MIL-DTL-81706B
4.5.3.2 Immersion procedure. Painted panels shall be immersed in distilled water as
follows:
3 panels of each substrate and finish for 24 hours at room temperature.
3 panels of each substrate and finish for 96 hours at 120 ±2 °F (49 ±1 °C).
3 panels of each substrate and finish for 168 hours at 150 ±2 °F (65.5 ±1 °C).
Upon completion of the immersion period, the panels shall be removed from the water, dried
using a clean, dry soft cloth, and be immediately evaluated as specified in 4.5.3.3.
4.5.3.3 Evaluation procedure. Panels prepared in accordance with 4.4.4.1 shall be tested for
paint adhesion in accordance with FED-STD-141, Method 6301.3, except that the scribed area
shall include the original paint, overlap area, and the repair area.
4.5.4 Coating weight (class 1A). Panels prepared as specified in 4.4.3 shall be tested as
specified herein for conformance to the requirements in 3.6. For type I coatings, within 3 hours
after applying the conversion coating, the panels shall be weighed to the nearest 0.1 milligram.
The coating shall not be aged for more than 3 hours since it will become difficult to remove and
the results will be inaccurate. Immediately after weighing, the specimens shall be immersed for
60 seconds in freshly made nitric acid solution, composed of equal parts by volume of
concentrated nitric acid (70 percent HNO3) and deionized water, maintained at room
temperature. Coating removal can be facilitated by brushing the specimen with a clean cotton
swab. For type II coatings, the method specified for type I coatings shall be used, unless an
alternative method is specified by the manufacturer. After removal of the conversion coating,
the specimen shall be rinsed thoroughly in deionized or distilled water, blown dry with clean,
filtered oil-free air, and reweighed. The weight of the chemical conversion film in milligrams
per square foot shall be calculated as follows:
Film Weight = (W1 - W2) x 2.4 for milligrams/ft2 (25.8 for milligrams per square meter)
where: W1 = Initial weight in milligrams
W2 = Final weight in milligrams
4.5.5 Contact electrical resistance (class 3 only). Panels prepared as specified in 4.4 (before
and after the salt spray exposure [see 4.5.1]) shall have the contact electrical resistance of the
coating determined for conformance to 3.7. Test equipment and circuitry as shown on figures 1
and 2 shall be used for measuring the electrical resistance of the class 3 material specimens. The
applied load shall be within one percent of the calculated 200 psi applied pressure. The
contacting electrodes shall be copper or silver-plated copper with a finish not rougher than that
obtained by the use of 000 metallographic abrasive paper. The electrodes shall be flat enough so
that when the load is applied without a specimen between them, light will not be visible through
the contacting surface. The area of the upper electrode shall be one square inch (25 square mm)
and the area of the lower electrodes shall be larger. Ten measurements shall be made on each
panel in the areas shown on figure 3.
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