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Description / Abstract:
This standard covers the requirements for a high temperature,
corrosion resistant coating with friction control. This coating is
for ferrous parts only.
Material Description.
This coating is a dipspin or spray type coating which provides
corrosion protection in operating range from -50 °C to 450 °C. The
coating is a baked on base coat providing corrosion protection. A
lubricant-integrated topcoat or additional lubricant maintains
consistent friction and is an integral part of an approved coating
systems.
Symbols. Not
applicable.
Typical Applications.
This coating is suitable for externally threaded parts (size M6 or
greater) and non-threaded ferrous parts where high levels of
corrosion protection at high temperature are required. The dip-spin
process is not recommended for the following:
• Bolts smaller than M6
• Parts with recessed features (such as internal drive
screws)
• Loose washers of all sizes
• Internally threaded parts (nuts)
Remarks.
Dip-spin Coating is a Bulk
Process. If parts are prone to nesting, stick together (flat
washers), or easily damaged by mechanical tumbling, do not use
dip-spin coating method. Alternatives include spray and dip-drain
methods.
Use of this coating system on threaded surface and/or bearing
surface of joints could affect the torque-tension relationship. It
is recommended that a torque-tension study of the fastener joint be
performed before releasing this finish on any new application.
Polytetrafluoroethylene (PTFE) shall not be used in topcoat or
lubricant for this specification due to the expected high operating
temperatures.
This coating process does not generate hydrogen; however,
pre-treatment processes, i.e., acid pickling, could cause hydrogen
adsorption. See precautions in 3.1.1.
The corrosion performance is influenced by part geometry,
substrate material, and application process. The coating systems
approved to this specification were tested to meet all requirements
using common steel parts. For new designs, applications, and parts
with complex geometries, or difficult to clean material such as
castings and powder metal, extra validation testing is highly
recommended.
Special design and process consideration must be made when
applying this coating on surfaces that are part of a clamped joint.
This includes the bearing surface against which the bolt underhead
comes in contact. On a bolt, stud, or screw, this includes the
underhead bearing surface. Excessive coating may creep resulting in
loss of clamp load.