MIL-PRF-27601C
produced on the surface of the copper shall not be greater than No. 3 of ASTM copper corrosion standards (ASTM
D 130). A slight discoloration of the cadmium shall also be permitted.
3.3.2.1 Resistance to oxidation. When tested as specified in 4.4.2, the fluid shall not have changed more than 10
percent from the original viscosity in centistokes at 40°C after the oxidation corrosion test. The neutralization
number shall not have increased by more than 1.0 over the acid or base number of the original sample. There shall
be no evidence of separation of insoluble materials nor gumming of the fluid.
3.3.3 Solid particle contamination. When tested with 4.4.2, the number of solid contaminant particles per 100
ml of the fluid shall not exceed the number specified in table II, nor shall the weight of the residue exceed 0.3 mg.
The filtering time for each determination shall be 15 minutes maximum.
TABLE II. Solid contaminant particle.
Particle size range
Allowable number (max)
(largest dimension)
each determination,
micrometers
automatic count
5 - 15
10,000
16 - 25
1,000
26 - 50
150
51 - 100
20
Over 100
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3.3.4 Foaming characteristics. The foaming characteristics of the hydraulic fluid shall not exceed the limits
indicated in table III when tested as specified in 4.4.2.
TABLE III. Foaming characteristics of finished fluid.
Test
Foaming tendency
Foam stability
Temperature
Foam volume, ml, at end
Foam volume, ml, at end
of 5 min blowing period
of 10 min settling period
Complete collapse 1/
25°C
65 ml (max)
1/
A ring of small bubbles around the edge of the graduate may be considered complete collapse.
3.3.5 Water content. The fluid shall contain less than 100 parts per million (ppm) total water when tested as
specified in 4.4.2.
3.3.6 Flammability.
3.3.6.1 Flame propagation. When tested as specified in paragraph 4.4.2, the flame propagation rate shall be not
more than 0.3 cm/sec.
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