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Adhesion between nickel sulfamate plate and acid copper plate

We plate aluminum. We zincate first then into a Nickel sulfamate plate for 7 minutes (pH of bath is 3.5 to 4.0), two flowing rinses at a ph of 7.5 to 8.5 and then into an acid copper bath. We have recently been having adhesion issues between the Nickel sulfamate and acid copper. Any suggestions? There is very little Copper or Zinc in the sulfamate and the Hull cell panel looks very clean.

William E. Johnson
plating shop employee - Milwaukee, Wisconsin
2005

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First of two simultaneous responses -- 2005

First, I recommend you talk to your chemistry vendors; they are a great resource in solving plating problems.

Having said that, I've always had an acid dip between nickel and subsequent plating.

James Totter, CEF
- Tallahassee, Florida

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Second of two simultaneous responses --

Copper is not my bag, but I thought that it took a copper strike for adhesion.
If a strike is not required, then the nickel is oxidizing because it is taking too long before it gets into the copper tank or the nickel surface is allowed to partially dry. If it were mine, I would want the rinses at 7 or below as some of the nickel being rinsed will turn to a super thin layer of nickel hydroxide which can stick to the metal surface like glue.

James Watts
- Navarre, Florida
2005