The Jax Copper Plating Solution will not work on stainless steel, but will work fine on all other irons and steels. Different surface finishes on the metal before using the plating solution is one way to get different effects (satin, polish, etc.). You can experiment with multiple applications, but a single coat is usually enough. This is a very thin coat of copper, and we would not recommend it on an exterior application unless you are also considering some very serious clear coating.