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Replating electroless nickel without stripping

Dear friends,

I need your help on the following

Can electroless nickel be plated on a steel part that has spots of electroless nickel on its surface? Stripping is not allowed by any means, mechanical or chemical, so it has to be plated as it is.

If so, what steps have to be followed? degreasing by a NaOH solution, deoxidizing by 30%HCl and then nickel strike is OK?

Thank you

Christos Sigalas
- Athens, Greece
2001

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A. Maybe try activating with acid salt, consisting fluoride.

Ken [last name deleted for privacy by Editor]
- Singapore
2001

A. Not easy, but possible. Concentrations-times temperature-current/voltage are critical. Look at activation steps for nickel and then the base metal and try compromises between both. Old EN is not easy to activate. Use a strong acid low-nickel Woods Nickel Strike after acid activation.

James Watts
- Navarre, Florida
2001

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2002

Q. I encountered the following problem, advice needed: Racking mark was observed on nickel finishing on stainless steel, after gone through proper cleaning and strike in Nickel bath.

Solution composition as follows:
Nickel sulphate 300 g/l
Nickel Chloride 85 g/l
Boric acid 45 g/l
pH 4.4
Temperature 45 °C
Current Density 1~2 A/dm2 May Soh
- Singapore