MIL-PRF-18458C
4.4.1.2 Panel finishing and cleaning.
The panel test surfaces shall be
finished and cleaned as follows:
(a)
After rounding the edges of the panel and reaming out the holes
used for suspension, wipe the surfaces as clean as possible
using solvent-soaked rags.
(b)
Scrub the panel with clean cotton or surgical gauze swab in a
beaker of hot non-aromatic petroleum solvent such as heptane.
Rinse in warm (21-27°C) [70-80°F] isopropyl alcohol, for at
(c)
least 10 seconds and air-dry the panel. If required, use a
vacuum desiccator and set it aside for later usage.
(d)
Buff the panel test surface with 240 grit aluminum oxide
abrasive with plain or paper backing so as to produce a surface
finish of 0.254-0.508 micrometers (10-20 micro inches) root
mean square. The final abrasion marks shall be in the
direction parallel to the length of the panel.
(e)
Wipe off superficial dust from the abrasion operation using a
clean, dry absorbent tissue or cloth.
(f)
Scrub abraded face of panel thoroughly with a clean, lint free
cloth until there is no dark stain on a clean section.
Surgical gauze held in a blotter holder is convenient for this
operation.
(g)
Spray the panel with hot, nonaromatic hydrocarbon solvent
(e.g., heptane) using a wash bottle or a spray gun. Hold the
panel in a rack at 20 degrees from the vertical. Direct the
spray vertically downward on the panel, flushing the test
surface progressively downward. Spray the test surface, back
face and finally the test surface again.
(h)
Finally rinse the panel in fresh boiling isopropyl alcohol.
Immerse the panel for at least 10 seconds to warm up to the
solvent temperature prior to withdrawal. Rinsing operations
shall be conducted under a hood for safety.
(i)
Permit the panel to dry and preserve it in a desiccator. Use
the panel on the day of preparation.
4.4.1.2.1
Precautions in cleaning and finishing procedure.
(a)
In all stages of treatment, handling of equipment with bare
hands shall be avoided. The panels shall be handled with
hooks, forceps, or similar devices, care being taken to prevent
contact of the panels with contaminated surfaces during the
cleaning procedure.
(b)
The utensils and cloths used in the preparation of the panels
shall be clean and free of contamination. Solvents shall be
clean and renewed frequently.
4.4.1.3 Coating of test panels. The greases shall be applied to the
panels with a spatula or other suitable tool, taking care to cover all
surfaces with a uniform thickness of grease. The total volume of the grease
shall be 1.0 + 0.05 milliliter (mL); actual measurement of grease quantity
shall be by weight. The weight corresponding to 1.0 mL can be calculated from
the density of the grease.
4.4.2 Salt spray test. Expose the grease coated panels to a 20
percent sodium chloride solution spray in a salt spray cabinet, in accordance
with method 4001 of FED-STD-791, for 10 days plus or minus 1 hour. Remove the
panels from the cabinet and rinse them in warm water to remove any remaining
salt residue. Rinse the panels in hot, nearly boiling, nonaromatic
hydrocarbon solvent (e.g., heptane) to remove the grease coating. Examine the
panels visually; disregard any corrosion appearing on the outer 0.635 cm (1/4
inch) of the panels. The panels shall be considered passing if none of the
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