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Need electrically conductive finish on aluminum casting to improve appearance, RoHS compliant

I am designing an OEM electronics module that will be enclosed in a small (1"x1"x3") aluminum casting (such as Bud Industries Cu-5123). I wish to improve the appearance to be one step better than the natural aluminum so that it looks like a finished product, but need to maintain RF shielding across the joints, and between coaxial connectors and the outer surface of the enclosure, so need good electrical conductivity in the finish. It must be RoHS compliant. Lot sizes will be modest: 20 - 50 units. This is an industrial/scientific product where people are more concerned with performance of what's inside the box than it's appearance, but I don't want the first impression to be that it was made in someone's garage, so I want it to look better than just a plain unfinished box. Yet I am cost conscious so am not willing to pay for a real dressy look. I have purchased enclosures that are powder coated and like the look, but figure that with the masking needed to keep paint from the joints and the connector mating surfaces it would be too expensive. I thought that Alodine or equivalent might be a possibility as I understand it is electrically conductive, though there appears to be some question about getting an RoHS certification. Let me mention that I will also need to label the connectors some how and put on a logo and part number; didn't figure that piece of it fit with this group, but maybe someone has an idea for a complete solution!
Thanks for any thoughts.

Paul Lingane
product designer - Redwood City, California, USA
November 29, 2009

Powder is a nice finish, but it is a good insulator, so from what you said, I doubt if it would work. Take a look at electroless nickel. It appears to fill your needs, It can be a bit expensive.

James Watts
- Navarre, Florida
November 30, 2009