Are you asking which kind of metal is most corrosion resistant?
If so you have to keep in mind when selecting a metal to use the overall strength needed for the application as well as cost and you do need to consider what sources of corrosion will be likely. You may end up compromising to come up with your final selection.
Stainless steel is pretty good when talking corrosion resistance, is more expensive than mild steel, not sure how it compares strength wise for same sized object.
Now since this is an elecrical forum we could be talking about which conductors are best suitable for use as conductors.
Some of the best conductive elements are gold and silver, but are too expensive and the use of copper and aluminum becomes the better choice because of cost. Gold and silver are used in limited amounts in areas where they provide better performance for a particular application.
