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Al-Brite A/B RD-21/RD-22

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Aluminum Deoxidizer-Desmut

Al-Brite A/B (RD-21/RD-22) is an Aluminum deoxidizing-desmut formulated to deal with the especially difficult problems of desmutting high alloy aluminum casting (typically alloy numbers 13, 360 and 380). Al-Brite A/B (RD-21/RD-22) can be used on any aluminum alloy as preparation for or replacement of chromate conversation coating or anodizing. However, the more difficult the desmutting operation, the more apparent will be the advantages of Al-Brite A/B (RD-21/RD-22).

Al-Brite A/B (RD-21/RD-22) renders aluminum surfaces brightened and activated and will give a much deeper and more uniform conversion coating. Metal loss from aluminum surfaces is negligible, unless the solution has been diluted with large quantities (greater than 25%) of water. Accordingly, it is important to make sure that parts, when entering the bath of Al-Brite A/B (RD-21/RD-22) solution, are as close to water-free as practical without actual drying. For best results rack the parts to minimize cupping. Make certain all water contained within channels or depressions is allowed to drain out.

The ideal process cycle before chromate conversion coating or anodizing is:

  • 1) Clean parts in Aluminum Prep™ (RD-20)
  • 2) (RD-20); [8 oz/gal, (60 grams/liter) 140 -160 F(60º-80ºC), 3-10 min].
  • 3) Rinse
  • 4) Etch (optional)
  • 5) Rinse (allow work to hang above rinse tank at least 30 seconds.)
  • 6) Desmut in Al-Brite A/B (RD-21/RD-22) (70 ± 10 F, 3-5 minutes).
  • 7) Rinse
  • 8) To chromate conversion coating or anodizing.

Al-Brite A/B (RD-21/RD-22) is supplied as a two-part system, Al-Brite A (RD-21) is the powdered acid activator and Al-Brite B (RD-22) the concentrated liquid acid base. Fill tank with Al-Brite B (be sure the tank is dry and do not add any water to the tank). Add 4 oz/gal (30 grams/liter) Al-Brite A. Stir well (Al-Brite A may not completely dissolve immediately, however, as it is consumed it will dissolve).

Temperature should be 70 -90 F. Al-Brite A/B (RD-21/RD-22) can be speeded up dramatically by agitating the solution (or the work). Do NOT use air agitation. The time required for compete desmutting will vary with the amount of the etch, the more metal removed in the etch, the longer the time required for complete desmutting.

Polypropylene tanks, with venting. Use only plastisol coated racks, do not use Stainless Steel racks.

Al-Brite can be effectively controlled by monitoring two variables: Water content, and Al-Brite A content. Water may be monitored by measuring specific gravity (Baume'). There is no absolute standard, the more water in the solution, the lower the specific gravity. Each user needs to determine the maximum allowable level of water contamination. When the water level gets too high, metal loss becomes excessive, and desmutting slows. When the water level reaches the maximum allowable, the bath should be re-made.

Al-Brite A (RD-21)concentration is best monitored using a Fluoride specific electrode, and maintaining the fluoride level at 10-20 grams per liter, equivalent to 15-30 grams per liter of Al-Brite A (RD-21).


Used solutions contain strong acids, including Nitric and traces of Hydrofluoric acid. Use with extreme caution. Workers exposed must wear splash goggles, Neoprene gloves, and other protection as required to keep Al-Brite solutions from contacting skin. Any contact should be washed with flowing cold water immediately, and treated, if necessary as a Hydrofluoric Acid burn. Al-Brite A/B (RD-21/RD-22) will give off acid fumes and must be used only in a well ventilated tank. Recommend 240+ Cubic Meters/minute air flow per meter of tank front. Consult Material Safety Data Sheet for further information.

Used solutions may contain heavy metals, which may have to be removed before solutions can be disposed of. These usually may be removed by neutralizing to pH>9.0, and precipitating, filtering off residue. Neutralization should be done only on diluted solutions, as concentrated acids will react violently with neutralizing alkali. Dispose of in accordance with Federal, State and local regulations. Contact your RD Chemical representative for further information.


Al-Brite A (RD-21) is available in 50# and 100# fiber drums. Al-Brite B (RD-22) is available in 15 and 30 gallon poly drums.