MIL-STD-186 Protective Finishing For Army Missile Weapon SystemsThis standard establishes the minimum requirements for procedures, materials, and systems for cleaning, plating, painting and finishing metals, wood, electronic materials, parts and assemblies for rockets, guided missiles, and components to protect them from deterioration.

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MIL-STD-186F (MI)

4.13.4 Steel, aluminum, and magnesium alloy tubing (large). Interior surfaces of sealed steel, aluminum, and magnesium alloy tubing which, due to size, weight, or geometry, are impractical to protect with corrosion preventive compound code 702, shall be protected by an application of volatile crystalline corrosion inhibitor. The crystalline inhibitor VCI material shall be applied at a rate of 2 grams per cubic foot of volume to be protected, code 711. The VCI material shall be applied to the enclosure through access holes in a manner that shall insure uniform distribution over the area to be protected. (A tube with an inside diameter of 5 inches and a length of 7.5 feet has a volume of approximately 1 cubic foot.) Access holes shall be sealed as specified in 4.13.3. Interior surfaces of large open tubes shall be given the treatment specified for exteriors wherever practical. Interior surfaces of large open steel tubes may be protected by application of wash primer code 401 and painted in accordance with code 402.

4.14 Rivets and threaded fasteners. Rivets and threaded fasteners in general shall be assembled with wet primer. If the fasteners are dissimilar to and

can result in a direct contact with magnesium, a washer of 5056 aluminum alloy, with an overlap of not less than 0.125 inch shall be used in addition to assembling with wet primer.

4.15 Star washers. Star washers may be used for electrical contacts provided they are protected after assembly using code 497, or equivalent.

4.16 Cadmium plating. Cadmium plating must be avoided when an alternative process can be used. Cadmium plating shall be restricted to essential applications only. Use zinc plating, tin plating, aluminum coating, zinc nickel, tin zinc, or other proven alternatives instead.

4.17 Cables, chains, close-wound springs. Control cables, chains, and close-wound springs shall be protected by coating with a corrosion preventive compound, code 701. Springs made of music wire or steel heat treated to 200,000 lbf/in2 (or higher ultimate tensile strength) shall not be plated, but shall be treated in accordance with code 701.

4.18 Plastics. In the selection of nonmetallic materials, every effort shall be made to select fungus-inert materials. MIL-HDBK-1250 or MIL-HDBK-454 may be used as guidance in determining materials considered fungi-inert. In the event that fungus-inert materials are not available, the materials selected shall be treated with moisture and fungus resistant varnish, code 497.

4.19 Elastomers. Elastomers, such as natural rubber, that are subject to ozone attack shall be treated with an anti-ozonant in accordance with code 712, but shall not be painted.