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)

94.4 percent clean, demineralized, oil free water

2.0 percent sodium metasilicate (Na2Si02)

3.6 percent surface-active detergent

5.  Water contact angle test.  A drop of distilled or demineralized water placed on a flat, dry, thoroughly prepared metal surface will spread rapidly and uniformly over the surface.  If the water drop does not so disperse itself, the metal surface is not properly prepared for subsequent adhesive bonding and must be reprocessed.  With proper instrumentation, the angle of contact of a drop of water with a base surface can be measured.  A low contact angle (10 degrees or less) indicates a surface satisfactorily prepared for adhesive bonding.  A satisfactory contact angle measuring apparatus consists principally of a

telemicroscope with a crosshair in a rotating eyepiece and with a prism on the objective end.  The process specification will include an effective quality control provision based on contact angle measurements and instrumentation described herein.

6.  Treatment of titanium prior to adhesive bonding.  The following treatment is suggested:

(a) Acetone wipe.

(b) Vapor degreasing

(c) Pickle in the following water solution at room temperature for 30 seconds:

Nitric acid - 15 percent by volume of 70 percent nitric acid solution. Hydrofluoric acid - 3 percent by volume of 50 percent hydrofluoric acid solution.

(d) Rinse in tap water at room temperature for 2 minutes.

(e) Immerse in the following water solution at room temperature for 2 minutes:

Trisodium phosphate - 6.68 ounces per gallon of solution. Potassium fluoride - 2.7 ounces per gallon of solution.

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Sodium fluoride - 1.2 ounces per gallon of solution.

Hydrofluoric acid (50 percent solution) 2.6 percent by volume of solution.

(f)  Rinse in tap water at room temperature. (g) Soak in 150oF tap water for 1.5 minutes. (h) Spray with distilled water and air-dry.

Note:  If heavy heat-treat scale present, molten salt descale prior to above procedure.

7.  Treatment of magnesium alloy, AZ-31-H24 prior to adhesive bonding.

The following treatment is suggested:

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