Need nickel plating Science Project Help

A. You can buy such materials from companies who sell plating kits.

But you might want to rethink whether this would be an appropriate science project for a 5th grader in our environmental age, Carolyn. A manager of a plating shop who gets caught dumping 2 quarts of nickel solution down the drain is probably looking at penitentiary time. Although draconian punishments won't be imposed on a 5th grader and her mom, what are you going to do with the two quarts of nickel plating solution after the project is over? You can't dump it, and it would cost your town over $100 to dispose of if they were to accept it from you in a haz waste collection.

The good news is that you can plate the pennies with zinc from a very dilute (and quite safe) vinegar ⇦in bulk on eBay or Amazon [affil links] solution per our "Electroplating: How it Works" FAQ. Zinc is not exactly the same color as nickel, but it's close enough for 5th grade.

Best of luck!

A. Hi Elena.
Before I address your questions of the equations and how to increase efficiency, let me start by saying that in conventional nickel electroplating (as practiced in thousands of electroplating shops), nickel anodes are used rather than platinum anodes. Then, if everything is working correctly, the equations are very simple --
At the anode, which is the positive electrode, from which the power supply is "taking electrons":
Ni⁰ - 2e^- --> Ni⁺⁺
The nickel metal is thus converted into positively charged nickel ions which dissolve into the solution.

At the cathode, which is the negative electrode, to which the power supply is "giving electrons":
Ni⁺⁺ +2e^- --> Ni⁰
The dissolved nickel ions are thus converted to nickel metal

Ideally, the HCl keeps the pH low, allowing the nickel ions to stay in solution, and the plating solution is basically a mix of hydrogen, chloride, and nickel ions (H⁺ & Cl^- & Ni⁺⁺) with the chlorine not participating in a reaction at the anode or the cathode. Similarly, the water, which ionizes very little, ideally does does not participate in the reactions at the anode and cathode.

If this ideal situation were maintainable, the 'efficiency' would be 100%. Please see our paper about Faraday's Law. In reality, the efficiency is not quite 100%. In commercial nickel electroplating it might be 95%, but in your case, yes, it might be 52-55%. What happens is that some of the electrons you are pumping to the cathode cannot be satisfied by the available nickel ions (because there is not enough of them, or whatever) but they must be satisfied. So what happens to a small extent is:
2H₂O + 2e^- --> H2^ + 2OH^-
This hydrogen is the gas bubbles that you see on the copper cathode.

When you use a platinum non-dissolving anode instead of a nickel anode, a few things work a bit differently. Since some amount of nickel is being electroplated out of the solution and onto the cathode, and no replacement nickel is going into the solution, the nickel concentration is declining, which causes the efficiency to decline. Further, since there is no nickel dissolving to provide the electrons which the power supply is "stealing" at the anode, something else has to provide those electrons, and your teacher is at least partially wrong in calling your equations nonsense, because the only thing that can then supply those electrons has to be the Oxygen and Chlorine ions forming diatomic gasses :-)
Most of the gas forming on the anode is Oxygen but some of it (the lower the pH, the more) is Chlorine gas. Feel free to search the site for "Wood's Nickel Chlorine Gas" for further info on this.

Regards,

A. Hello again, Sara-Elena.
Boric acid is a buffer which works to keep the pH of the nickel plating solution from varying. Thread 10210 gives a detailed and wonderful explanation of why this is so important. Apparently, without it the pH right at the surface of the cathode would immediately and substantially change because of the
2H₂O + 2e^- --> H2^ + 2OH^-
reaction, and mess things up very badly. NiCl₂ simply ionizes into Ni⁺⁺ + 2Cl^-, and the Cl^- stays dissolved in the solution, while the Ni⁺⁺ is converted to Ni⁰ metal depositing on the cathode.

Regards,