FED-STD-791D
6.2 Preparation of apparatus.
6.2.1 Cutting test cells - The cells are cut in two, either on an emery cutoff wheel or by
circumscribing the tube with a hot wire about 17 cm from the bottom.
NOTE 1:
Circumscribing with a hot wire is preferred because it is cleaner and safer.
6.2.2 Cleaning test cell - Clean the divided test cell by scrubbing with a suitable
detergent, rinsing in tap water, heating in hot nitric-sulfuric acid mixture, rinsing with distilled
water and drying in an oven at 105C (225F) for l h. The cells can be stored in a desiccator
until used.
6.2.3 Preheat and adjust aluminum block or heating bath temperature to 274 1C
(525 2F).
6.2.4 Preparation of steel specimens.
6.2.4.1 Cut samples approximately 0.15
0.7
7.5 cm.
6.2.4.2 Remove pits and other imperfections on a fine grinding wheel.
6.2.4.3 Polish with 240 grit silicon carbide paper to remove all surface blemishes from
both sides and all four edges.
In all succeeding steps, handle the steel specimens with filter paper or forceps.
NOTE 2:
6.2.4.4 Clean all metal dust from the samples by rubbing vigorously with lint-free tissue.
6.2.4.5 Wash sample strips in warm toluene, then in warm acetone and allow to air dry.
6.2.4.6 Weigh each specimen to within 0.1 mg.
6.3 Test procedure.
6.3.1 Duplicate tests are conducted.
6.3.2 A freshly prepared steel specimen is placed in the lower half of the cleaned cell,
which is then fused to the top half.
NOTE 3: Proper annealing of the fused glass cell will prevent rupture and leaks during
testing.
6.3.3 Introduce 6 mL of the oil samples below the capillary end of the test cell with the
aid of the hypodermic syringe.With this sample volume the metal strip is only partially immersed
in the oil leaving approximately 1.3 cm (1/2 in) exposed.
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