MIL-PRF-3420H
4.5.2.2 Procedure.
4.5.2.2.1 Assembly of box. A new weather-resistant fiberboard box 12 x 12 x 12 inch
inside dimension shall be assembled with the top remaining open. The seams on the bottom of
the box shall be sealed with 3 strips of 3 inch wide tape conforming to ASTM-D5486, Type I.
The inner walls, except the top, shall be lined with a single layer of wrapping material, treated
side facing the center of the box.
4.5.2.3 Placement of panels in box.
4.5.2.3.1 Panel number 1. Panel 1 shall be centered on a 6 x 6 inch piece of wrapping
material sheet. The sheet shall be tightly wrapped around the short dimension of the panel and
fastened with a double fold at the middle of the panel face; a single fold of the sheet shall be
made at the ends of the panel. The wrapped panel shall be placed in the prepared box with the
folds of the sheet against the bottom of the box and secured with nylon thread.
4.5.2.3.2 Panel number 2. A stainless steel or nickel-chromium alloy wire shall be attached
to each of the two 1/8 inch holes in panel 2, then each wire attached to opposite sides of the top
of the box in such a way as to center the panel at the center of the box.
4.5.2.3.3 Panels 3 and 4. Repeat the procedure for panel 2 except that these panels shall be
suspended at the same level and parallel to panel 2, and at least one inch from panel 1 and the
sides of the box.
4.5.2.4 Box closure and exposure. Close the box and seal the top as specified in 4.5.2.2.1.
The tape applied over the center lengthwise seams shall extend at least 3 inches onto each of the
end panels. The manufacturer's joint shall be taped to establish a completely sealed container.
The sealed box shall be exposed outdoors for 12 months in a louvered shed. Upon completion of
the exposure period, the panels shall be examined visually for conformance to the requirements
in table I.
4.5.3 Compatibility with copper.
4.5.3.1 Preparation of test assembly panel. Three panels of cold rolled, hard temper copper
conforming to ASTM-B152/B152M and measuring 1/16 by ½ by 3 inches shall be polished to
remove pits and irregularities from all surfaces. The panels shall be polished with 240 grit
aluminum oxide. The use of "wet or dry" paper is prohibited. Iron oxide abrasives shall not be
used. The final abrasion shall be in a direction parallel to the length of the panel. Each panel
shall be bent into a "U" shape having a radius of ¼-inch and a distance of ½-inch between side
walls at the ends. The U-shaped panel shall be wiped clean using laboratory tissue dampened
with methanol. A sample of wrapping material measuring ¾ by 3½ inches shall be tightly
wrapped around each "U" shaped panel with the treated side in contact with the copper, so that
the material is perpendicular to the longitudinal axis and at the base of the open section of the
"U". The wrapping material shall be secured with nylon thread.
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