plating, anodizing, & finishing Q&As since 1989
Standard commercial zinc plating and hexavalent chromium
I have been told that standard commercial zinc (clear) plating contains hexavalent chromium in excess of RoHS allowance (1000 ppm). What % or how many ppm of hexavalent chromium is there in zinc plating commonly used to plate fasteners?Mike Bane
We are a fastener direct importer and distributor involved with many electronic manufacturing organizations, including HP, Dell, and Motorola. We have bee supplying "RoHS"-compliant products for nearly 2 years and have found some very interesting data from product testing.
Extensive testing of deliverable fasteners we had manufactured domestically (USA) and in Asia show that there is nearly zero (0) +6 Cr (hexavalent Cr) detectable on most. This has been true using hex Cr and tri Cr processes. Even testing of zinc with yellow chromate product normally results in less than 5 ppm +6 Cr, often the result is reported as "not detected, <2 ppm". We use only accredited testing organizations and USA EPA designated methods. We are continuing to investigate the cause and ramifications of these results (no... we will not share this with others, so please do not ask!).
Our frustration has been customers that assume to understand the Directive, but have "expanded" the RoHS statements by banning some materials at any point in the supply chain.
This response is intended to address the question asked. The answer is far, far from simple. Base material composition, plating process selection, plating bath composition, passive layer generation methods and materials, and many other factors determine if the product is "RoHS-compliant". Remember that the Directive itself covers products placed in the European States for sale with the intent of reducing the hazards of recycling or scrapping these products at end-of-life. The focus is on the actual product put on the EU market, not on the processes used to produce the deliverable.
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