TM 1-1500-204-23-9
NOTE
The wrong thinner may destroy certain
characteristics of a coating material
without
immediately
giving
visual
evidence in the wet state.
viscosity due to evaporation will require corrective
additions. However, some coatings which undergo
chemical processes, such as polymerization to create a
film, cannot be thinned beyond a certain point and
remain useable; nor can they be brought back to the
correct viscosity by thinning after the chemical action
has progressed beyond a critical point. This is the case
with epoxy and polyurethane.
(2)
Thinning shall be controlled by weight,
volume, or viscosity measurement to obtain and
maintain proper and uniform consistency. If there is no
specification covering the coating, thin according to
manufacturer's instructions.
NOTE
Do not mix coatings of the same
specification but supplied by different
manufacturers during application. This
will avoid problems of incompatibility in
the liquid and curing phases.
(3)
Strain all material to be used in spray
equipment through clean 60-90 mesh metal strainers in
accordance with paint or equipment manufacturer's
instructions.
n.
Painting Difficulties and Remedies. Common
painting difficulties and ways to fix them are described
in the following paragraphs.
(1)
Coating troubles. Coating troubles may
be divided into six groups: (1) Inadequate surface
preparation
(including
temperature),
(2)
incorrect
methods or techniques of application, (3) unusual and
unsuitable climatic and atmospheric conditions, (4)
unsuitable and improperly adjusted equipment, (5) faulty
finishing surface or improperly mixed or agitated
components and (6) systems not purged of previously
mixed materials. An experienced finisher may be
capable of adjusting to obtain proper results with faulty
materials, but this is an emergency measure only and
must be with the cognizance and authority of the quality
control facility. The practice is not advised. Incorrect
methods of application should be discontinued upon
discovery of the discrepancy. Areas painted prior to the
discovery of such discrepancies must be inspected and
remedial
measures taken when necessary. Brushing and roller
coating on certain surfaces must be used in confined
areas. Remedying incorrect applications, however, also
calls for training. The practice of allowing inadequately
trained personnel to apply Military Specification MIL-C-
46168
coatings
is
unauthorized
and
dangerous.
Unusual
or
unsuitable
climatic
and
atmospheric
conditions are normally not a problem since manual
spray painting must be accomplished in an approved
facility which usually compensates for such conditions.
Unsuitable or faulty equipment can only be remedied by
obtaining proper equipment or repair. TM 55-
150034523 shows common troubles of spray coating
operations' with suggested remedies or methods of
avoidance.
(2)
Spray patterns. Faulty spray patterns and
suggested corrections are shown in TM 55-1500-34523.
(3)
Blushing. Blushing of coatings is the
result of water condensation from the atmosphere
within, or on, an applied organic film. It occurs when the
temperature of the work surface falls below the
prevailing dew point. (It shall always be looked for in
production coating whenever other than average
atmospheric conditions prevail. ) It shows as a lighter
than normal or bleached discoloration or increased
opaqueness of the film. It may occur to the extent that a
surface powder develops which can be removed by
fingernail or by light rubbing. (Rubbing will not cure the
condition. ) It may be almost imperceptible, and
blushing inducing conditions may escape notice on test
panels sprayed prior to production coating due to the
temperature differences between test and production
environment. Though MIL-C-46168 painted items are
not
susceptible
to
water
or
moisture
damage
immediately after proper application to items, great care
must be taken to avoid surface condensation prior to
coating or water induction, in any form, into unmixed
components or the mixture prior to or during application.
Water will not affect the cure process after proper
application. Water will affect paints other than plural
component catalytic paints.
o.
Finish Painting. MIL-C-46168 is the Army
standard tactical topcoat for ground support equipment.
(1)
Preparation of MIL-C-46168 polyurethane
paint. Preparation of this paint is detailed in the
following procedures:
(a)
Polyurethane, MIL-C-46168 paint is
a plural component, low reflective paint formulated to be
lead and chromate free. The components of this paint
must be thoroughly mixed prior to pouring into the
application container when transfer is necessary. Care
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