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.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13

MIL-STD-1503C

g.    Step Number 7: Zinc immersion plate with moderate part agitation in the following solution:

Sodium Hydroxide                                         450 - 525 g/l    (60 - 70 oz/gal) Zinc Oxide                                                      75 - 97.5 g/l     (10 - 13 oz/gal) Ferric Chloride Hex hydrate                           0.75 - 0.97 g/l    (0.10 - 0.13 oz/gal) Rochelle salt                                                  7.5 - 9.75 g/l    (1.0 - 1.3 oz/gal) Temperature                                                  21 - 27 °C    (70 - 80°F)

Time                                                               30 - 60 seconds

h.   Step Number 8: Rinse thoroughly in clean water.  The rinse water temperature should be ambient.

i.    Step Number 9: Remove zincates using solution 4.1.3.2 (De Smut

Number 2) or equivalent.

j.    Step Number 10:  Rinse thoroughly in clean water.  The rinse water temperature should be ambient.

k.    Step Number 11:  Zinc immersion plate in the zinc immersion solution, paragraph 5.3.7 for 30 - 40 seconds.  It is essential that the immersion time in the zincates solution be closely controlled to prevent formation of an extremely heavy coating.  The proper coating will be smooth and continuous and in some cases, can be achieved without the use of Step Number 7 through 10.  Repeat step number 7 through

10 until the desired coating is obtained.

l.    Step Number 12: Rinse thoroughly in clear water.  The rinse water temperature should be ambient.

m.    Step Number 13: (Optional) Copper strike at 2.5A/dm2  (24A/ft2) for approximately 3 minutes, then reduce the current to 1.25A/dm2  (12A/ft2) for 10 to 15 minutes.  Apply voltage so that current will flow upon the immersion of parts.  Copper strike in the following solution:

7