have periodic physicals during the time you are
working with these coatings.
There are two types of polyurethane systems used
on naval aircraft-the aliphatic type (used in
MIL-C-85285 and TT-P-2756 polyurethane paints)
and the aromatic type (used in polyurethane, rain
erosion-resistant coatings, MIL-C-85322). These
materials present no special hazard to health when
cured (dried), but they require special precautions
during preparation, application, and curing due to the
isocyanate vapors produced. The isocyanates vapors
can produce significant irritation to the skin, eyes, and
respiratory tract even in very small concentrations.
They also may induce allergic sensitization of
personnel exposed to their vapors and mists produced
during spray applications. Aliphatic polyurethane.
MIL-C-85285, is the standard, general-purpose,
exterior, protective coating for aircraft surfaces.
The polyurethane finish comes in kits that consist
of a two-component material resin and a catalyst. The
touch-up kits are prethinned and ready for use when
they are mixed according to the instructions in the kit.
Use aliphatic polyurethane over epoxy polyamide
primer and for touch-up and insignia markings over
polyurethane paint systems only.
Acrylic lacquer (gloss and camouflage)
MIL-L-81352 is the preferred topcoat material for
aircraft markings that identify the reporting custodian
and for propeller safety stripes.
Most enamel finishes used on aircraft surfaces are
baked finishes that cannot be touched up with the same
materials in the field. Minor damage to conventional
enamel finishes ordinarily used on engine housings is
repaired by touching up with epoxy topcoat material
or air-drying enamel.
Elastomeric Rain Erosion-Resistant
Elastomeric coatings are used as a coating system
to protect exterior laminated plastic parts of
high-speed aircraft, missiles, and helicopter rotary
blades from rain erosion in flight. They offer good
resistance to weather and aromatic fuels in addition to
rain erosion. Excellent bonding is obtained after a
7-day drying period.
Repair to these coatings in the field is not practical
due to this long curing time. Kits are available for
repair of coatings where limited touch-up is required.
These kits contain a primer, neoprene topcoat, and
antistatic coating. If the radome or leading edge
coatings are in bad condition, they should be stripped
completely and recoated with epoxy primer and
acrylic topcoat as a temporary measure. If schedules
and conditions permit adequate curing of elastomeric
coatings, the original coatings may be replaced.
The repair kits are normally bought as an open
purchase to ensure that fresh materials are available.
Since heat accelerates aging, repair kits should be
stored in a cool place or refrigerated. Stripping of fiber
glass surfaces should be done according to current
maintenance instructions. Elastomeric coatings are
toxic and flammable, and must be used with care.
The spray gun atomizes the material to be sprayed,
and the operator directs and controls the spray pattern
through manipulation and minor adjustments of the
spray gun. Spray guns are usually classed as either a
suction-feed or pressure-feed type. The type of spray
gun can be determined by two methods-by the type
of container used to hold the paint material and by the
method in which the paint is drawn through the air cap
assembly. For information on the types of spray guns,
refer to NAVAIR 01-1A-509.
The suction-feed spray gun is designed for small
jobs. The container for the paint is connected to the
spray gun by a quick-disconnect fitting, as shown in
figure 4-33. The capacity of this container is
approximately 1 quart. The fluid tip of this spray gun
protrudes through the air cap, as shown in figure 4-34.
The air pressure rushing by the fluid tip causes a
low-pressure area in front of the tip. This causes paint
to be drawn up through the fluid tip, where it is
atomized outside the cap by the air pressure.
The pressure-feed spray gun is designed for use on
large jobs where a large amount of spray material is to
be used. With this type of spray gun, the material is
supplied to the gun through a hose from a pressurized
tank. This spray gun produces a high volume of spray
material metered at a low air pressure. This type of