Class I is a rain erosion-resistant coating that is
furnished in kit form. This kit consists of a primer,
accelerator, diluting solvent, and neoprene.
Class II is a rain erosion-resistant coating with an
additional surface treatment to minimize radio noise
This coating is also supplied in kit form and consists of
a primer, accelerator, diluting solvent, neoprene, and
These kits (MIL-C-7439, Classes I and II) are
packaged unaccelerated to provide longer shelf life.
The neoprene is ready to use only after the catalyst
(accelerator) has been added. The material in these kits
should be mixed and applied in accordance with the
instruction sheet supplied by the kit manufacturer.
Observing Safety Precautions
The following general safety precautions should be
observed when you make repairs to reinforced plastic
components. You should review these safety
precautions before attempting any repairs to reinforced
1. Local station safety regulations as to fire and
health hazards must be complied with.
2. All solvents are flammable; therefore, observe
proper handling procedures.
3. Personnel involved in the mixing or handling
of catalyzed resin prior to the curing operations should
wear rubber gloves. After using rubber gloves,
personnel should clean their hands with soap and water
and rinse with vinegar to neutralize any catalyst
Figure 5-15.--Foam-type puncture repair.
4. Never mix the catalyst and promoter together,
as they are explosively reactive as a mixture. Always
materials recommended in the applicable structural
mix the promoter with the resin first, and then add the
repair manual for refinishing both the interior and
catalyst to the mixture.
exterior surfaces of reinforced plastic components.
5. The toxicity of polyester formulation has not
Reinforced plastic components whose frontal areas
been definitely established. Some of the components
are exposed to high speeds are frequently coated with a
are known to cause nasal or skin irritation to certain
rain erosion coating. Rain erosion coatings protect the
individuals. Adequate ventilation should be provided.
component against pits that are caused by raindrops
6. The sanding operation on glass cloth
hitting the component at high aircraft speeds. These pits
reinforced laminates gives off a fine dust that may cause
or eroded areas can cause delamination of the
skin, eyes, or respiratory irritations. Inhalation of
component glass cloths if allowed to progress
excessive amounts of this dust should be avoided.
Protection should be provided for respiration, eyes, and
Rain erosion-resistant coatings for reinforced
plastic components conform to Specification
7. Do not store catalyzed resin in an airtight
MIL-C-7439. Coatings that conform to this
container or an unvented refrigerator.
specification are classified as Class I and Class II.