Science Project: Effect of Voltage on the amount of Metal Electrodeposited

A. An interesting project, Cesar, but you'll have some issues. It's not only that you'd need a way of keeping the temperature constant (maybe an aquarium tank with a heater?), but as soon as you apply a chemical to speed up the corrosion you have corrupted your premise, and all you will have left to report on is the effect of that particular chemical on that particular metal at that particular temperature.

As an example, suppose we tell you that salt will speed up the corrosion; now with salt added, the stainless steel may corrode quickly; whereas without the salt it might have lasted millenia. If we suggest a mild mineral acid, that will dissolve the zinc in an instant while having almost no effect on the copper; nitric acid will wreak havoc on most of the metals without bothering aluminum; caustic will quickly dissolve aluminum but not bother stainless steel, etc.

Another issue is that galvanized metal is steel that has been coated with zinc; it's not really comparable to the other metals which are 'solid'. Once you get down to the steel, you have a different situation.

The purpose of the study of science is to help us understand the world we live in, so I'd try for something broad and vaguely related to a real life situation. Like maybe what is the effect of splashing sea water on these materials at subfreezing (your freezer), cool temperatures (your refrigerator), relatively constant temperature (indoor room temperature) and varying outdoor temperature. So I'd say mist them with salt water a couple of times a day. I think you'll find that if you can leave them in the sun so they wet and dry, that you will find the quickest corrosion. But that's a guess, and one experiment is better than a thousand guesses.

A. Ted,

I recall, a couple of months ago, a girl had asked for help on a similar problem where she was trying to see the effect of soil on steel shovel at different temperatures [letter 24686]. I wonder if that discussion could be of help to Cesar here.

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A. The amount of deposit on the cathode is directly proportional to the current times how long you plate for (ampere-hours) according to Faraday's Law. And the current is 'sort of' proportional to the voltage in accord with Ohm's Law. The 'sort of' proviso is because of some fixed losses in the system. So, yes, you could relate the voltage to the amount of metal deposited.

Aluminum is not electroplateable, so don't use that as the anode (you can't electroplate aluminum because all of your energy will liberate hydrogen from water instead of depositing aluminum. Use a copper anode.

Depending on what grade you are in, and how watchful the eyes that will keep your classmates out of the experiment, different acids are appropriate. Dilute sulfuric acid [affil links] is a good choice if you're in a high school lab. Good luck.