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Adherence of Electro Formed Nickel to Low Ra Steel

September 28, 2009

We have a process for plating Watts nickel on Stainless Steel at thicknesses from 0.003 to 0.006 inches.

A Problem we encounter is that while the nickel sticks well on most stainless ( 300 series ) it does not stick well if the Ra of the surface is 0.10 or below.

We see this even though we plate the two simultaneously at the same temperature. current density pH etc, etc

Is there a cure for this problem?

Ronald Tripp
nickel Electro forming - Johnson City, New York

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September 28, 2009

Hi, Ronald., You would need a Wood's Nickel Strike too get real adhesion on stainless steel. Details of how it works and quantitative data about how well it works can be found in Dini's "Electrodeposition".

But you say you are doing electroforming, so you probably have a different concept of adhesion than most electroplaters. I suspect that you are not looking for real adhesion, but sufficient grip that the electroform doesn't spontaeously fall off, with poor enough adhesion that you can remove the electroform when you are ready.

When, as in your case, you don't have actual metallic adhesion, but only a mechanical "keying" effect, it is no surprise that you get a better key on rough parts than on smooth parts. Maybe you can get sufficient adhesion on these smoother parts by adjusting or eliminating the passivation step.

Regards,

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

Check the stress too, watts nickel usually has high tensile stress which will cause the nickel to separate from the mandrel at the edges of a plate or cause blister like or wrinkling of the electroform. Electroforming of nickel is usually carried out using a sulfamate nickel bath because the stress is much lower. I agree with Ted that a woods nickel strike will adhere no matter how smooth the mandrel surface is.

Russell Richter
- Danbury, Connecticut, USA
October 1, 2009