With my models, there is a large number of ZAMAK castings. ZAMAK is largely alum of course. I use Birchwood-Casey Alum Black prior to painting. Not so much a primer as a "backup" for scratches or flaking. The desired finish color is not a true black, but rather a variable very dark gray. By using the Birchwood-Casey product, a chip is virtually unnoticable.
But, and this does matter, the models are not "handled" on a serious basis. The "pre-blackening" is often used as a temporary coloring agent until I can get around to painting. It is not a true black and it doesn't stand up very well to handling. For something that would have constant handling, I would use a "Plasti-Dip" like product in the appropriate color. For handling as well as the electrical insulation properties.
Anodizing is not a solid option for several reasons, nor is powder coating. Setup time is a portion of this, as is the small quantities involved. In my case, very small details are inportant. Powder coating wouldn't work for that reason alone. I've never seen Plasti-Dip in black, but it should be available somewhere by someone.
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