With regards to plating steel and rust prevention, mind that there are two ways to do it: plating with a more noble (cathodic) metal then steel, and a less noble (anodic) metal. A less noble metal like zinc will protect steel as a sacrificial metal. Even if the steel gets exposed, it is protected by the zinc, because the oxygen will react with the anode (positive charge).
Copper is more noble then steel, which means that copper on it's own will not corrode as fast as steel. But when copper plated steel gets exposed, then the steel will become the anode, and the reverse will happen: the st