MIL-PRF-18458C
panels show more than three corrosion spots, each of which is not greater than
1 millimeter (mm) in diameter.
4.4.3 Accelerated weathering test. Three specimens prepared as
specified in 4.4.1.3 shall be exposed in a single open-flame sunshine carbon-
arc lamp apparatus in accordance with ASTM G 152 for 10 days plus or minus 1
hour. Black panel temperature shall be 48.9°C + 1.7°C (120°F + 3°F) during the
light-on, without-water-spray period of the test cycle.
Apparatus shall be
operated 18 hours for each of the testing days.
At the end of the exposure
period, the panels shall be removed from the test equipment. Rinse the panels
in hot, boiling, nonaromatic hydrocarbon solvent (e.g., heptane) and examine
the panels as in 4.4.2. The panels shall be considered passing if none of the
panels show more than three corrosion spots, each of which is not greater than
1 mm in diameter.
4.4.4
Low temperature flexibility.
4.4.4.1
Apparatus and material shall be as follows:
(a)
Brass strip, approximately 10.16 cm by 1.27 cm by 0.01778
cm (4 inch by 0.5 inch by 0.007 inch)
(b)
Strip coating apparatus as shown in Figure 1
(c)
Mandrel 3.81 cm (1.5 inch) in diameter
Constant temperature box maintained at minus 6.67°C (20°F)
(d)
4.4.4.2 Procedure. Clean the brass strip with 240 grit abrasive
paper the long way of the strip. Wash with non-aromatic petroleum solvent and
dry. Clamp the strip between the top plate and bottom plate in the strip-
coating apparatus. Coat the strip by spreading the grease over the surface of
the thickness to 0.127 cm (0.05 inch) by drawing a knife-edge across the top
of the grease well. Remove the strip from the coating apparatus. Place the
strip and mandrel in the constant temperature box for 1 hour. With the bare
metal next to the mandrel, bend the strip with a steady slow motion for 180
degrees around the mandrel in the box. Care must be taken to not touch the
film before or during the test and complete the bending in not more than 2
seconds.
Remove the bent strip from the box and examine the coating for
cracks. Check for retained flexibility. The material shall be considered as
meeting the requirement if the grease surface does not crack during this
procedure.
4.4.5 Volatile matter. Approximately 2 grams (g) of the grease shall
be weighed to the nearest milligram in a tared aluminum foil dish 5.0 cm (2.0
inches) in diameter. The dish shall be placed in an explosionproof, gravity-
convection oven maintained at 105°C - 110°C (221°F - 230°F) for a period of 3
hours. The volatile contents are determined from the resultant weight loss.
4.4.6
Adhesiveness.
4.4.6.1
Apparatus shall be as follows:
(a)
Disc and shaft as shown in Figure 2
(b)
Vertical shaft and motor assembly capable of rotating disc
at 150 + 10 revolutions per minute (rpm)
Oven maintained at 66.1°C + 1.1°C (151°F + 2°F)
(c)
(d)
Drip shield suitable for catching grease flung centrifugally
from spinning disc
4.4.6.2 Procedure. Weigh the clean, dry disc and fill its concave
side with the grease. Strike off level with a straight edge. Weigh disc and
grease. Place the disc, with the grease side up, on the end of the shaft in
8
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