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Handling dangers of yellow zinc plated hardware





October 23, 2012

Q. What are the dangers of touching and handling yellow zinc dichromate hardware/bolts/screws on a everyday basis? I thought that zinc dichromate was being outlawed, but I see quite a few new yellow zinc screws, bolts, etc on the market. They are do not appear to be just dyed yellow trivalent zinc, but have the appearance of zinc dichromate. I know some of this hardware is from China, and not sure of their regulations. But the main question pertains to the day to day danger of handling this product, then touching other items, possibly eating after touching. What is the realistic danger if they are truly hexavalent zinc coating? I am a medical doctor, and am trying to establish a realistic risk assessment.

Steven Kulik
- Baltimore, Maryland, USA



October 24, 2012

A. Hi Steven. Hexavalent chromate is not outlawed here, although it's pretty much forbidden in Europe due to RoHS, EoLV and other restrictions. Those restrictions in turn led to all automobile manufacturers and many other manufacturers switching to trivalent chromating exclusively, which in turn led to many plating shops converting from hexavalent to trivalent chromating.

Letter 2064 from 1998 alludes to suspicion that handling of chromated parts by production workers might lead to greater incidences of skin cancer, but I suspect that the rapid widespread adoption of replacement technology removed the urgency for such studies, so they may be limited and hard to find. Certainly, casual handing by the general public was a commonplace for decades though, and most people probably still handle a lot of hexavalent chromated stuff around their house -- for example screws, knobs, hinges, and nuts & bolts in their garage or shop, and door latch hardware, etc., because most of this stuff may predate the widespread changeover.

I don't doubt that the yellow hardware that you see from China and that you think is hexavalent chromated actually is. Hexavalent is cheaper and more robust & forgiving, so the changeover on imported loose hardware will probably be slower.

Regards,

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


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