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)

5.2.2 Magnesium alloys.

5.2.2.1 Method. All magnesium alloys shall receive an anodic coating in accordance with ASTM-D1732, Class II, Types II or III. Anodic coating applied in accordance with ASTM-D1732 shall be used for parts subject to abrasion, erosion, or wear. Note: SAE AMS-M-3171 treatments shall only be used for temporary protection or as a paint base.

5.2.2.2 Touch-up. All surfaces which have the anodic coating removed or damaged shall be touched-up, using either the type I or type VI process of SAE AMS-M-3171. Damaged or touched-up magnesium surfaces, previously anodically coated in accordance with ASTM-D-1732, may be reanodized.

5.2.3 Iron and steel. Immediately following cleaning and before the surfaces show any evidence of rusting or other soiling, all iron and steel surfaces to be painted shall be zinc base phosphate treated in accordance with TT-C-490, Type I. Iron base phosphate treatment, TT-C-490, Type II, shall be used if the paint system to be applied requires baking at temperatures exceeding 190.5°C or if the part is to be formed or shaped after phosphating. In the event that phosphating cannot be applied, the clean surfaces shall be coated with wash primer conforming to DOD-P-

15328. Epoxy primer may be applied directly on steel that has been grit blasted to white metal.

5.2.4 Corrosion and heat resistant alloys. The 200, 300, and 400 corrosion- resistant steels shall be passivated by immersion for 30 minutes in a hot (48.8° to

54.4°C) aqueous solution containing 20 percent by volume of nitric acid (specific gravity 1.42) and 2 percent by weight of sodium dichromate, rinsed in clean hot water, then thoroughly dried. This is normally the final finish requirement for the 300 grades of stainless steel. The 400 grades of stainless steel will not accept passivation unless fully hardened. Precipitation hardening stainless steels require certain preparations, if and when passivated, such as baking or shot peening. Stainless steels other than the 300 series usually require additional protective finishes. Monel, Inconel, or nitrided surfaces shall not be passivated. Monel, Inconel, Hastelloys, and titanium surfaces do not normally require further treatment after cleaning. Surfaces to be painted shall be coated with wash primer DOD-P-

15328.

5.2.5 Cadmium. Cleaned surfaces shall be kept free of finger marks, dirt, and dust or other contaminants and shall be chromate treated according to QQ-P-

416, type II. In the event that chromate treatments cannot be used, the surfaces shall be treated with wash primer DOD-P-15328 prior to applying a paint system.

5.2.6 Copper and copper alloys. Surfaces to be painted shall be given a black oxide coating. The surfaces shall be protected from all contamination prior to the paint application.