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Painting over Iridited aluminum

My company is building a UAV that is made primarily of machined and extruded aluminum parts that have been coated with Iridite. I am looking for a paint process that will give a tough coating to the aluminum.

It will lead a rough life and often be stored outdoors and be exposed to the elements. I am aware that aluminum needs to be etched prior to painting, but I have also read that the Iridite coating can take the place of etching and priming.

Is this true and as a result will we be able to simply apply the paint of our choice directly over the Iridite without further preparation?

Thank you,

Connell Siddons
- Ottawa, Ontario, Canada
2003

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There are many trade names for "Chromate Conversion Coating on Aluminum" that meet MIL-C-5541f. There are many shops in your area that apply this type of coating, but most of them are "platers" and not "Painters" and do not understand the following.

Be sure your applicator understands clearly that you are going to paint and that the coating should be a very thin very light colored film. Thick chromate shears and the paint peels with it.

A thin chromate will enhance adhesion and deter corrosion spread if the paint is scratched. A heavy chromate will do just the opposite.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003