MIL-DTL-81963C
3.4.7 Electrolytic corrosion protection. Where it is unavoidable that combinations of dissimilar metals
be in contact, the following methods or combinations of methods shall be employed unless electrical
consideration precludes their use.
a. A material shall be interposed between the metals so as to reduce electrolytic potential
differences, such as steel in contact with aluminum should be cadmium plated.
b. An inert material shall be interposed between dissimilar metals, to act as an insulating barrier.
c. Corrosion inhibitors shall be applied to the faces of each of the dissimilar metals; for example,
nickel-plated brass screws in contact with aluminum shall be coated with zinc chromate paste.
d. The contact areas of each of the dissimilar metals shall be coated with an organic coating; for
example, aluminum and steel surfaces in contact should be painted. For additional information, see
6.14.
e. The requirements of 3.4.6e shall apply.
f. The amount of aeration reaching the dissimilar contact areas shall be restricted; for example,
steel bolts in contact with aluminum should have all contact surfaces sealed with zinc chromate
primer or with a vinyl or equivalent film.
g. Any other systems of protection, which are designed to alleviate electrolytic corrosion, shall be
subject to the approval of the procuring activity.
3.4.8 Aluminum. All parts made of aluminum or aluminum alloys shall be anodized, in accordance with
MIL-A-8625.
3.4.9 Restricted materials. Flammable or explosive material, magnesium or magnesium alloys,
material which can produce toxic or suffocating fumes (see 3.4.1), cotton, linen, cellulose nitrate,
regenerated cellulose, wood (untreated), jute, leather, cork, organic fiberboard, paper and cardboard, hair
or wool felts, plastic materials employing paper, cotton, linen or wooden flours as a filler, materials
composed of phenolic, mercury or mercuric compounds shall not be used. Materials shall not sustain
combustion when burned.
3.4.10 Fungus-resistant and moisture-resistant materials. Materials which are not nutrients for fungi
and which are moisture resistant shall be used.
3.4.11 Collector rings. Collector rings, when required, shall be of gold alloy material.
3.4.12 Ball bearings. Ball bearings of the radial thrust type shall conform to MIL-B-81793, tolerance
ABEC-5P or better. Double shielding shall be employed, where space permits. Balls, races, retainers
and shields shall be made of corrosion-resistant steel and shall be in accordance with MIL-B-81793.
3.4.13 Lubricants. Lubricants used in servocomponents shall be consistent with the requirements
herein, in regard to fungus and moisture resistance, corrosion, emission of toxic fumes, and the ability to
withstand prolonged storage while enabling the servocomponent to meet all the performance and
environmental requirements of this specification.
3.4.14 Threaded parts. All screw threads and tapped holes used in the construction of
servocomponents shall be in accordance with FED-STD-H28/2. The number of threads and dimensions
shall be those specified for Unified Inch Screw Threads. Unified Coarse Threads are preferred, except
where definite improvements in design or operating characteristics would be affected by use of Unified
Fine Threads. Servocomponents shall be supplied complete with associated terminal screws and
washers, and drive nut and washer, as appropriate.
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