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Is copper underplate required for electroless nickel plating?

October 13, 2009

Hi Everyone,

I need to plate electroless nickel over aluminum substate.

The proposal is to plate with .0005 to .0007 mid phorphorus electroless nickel, over .0001 to .0002 copper underplate, over zincate.

Our new vendor requires the copper underplate in order to protect the "sharp" edges of our part for 48hr salt spray. Apparently the electroless nickel adheres better over copper.

But I had the same parts from our current vendor that meet the same salt spray requirements without the need for copper underplate.

Does anyone have any further explanation on how the copper underplate works? Is there something else that can be done to improve salt spray performance without changing my fore-mentioned proposal less copper underplate?

Thanks,

John Cheng
engineer - Toronto, Ontario, Canada

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Hi, John. The basic situation is that in order to plate onto aluminum you must zincate it, and the zincate is a thin and rather delicate coating that would dissolve if you placed it into an acidic bath. So you can either cyanide copper plate the zincate or you can directly electroless nickel plate it, providing that the electroless nickel bath is non-acidic and compatible with zincate.

Is it possible that the new plater's electroless nickel bath is not fully compatible with the zincate and dissolves it at thesse edges?

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 2009

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Your plater's process is common. I strongly feel that an alkaline electroless nickel strike gives better EN top coat adhesion and better salt spray. James Watts - Navarre, Florida 15 years ago when I converted Navy Jacksonville from copper cyanide underplate to ALKALINE electroless nickel understrike followed by 0.060 sulfamate nickel, , their adhesion rejects dropped from over 50% to under 2%. Robert H Probert Robert H Probert Technical Services Garner, North Carolina

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Thanks for all your suggestions...I'll do some experiments accordingly and post my results...

John

John Cheng
- Toronto, Ontario, Canada
October 16, 2009