Aluminum Anodizing and RoHS compliance

A. Hi Bruce. Other standards like REACH may effect what chemicals you can use in a process within the European Union, but RoHS is primarily about recycling and is concerned with what is actually in/on the parts you ship into Europe. Assuming reasonable rinsing, a deoxidizer used before anodizing should be non-detectable in the finished product.

Regards,

A. Hi all.

Adding to Ted's comment, when talking about RoHS requirements ala Directive 2002/95/EC: in the case of Hex chrome, RoHS compliant doesn't means 0, the tolerable limit of Hex Chrome is 1000 ppm.
My last reading was way back, don't know whether there were further amendments.

Good Luck.

A. The only exemption for CR6 is due to an unintentional amount. The second that you put on your drawing that you want something on your part it's no longer unintentional. By unintentional they mean that perhaps your plater didn't get his tanks completely clean before he put the trivalent compound in if they are putting anything with hex chrome on your parts you are NOT compliant. The ONLY way to control that is to put the exact chemical that you require on your drawing for your part then force the manufacturer to certify that is what they used.

Thanks William, and I'm sure you're right regarding anodizing and post-treatments as well as chem-filming / chromate conversion coating). But can you offer a reference so we can further investigate Bruce's question about desmutting?

Chrome plating is allowed under RoHS although it involves hex chrome because none is left on the components when the process is complete. There are many other pretreatment processes applied in industry which involve toxins which don't end up on the shipped components.

Chromic acid desmutting is an early process step, and I doubt that it leaves any hexavalent chromium on the parts, so I'm having trouble understanding how it would fail to comply with the RoHS directive.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. The specification is actually very clear that incidental content of CR6 is ok in very trace amounts. Again the SECOND that you reference one of the mil specs or ASTM specs without being specific on the dye used you run the risk of being out of compliance. It's not a guarantee however due to the subjectiveness of the specs. But those specs do NOT drive any sort of compliance UNLESS you tell your supplier your requirements are more than just black anodize.

William Deberard [returning]
- Brighton, Colorado

A. As far as I can tell via the directive the material, as is, is RoHS compliant. If it has a chem. film containing Hex chrome it would not comply.

A. Hi, Alex

Any chromium within a metal alloy is itself metal, at oxidation state 0. The concern over hexavalent chromium, as far as I know, is restricted to certain types of coatings. There is a chromic acid anodizing process that could leave chromic acid (hexavalent chrome) on the parts; there are chromic acid sealing processes that could leave hexavalent chrome on anodized parts; and there are hexavalent chromate conversion coatings that could leave hexavalent chrome on the parts.

While a metal itself does not contain hexavalent chrome, there are anodizing processes and conversion coating processes available that leave it hexavalent-free and RoHS compliant. When you send the parts out for finishing, do not specify chromic acid anodizing or a chromic acid seal, and do specify "RoHS compliant". Best of luck!

Regards,

A. Possibly, if the dyes are metallic? How about dichromate seal?

A. Not ordinarily, but there are a few things you should check:

1) - make sure that they black dye doesn't have hex-chrome in it. Most have trivalent chrome, but that is okay.

2) - while it would be VERY unlikely, make sure that the parts aren't sealed in sodium dichromate or potassium dichromate. This won't normally be a problem because of discoloration issues anyway.

3) (sorta) I don't think that nickel is part of ROHS, but if it is, get the parts sealed in hot DI water instead of nickel acetate.

Otherwise, you're probably okay. But, there is always the potential that your anodizer does something weird, so get the list of metals you're worried about and check with them.

A. Who's gold colorant? Our dyes are RoHS compliant, but I had to call the mfgr. of our dyes to confirm that. I would suggest you do the same!
Good luck,

A. Eloxation = anodizing, from the German "Electrolytisch Oxidiertes Aluminium." Originally oxalic acid anodizing (Eloxal GX, GXh, WX, WGX), but now more commonly sulfuric acid anodizing (Eloxal GS) approximately MIL-A-8625 / MIL-PRF-8625 [on DLA]F Type II.

Should be RoHS compliant unless dichromate sealed or if a leaded, free-machining alloy (Al 2007, 2011, 2030, etc.) is used.