Here are the standard electrode potentials of elements .
Here are the five ways:- Paint the surface of metal. Oil the surface of metal or keep it covered with grease. Electroplating it with a less reactive metal will keep it safe. Galvanisation that is covering it with Zinc metal it is also called sacrificial protection. Making it cathode, most of the underground pipes are
Lets look from a different angle corrosion is basically oxidation and in oxidation the electrons are lost. Here we have zinc coated on iron being more reactive the zinc will tend to loose the electrons even if the iron is exposed, even then being good conductor the electrons are given to the iron by the