Mild steel is a low carbon steel that is mostly used in the building of structures. This type of steel is expandable and can expand too many different applications. To protect this form of steal from eroding, three methods are used: passive barrier protection, active protection, and sacrificial protection. Passive barrier protection is a coating that keeps water, salts, and oxygen way from the steel. Active protection is a chemical that is applied to the steel that disrupts the normal formation on the surface of steel. Sacrificial protection is made of zinc and when in contact with steel, it greatly reduces the rate of corrosion.