TM 1-1500-204-23-9
(3) Copper and copper base alloys. Mechanical
removal of paint is recommended on copper and copper
alloys where chemical removal would be impractical
because
of
structural
complexities
and
rinsing
difficulties. Proceed as follows:
WARNING
Drycleaning solvent is flammable and
solvent vapors are toxic. Use P-D-680,
Type II Solvent in a well-ventilated area.
Keep away from open flames. Avoid
prolonged solvent contact with skin.
(a) Remove oil, grease, and dirt with dry-cleaning
solvent,
Federal
Specification
P-D-680,
dichloromethane,
MIL-D-6998,
or
trichloroethane,
Federal Specification O-T-620.
(b) Remove paint with brass wire brush or 400
grit abrasive paper. Sand blast with extremely fine grit if
necessary.
NOTE
Do not sand blast braided copper flexible
lines.
(c) Remove loose particles of paint with bristle
brush.
Wipe
area
with
cloth,
moistened
with
trichloroethane, Federal Specification 0-T-620.
e. Surfaces to be painted will be cleaned prior to
painting and prior to the application of the chemical
treatment process or processes listed in TM 55-1500-
333-24. Cleanness is determined by the following steps:
(1) The water break test is a method of evaluating
the degree of cleanliness of a metal surface. It is based
on the ability of a clean surface to sustain an unbroken
film of water. Test representative areas of the surface
to be painted by projecting distilled water on it using an
atomizing device such as a nasal atomizer. Do not use
a paint sprayer for this pulse as the excessive pressure
will defeat this test. Read results as follows:
·
If water gathers into separate droplets
within 25 seconds (that is, if the surface
shows a water break) the surface has
failed the cleanliness test.
·
If, on the other hand, the water
suddenly flashes out into a film over
a large area, an impurity such as
alkali detergent, etc., is on the
surface and it has failed the test.
·
If the water merges into a continuous
film without a sudden flashout, the
surface has passed the water break
test.
(2) Insufficient rising after cleaning may leave an
unacceptable surface. For best adhesion of coatings,
metallic surfaces should give either a neutral or a
slightly acid reaction when alkaline cleaners are used.
Moistened red litmus paper, when applied to surface,
shall not react by turning blue. If such color changes
occur, apply a 0.20 to 0.25 percent chromic acid O-C-
303 solution until a piece of blue litmus paper applied to
the treated surface turns red, which indicates an acid
surface. Permit the acid solution to remain on the
surface from two to five minutes. Follow with a water
rinse and then wipe dry with clean, lint-free cloths.
(3) Determine whether the surface has appropriate
surface treatment in accordance with TM 43-0105.
(4) When a special solvent cleaning requirement
exists in painting operations, use a hand solvent
wipedown consisting of 50 percent toluene, Federal
Specification TT-T-548 and 50 percent methyl ethyl
ketone, Federal Specification TT-M-261. Additionally,
each time the painting sequence of equipment is broken
overnight or longer, this same procedure shall be
performed immediately prior to application of further
coats to insure cleanliness and proper paintability of the
surface.
(5) Examine for presence of corrosion or foreign
matter retained in seams and crevices, etc., and for oily
films or deposits which may have accumulated after
cleaning. If any of these are present, remove or treat as
directed in TM 43-0105.
(6) Assure that all metal surfaces and all seams
and crevices are dry prior to application of paint.
Pressurized filtered air may be used to dry these areas.
(7) Nonmetallic surfaces should be dry, free of
contamination; all pores sealed and scuff sanded with
an abrasive nylon mat in accordance with MIL-A-9962.
f. Pretreatment and Sealing of Bare Metal Surfaces.
The
following
paragraphs
describe
treatment
requirements for aluminum, magnesium, copper and
steel.
9-8
