MIL-PRF-14105E
which the panels shall be blast cleaned with a low profile depth of 1.0 - 1.5 mils (25.4 - 38.1 microns)
maximum or mechanically wire brushed according to manufacturers' instructions.
4.7.2 Coating and conditioning of test panels. Spray coat the panels to produce a dry film
thickness of not greater than 2.5 mils (63.5 microns). Then air dry or bake and condition as
specified herein. Air drying shall be accomplished at 77 ± 4 ºF (25 ± 2 ºC) in an atmosphere of
50 percent ± 4 percent relative humidity. Baking shall be accomplished in a well-ventilated
laboratory oven at 400 ± 4 ºF (204 ± 2 ºC). Conditioning of the coated panels for the tests
specified herein shall be at atmospheric conditions for air drying.
4.8 Color. Determine color on coated test panels prepared as specified in 4.7.1 and 4.7.2.
Visually compare the color to the appropriate color chip from FED-STD-595. Nonconformance
to 3.2 shall constitute failure of this test.
4.9 Pigment analysis. Extract the pigment as in ASTM D2371, except use ethanol for the
extraction. Make appropriate qualitative and quantitative tests on the extracted pigment to
determine if only permissible pigments were used. Nonconformance to table I shall constitute
failure of this test.
4.10 Hexavalent chromium. Determine the presence or absence of hexavalent chromium by
either of the following chemical reagent screening techniques:
(a) Weigh approximately 250 mg of pigment into a small glass test tube. Add 5 ml of 25
percent aqueous KOH and shake vigorously for 1 - 2 minutes. Decant a 1 ml aliquot into a
plastic micro-centrifuge tube and centrifuge for five (5) minutes at 17,000 rpm, balancing the
centrifuge with a tube containing 1 ml of the KOH solution. The resulting supernatant liquid
shall be nearly colorless. Use the tube containing the KOH solution as a reference. A distinct
yellow color indicates the presence of hexavalent chromium, and, therefore, shall constitute
failure of the test requirement.
(b) Weigh approximately 50 mg of pigment into a small glass test tube. Add 5ml of 10
percent aqueous H2SO4 and shake vigorously for 1 - 2 minutes. Decant a 1 ml aliquot into a plastic
micro-centrifuge tube and centrifuge for five (5) minutes at 17,000 rpm, balancing the centrifuge
with a second tube containing one ml of the H2SO4 solution. The solution in the second tube shall
act as the test "blank". Immerse a chromate ion (CrO42-) test strip into the supernatant from each
tube. Shake off the excess liquid, and, after approximately one minute, compare the color change
in the reaction zone of the strips to the color scale (concentration levels) provided by the
manufacturer. The appearance of a purple/violet color from the "sample" strip is indicative of
hexavalent chromium, and, therefore, shall constitute failure of the test requirement. If a color
change is apparent from the "blank" strip, rerun the test using fresh, chromium-free reagents. The
appearance of a pronounced color change is indicative of hexavalent chromium, and, therefore,
shall constitute failure of the test requirement.
4.11 Lead content. Determine the presence or absence of lead by weighing 50 mg of pigment
into a small glass test tube. Add 5 ml of dilute HNO3 and shake vigorously for
1-2 minutes. Decant a one ml aliquot into a plastic micro centrifuge tube and centrifuge for five
(5) minutes at 17,000 rpm, balancing the centrifuge with a second tube containing 1 ml of the
dilute HNO3 solution. The solution in the second tube shall act as the test "blank". Immerse a
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