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  for Metal Finishing since 1989
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Zincate Dissolution in EN-B Bath

I have a need to possibly zincate an aluminum surface before proceeding to the EN step. The EN solution will have a pH of 8-10, temp = 160 F. Is this bath strong enough to break down the zinc layer?

Patrick Franklin
- Santa Barbara, California
2000

As as soon as the zincate layer dissolves into the EN solution , it codeposits with nickel on to the substrate.So there is always a zinc layer between the substrate and EN coating. This layer is called ZRZ and its thickness depends on the composition of zincate solution and also the concentration and the type of inhibitore which is used as a constituent of EN bath.

Nazila Dadvand
- Halifax, Canada
2000

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This may be old information, but zinc used to build up in the Electroless nickel solution used to plate over a zincated aluminum part, eventually poisoning the E'less bath. So at least some of the zinc dissolves into the nickel bath, and does not codeposit at the interface.

  
Tom Pullizzi
Falls Township, Pennsylvania
2000

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In order to avoid the accumulation of zinc in the EN (as Tom mentioned) and to get a better adhesion , use an alkaline EN with PH approx. 8 prior to the low PH 4.8-5. The EN with the low PH has a higher attack the zincate layer.

Sara Michaeli
Tel-Aviv-Yafo, Israel
2000