TM55-1500-345-23
paint and one volume of MIL-T-81772 thinner. The
b. Areas Not to be Painted (Specific). Do not
paint must be thoroughly mixed with the thinner
prime or apply any paint to any of the following
and continuously agitated during application.
surfaces on OH-6 helicopters.
Where quantities permit, and to eliminate
d.
(1) Bolts, externally relieved (4 each per
the 30 minute deaeration time and potential
aircraft) located at the outboard end of each main
waste, plural component spray units can be used
rotor pitch housing.
which automatically and proportionally mix the
two components directly at the spray gun nozzle.
(2) Pins, main rotor (4 each per aircraft)
Since the two components are kept separate, the
located at the inboard trailing edge of each main
pot life consideration is also eliminated.
rotor blade.
The polyurethane paint can also be
(3) Pins, main rotor blade (8 each per air-
e.
applied by conventional, airless, or electro-static
craft) located at the root end of each main rotor
spray equipment. In cases where this type of
blade.
equipment is used, the viscosity can change. The
applicator should check with the paint company
4-3. PREPARATION OF
MlL-C~46168
and equipment supplied for the exact criteria for
POLYURETHANE PAINT.
viscosity, thinning and the best application pro-
Polyurethane, MIL-C-46168 paint is a
a.
cesses.
plural component, low reflective paint formulated
f.
Whatever spray equipment is used, it is
to be lead and chromate free. The components of
necessary that all spray guns, lines and nozzles,
this paint must be thoroughly mixed prior to pour-
when applicable, be thoroughly cleaned after use
ing into the application container when transfer is
to prevent hardening of the coating system. If the
necessary. Care should be taken that all of the
coating hardens in the system, the system cannot
pigment matter has been included in the mixture.
be cleaned. That portion of the unit in which the
paint has gelled or hardened, must be discarded.
--
b. Mixing and application equipment. Mixing
MIL-C-46168 paint may be applied over a
g.
requirements for the two component polyure-
wide range of temperatures. Temperatures from
thane paint, when applying by conventional air
50 F (24 C) to 90 F (32 C) are recommended for
atomized or airless spray is to mix four parts of
best results.
Component A, which is the polyester portion, to
one part of Component B, which is the catalyst or
NOTE
isocyanate portion. After the two components are
mixed, the total mixture is left to stand for at least
MIL-C-46168 paint is a catalytic paint
30 minutes to deaerate. The mixture (batch) is
and will cure under most atmospheric
then thinned to the proper viscosity depending
conditions after application. However,
upon the spray equipment. The mix at the speci-
at very low temperature, curing is
fied ratio will produce a pot life of eight hours.
retarded.
Therefore. no more paint should be mixed than
can be used in an eight hour shift or period.
Test the mixture, pressure and spray
h.
equipment settings by applying a test coating to
masking paper or similar smooth surfaces prior to
c.
MI L-C-46168 paint must be thinned to
application to aircraft or components. Adjust
spraying viscosity, determined by the user and the
paint and/or equipment until proper test coating is
type of spraying equipment to be used. A
achieved. Paint and equipment are then ready for
suggested starting point is obtained by mixing
application to aircraft or components.
approximately four volumes of mixed MIL-C-46168
