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Growing nickel oxide on nickel

2005

Hello,

I have some nickel foil and I want to grow a layer of nickel oxide on it. I can't heat it above about 350 °F, so heating it in air won't work. Thus, I'm hoping to find a recipe or method similar to anodizing aluminum. This is for a lab-scale experiment.

I saw a post that suggested "incorrect" nickel plating would grow an oxide, so I bought some nickel chloride hexahydrate. Before I just launch into acid baths, random salt concentrations and electricity, does anyone have any suggestions?

Ellen Heian
Research materials scientist - Baltimore, Maryland, USA

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First of two simultaneous responses --

350 F will form an oxide layer, just not thick and not fast. Note that your electric home oven will go to about 650 °F on the oven clean cycle.
I really doubt if there is a way to plate an oxide layer. I have never heard of an anodizing method, but there might be one. Note that there is one advertiser at this site that has a method of anodizing stainless steel. I think that that coating comes out black. You might check with them to see if it will work on nickel.

James Watts
- Navarre, Florida
2005

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Second of two simultaneous responses -- 2005

Ellen,

I guess it depends how thick you need the oxide layer. Nickel will naturally form a thin oxide layer after plating, this is why its common practice to immediately chrome the nickel before it goes passive.

I've no idea how you would go about forming a very think and adherent nickel oxide layer though. I would expect it turn powdery as the thickness increases.

what post did you see and did you evaluate the source of the info?

Peter Van de Luecht
- Melbourne, Vic, Australia

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2005

Thank you for your comments. James, I can't heat the nickel to grow an oxide because it is wrapped around something that can't take the heat, so I think I'm stuck with wet chemistry.

I've been trying a few things. Peter, you are right, I grew a green oxide layer but it's powdery and rubs off my nickel foil. I put 20 g NiCl2 in 0.5 L distilled water, then connected a piece of nickel foil as the positive electrode and another piece of nickel foil the same size as the negative electrode. When I turn up the voltage (I've tried about 9 A/sq.ft.) I get bubbles rising off the negative electrode and growth of a layer. I've been adjusting the pH with HCl and NaOH to see how that affects this coating. I'm confused because in aluminum anodizing, you grow the coating on the positive electrode, not the negative. Another odd thing is that when I added base, white flocculent formed and sank to the bottom of the beaker [beakers on eBay or Amazon]. Is that nickel oxide too?

The post I saw that mentioned formation of an oxide layer was letter 28232: a student in Scotland was trying to plate nickel but kept getting nickel oxide. The consensus was that his/her pH must have been too high. A pH about 6 or 7 did grow more oxide than a pH of 2 in my experiments. Any more thoughts? Would bubbling air into my solution help?

Thanks much.

Ellen Heian
- Baltimore, Maryland, USA