How does galvanising protect against rust?

Galvanising protects against rust by providing a protective zinc coating that prevents water and oxygen from reaching the metal.

Galvanising is a process that involves coating a metal, usually steel or iron, with a layer of zinc. This is done to prevent the metal from rusting, which is a form of corrosion. Rusting occurs when iron or steel comes into contact with water and oxygen, leading to the formation of iron oxides. These iron oxides are what we commonly refer to as rust.

The zinc coating in galvanising acts as a physical barrier that prevents water and oxygen from reaching the underlying metal. This is because zinc is more reactive than iron or steel. When the zinc coating is exposed to the environment, it reacts with oxygen and carbon dioxide in the air to form a tightly adhering zinc carbonate layer. This layer is impermeable to water and oxygen, thus protecting the underlying metal from rusting.

Moreover, the zinc coating also provides what is known as 'sacrificial protection'. This means that even if the coating is scratched and the underlying metal is exposed, the zinc will still corrode first. This is due to the fact that zinc is more reactive than iron or steel. This sacrificial protection ensures that the metal remains protected from rusting, even if the zinc coating is damaged.

In summary, galvanising protects against rust by providing a protective zinc coating that prevents water and oxygen from reaching the metal. It also offers sacrificial protection, ensuring that the metal remains protected even if the coating is damaged. This makes galvanising an effective method for preventing rust and prolonging the life of metals.