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|  MIL-E-24763A(SH)
w/INT. AMENDMENT 1
4.6.9. Resistance to biological growth. The biological growth on the surface of the enamel shall be
determined in accordance with ASTM D3274. The extent of surface disfigurement shall be evaluated in accordance
with ASTM D3274. Fungal mycelium and spores, slime, and dirt or soil accumulation shall be considered
disfiguring agents in the evaluation. The rating shall be as specified in 3.8.2.
4.6.10. Freeze-thaw stability. Enamel shall be tested in accordance with ASTM D2243, except after
completion of the exposure and room temperature equilibration, the exposure shall be repeated twice before
proceeding to the examination (three exposure cycles to 0F and three equilibrations). Consistency shall be
determined in accordance with ASTM D562; contrast ratio, gloss, and reflectance shall be determined as specified in
table IV; and characteristics shall comply with the requirements of table III (see 3.7.2 and 3.8.3).
4.6.11. Primer compatibility.
4.6.11.1. Dry adhesion. The 14 test panels shall be as specified in 4.5.1.1. Six panels shall be primed with
two coats of an epoxy-polyamide material in accordance with MIL-DTL-24441 and MIL-DTL-24441/1. Four
panels shall be primed in accordance with TT-P-645. Four panels shall be prepared with a NAVSEA 03M1
approved inorganic zinc-rich primer in accordance with manufacturer's instructions. Two panels, each prepared
with MIL-DTL-24441/1, shall dry for 6, 24, 168 hours, respectively, at standard test conditions (see 4.5) before the
application of two spray coats of enamel conforming to this specification. Film thickness shall be 2 to 4 mils for the
MIL-DTL-24441/1 primer and 1.5 to 2 mils for TT-P-645, respectively. The panels dried for 168 hours prior to
application of the enamel, shall receive a tack coat of the MIL-DTL-24441/1 primer (a wet film application of 1 to 2
mils). Two panels, each to which primer in accordance with TT-P-645 is applied, shall be dried for 24 and 168
hours, respectively, at standard test conditions (see 4.5) and overcoated with enamel conforming to this specification
in like manner as the panels treated with the epoxy-polyamide material. Panels of the NAVSEA 03M1 approved
inorganic, zinc-rich primer shall be overcoated in the same manner as the TT-P645 test panels. Overcoated primed
panels shall be dried for 168 hours under standard test conditions (see 4.5). Panels shall be tested as specified in
4.6.13. The tape test shall be performed in accordance with ASTM D3359, method A, except that the tape used
shall be commercially available masking tape. Following the tape test, lifting characteristics shall be determined
between the enamel and the primer at the scribe and at a distance up to 1 inch perpendicular to the scribe using the
aid of a microscope. The test results shall conform to the requirements of 3.8.9.1.
4.6.11.2. Wet adhesion. Application of primers and enamel shall be made as specified in 4.5.1.1 and the
systems shall be dried as previously indicated. At the conclusion of the drying cycle, the panels shall be scribed
using a tool in accordance with ASTM D1654 and immersed in distilled water at standard test conditions (see 4.5)
for 24 hours. While immersed, the panels shall be examined for evidence of blistering, wrinkling, or other evidence
of adhesion failure of the test enamel to the primers. Test for wet adhesion shall be in accordance with method
6301.3 of FED-STD-141, except the tape used shall be commercially available masking tape. Following the tape
test, lifting characteristics shall be determined between the enamel and the primer at the scribe and at a distance up
to 1 inch perpendicular to the scribe using the aid of a microscope. The test results shall conform to the
requirements of 3.8.9.2.
4.6.12. Enamel recoatability. Ten test panels of aluminum having nominal dimensions of 150 x 300 x 3
millimeters (6x12x⅛ inches) shall be prepared. The test requires 10 test panels. Test panels shall be degreased in
accordance with methods B, C or D of ASTM D609. The degreased test panels shall be abrasive blasted with new,
clean aluminum oxide to provide a profile pattern of 0.0253 to 0.0506 mm (0.001 to 0.002 inch) (average). All test
panels shall be primed with 2 coats of MIL-DTL-24441 type III or IV formula 150 green primer. Each coat of MIL-
DTL-24441 shall be applied to 0.051 to 0.101 mm (0.002 to 0.004 in) dry film thickness and allowed to cure 24
hours at ambient laboratory conditions before being overcoated. Two coats of the test enamel shall be spray applied
on the MIL-DTL-24441 F.150 coated panels to obtain a final dry film thickness of the test topcoat of 101 to 151 mm
(0.004 to 0.006 in). Allow not less than 24 hours dry time between applications of the coats of test topcoats at
ambient laboratory conditions. The completed painted test panels shall be cured for not less than 7 days at ambient
laboratory conditions before proceeding to the mounting on the test rack. Spraying properties shall be in accordance
with 3.8.5, as appropriate. Test specimens shall be mounted on a test fence having a 45-degree south facing rack at
a distance of not greater than 30 meters (100 feet) of an ocean high tide line. The exposure shall be for a period not
less than 1 year (365 days) in accordance with paragraph 6 of ASTM D1014. The fence shall be at the Naval
Research Laboratory, Marine Corrosion Laboratory, Key West, Florida, USA. After the exposure period of 1 year
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