plating, anodizing, & finishing Q&As since 1989
Chem teacher keeps getting Nickel Hydroxide in his Nickel Electroplating
August 31, 2012
I'm a young chemistry professor and I'm trying to nickel plate a iron piece. I found this web site a week ago and I'm reading its posts restlessly (I already bought the amazon Electroplating: Fundamentals of Surface Finishing), but it still didn't arrive and so I'm in need of help.
The condition I'm using is this:
- Nickel nitrate solution 100 g/L
- 4 - 9 volts (I've tried with different volts)
- And a piece of iron (pre-treated with mechanical and acid treatment)
- Citric Acid Buffer Solution (pH 4)
The problem is:
I keep getting this green mass around my iron piece. Reading here in forum, I found this substance is Nickel Hydroxide and that's when I started to use the Citric Acid Buffer solution. But even at pH 4, I keep getting this Nickel Hydroxide and no nickel plating.
Thank you and sorry for my bad English.
I hope you can understand me.
Chemistry Teacher - Sao Paulo, SP, Brazil.
A. In plating, I found out early that you can't just throw some chemicals together and expect them to work. There are few successful formulas and most required much experimentation to make them workable.
My guess is that the formula you're using is so inefficient that most all of the amperage is being used to split water at the cathode - this produces hydrogen gas and (OH)- ion. The (OH)- immediately combines with the nickel ion and forms nickel hydroxide at the cathode surface.
The solution to this is to use a proven formulation. I would suggest doing a search for "watts nickel", which is probably the most widely used formulation and has been for the last 100 years, or so. It contains nickel sulfate, nickel chloride, and boric acid. Make your bath up and operate it exactly as the literature dictates. Use a nickel anode. Forget the nickel nitrate.
- Nevada, Missouri, USA
September 6, 2012
Thank you so much for your reply.
I surely will search for this formula. I used nickel nitrate cause our lab didn't have another nickel salt at the moment. But by the time my question was published I was able to get a fine nickel plating.
When I started the experimentation, instead of letting the iron piece rest, I started moving it up and down into the solution while the electricity was on. With this agitation, no Nickel Hydroxide was formed, just the plating.
But I will surely get the formula you mentioned so I can improve my nickel plating.
I read somewhere that Zinc is much better plated on a previously nickel plated iron piece.
Is that information true? Do you think is it better to teach nickel plating before zinc plating?
Thanks for your help.
- Sao Paulo, Brazil