I would think that bluing (talk to a gunsmith about this) would be a good alternative as it penetrates the metal, and doesn't add thickness and throw off clearances as powdercoating does. However, the prep work is a pain in the a**.
I had to modify a
Floyd Rose R5
locking nut to fit a 540 pii neck. The machining peeled off the original plating. My chromer said that black chrome wouldn't flow into the crevasses well, and powdercoating added way too much thickness (trust me, I tried). After about 2 hours of filing and ginding to get all the nickel off, hot bluing worked well. It isn't a perfect match for cosmo chrome, but its close enough.
