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topic 2099

Improving adhesion with a two step zincate


(1998)

I am actively working on NiP plating pretreatments. If anyone has any suggestions as to how to improve adhesion with a two step zincate. Mainly, I would like to contact those working on these types of problems to discuss options. has anyone used the recycling methods from Oak Ridge? Also, what aspects of the NiP bath effect adhesion?

Tom Read
- San Jose, California


(1998)

Dear Tom ,

I am generally not a fan of double zincating , having said that I know of shops where it was the answer to ongoing problems , However , in my opinion the best zincate is one that gives an even dark grey color without any splotches or light colored patches , to achieve this I would recommend a dip time of approximately 2 minutes , agitation of the zincate ( not violent but enough to keep it moving ) and most importantly frequent analysis to establish a drag - out figure and hence a solution maintenance schedule .

What you must remember is that the Zinc dissolves in the NiP very quickly and any patches that bare up before plating has initiated will give rise to bad adhesion problems , remember also the rate of dissolution of the Zinc film increases rapidly as the temperature increases .

Have you considered an Electrolytic Strike of say Watts Nickel between Zincate & NiP coating ?

Regards

John Tenison-Woods
John Tenison - Woods
- Victoria Australia


(1998)

John is right, the zincate layer dissolves in the NiP solution, that's why you should use a special NiP with high PH (8-9) that are specialy formulated for EN plating on aluminum. You can use a high PH En soltion to plate a flash EN layer and then enter into a regular low PH (4.6-5) for the heavy layer plating.

Beside, I hope you use a cleaner and deoxidizing agent prior to the double zincate.

sara michaeli
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel




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