The more active metal will serve as an anode and will be corroded instead of the less active metal. The anode is then called a sacrificial anode. Deforming the metal creates more dislocations which entangle, pinning them and thereby strengthening the metal. The carbon atoms distort the BCC ferrite into a BC-tetragonal structure. Oxidation occurs at the electrode called the anode.
Reduction occurs at the cathode.
Steel usually contains some other alloying elements such as silicon, manganese, etc. as well as impurities such as sulfur and phosphorus. High toughness requires both high strength and high ductility. The smallest repeating array of atoms in a crystal.