Galvanising

Galvanising coats iron or steel with zinc. An intact zinc coating separates the iron from air and water, but it also provides sacrificial protection. Zinc is more reactive than iron, so zinc corrodes in preference to the iron.

Galvanising illustrates both methods at once. Its zinc coating keeps oxygen and water away from the iron underneath. If the coating is scratched, zinc in contact with the iron can still oxidise preferentially, protecting the exposed patch.

Galvanising coats iron or steel with zinc. The zinc layer blocks oxygen and water, but it has a second advantage: if the coating is scratched, nearby zinc can still corrode sacrificially and protect the exposed iron. That is why a zinc coating and a tin coating do not behave in the same way after damage.

Galvanising means coating iron or steel with zinc. An intact zinc coating acts as a physical barrier. If it is scratched, zinc can still oxidise in preference to the exposed iron, so galvanising combines barrier protection with sacrificial protection.