The steps for tank plating of Chrome over steel, pot metal, zinc diecast or other metals is very similar to the tank plating of any common metal other then aluminum. Like any plating, most of the work is in the preparation. Preparation for plating is very similar to preparation for painting. The end results can only be as good as the finish on the piece before you start plating it. Sand, buff or polish the piece to get a good surface finish. Make sure you have removed all of the paint on the area that you want to plate.
The next step is cleaning the piece making sure that all of the dirt, oil and grease is off of the work piece. You can clean it with Electro cleaner, detergent and water or a good degreaser. The main thing is to give it a water test after cleaning it. In a water test, when you rinse the piece, check to see if the water flows evenly across the work piece without any breaks. If the water doesn't flow evenly over the piece or it breaks up, then you know the that the piece still has dirt or grease on it and more cleaning is necessary.
The work piece is first plated with .an alkaline copper as an acid base copper would attack the steel or pot metal. In the old days, cyanide copper was used for the first step but over the years alkaline copper has replaced the cyanide. The only problem with an alkaline or cyanide copper is that they are a preplate and will not grow thickness.
After cleaning the piece the copper step is followed by plating with Nickel. The main thing to remember is make sure that the nickel is shiny if that is the finish that you want on your chrome. Whatever the finish is on the nickel will determine the finish on the chrome. If you wanted part of the piece to be shiny and part of the piece to have a satin finish, then that is how you want the finish on the nickel. After polishing the nickel make sure that you clean the piece before going on to the chrome plating step.
No matter if you plated the copper and nickel by tank or brush you will plate the chrome by brush plating. In most states it is illegal to tank plate chrome. Only businesses that are grand fathered in can tank plate chrome. Because of environmental concerns, even existing plating shops are harassed by the government about tank plating of chrome. Brush plating chrome is considered environmentally friendly because brush plating does not release a lot of acids into the air and since all of the chemical is used up there is not a lot of waste.