MIL-PRF-81352C
4.5 Test panels. Test panels shall be prepared under laboratory conditions (see 4.2). The
dimensions for all test panels shall be 0.020 x 3 x 6 in. (0.5 x 76.2 x 152.4 mm). Unless
otherwise specified in the test method, the test panels shall be Alclad aluminum alloy 2024
(T3 temper) conforming to SAE-AMS-QQ-A-250/5.
4.5.1 Panel preparation. The panels shall be treated with a conversion coating conforming
to MIL-DTL-81706, class 1A.
4.5.2 Application of coatings.
a. Primer coating. One cross-coat of a primer coating conforming to MIL-PRF-
23377 or MIL-PRF-85582 shall be spray-applied to a dry film thickness of 0.6 to
0.9 mils (15 to 23 µm) in accordance with ASTM-D823. Air-dry the primer for a
minimum of one hour. The primer surface shall be tack-free prior to topcoating.
b. Topcoat. Prepare the coating in accordance with the manufacturer's instructions
(the admixed topcoat shall be reduced with thinner conforming to MIL-T-81772 if
so instructed by the manufacturer). If reducing with thinner, do not exceed the
maximum allowable VOC content (see 3.3.1). Spray-apply the coating in
accordance with ASTM-D823 to a dry film thickness of 1.7 to 2.3 mils (43 to 58
µm). Prior to testing, the applied coating shall be air-dried for a minimum of 14
days at room temperature.
4.6 Test methods. The tests of this specification shall be conducted in accordance with
table II and 4.6.1 through 4.6.7 with test panels prepared in accordance with 4.5 through 4.5.2.
Unless otherwise specified in the test method or paragraph, all testing shall be conducted under
the inspection conditions specified in 4.2.
4.6.1 Accelerated storage stability. The coating, in its original, unopened container, shall be
stored at 125 ±3 °F (52 ±2 °C) for a minimum of 14 consecutive days. During the storage period,
the container shall be placed in a larger, vented container to confine any splashing that may occur
if the lid of the unopened container is blown off by increased internal pressure. At the end of the
14 day period, remove the container and allow it to cool to room temperature. If the unopened
container is deformed upon removal from storage, do not open and discard. If it is not deformed,
open the container carefully and examine its contents for conformance to 3.4.2.
4.6.2 Surface appearance. The coatings shall be applied to test panels in accordance with
4.5 through 4.5.2 for conformance to 3.6.3.
4.6.3 Specular gloss. The coatings shall be applied directly to the unprimed test panels and
air-dried for 14 days. Examine in accordance with ASTM-D523 at a 60° geometry for
conformance to 3.7.2.
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