to form a
chemical bond between the mating threads. This bond prevents
loosening of fasteners from shock, vibration, and thermal
effects.
Note: A fastener with preapplied adhesive shall
not be reused.
The preapplied adhesive material approved to this specification
is designed to perform up to the temperatures stated in 1.1. For
severe service conditions, such as higher temperatures, vibration,
and environmental conditions, it is recommended that the fastened
joint be validated using intended components, preapplied material
and process before release.
The performance of the preapplied adhesive material may not
perform as well as expected if coated parts are exposed to
excessive humidity, oil and dirt. It is recommended that coated
parts be handled with care after coating. Similarly, over time, the
coating material will degrade from oxidation and other
environmental effects. If coated parts are to be stored for more
than one (1) year, it is recommended that the appropriate
performance test be performed prior to installation.
Not all finishes (coating/plating) are tested to be compatible
with all GM approved preapplied adhesive materials. It is
recommended that the appropriate performance test be performed to
ensure compatibility.