How does zinc protect iron and steel from corrosion?

Zinc protects iron and steel from corrosion primarily through a process known as galvanizing, which provides defense in two distinct ways.12

First, zinc acts as a physical barrier. By coating the surface of the iron or steel, the zinc creates a reasonably impermeable layer that prevents the underlying metal from coming into contact with corrosive atmospheric agents like moisture and oxygen.12

Second, if the physical barrier is breached or develops porosity, zinc provides sacrificial protection. Because zinc is more electronegative than iron, it functions as a sacrificial anode in an electrochemical reaction. In this state, the zinc corrodes preferentially, effectively sparing the iron or steel from oxidation as long as the two metals remain in contact.12

Common methods for applying these protective zinc coatings include hot-dip galvanizing, where the metal is submerged in molten zinc, and electroplating, which uses electrolytic deposition to create a controlled coating. Additionally, zinc-rich paints can be applied to provide similar sacrificial protection to steel structures.12