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Percent hexavalent chrome in our parts?

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We manufacture parts that are plated with zinc & yellow chromate to Spec QQZ325, Type 2, Class 2. I have been asked to report on the percent of hexavalent chrome in our parts and have been unable to get this information from our plating vendors. Where can I get the total weight per volume of this plating and the percentage fo the plating that is hexavalent chrome?

Timothy Dahlstrom
Manufacturing - Torrington, Connecticut, USA

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In an article titled 'Replacing hexavalent chromium' by Paul Wynn published by a few trade magazines on both sides of the Atlantic (do a web search and you'll find it) it is stated that 'electrozinc and yellow CRVI has a film weight of 12 mg/dm2, of which 70% is identified as CrVI'.

Dougie Lightfoot
- Fife, Scotland

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Dear sir,

I don't know that spec, our company works with VW specs (VW 13750), but typical values for content of CrVI in the yellow passivation layer are 80-220 mg/m^2 (thickness: 250-500 nm). For further information, you can contact IMDS system (www.mdsystem.com). In case you have access to it, search for "Chromate film yellow Zn/ZnFe/ZnNi".

Best regards.

Francisco Ferro
- Lisboa, Portugal