After a layer of primer (which helps to smoothe the surface of the object to be chromed and prepare it for further treatment) and a session in the drying oven, a blast in the spray booth sees each component treated with up to four layers of a conductive compound. The important word here is "conductive". This allows the chroming process (which relies on electric current to deposit pure metal onto the surface of the object being chrome-plated) to occur once the object is hung in the plating tanks and a jolt of current sent through it. That's why thick copper wire is used- to deliver the heavy current from the object.