MIL-C-13924 is an alkaline product in powder form which produces a durable, gleaming or matt, black or bluish finish on iron and steel parts for decorative effect and corrosion resistance.
The finish produced by MIL-C-13924 neither increases or decreases the dimensions of the treated metals. The finish actually forms a part of the metal itself.
MIL-C-13924 meets the requirements of MIL-C-13924, CLASS 1.
1o Stage: DEGREASING
Concentration : 5-10%
Temperature : 70-80 ℃
Immersion Time : 5-10 minutes
2o Stage: RINSE
Thoroughly rinse in clean overflowing water, preferably warm. A cascade rinse tank proving two rinses is advised at this stage.
3o Stage: BLACK OXIDE
Concentration : 1200 grams per liter water
Temperature : 143 + 2 ℃
Immersion Time : 15-30 minutes (depending on desired results)
4o Stage: RINSE
Use stage 2
5o Stage: SEALING
Concentration : 0,2 % (2 grams per liter water)
Temperature : Ambient
Immersion Time : 2 minutes
6o Stage: PRESERVE
Immerse parts in WATER DISPLACER (water-displacing rust preventive)
Charging the tank
Carefully add the MIL-C-13924 powder to the cold water under constant agitation or stirring to insure dissolving. When MIL-C-13924 has been mixed and dissolved, heat the tank until 143 ℃ is reached.
Strict maintenance of the temperature is imperative.
Once a MIL-C-13924 solution has been prepared it is wise to remember two important facts:
- Adding MIL-C-13924 salts will automatically increase the boiling point.
- Adding water will automatically decrese the boilin point.
The MIL-C-13924 solution should be maintained warm or hot at all times. If solution is allowed to cool too much, the salts will precipitate out to form a hard cake. Then when the tank is reheated uneven heating will occur and the salts will “burn”. Parts processed in “burnt” salts may not produce a satisfactory black finish.
If the tank is used only a portion of the day, maintain sufficient heating during idle hours to prevent solidification of the solution (70-90 ℃).
The MIL-C-13924 solution remains effective if it used properly and only replacing dragout losses is necessary.
Control of the solution
Maintain the boiling point of the solution at 143 + 2 ℃. If the solution boils at a lower temperature than 143 ℃, add MIL-C-13924 until the boiling point is established at 143 ℃. If the solution boils at an upper temperature than 143 ℃, add water until the boiling point is established at that point.
Protection of the solution
Do not use or immerse incompatible or reactive metals, such as aluminium, brass, copper, bronze or tin, cadmium and zinc plated parts. The solution will be poisoned and it will become unusable.
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