The problem with the steel is, if you manage to get it on, how are you going to etch your tracks?
They are usually fibreglass (or similar) with a layer of copper on one or either side. Once the copper is removed by the etching process you have sections which conduct (the tracks) and the fibreglass material which doesn't conduct. The problem with the steel is it all conducts and you can't exactly 'etch' it. Resulting in one big short circuit.
If anyone has a way, however, I stand to be enlightened.