3.4.9 Protection against corrosion. In order to prevent corrosion, metal
parts which are not to be painted shall be of corrosion-resistant materials or
other materials treated as specified in 220.127.116.11 to render them adequately
resistant to corrosion. Internal parts fabricated from nonferrous materials
contained in a watertight enclosure need not be given a corrosion-resistant
18.104.22.168 Corrosion-resistant treatments. Corrosion-resistant treatments
shall not be applied to surfaces which are in functional contact where gouging
or binding may be a factor or where the treatment might interfere with normal
functioning or where electrical grounding through the surface is required. The
most applicable corrosion-resistant treatment of those listed below shall be
applied after fabricating operations such as welding, machining, drilling, and
tapping have been completed.
Zinc coating, hot dip galvanizing conforming to ASTM A 153,
for parts other than threaded fasteners, unless part speci-
fications contain other requirements.
Electroplating of zinc conforming to type II, Fe/Zn 13 of
ASTM B 633, for surfaces not to be painted except that Fe/Zn 8
thickness may be used for externally threaded parts, bolts,
studs, and washers. Type 1, Fe/Zn 13 of ASTM B 633 may be
used on parts which are continuously exposed to temperatures
in excess of 150 degrees Fahrenheit ("F), or are intermittently
exposed for short periods to temperatures of approximately
300°F. Either Fe/Zn 13, type II, or Fe/Zn 13, type IV of
ASTM B 633 shall be used on surfaces that are to be painted.
Electroplating of chromium conforming to QQ-c-320.
Chemical conversion coating in accordance with class 1A of
MIL-C-5541, except the surface temperature of the coating
may not exceed 140°F during drying or curing and the salt
spray test is not required.
22.214.171.124 Selection of metals. In order to minimize corrosion attack due
to electrolytic action between dissimilar metals when used in contact with each
other, selection shall be in accordance with MIL-STD-889.
3.4.10 Printed wiring board materials. Materials for printed wiring
boards shall be in accordance with MIL-P-13949.
3.4.11 Laminated materials. The use of laminated materials (that is
melamine, glass epoxy) for mechanical insulating linkages is prohibited.
3.5 Parts and features - mechanical. The following mechanical parts and
features are applicable to the switching equipment specified herein:
3.5.1 The following requirements of MIL-STD-454 shall apply:
Requirement 12 - Fastener hardware (see 126.96.36.199)
Requirement 21 - Castings
Requirement 63 - Special tools