Metal finishing Q&As since 1989

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Electroless Ni vs electrolytic Ni - why is e-less less ductile and has lower melting temp

2002

I have learned that electroless Ni plating (with varying amounts of P to increase corrosion resistance) is less ductile than electrolytic plating.

Can someone explain to me why electroless Ni is less ductile? Is it to do with the P content or the plating itself? Also, electroless Ni has a lower melting temperature than electrolytic Ni. Also, what is that due to? Is that due to the P content or the plating itself?

Thanks,

Andre Wong
- Santa Clara, California, USA

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An electroless nickel plating is not nickel, it's a nickel phosphorous alloy. People sometimes refer to it as a metallic glass. Reduced ductility is probably an intrinsic property of the deposit.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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First of two simultaneous responses -- 2002

Andre,

I am not a plater and therefore highly ignorant of actual plating processes.

But you mention 'P' which I am led to believe stands for Phosphorus .... and in the manufacture of iron, both P & S are highly detrimental and have to be reduced (to 0.06%, I forget) BECAUSE they cause embrittlement ... P at higher temperatures and S at lower temperatures (maybe the other way around, I forget, seeing that I learnt this 50 years ago).

Hence, I'd assume that an increase in 'P' would make the ductility worse, eh?

As far as the lower melting temperature is concerned, heck, if you 'alloy' a metal, I'd assume, depending upon the alloy, that the melting temperature will ALWAYS increase or decrease. That does make sense, doesn't it.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

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Second of two simultaneous responses -- 2002

Answers: 1-Yes. 2-Yes.
Electrolytic nickel is almost pure. On the other hand, the predominant consituent in EN's is nickel phosphide which is hard and brittle. Something else, many EN's are amorphous (do not have a definite crystal microstructure under microscope very much like glasss), you need to look with super microscopes to see something. This gives better corrosion resistance as corrosion finds it more difficult to find a weak point to begin. Also, as most alloys, EN exhibits a melting point directly proportional to its chemical constituents and as you know Phosphorous has a very low melt point.

Bye,

Guillermo Marrufo
Monterrey, NL, Mexico