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)

Appendix I

Suggested Surface Preparation Procedures Prior to Bonding of Metal

Faying Surfaces

1. Wrought aluminum and aluminum alloys (except sandwich cores).

Degrease surfaces with an organic solvent, immerse for 10 minutes at

150o to 160oF (65.6o to 71.1o C) in a chromic acid solution of approximately the following composition by weight:

30 parts clean, demineralized, oil free water

10 parts concentrated sulfuric acid (1.84 specific gravity (sp gr))

1 part sodium dichromate (Na2Cr207 - 2H20 - technical grade).

Rinse in demineralized water at a temperature no higher than 150oF (65.6oC) and with a pH no greater than 7.5. 0bserve immediately for water breaks on the surfaces as evidenced by the water not cascading from the parts or specimens in a smooth, continuous sheet. If water breaks occur, repeat, above treatment. Dry the rinsed parts or specimens for 30 minutes, or until thoroughly dry, at a temperature no greater than

150oF (65.6oC), and repeat the water-break test or subject to instrumentation test as specified in 5.

2. Stainless steel (except sandwich cores). Degrease and proceed as specified in 1, except that immersion will be for 15 minutes at 150F to

160oF (65.6 to 71.1oC) in a strong acid-dichromate solution of the

following composition:

96.6 percent by volume concentrated sulfuric acid (1.84 sp gr)

3.4 percent by volume saturated water solution of Na2Cr207 - 2H20.

3. Sandwich cores (aluminum alloys). Degrease and proceed as specified

in 1 except that immersion will be for 15 minutes at 150o to 160oF (65.6o to

71.1oC) in a mild acid -detergent solution of the following composition by weight:

92.9 percent clean, demineralized, oil free water

1.0percent concentrated sulfuric acid (1.84 sp gr)

6.0 percent sodium dichromate (Na2Cr207 - 2H20 - technical grade)

0.1 percent surface-active detergent

4. Sandwich cores (titanium and 302 type stainless steel). Degrease and proceed as specified in 1, except that immersion will be for 15 minutes at

150o to 160oF (65.6o to 71.1oC) in a detergent solution of the following

composition by weight: