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Electroless nickel

I need some help on a problem - I have been attempting to do some electroless nickel plating and have come across several problems that I have overcome except one. When I submerge the substrate in the solution for approximately ten minutes the underside of the substrate nickel plates without any defects but the top turns a blotchy black in appearance and does not seem to adhere to the substrate very well.

Could you please help with this problem?

John Cochrane
- Eden, New South Wales, Australia
2001

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First of two simultaneous responses --

Could be several things. First I would check for floating oil in your cleaners, rinses and acids. It also could be a bath problem with too much lead, cadmium or sulfur due to improper make up, manufacture, plating of leaded metals or drag in of sulfur containing oils.

Todd Osmolski
- Charlotte, North Carolina, USA
2001

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Second of two simultaneous responses -- 2001

Hi,

To solve this more information is needed,

Substrate material and pretreatments.

Temperature of nickel and if it is home brew or off the shelf.

The one thing it sounds like is a stabiliser problem but I have never seen one that just affects one area of a part.

Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

Hi John:

If only the top side of your part is coming out rough and dark, it means that, apart from substrates, pretreatments, etc., your problem must be "suspended particles". The most probable causes are excessive activity due to improper balance (the particles are spontaneous precipitated nickel) and improper filtration (any particle will accelerate reaction). Stabilize your reaction or lower it a little (temp, pH, load, you know) and improve filtration. Your supplier should help you. Even if you're using a home brew formula, the companies that sell the hypo normally can help.

Good luck.

Guillermo Marrufo
Monterrey, NL, Mexico
2001