MIL-PRF-23236D
(2) After the air dry of the first coat has been accomplished, using an adjustable gap clearance film
applicator ("doctor blade"), draw down a 305-millimeter (12-inch) wide by 408-millimeter (16-inch)
long wet film of the second coat (intermediate or topcoat, as applicable) of the coating system
perpendicular to and across the dry first coat. The coating shall be prepared (mixed) in accordance
with manufacturer's instructions and the wet film thickness shall be the same as the manufacturer's
recommended wet film thickness. Air dry this draw-down for 24 hours at 20 to 27 °C (68 to 81 °F).
(3) Repeat the procedure in (2) above for each additional coating in the coating system.
(4) Allow the completed test sample to cure for 7 days at 20 to 27 °C (68 to 81 °F) after the application of
the final coating.
b. Bell jar preparation. Attach a bell jar of 500-milliliter capacity to the coated surface prepared in (a) above
with molten paraffin wax. The bell jar shall be fitted with a tightly fitting stopper to prevent loss of volatile halogen
reactants during testing.
4.5.11.1 Color in water (Class 9). Prepare for test as specified in 4.5.11. Fill the bell jar with 200 parts per
million chlorinated ASTM D1193 (any type) distilled water and age for 24 hours. Remove the chlorinated water by
suction and rinse the bell jar twice with ASTM D1193 (any type) distilled water. Discard the 200 parts per million
and rinse water. Prepare a solution of 0.2 parts per million chlorinated ASTM D1193 (any type) distilled water and
determine the exact chlorine concentration using the DPD colorimetric method of APHA 4500Cl-F. Refill the bell
jar with determined 0.2 parts per million chlorinated distilled water solution. Age the 0.2 parts per million
chlorinated water solution for 24 hours in the bell jar at 20 to 27 °C (68 to 81 °F). Also retain and age the
200 milliliters of the 0.2 parts per million chlorinated water solution (control) in a clean, sealed glass container at 20
to 27 °C (68 to 81 °F). Withdraw 100 milliliters of water from both the bell jar and the control and determine the
color of the water in the bell jar and the retained control water using APHA 2120B. Correct the bell jar color value
for any change in the control color by subtracting the color change value of the control from the color change value
of the bell jar water. Color value shall be in accordance with the requirements of 3.4.2.
4.5.11.2 Taste in water (Class 9). To assure taster safety, the taste test shall be performed only after a coating
system has been found to comply with all other requirements of this specification. The remaining chlorinated water
in the bell jar in 4.5.11.1 shall be used for the taste in water test specified in APHA 2150B. The remaining water
shall be withdrawn from the bell jar by suction and placed in a clean glass container and tightly sealed. The sealed
container of chlorinated water shall be equilibrated to 40 °C (104 °F) in a water bath. Threshold taste values shall be
in accordance with the requirements of 3.4.3.
4.5.11.3 Odor in water (Class 9). After the chlorinated water has been removed from the bell jar (4.5.11.1) for
the taste in water test (4.5.11.2), rinse the bell jar twice with ASTM D1193 (any type) distilled water. Prepare a
solution of 0.2 parts per million chlorinated distilled water and determine the exact chlorine concentration using the
DPD colorimetric method of APHA 4500Cl-F. Refill the bell jar with determined 0.2 parts per million chlorinated
distilled water solution. Age the 0.2 parts per million water solution for 24 hours in the bell jar at 20 to 27 °C (68 to
81 °F). Conduct the odor in water test in accordance with APHA 2160B. The water bath temperature for this test
shall be equilibrated to 40 °C (104 °F). Threshold odor values shall be in accordance with the requirements of 3.4.4.
4.5.11.4 Chlorine residual (Class 9). Prepare for test as specified in 4.5.11. Fill the bell jar with 200 parts per
million chlorinated ASTM D1193 (any type) distilled water and age for 24 hours. Remove the chlorinated water by
suction and rinse the bell jar twice with ASTM D1193 (any type) distilled water. Discard the 200 parts per million
and rinse waters. Prepare a solution of 10 parts per million chlorinated ASTM D1193 (any type) distilled water and
determine the exact chlorine concentration using the DPD colorimetric method of APHA 4500Cl-F. Refill the bell
jar with determined 10 parts per million chlorinated distilled water solution. Age the 10 parts per million
chlorinated water solution for 24 hours in the bell jar at 20 to 27 °C (68 to 81 °F). Also retain and age the
200 milliliters of the 10 parts per million chlorinated water solution (control) in a clean, sealed glass container at 20
to 27 °C (68 to 81 °F). Determine the exact chlorine concentration of the water in the bell jar and the retained
control water using the DPD colorimetric method of APHA 5530D. Correct the bell jar chlorine value for any loss
in the control by subtracting the loss in chlorine parts per million of the control from the loss of chlorine content in
the bell jar water. Chlorine residual value shall be in accordance with the requirements of 3.4.5.
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