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topic 11953

Environmental concerns re zinc or yellow di chromate zinc plating


My company makes lubrication systems and the bulk of our parts are currently zinc plated. The specification reads:

Federal Specification: QC-Z-325
Coating Specification: ASTM B633 [link by ed. to spec at TechStreet]
Classification: Fe/Zn 5
Type III with colorless chromate conversion coating.

We are proposing to replace this with Yellow Di Chromate Zinc plating because it is a better protector than what we are currently using. We do not do the plating here. It is done by a local plating specialist. I serve as environmental officer here and I have read that any plating process that involves hexavalent chrome is under investigation for environmental concerns. What is the status of this investigation?

Susan E. Burke
- Cleveland, Ohio


Hexavalent chrome has been identified as a carcinogen. This material is the subject of the mainstream movie "Erin Brockovich" [link is to movie info at Amazon] starring Julia Roberts. The automotive industry is beginning efforts to eliminate the use of this material in plating systems by model year 2003.

I wouldn't worry about switching from colorless to yellow passivation. Both of them are based on hexavalent chrome. You already buy hex chrome on your parts. If you would like to get away from hexavalent chrome, you should look into using trivalent chrome passivation. Platers are just starting to use these systems, and a few proactive platers already use this new system in production.

I do not think there has been no recorded concern with exposure to hexavalent chrome in a plating system. I handle plated parts that have hex chrome in them all the time, and am not concerned. I would be more concerned with the big vat of hex chrome used in the plating process. Even here, I do not believe there are any documented health concerns with chromic exposure. The effort to get away from hexavalent chrome actually was the result from European recycling initiatives.

You can request a material safety data sheet from the manufacturer of the chromate solutions.

tim neveau
Tim Neveau
Rochester Hills, Michigan


Hexavalent Chrome will be eliminated in the automotive industry in North America starting per USCAR steering (Ford, GM, DaimlerChrysler).

Many suppliers are scrambling to replace their current hex chrome parts with alternate technology. USCAR has done extensive research on alternative coatings and most applications are switching to Chrome-Free Zn/Al coatings that meet OEM specs (Ford WSSM21P36, GMW14, GMW 3359, DaimlerChrysler PS5873). The performance of these coatings surpass the performance of standard Zinc + Yellow (hex chrome) and far surpass the Zinc + Blue (new Trivalent Chromates).

Andrew R. Pfeifer
- Chardon, Ohio

Ed. note: this thread is dated, and mostly of historical value; but there are more than 50,000 newer threads on, and you can keep current by searching the site for "RoHS chrome".

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