Process difference between Cr6 vs Cr3 plating 1

[malcolm123]

I am trying to do an investigation between the two processes as a costing excercise is there any one out there who can give me a breakdown of the two processes? What is the difference in equipment and products used to perform each method of chrome plating...

 

[CoryPad]

Usually, hexavalent and trivalent chromium are part of aqueous solutions that deposit onto metallic substrates and are called conversion coatings. Metallic chromium plating (hard chrome, decorative chrome, etc.) is completely different. If you mean conversion coatings, then there is no difference between the actual application processes, just different starting materials.

Regards,

Cory

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[malcolm123]

Cory
Thanks for the feedback, if there is essentially no difference in process, then how is it that the Cr3 is more expensive?

 

[CoryPad]

Supply and demand, new technology required to produce the initial conversion coating liquid, etc. I assumed you were asking about applying the final conversion coating, but if you are asking about the chemical processes used to make the starting liquid, then I can't help.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[malcolm123]

Thanks anyway

 

[ivymike]

I thought that the use of CR6 in piston ring coating applications had been outlawed in many places due to environmental concerns.

 

[malcolm123]

Cr6 Is outlawed and I believe the new laws come in 2007. If Cr3 is the way to go how come we are paying more for it???? Especially if the process doesnt differ?

 

[ivymike]

recently increased demand?

 

[HDS]

If you are required to use it by law that increases the demand and reduces the competition.

The basic process is the same but there are different details. Because tri is a lower performance material you have to do other things to restore the performance to where it was with hex. If it is a decorative part you similar problems. That is one of the reasons tri never replaced hex in the past.

There is "essentially no difference in process" between Budwiser and Guiness. Why does one cost more?

 

[CoryPad]

Malcolm,

Let me use an example. Externally threaded fasteners (screws) used for automobile production, approximately 1 million pieces per year. After forming the screw, they are electroplated with zinc. Then, they are immersed in a liquid bath to form a conversion coating containing hexavalent chromium. To meet the European Union directive regarding End of Life Vehicles, the conversion coating must be changed to trivalent chromium. If I am making the screws, I now use a different liquid to immerse my zinc-plated steel screws. My process is not different.

To make the conversion coating liquid, my supplier must do different things (like extremely complex testing to differentiate between the two valence states for chromium). Since this was a mature industry, but now had a large change in a short time, there is an inevitable cost increase. Perhaps the cost will decrease with time.

If you want more information, try contacting the conversion coating manufacturers.

Atotech

http://www.atotech.com/start.php3?cl_my_id=1003980

Aldoa

http://www.aldoaco.com/

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[malcolm123]

Well what can I say, I've only been a memeber for a day and already have made so many new acquaintences, many thanks one and all and well done this site

I shall be perusing the site regularly who know I may even be able to contribute something worthwhile.