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|  MIL-S-17000N(SH)
3.4.4 Metals.
3.4.4.1 Aluminum. Where the use of lightweight corrosion-resistant metal
is desired, wrought aluminum alloys of the 5000 series shall be used insofar as
practicable. These aluminum alloys shall conform to QQ-A-200, QQ-A-225, or
QQ-A-250. In general, aluminum alloy castings shall conform to alloy A360 of
QQ-A-591 or to alloy A356 of QQ-A-596, or QQ-A-601. High strength aluminum
alloy castings shall conform to alloy A356 of MIL-A-21180.
3.4.4.2 Magnesium.
Magnesium and magnesium alloys shall not be used.
3.4.4.3 Nonferrous metals. Nonferrous metals, except as specified
herein, shall not be used.
3.4.4.3.1 Zinc. Zinc shall not be used where the increased electrical
resistance of the surface, due to the protective treatment, might have a
detrimental effect on electrical performance.
3.4.4.4 Springs (material).
Material for springs shall be in accordance
with QQ-W-423.
3.4.5 Plastics. Plastics used in switching equipment shall be in accord-
ance with requirement 11 of MIL-STD-454 and 3.4.5.1 through 3.4.5.3.
3.4.5.1 Molded parts. Molded parts for circuit breaker mounting bases
shall conform to the requirements of MIL-C-17361 or MIL-C-17588 as applicable.
3.4.5.2 Plastic description plates. Plastic for description plates (see
6.5.8) shall be in accordance with L-P-387.
3.4.5.3 Dials and transparent or translucent parts. Plastic for dials
(for other than switchboard meters) and other transparent or translucent appli-
cations shall be in accordance with MIL-P-5425. Polystyrene, methacrylates,
allyls, cellulose acetate butyrate, vinyl chloride-acetates, and melamine are
acceptable materials for dials and related translucent or transparent parts.
3.4.6 Ceramics.
Ceramics shall not be used.
3.4.7 Glass. Glass, when used for meter and indicator dials, shall be
clear, presenting no evidence of distortion when viewed from any angle.
3.4.8 Painting. After machining, welding, and brazing operations have
been complete, the surfaces of metal enclosures and parts to be painted shall
have rust or other visible corrosion products removed and shall be thoroughly
cleaned of grease, oil, and dirt and painted in accordance with the requirements
of system 37 of MIL-STD-13030 (Chemical conversion coating in accordance with
class 1A of MIL-C-5541 may be used as an alternative to the primers specified
in system 37. See 3.4.9.l(d) for modification of MIL-C-5541.) Specific surfaces
that require painting are shown in the applicable specification sheet and in
requirements of MIL-sTD-1657.
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