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Galvanized finish RoHS compliant?

2006

Is a Clear or yellow zinc Di-chromate? finish RoHS compliant?
I've read here that clear or yellow zinc with Trivalent chromium is compliant. Is that two separate process's (zinc plating, then Trivalent chromium)?

Galvanized is certainly NOT compliant correct? Or is there a process that can make this compliant?

Rubens Chiluk
- Lincolnshire, Illinois, USA

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Hi Rubens. Zinc electroplating is a useful corrosion resistant finish for steel, but the zinc in turn tends to form a white rust. To prevent this, zinc plating is almost always chromate conversion coated. Traditionally, this dip, although usually proprietary with carefully designed amounts of fluorides and so on, was basically based on hexavalent chromium (which is not RoHS compliant). Today's chromate conversion coatings are based on trivalent chromium and are rather high-tech chemically, so they are almost always proprietary. Trivalent chromates usually require a further dip into a silicate or zirconium or other post-dip to match the performance of hexavalent chromates.

"Galvanizing" usually refers to hot-dip galvanizing (molten zinc) rather than an electroplating process. Galvanizing tends to have less issue in chromate compliance than electroplating because the zinc is much thicker and the EU in their boundless wisdom considers the zinc and the chromate together to be a "homogeneous" coating despite the fact that it's clearly not, and regulates the allowable percentage of hexavalent chromium in these combined layers. Galvanizing can, however, have the additional compliance issue of unacceptable amounts of lead. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 2013