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FAQ: How can I do an electroplating demonstration for my science class?


It seems that nearly everybody saw a plating demonstration years ago, and now they are firmly convinced that the instructor showed them how to electroplate bright, shiny, sparkly, copper onto old steel with copper sulphate and a battery. But memories are faulty things. They probably saw a demo of copper spontaneously depositing onto steel or onto a nickel from that cool blue solution; but over the years, as they read about electroplating in a science book, their minds melded what they actually saw with mental pictures of what they read about, and the shiny products they've bought, yielding a faulty recollection.

Actually, you can't electroplate copper out of a copper sulphate solution onto steel (or aluminum or zinc either) really satisfactorily! Rather, it spontaneously plates out as a thin, powdery, non-adherent (immersion plating) coating.

The best demo I every saw--by far--was a gold plating demo put on by Technic of Providence RI. They took nickel plated bracelets, dipped them in a beaker of cleaning solution, then activating acid, then into a large beaker of gold plating solution for 15-20 seconds (rinses in between, of course). Because both the beaker and plating solution were clear, the students could watch the piece turn to gold right before their eyes. Then the instructor took out a pocketful of such bracelets, hooked a piece of copper wire around each, did the precleaning, and handed one to each student who wanted to try it. There wasn't one who didn't jump to his/her feet to get on line! My kids still have theirs. And the kids instantly understood Faraday's Law and wanted to leave their bracelet in the solution as long as they could get away with :-) If you want a plating demo that is really impressive, that's the one, but it has to be led by professionals.

For a do-it-yourself project, we recommend the zinc plating of copper pennies or the copper plating of quarters, which are described in detail in "Electroplating -- How it Works". You can also zinc plate or copper plate a brass key, but a brass key tends to not be very shiny, and the plated item will be no shinier than the starting point.

A key, copper plated by Ted Mooney in a pyrex desert bowl from a solution of vinegar with a pinch of salt and pinch of sugar, with copper wire used as the anode material and a 1-1/2 volt dry cell as the power source. An identical unplated brass key is shown on the right.

If you would like other opinions and ideas, here are some letters on the subject of plating demonstrations:

Good luck! -- Ted.

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