MIL-P-38336A(USAF)
4.6.4 Mixing. A one quart sample of the primer shall be mixed according to the manufacturer's instructions. The material shall be briskly stirred, by hand, during the mixing. The complete mixing shall be accomplished in not more than five minutes. After the mixture appears homogeneous or at the end of the five minute period, whichever occurs first, the material shall be allowed to stand for one minute. It shall then be poured slowly into another container. The primer shall be observed during pouring and the residue remaining in the mixing container observed for any evidence of lumps or pigment that has not been wetted by the liquid vehicle.
4.6.5 Primer stability. A one quart container shall be filled to within approximately 1/2 inch from the top with well mixed primer. The container shall be sealed and stored at 75°F +2°F undistributed for six hours. At the end of this period the container shall be opened and the primer handmixed for not more than three minutes. There shall be no evidence of undispersed lumps of pigment remaining after completion of the stirring. (Small amount of pigment clinging to the stirrer shall not be cause for rejection.)
4.6.6 Coating. Panels shall be prepared, cleaned, and coated in accordance with 4.4.1, 4.4.2, and 4.4.3, respectively. The coated panels shall be examined for conformance with 3.5.1.
4.6.7 Drying time. The drying time of the primer shall be determined in accordance with ASTM D1640, except that the primer shall be sprayed on a cleaned steel panel, as specified in 4.4.2.1, to a dry film thickness as specified in 3.5.1. The drying time shall be in accordance with 3.5.3.
4.6.8 Flexibility. Solvent cleaned panels coated with primer as specified in 4.4.3, and cured as applicable, shall be bent 180 degrees over a l inch mandrel in accordance with ASTM D522, method B. Similar panels shall be conditioned for one hour at 0°F and while still at that temperature, bent around a 4 inch diameter mandrel. The panels shall be visually examined immediately for evidence of failure, and then after conditioning to room temperature, shall be re-examined to determine compliance with 3.5.4.
4.6.9 Adhesion tests of primer coated panels
4.6.9.1 Unexposed and exposed to aqueous media. Test panels cleaned by each of the three methods in
4.4.2, shall be coated with the primer and cured as specified in 4.4.3. Two parallel scratches down to metal, using a stylus, shall be made 1 inch apart. A 1 inch wide strip of masking tape conforming to UU-T-106 shall be applied, adhesive side down, across the scratches. The tape shall be pressed down using two passes of a 4-1/2 pound rubber-covered roller approximately 3-1/2 inches in diameter by 1-3/4 inches in width, the surface of which has a durometer hardness value within the range of 70 to 80. The roller shall be moved at the rate of approximately 1 inch per second. The tape shall be removed in one abrupt motion with the pull exerted at approximately a 90 degree angle to the panel, and the panel examined for removal of primer from the metal. Stripping of the tape shall be accomplished immediately after application.
4.6.9.2 Exposed to nonaqueous media. Test shall be accordance with ASTM D2197.
4.6.10 Fluid resistance properties. Test panels prepared, coated, and cured as specified in 4.4, shall be half immersed in the fluids (see 3.5.6) and tested in accordance with ASTM D1308, method 6.4. Resistance properties shall conform to the requirements of 3.5.6.
4.6.10.1 Water resistance. Immersion in distilled water shall be 14 days at 75°F. Twenty four hours after removal from water, the immersed portion of the film shall be equal in hardness and adhesion to the unimmersed portion as determined in 4.6.9.1.
4.6.10.2 Hydrocarbon resistance. Immersion in fluid conforming to TT-S-735, type III, shall be 24 hours at
75°F. Twenty four hours after removal, the immersed portion of the film shall be equal in hardness and color to the unimmersed portion as determined in 4.6.9.2.
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