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RoHS compliance and chromate conversion on aluminum

We need clarification on the RoHS Directive (Directive 2002/95/EC), regarding the 0.1% by weight of chromate conversion coating on aluminum, with regard to the statement Homogeneous Material". If the coating can not be separated from the substrate is is considered homogeneous.

Thank you

Dave Sommervold
- Prescott, Wisconsin
2004

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From the way I've been following the Chromate Conversion Coating RoHS issue, this is my take:

In the joint industry guide - material composition declaration guide of Sept. +++ - Materials and Substances:

For Hexavalent chrome/hexavalent chromium compounds (RoHS), the threshold given is either 1000ppm or Intentionally Added.

Since hex chromate films are intentionally added, they are not less than the threshold level and therefore prohibited.

Steve Richardson
- Randolph, MA, U.S.A.
2005

The RoHS directive does not mention "intentionally added"

C James
- Swindon, UK
2005

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A simplified definition of homogeneous - both chemical composition and structure are the same. (it leads to the same repeating unit cells extending in 3 dimensions)

Although the coating cannot be separated from the aluminum substrate physically, they are not homogeneous since the chemical composition and structure of the coating and the aluminum substrate must be different.

Structure must be considered. Example, a graphite coating on a diamond, they are not homogenous although the chemical composition of them is the same (assume pure carbon).

Asa Chung
- Hong Kong
2005