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Reworking of reject electroplated zinc die castings

 

In stripping nickel plated zinc die castings one is effectively stripping nickel from copper. I have tried various methods which one finds in the plating manuals but find them very slow. Can anyone advise of a faster method which they may have developed themselves? An alternative to stripping would be to plate over the old nickel which we have tried with some success but also with a lot of failure especially with regard to adhesion. Can anyone advise of a consistently successful method of plating nickel over nickel ? t

Thank you in anticipation.

Trevor Milton Fox
electroplaters - Boksburg, South Africa

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First of three simultaneous responses --  

Dear Mr. Fox,
Here in the U.S., people use proprietary chemicals very widely. For example, strippers for taking nickel off of copper are available from Metalx . When you add the restriction "which they may have developed themselves", which I read as implying that you don't want to use proprietary chemicals, you have to recognize that you are excluding the answers that work consistently :-)

But it is possible to plate nickel-on-nickel and it is widely used as a way of dealing with rejected parts in plating of truck bumpers for example. You need to develop a highly active nickel strike and you need to identify replated rejects so that you do not attempt to plate them more than twice.

Ted Mooney, P.E. finishing.com Brick, New Jersey

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Second of three simultaneous responses --  

To re-activate and plate nickel upon nickel for good adhesion, you must run the nickel plated castings through an activation cleaner and follow with an actisalt (acid) step. Both of these steps may/may not require currect (electro). These are proprietary. Your nickel vendor should have these chemicals and guide you on how to use them. In fact, if you are using a cleaner right now for specifically cleaning diecast, it may be the one for re-activation of the plated nickel. You cannot normally use a steel cleaner for this. You cannot use a liquid acid for good success either.

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan

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Third of three simultaneous responses --  

Talk to the folks at Metalx in North Carolina. Very tiny company, but great folks. You might-just might- experiment in the lab with a soak, short anodic and then negative in a Woods nickel strike. No other strike will work as well as a high acid lower nickel for sticking to nickel, especially old nickel. If it were on anything other than zinc, I would suggest a short dip in a nitric hydrofluoric acid vat. It will evaporate zinc faster than you can get it out of the tank if it finds a contact point.

James Watts
- Navarre, Florida