How zinc coating provides corrosion resistance

Zinc coating is used widely to protect iron and steel from corrosion. Corrosion occurs when metals react with oxygen and moisture in the environment, then forming rust. Applying a layer of zinc acts as a special shield, preventing the underlying metal from direct exposure to any contaminants – this method is commonly known as galvanisation.

Barrier Protection

The main way that zinc protects steel is by acting as a physical barrier. When steel is coated with zinc, the layer covers all surfaces, including corners and edges, preventing water, air, and corrosive substances from reaching the steel beneath. Even if the zinc layer is scratched, after a zinc nickel coating, such as https://www.poeton.co.uk/surface-treatments/plating/zinc-nickel-plating/, the coating will continue to give protection and corrosion resistance to the metal.

Sacrificial Protection

Zinc also protects steel through a process called sacrificial, or galvanic, protection. Zinc is more reactive than iron in electrochemical terms. If the coating is damaged, zinc corrodes preferentially and the electrons that are released from zinc corrosion help to prevent the iron from then oxidising. Essentially, zinc “sacrifices” itself to save the steel.

Forms a Protective Patina

As zinc corrodes, it forms a layer of zinc oxide, which can then react with carbon dioxide and moisture to create zinc carbonate, a thin, tightly bonded layer or patina. This compound is insoluble and sticks tightly to the surface. It acts as an additional barrier against moisture and air, slowing down further corrosion. This patina is self-healing and can protect the steel for decades, even when exposed to moisture, chemicals and temperature changes .