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"Should we worry about Hexavalent Chromium on finished products?"


Q. The question presented to me was, " Is there any hexavalent chromium on a component after it is plated, rinsed, dried, and finished?" The part is a machine component sold around the world. The machine cannot be sold in Europe if any Cr6 remains on the component. Supposedly, the Cr6 becomes Cr after the process is complete and we are confident that it does. What would have to go wrong for the Cr6 to stay, and how likely is it to happen?
Should this even be an issue we have to worry about?

Thanks Again

James Haney
Enviromental Engineer - Cleveland, OH, US

simultaneous 2005

A. Just to clarify - are you talking about chrome plating or zinc plating with a chromate topcoat?

If you're talking about chrome plating, the only possible way hex-chrome would be involved at the end was if chemical was entrapped - and this would actually end up giving you much bigger problems and be noticeable rather quickly. It isn't something you need to worry about, to the best of my knowledge.

If you're talking about zinc plating with a chomate topcoat, then hex-chrome is involved unless you specify otherwise. To avoid it just make sure that you specify a hex-free chromate.

Good luck.

Jim Gorsich
Accurate Anodizing Inc.
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Compton, California, USA
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A. RoHS questions from an Environmental Engineer...this has to be a first! At least you have some knowledge of chemistry and are likely to grasp the concept! However, you didn't tell us what plating you're dealing with: is it zinc with a chromate post treatment? or chrome plating? or black chrome plating? If it's zinc or cadmium it's likely to contain hexavalent chrome. If it's chrome plating including either decorative nickel chrome or hard engineering chrome, it should be chromium metal with a valence of zero - that is non-hexavalent! Any residual hex chrome that remains could be construed as a contaminant and not intensional, thus is permissible up to the 1,000 ppm threshold. Black chrome plating is another story and as far as my firm has tested, it contains hex chrome as it deposits chromium trioxide which means the chromium is hexavalent! It's encouraging that someone with an engineering background is finally asking the right questions - congrats to you!

milt stevenson jr.
Milt Stevenson, Jr.
Anoplate Corporation
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Syracuse, New York
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