letter 25291

Should EN baths have wetting agents or not?  

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I am starting into electroless nickel plating. I have tried 3 different baths from 3 suppliers, and all baths apparently came without wetting agent. Is there any reason to use no wetting agent in EN baths? There was something like pitting on the parts plated with low-phosphorous nickel, so I thought that proper wetting agents would help. I will appreciate any experience or opinion.

Thanks,

FRANTISEK HAAS
glass products - JABLONEC N.N., BOHEMIA, CZECH REPUBLIC

This seems to be a complaint to your suppliers. What do they have to say about it? Every chemistry is different, so it is very difficult to recommend an addition not knowing what is in your bath,

G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico

Good question. Generally alkali electroless nickel baths don't have wetting agents, but many acid based baths do include them. Wetting agents are there to make the substrate more wettable and with alkaline baths, especially ones using sodium hydroxide, have a "built-in" wetting agent, namely caustic soda. Conversely, acid based baths don't have this luxury.

Trevor Crichton R&D practical scientist - UK

Guillermo,

I don't complain to my suppliers, I only wonder, why there is no wetting agent in EN baths. Other week acid processes (electroplated nickel or zinc)always use wet. agents, so why not EN? Is there any fundamental reason? Trevor says,there is not. Many thanks for your responses.

FRANTISEK HAAS
glass products - Jablonec n.N., Czech Republic

Wetting agents are usually not necessary in electroless nickel plating solution because the hydrogen gassing occurs quickly enough that bubbles leave the surface without causing pitting. Why add something ( wetting agents, i.e. surfactants when not needed?) Some surfactants are or become organic contamination to electroless nick plating solutions. If there is oil or other organic contamination introduced into the EN plating solution, wetting agents will help temporarily, other wise they should be avoided. There are only a few wetting agents suitable for electroless nickel solutions. If pitting is encountered it is almost always because of improper preparation, i.e. something is left on the part, not removed by cleaning, or there is a pit in the basis metal that has entrapped cleaner or other materials.

Don Baudrand Don Baudrand, Consultant   Poulsbo, Washington

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