RoHS compliant plating queries - take two!

[nigelt]

Perhaps I just have really poor resources, but hands up anyone else who is struggling with finding clarity on issues surrounding plating finishes and RoHS compliance?

We are looking at it from the design & specifying side & we hear so many myths about what is & isn't compliant.

I have queries for:
(1) bright "white" chrome on sheet steel.
(2) bright "white" chrome on Zinc alloy ( eg.Zamac) die castings.
(3) bright black or gunmetal chrome on Zn alloy die castings.
(4) bright black chrome on machined brass hardware.

Are there RoHS issues here? I know that's a lot of questions, so I'll be happy with a general answer.

Thanks in advance!

"You will master any feeling of inadequacy you may be having"
....from my fortune cookie @ the buffet!

 

[kenvlach]

(1), (2): Metallic chromium plating is RoHS-compliant (no Cr[sup]+6[/sup]).

(3), (4): Possible problems. A common black chrome formula [MIL-C-14538C & newer version MIL-DTL-14538D Chromium Plating, Black (Electrodeposited)] is considered to produce hex-Cr. I believe it may actually produces Cr[sup]+5[/sup] in the form Ba[sub]3[/sub](CrO[sub]4[/sub])[sub]2[/sub].
However, chemical suppliers have proprietary trivalent black processes available; e.g.,

http://www.luster-on.com/html/chemicals.html

If referring to black chromate conversion coatings on zinc (rather than chromium plating), both hex- and trivalent chromates are available, nearly all proprietary.