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Yellow chromating remachined area on black anodized part

(-----) 2006

We currently Black Anodize per Mil-A-8625 [link is to free spec spec at Defense Logistics Agency, dla.mil] Type II Class 2 a small machined part. After Black Anodize, my customer re-machines a small area & returns to us for yellow chromate PER Mil-C-5541 [link is to free spec at Defense Logistics Agency, dla.mil] Class 1A of that machined area.

The problem is, to get a good yellow chromate on the re-machined area risks damaging & discoloring the black anodize.

We have run this job for quite some time & mostly get good results but there is a fine line where the chromate is too light, but if you go darker, like the customer wants it, you discolor the black.

Should we give up on this method & simply re-quote the customer based on chromate all over, mask & then black anodize we of course know that will work, but may be too costly.

Anyone have any suggestions?

David A. Kraft
- Long Island City, New York


My suggestion would be to re-investigate masking if you haven't done so very recently, David. Sometimes precision masking is employed today for situations like this. Think of today's high definition circuit boards and realize that super precision is not a problem if it makes sense considering the alternatives.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


Why not use a touch up kit. The two biggest names in chem film [Ed. note: Henkel, Macdermid] used to sell kits, and sometimes they would tell you how to make it up from their material that you probably already have. A little time consuming, but you indicated that it was only a small area. We had set a couple of customers up with the kits, so they could do it themself and avoid the paperwork and the travel time. Both thought that we were good guys for the time savings.

James Watts
- Navarre, Florida

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