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topic 2713

Iridescent zinc plating without hex-chrome


Do you know of any alternatives to iridescent zinc plating which do not contain Hexavalent Chrome? I have heard of Deltacoll, produced by Ewald Dorken in Germany (Magni Industries in America). Trivalent Chrome is being used for our other zinc colours, however iridescent is our biggest running zinc finish.

Any assistance would be most appreciated.

Kind Regards

Colin Smith, Engineering Technician
- Victoria, Australia


(1999)

Dear Colin , First you have to understand that a "Yellow" Chromate finish is yellow because of the Hex - Chrome in that chromate finish . As a lot of the work that you do is supplied to the Motor industry (or used to be) the colour is important and more importantly the parts must meet "Salt Spray" performance and to my knowledge the Dyes that can be used over Blue chromates whether trivalent or not only degrade the Film and do not stand up under Salt Spray . There are some finishes that are available that require you to produce the "Yellow Chromate" by electrolytic means from Tri-Valent solutions , I suggest you call one of the 4 major suppliers in the Melbourne phone book and enquire of them . Regards

John Tenison-Woods
John Tenison - Woods
- Victoria Australia


(2000)

There are many alternatives available for Hexavalent Chrome in zinc plating and non-electrolytically applied coatings. In Austrailia (through Nippon Dacro Shamrock) a product called Geomet(r) which is a Zinc/Aluminum, Chromium-Free coating that outperforms most commercially available finishes is available for an application that you are describing.

Andrew R. Pfeifer
- Chardon, Ohio


If I am reading correctly, Colin, you are asking how to get an iridescent yellow color without hexavalent chrome. Changing from zinc plating to zinc-rich dip-spin coating doesn't achieve that goal to my knowledge.

But I am of the opinion that all of us in the finishing industry should be pushing hard to dump the yellow color as we dump the hexavalent chromium from the finish. The yellow is the natural color of that specific toxic, carcinogenic substance and as we eliminate it, it strikes me as foolish to work hard to put the new environmentally friendly finishes in the guise of the poison itself. However, if you can't sway the customer to that mind set, there are now some trivalent chrome finishes that are yellow, although perhaps not fully iridescent.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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