How can you chemically coat copper coins with a layer of zinc?

1 Answer

Zinc powder and 6 M NaOH.


I have used this for years in class. I put an evaporating dish on a hot plate and then put some 6 M NaOH and some Zn dust in it. I don't know if the exact amounts matter much.

It needs to get hot but you don't want it to boil because the fumes are unpleasant. The pennies are dropped into the hot mixture and in a few minutes, they get coated by the zinc and look like silver. The time that it takes to coat them depends on how hot the mixture is. If it is hotter, it goes faster.

Flinn Scientific has a method that does not involve hot NaOH but I haven't used it. Look on their website and search for "The Gold Rush" and you'll find a kit for sale with instructions.

Back to my method, I warn the students about the hot NaOH and I haven't had any real problems since I have warned them to wash the pennies well and beware of a slippery feel to their fingers. I often end up with peeling skin on my fingertips because of the cleanup that I do afterwards.