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Clear vs yellow chromate

I work for an automotive supplier, and I have been testing hex chrome free alternatives to current production part. I am currently attempting to understand the results of these tests and our new specs for trivalent chromium. I have been told that trivalent chromium comes in clear and yellow forms. Is this true and what is the difference? I have also been given the term "ELV high corrosion chromate." What does "ELV" mean and does this correspond to yellow chromate? Also, is it possible to get trivalent chromium in the many colors that hex chrome is available in?

Katie Eaton
- South Bend, IN, USA
2002

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ELV is, I believe, an acronym for "End-of-Life, Vehicle" and it alludes to the directive of the European Parliament that, to improve recylability, so little hexavalent chromate is permitted on a vehicle that, for practical purposes, it is banned.

It is possible to dye the trivalent chromates to a yellow color. But I don't understand why the automakers are interested in this kind of deception--and it strikes me as short-sighted. Here's a wild prediction: someday soon we are going to be ordered to remove all hex chromated hardware and components from the junkyards and treat these parts as hazardous . . . and people will be writing to finishing.com asking for an easy way to quickly distinquish actual hexavalent chromated hardware from trivalent chromate hardware that was dyed yellow to make it look like the banned hexavalent stuff :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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Everything Ted Mooney said is important. Some years back on a casting for the automotive industry we were zinc plating then yellow chromating, then applying the silicate type coating per that company's automotive spec. We got 500 hours 5% salt spray. When we had to ship parts to Europe we use Zinc Nickel Alloy topped off with a proprietary non-chromate blue color and got 500 hours 5% salt spray.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003

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I attended a meeting awhile back centered on replacement of cadmium and hex chrome for the military. The military's problem with tri chromate was the color. Being clear, it makes it difficult to tell if the chromate coverage is complete. It seems that other conversion coatings suffer from the same problem. So adding the color could be very important.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover - San Diego,
California
2003

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How about pink, purple, pastel green, or a thousand other shades then, Jim? Why does it have to disguise itself as hexavalent when that's only going to get people in trouble anyway :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003