FED-STD-791D
a. Polish the faces and edges of the panels with steel wool until a uniform bright
surface is produced.
CAUTION:
When polishing the lead panel, avoid excessive pressure which may
cause the steel wool to become embedded in the lead.
b. Remove all loose particles from the panels, using naphtha-soaked cotton pads.
c. Rinse with fresh naphtha, and allow to air dry.
6.7 Using forceps to handle the panel, record the weight of the lead panel to the
nearest mg.
6.8 Clean the stirrer shaft and panel attaching hardware by rinsing with naphtha,
using naphtha-soaked cotton pads or steel wool as required. Rinse in clean naphtha, and
allow to air dry.
6.9 Using forceps to handle the panels, mount both panels on the shaft as shown
in Figure 2.
6.10 Attach stirrer motor to the shaft, and lower the shaft into the sample tube so
the center of the lead panel is centered in the tube approximately 7.5 cm (3 in) from the
bottom.
6.11 Start the stirrer and immediately adjust the air flow 0.940 " 0.047 L/min (2
3
" 0.1 ft /h). Continue the operation for 60 " 1 min.
6.12 Remove the stirrer assembly, and detach the lead panel from the shaft.
Swab the lead panel lightly with naphtha-soaked cotton pads to remove any loose surface
deposits. Rinse with fresh naphtha and then with acetone, and allow the panel to air dry.
6.13 Reweigh until there is no change in the weight.
7. CALCULATIONS
7.1 Calculate the change in weight in mg/cm2 (mg/in2) of the exposed surface
area (including the faces and edges, but excluding the areas covered by the washers).
8. REPORTING
8.1 Report the change in weight to the nearest 1.5 mg/cm2 (mg/in2).
9. PRECISION
9.1 Repeatability. Results by one operator using the same apparatus must not
differ:
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