Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)

by Randy Taylor, Advanced Tooling Corporation
April, 2008

 

Hard Chrome and RoHS Compliance

Q. Directive 2002/95/EC of the European Parliament and of the Council on the restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS) restrict the presence of Hexavalent Chromium to 1000 ppm per homogenous material. I have parts that are plated with hard chrome and was wondering if they are RoHS compliant. I've done a bit of research myself and found that the process includes a lot of CrIV but I can't conclude whether the hard chrome material contains any. So, does the actual hard chrome material contain Hexavalent Chromium and if so, is it above or below 1000ppm.

A. Although hard chrome is plated from a hexavalent chromium bath, in most instances, little or no hexavalent chromium remains with the part/deposit.  Limited testing has shown that hexavalent chromium may be included in the deposit under certain conditions.  I suspect that the porosity of chromium deposits (micro-structure) has something to do with it.  Small pores could theoretically collect hexavalent solution and if these pores are subsequently enclosed by the deposit, then small amounts of hexavalent chromium could reside within the deposit.  Since the porosity of the deposit is dependent of a number of variables (e.g., preplate procedures, current density, and bath chemistry), the amount of hexavalent chromium included will also vary widely from process to process and shop to shop.  If you have a significant concern about RoHS compliance, perhaps the safest route to show due diligence is to have some representative test coupons analyzed.  I believe this involves attempting to leach and test for hexavalent chromium from a metal plated sample with known surface area.  As more data are made available world-wide, hopefully this concern can be eliminated.

RT