Physical & Environmental Characteristics
The coating shall withstand immersion in a solution of water and sodium Ch (4.5% salt by weight) for a period of 24 hours. Reference MIL-C-675C, paragraph 4.5.7.
The coating is exposed to a continuous salt spray for 50 hours in accordance with MIL-STD-810F, Method 509.2. (Salt Foa). After this test, the coating is inspected for signs of physical or spectral degradation.
Samples are exposed for minimum of 24 hours to an atmosphere of 95±5% relative humidity at a controlled temperature of 120±4F. After this test, the coating is inspected for signs of physical or spectral degradation. Reference MIL-C-14806A, paragraph 4.4.6.
A standard eraser is stroked across the coated surface using approximately 2.5 lbs of force for 20 complete strokes. After this test, the coating is visually examined for coating or coating removal. Reference MIL-C-14806A, paragraph 4.4.7.
The coated optical surface shall show no evidence of coating removal when cellophane tape is pressed firmly against the coated surface and quickly removed at an angle normal to the coated surface. Reference MIL-C-675C, paragraph 3.8.5.
Surface and Coating Quality
Scratch/Dig specifications defined in MIL-O-13830A. The scratch number corresponds to the maximum apparent size of allowed scratched in units of 0.001mm. The maximum length of such scratches must not exceed 1/4 of the diameter of the useful aperture of the optical element. The dig number corresponds to the maximum allowed diameter of defects, such as bubbles, coating pinholes and inclusions measured in units of 0.01mm. The permissible number of maximum size digs within the useful aperture is one. A common scratch/dig specification for many visual display applications is 60/40 corresponding to a maximum apparent scratch size of 0.060mm and a maximum dig diameter of 0.400mm.
Note: The listed data are standard value. Because of continuous product improvement, the various data listed are subject to change without notice.