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Replacement for Hard Anodize in a Casting

We presently produce a line of vacuum regulators out of machined 6061 Aluminum. The base parts are hard anodized and colored black for both functional and aesthetic requirements. We would like to move this product into a die casting but the finishing aspect is the holdup.

The ability to hard anodize castings is fairly limited, at least from the research on this site and others. The hard anodized castings we have looked at have not had a uniform coloring that match the appearance of a machined / hard anodized part.

Is there another plating/conversion coating for a casting that will yield a usable wear surface and still maintain decent aesthetic qualities?

We have been looking at electroless nickel since we can trade off some of the hardness of the present product, but we would still like to come back with something dark in color (which EN is not). Cost is always an issue as well.

Kevin Klocek
laboratories - Norristown, Pennsylvania, USA
2006

EN can be blackened with little effort in diluted nitric acid. There will be some objectionable odors and hazardous waste although.

Guillermo Marrufo
Monterrey, NL, Mexico
2006