MIL-STD-1503 Preparation Of Aluminum Alloys For Surface Treatment And Inorganic CoatingThis standard describes the cleaning, activation and under-plating process, and material required for aluminum and aluminum alloys prior to applying inorganic coatings. It is intended that this standard be used in conjunction with other process documents, where the technical requirements are for the application of surface treatments and inorganic coatings on aluminum and aluminum alloys.

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MIL-STD-1503C

5.1.2 Alkaline Etch. Remove scale, corrosion, carbon, etc in the following inhibited alkaline etch or equivalent:

5.1.2.1 Etching Solution.

a. Sodium Hydroxide 3.75 - 11.25 g/l (0.5 - 1.5 oz/gal)

b. Trisodium Phosphate 30.0 - 90.0 g/l (4 - 12 oz/gal)

c. Sodium Carbonate 7.5 - 45.0 g/l (1 - 6 oz/gal)

d. Sodium Gluconate 22.5 g/l (30.0 oz/gal) minimum e. Temperature 52 - 57°C (125 - 135°F)

f. Time two (2) minutes maximum

5.1.3 Smut Removal. Remove smut in the following solutions or equivalent:

5.1.3.1 De-Smut Number 1:

a. Nitric Acid 60 - 80% by volume b. Hydrofluoric Acid 15 - 20% by volume c, Temperature ambient

d. Time 30 seconds approximately

5.1.3.2 De-Smut Number 2:

a. Nitric Acid 40 - 60% by volume b. Temperature ambient

c. Time 30 seconds approximately

5.1.3.3 De-Smut Number 3:

a. Nitric Acid 40-60% by volume

b. Sulphuric Acid 20 - 30% by volume

c. Ammonium Biflouride 105 - 135 g/l (14 - 18 oz/gal)

d. Temperature ambient

e. Time 30 seconds approximately

5.1.3.4 De-Smut Number 4: