MIL-R-19309D
3.3.6.4.2 Passivation. Immerse the clean metal in a solution of equal parts of nitric acid (40 degrees Baume) and water, held at a temperature of 71°C (160°F), for five minutes. Rinse first in clean cold water followed by a rinse in hot water. Then blow dry with compressed air.
3.3.6.5 Anodic film. Parts fabricated from aluminum or aluminum alloys shall be anodized in accordance with
MIL-A-8625 or chemically treated in accordance with MIL-C-5541 when surfaces are to be painted.
3.3.6.6 Magnesium and magnesium alloys. Magnesium and magnesium alloys, when authorized, shall be finished in accordance with SAE-AMS-M-3171.
3.3.6.7 Painting. If painting is selected as the final finish, the following processes shall be used.
3.3.6.7.1 Cleaning. Surfaces to be painted shall be free of dirt, dust, grease, mill scale, welding flux, and other foreign matter. Cleaning may be accomplished with volatile grease solvent, vapor degreasing detergents, hot alkali cleaning solutions, or other processes which have no deleterious effect on the surfaces. Welding irregularities shall be removed. Alkali cleaning shall not be used on aluminum or aluminum alloy surfaces. When an alkali cleaning solution is used, the final rinse shall consist of a dilute chromic acid solution (0.5 pound of chromic acid per 100
gallons of water). When fabrication involves overlapping joints, vapor degreasing is the preferred method of cleaning.
3.3.6.7.2 Pretreatment. Steel surfaces to be painted shall be pretreated by either of the following:
(a) One coat of wash pretreatment in accordance with best commercial practices, applied as a continuous film
.0004 to .0005 inch thick; or,
(b) A phosphate coating conforming to TT-C-490, Grade I.
3.3.6.7.3 Primer. All painted surfaces shall have a primer coat applied as a continuous film .0004 to .001 inch thick. For steel surfaces, the primer shall be in accordance with SSPC-PAINT-25 or TT-P-1757; and for nonferrous surfaces, the primer shall be in accordance with TT-P-1757.
3.3.6.7.4 Enamel. Two coats of enamel, light gray, MIL-DTL-15090, Class 2, applied as a continuous film approximately .001 inch thick.
3.3.6.7.5 Exceptions. The following surfaces shall not be painted: Mounting surfaces, pins, and threaded parts.
3.3.7 Marking. Marking shall be in accordance with Drawing 1521140. Marking shall be by means of engraving, metal stamping, embossing, by permanently affixed nameplate, or by marking with ink, stencil, A-A-208. Ink shall be black or a color contrasting to the surface to which applied. Ink A-A-208, when applied to an enamel surface, shall be covered with varnish, moistureproof, MIL-V-16399; when applied to other surfaces it shall be covered with lacquer,
A-A-3003, Type I.
3.3.7.1 Marking data. Unless otherwise specified in the contract or order, or detailed in the applicable drawings, marking shall include the following:
(a) In Area B, Drawing 1521140: Name of item or assembly; drawing number and drawing revision letter; operating voltage or current; contact rating; coil resistance; manufacturer's name, symbol, or trade mark; and manufacturer's part or assembly number (if desired).
(b) In Area A, Drawing 1521140: Schematic diagram. (c) The index mark, as indicated on Drawing 1521140.
NOTE: The date and place of manufacture shall not be shown.
3.3.8 Threaded parts. Bolts, nuts, screws, and studs shall conform to the requirements of MIL-DTL-1222 or
FF-S-86, FF-S-92, and FF-N-836. Screw threads for all threaded parts shall be in accordance with FED-STD-H28, and shall be of size 2-56, 4-40, 6-32, 8-32, 10-32, 1/4-20, or 1/4-28. If larger sizes are needed, they shall be of the
coarse-thread series. Threaded parts (other than bolts, screws, studs, and nuts) requiring threads of special
diameter and pitch shall employ the special pitch of 16 threads to the inch. For applications where a finer pitch is necessary, one of the following shall be selected: 20, 28, 36, 44, or 56.
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