Summary for replating electroless nickel Discussion
Replating electroless nickel without stripping is possible, but it is not easy and the activation window is critical. Christos Sigalas asked whether a steel part with spots of existing electroless nickel could be plated again without any mechanical or chemical stripping, and suggested NaOH degreasing, 30% HCl deoxidizing, and a nickel strike. Ken suggested trying an acid salt activator containing fluoride. James Watts said old electroless nickel is hard to activate and recommended looking at activation steps for both nickel and the base metal, then finding a compromise; he specifically advised a strong-acid, low-nickel Woods nickel strike after acid activation. The thread does not give a guaranteed procedure, but it does indicate that careful activation and strike conditions are the key to getting new nickel to adhere over existing electroless nickel.
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
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
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