MIL-DTL-917F(SH)
3.3.1.10 Fragile or brittle materials. Fragile materials include any materials which are fragile in the form, size,
and manner in which they would be used. Brittle materials, in general, fall within this category from the stand-point
of use as structural members. However, certain brittle materials may be used in small quantities, within a part, when
the materials is so mounted, constrained, or otherwise disposed within the part that it will not be strained under any
processing, environmental, and handling conditions to which the part reasonably may be subjected. (For example,
glass and ceramic terminal seals and bushings have been employed successfully in packaging certain semiconductor
devices.) Any material in a frail form which is not positively protected against mechanical damage as used in a part
or subassembly falls within the prohibited fragile category. Cast iron, semi-steel, porcelain, and similar brittle
materials shall not be used for frames, brackets, mounting panels, spacers, or enclosures for equipment, and parts
thereof, which are intended for use aboard ship.
3.3.2 Metals. Metals shall be selected or processed and applied in a manner that provides corrosion resistance.
Metals that are not inherently corrosion-resistant (see 3.3.2.3) shall be processed (treated, plated, or painted) to
provide corrosion resistance (see 3.14.1).
3.3.2.1 Selection of metals in direct contact. Equipment shall meet guidelines for minimizing attack due to
electrolytic action between dissimilar metals in contact with each other in accordance with MIL-STD-889.
Metal-to-metal contact is not normally considered to exist if one of the contact surfaces is hardcoat sulfuric acid
anodized aluminum in accordance with MIL-A-8625, Type III, or equivalent, that has not been previously exposed
to a corrosive environment. If a metal is coated or plated, the coating or plating metal rather than the base metal
shall be considered.
3.3.2.2 Malleable iron and nodular graphitic iron castings. Malleable iron castings or nodular graphitic iron
castings shall not be used unless specifically permitted by the individual equipment specification as specified
(see 6.2). When permitted, malleable iron castings and nodular graphitic iron castings shall be in accordance with
MIL-C-24707 and MIL-C-24707/5.
3.3.2.3 Corrosion-resistant metals. The following commonly used metals, when properly applied, are
considered to be inherently corrosion-resistant without further processing when the service environment precludes
immersion, condensation, or periodic wetting of the surface. These metals are suitable except where individual
equipment specifications require use of specific corrosion-resistant metals for equipment subjected to severe
environmental conditions.
a. Brass. Brasses containing 20 to 40 percent zinc are highly susceptible to stress corrosion cracking in
marine environments when highly stressed.
b.
Bronze
c.
Copper
d.
Copper-nickel alloy
e.
Copper-beryllium alloy
f.
Copper-nickel-zinc alloy
g.
Nickel-copper alloy
h.
Nickel-copper-silicon alloy
i.
Nickel-copper-aluminum alloy
j.
Aluminum alloys, Types 3003, 3004, 5052, 5056, 5083, 5085, 5086, 5154, 5456, 6061.
k.
Titanium
l. Austenitic steels, corrosion-resistant, Types 202, 301, 302, 303, 304, 304L, 309, 310, 316, 316L, 321,
324A, 347. Austenitic stainless steels are susceptible to stress corrosion cracking in marine environments when
service temperatures exceed 150 °F (65 °C).
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