Does the plating of a penny with zinc, leading to the formation of a br layer, indicate a chemical change?

So I'm doing a lab report for my chemistry cl, and what we did in the lab was plate pre-1982 (mostly copper) pennies with zincate by heating the pennies in a beaker filled with zinc and sodium hydroxide on a hot plate. At that point, the pennies appeared silver. Then, we put the pennies in distilled water so they could cool off, and they still appeared silver. Next, we put the silver pennies directly on the hot plate until they appeared gold in a few seconds. My question is - was the penny chemically altered? I know that a br layer was formed because of the alloy of zinc and copper to make it appear gold, but apparently, if I heated the pennies for a longer period, the zinc would have melted off. Since it was merely the plating of the penny by another metal, doesn't that mean that the chemical composition of the penny itself didn't change, or since some of the copper in the penny was used to create the br, does that mean a chemical change occurred? Thanks!