Actually it's what galvanized hardware is coated in. That too corrodes very quickly.
The zinc coating is there to protect the steel it coats. It has a higher oxidation potential than iron and therefore acts as a sort of sacrificial anode.
They used to coat cans with tin. The tin provided a non-corroding barrier. The only problem is if the slightest nick penetrated the layer, the steel would corrode at the expense of the tin, because unlike zinc, tin is more "noble" than iron, that is iron has the higher oxidation potential.
So today "tin cans" are coated with epoxy not tin.