Metal finishing Q&As since 1989

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Nickel plating on wire

We have been plating silver and tin on copper wires without problems but when we tried nickel we were not very successful. We have to plate 8-9% nickel on .350mm wire the plating we did was perfect but the problem is that we have to draw this wire down to .129mm and .08mm, this where we start having problems the wire becomes very brittle after plating that we cannot draw it down. On doing a bend test with the wire it breaks after 4 bends of 180'. We have tried using a sulphate as well as sulphamate bath. The anodes we used are Nickel plates suspended in the tank with anode bags. We did try additives to get a soft deposit but nothing helps. We then read that for this we should try using S-Nickel pellets. What could be the problem ?

ASIT KUMAR
- New Delhi, INDIA
2003

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First of two simultaneous responses --

I'm thinking that the copper wire is more at fault than the process. Anyone else ?

Bill Grayson
- Santa Cruz
2003

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Second of two simultaneous responses --

Nickel is not usually regarded as an easily drawable metal whilst both tin and silver are soft and therefore easily drawn. I suspect was has happened is that when you have tried to draw it, the nickel has work hardened and when you have bent it it will break because it has become embrittled. The energy in the crack propagation is then easily sufficient for the copper wire to break. Sulphamate nickel with S-nickel rounds as anodes will give a less stressed deposit, but that will not necessarily affect the brittleness when it is drawn.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003