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Control the phosphate % in EN deposit layer

In the production of EN on brass substrate, I found that the phosphate deposit content is vary from 3% to 9%. I want to know how to control the phosphate deposit in ~8-9%. If anyone know, please reply to me. The bath operation data is stated as below, Ni content 5-6g/lt Sodium hypophosphite ~30g/l Operation Temp 90C Bath Life cycle maintain up to 8 MTO.

Thanks for your attention.

David Koo
- China
2003

You didn't mention it, but pH of solution, specially close to the surface, is one of the more important variables to affect P in the deposit. Obviously, the type of complexors and buffers play the important role in this variable. Too complicated a question to be fully answered in a forum like this. You should contact your vendor.

Guillermo Marrufo
Monterrey, NL, Mexico
2003

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2003

Dear David,

Guillermo is correct, you should contact your supplier. If the P content varies so much, then there is something wrong with the chemistry.

Regards,

Jonatha Timms
- Hong Kong

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2003

Ok lets see how far I can get my foot in my mouth. My EN work is 15 years old. The deposition of N is thermodynamic controlled and the P is kinetic, or maybe I have it backward. Any case as you increase plating rate the amount of P co-deposited goes down. Also(help someone) does not an aged bath tend to have a higher P?

So while the world demands fast turn around at a cheap price, good EN wants a slower deposit rate to have higher P. Either case I got out of the EN market as I saw an engineering coating being applied with too much demand on bright and shinny.....Fast rate= low P = poor corrosion protection.

Bright coating = coating with more voids and hence poor corrosion protection. (Thiourea ⇦this on eBay or Amazon [affil links] , Cd)

Jon Quirt
- Minneapolis, Minnesota