Copper plating is done with the help of electricity, copper can also be plated electrolessly with complex chemical formulas or it can also be plated directly into carbon steel /iron by immersion plating and iron displaces the copper from its solution and the copper coats the steel part, in This how to you will see how a strong and adherent copper layer can be plated directly to Brass and many other nobler metlas(have tested on silver and gold) by contacting a noble metal with a reactive transitional metal that reacts well with copper, by doing this the noble metals will inherit the transitional metal's galvanic potential and are coated with copper.
Step 1: List of Materials.
Copper Sulfate(root kill, but I purchased lab grade for an earlier project).
Battery Acid(Sulfuric acid by 30%, that is what battery acid is made of).
Small container made out of steel, I used a cap made out of steel sheet.
Brass Keys, Quarter Coins and basically any other metal(silver, gold all work too).
Safty gloves and glasses.
Step 2: Prep Work and Copper Plating.
With a steel wool clean the steel container and wash it with dish soap to remove any greast, the brass keys and coins must be washed and cleaned too.
Mix 300 ml of battery acid with 10 grams of copper sulfate, allow for about 10 minutes of the chemestry to mex well, temperature above 70 degrees F.
place the brass keys and coins into the steel container, add enough liquid copper sulfate to the container to cover the keys and coins, manually turn the keys and coins every 40 seconds, you can do that for about 3 minutes, there will be enough adherent and strong copper coat on these pieces to allow for manual polishing to give them a bright copper look, but the copper on the steel container is not adherent at all and can be removed rather easily.
Step 3: After Copper Plating.
These pieces can be manually polished with polishing compounds to give them a beautiful appearance and they can later be nickel plated or sealed with protective lacker to prevent tarnish or allow to tarnish and get a beautiful green copper oxide coat.
Here is a Video of the copper plating.