4010. Analytical methods needed for a nickel-phosphorus electroplating bath

Letter 4010

Analytical methods needed for a nickel-phosphorus electroplating bath.

Dear Sir / Madam,

We are starting up a nickel - phosphorus electroplating bath and can use some help with the analytical methods. We are fine with the nickel and pH. (1) But, how do you check the ratio of Phosphorus to Phosphoric acids? (2) Nitric acid on the deposit changes the phosphorus to phosphate and we would love a good analytical method for the phosphate.

Any other tips on the operation of this chemistry would be most appreciated. Thanks in advance,

Fred Mueller, CEF
- Royersford, PA

I am in the metal finishing business for more than twenty years and did not hear of a nickel phosphorous electroplating process yet. Are you sure you did not mean electroLESS?

Sara Michaeli
chemical process supplier
Israel

Hello Sara,

It's nice of you to respond to my letter. The nickel - phosphorus electroplating bath is a very neat story. In 1946 Brenner and Riddell were looking to alloy Phosphorus with all kinds of different metals and had the most luck with nickel. In looking for sources of phosphorus they tried hypophosphite and got cathode efficiencies of over 100%. The rest, as they say, is history.

Bath runs 170 - 190 degrees F. is 50% efficient at the cathode (needs constant acid / nickel additions). Nickel anodes (100% efficient) make the solution grow. Bright WITH OUT additives or wetters and will not "Plate out" on the tank walls. Runs at a pH of 1 - 2, and the low pH "salts out" organics (wetters). Our interest in the bath (we are running trials now) is due to the fact that it will deposit higher percentages of phosphorus than will electroless.

Regards,

Fred Mueller, CEF
Wendt Dunnington - Royersford, PA

I can't reveal much more, Fred, except to say that you are not the only one interested in that bath these days :-) Other people are working on it too; some of the advantages of plating nickel phosphorous compounds hold true whether it be deposited electrolessly or electrolytically.

Ted Mooney
finishing.com - Brick, NJ

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