TM55-1500-345-23
the aircraft and it should be identified by the
b. Coating Thickness Measurements. Wet and
dry film gages are available as local purchase
name of the operator, aircraft model, and the date
items from various laboratory or paint supply
of painting in order to provide follow-up data dur-
houses. If paint film thickness measuring instru-
ing any subsequent service evaluation. The panel
ments are not available, small (5 x 16 inches)
is applied by the use of a small section of one-
anodized aluminum test panels will be employed
inch width masking tape doubled upon itself with
for the measurement of the paint thickness after
the adhesive side contacting the panel and the air-
drying. These panels will be applied to each side
craft surface. Slight errors in paint thickness -
of the fuselage prior to the painting operation.
measurement
can e x i s t d u e t o t h i c k n e s s
One end of the panel should be masked with tape
tolerances permitted by the basic aluminum pro-
for a distance of approximately two inches to pro-
curement specification. This factor must be taken
vide a comparison of the original panel system.
into consideration in the measurement of the
Removal of the panel after application of the
thickness of the paint deposit. Measurement of the
epoxy primer is recommended so that immediate
paint thickness is best accomplished by the use of
touch-up operations can be employed to cover
an ordinary micrometer possessing flat contact
those areas previously protected by the panel. This
surfaces when smooth textured paints are used.
procedure will also permit relocating of the panel
Micrometers possessing pointed or rounded con-
on various portions of the same aircraft to provide
tact surfaces are recommended when extremely
a good indication of the overall paint thickness ap-
rough textured paints are used. At least six
plication. The location of the panel is dependent
readings should be taken on both painted and un-
upon i n s p e c t i o n p r o c e d u r e s a n d m a y vary
painted portions of each test panel to provide an
throughout the aircraft. Each aircraft should
average paint thickness measurement.
possess a panel for each operator employed on
Section
Il.
PRIMERS
3-13. GENERAL.
which are lead and chromate free are
a. U s e , G e n e r a I . P r i m e r s a r e u s e d o n
desireable for most applications and required
metals to provide a coating to which subse-
in applications where lead and zinc chromate
quent coatings will firmly adhere and provide
are prohibited.
protection for the substrate metal against cor-
rosion. The pigment portion of primers for fer-
Use, Aircraft. Primers are used as corro-
b.
rous base metals usually consists of iron ox-
sion-inhibiting coatings on aircaft metal surfaces
ide, chromate, red lead, zinc chromate, zinc
to inhibit corrosion and provide good adhesion for
oxide, zinc dust, or a mixture of these. Zinc
olstrontium chromate is the pigment in some
the topcoat. Primers will conform to Military
Specification
MIL-P-52192,
MIL-P-23377
or
primers u s e d o n s u b s t r a t e s o f m a g n e s i u m ,
MIL-P-85582.
aluminum
and their alloys. Other primers
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