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Process steps for Iridite plating

We have aluminum castings that have a black dust on all surfaces. What are the proper steps for clear Iridite of an aluminum casting? What might best remove this dust?

Phil Nutting
- Beverly, Massachusetts
2002

2002

Clean in a non-etch cleaner. Do not alkaline etch because is will increase the area of silicon and decrease the area of aluminum which is exactly the opposite of what you need to do.

If sand casting, dip in 100% NItric Acid plus 2 pounds per gallon ammonium bifluoride until the part turns "frothy white" all over. Rinse two times, do not stop to look. Plunge into the chromate.

If die cast,use only 50% Nitric Acid plus only 1 pound per gallon ammonium bufluoride.

The chromate brand name you sighted is available for full yellow and under a different trade name for clear. The clear is just a weaker version.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

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