I thought it would be fun to try electroplating with nickel, since nickel has a fancy golden-silvery hue and doesn't tarnish easily. To start, I followed this Instructable to make a dilute solution of nickel acetate. In summary, nickel metal is electrolyzed in a solution of vinegar and salt using 12V. I used two Canadian nickels and my ATX lab power supply's 12V. Some Canadian quarters, dimes, and nickes are pure nickel; check with Wikipedia to see if the coin's year means it is nickel or not. I let my coins dissolve until the solution was a nice bright green color. Once the nickel acetate electroplating bath was done, I moved on to the fun part--electroplating!
To prepare my copper pennies for electroplating, I first dipped them in dilute sulfuric acid and then in a sodium hydroxide solution. The acid removes some surface contaminants and the base removes others. A very clean surface is necessary for a good, solid plating. Once the pennies were clean, I attached them to the negative clip of a 3V AA battery pack. For nickel plating, lower voltages are usually better, and lower amperages also help with smooth finishes. Thus, batteries at low voltage and low current are better than, say, an ATX 12V line. The anode, or positive terminal, of the plating bath was a nickel coin. It is important to note that the anode alligator clip should be above the water line or else it will be corroded away along with the nickel coin.
With the penny in the solution, I rotated it every thirty seconds to give it an even plating. After about a minute, I moved the battery pack alligator clip to a new position on the coin so that every area was plated. Once I had plated the coin for about three minutes, I washed it off and it was brilliantly shiny!
The coins didn't need any polishing at all, which I thought was really cool--my experiments with zinc plating were never this shiny. When compared with the blue-tinted zinc-plated coins I already had, the nickel-plated ones had a very beautiful golden-silver tint. I also plated steel with success by washing it in the acid and base and then repeating the plating procedure.
After I was done electroplating, I evaporated the nickel acetate plating solution by letting it sit uncovered for a month or so. This made some really nice chips of bright aqua nickel acetate crystals. I also made copper acetate by the same electrolysis method, and that evaporated down into very dark green kite-shaped crystals.