Why does galvanised (coated in zinc) iron unlikely to go rusty even when the zinc layer is scractched off?

I dont understand..Why does galvanised (coated in zinc) iron unlikely to go rusty even when the zinc layer is scractched off?
The answer is simple: NO! It does not.





The zinc layer protects the iron molecules from the attack by oxygen molecules in the air. Destroy this protective layer, and you got yourself ';rust';. If you have witnessed a scratch that does not rust, it ain't deep enough.





Here is an experiment: buy a small galvanised vessel - put plain old salt in it. The salt will eat off the zinc in no time (forming ZnCl2), and then the iron starts to rust.Why does galvanised (coated in zinc) iron unlikely to go rusty even when the zinc layer is scractched off?
Zinc will protect the iron from rusting because zinc is more reactive than iron. When some of the zinc layer is scractched off, the iron and zinc metal are exposed to water and oxygen. In the presence of water that acts as electrolyte, it forms an electrochemical cell. Zinc being more reactive than iron will act as anode and undergoes oxidation whereas iron will act as cathode and undergoes reduction. Since it is zinc that undergoes oxidation, zinc will form oxide and it will protect the iron metal from rusting.(iron cannot form iron oxide or rust)
If the scratch is small enough, the zinc is able to still protect that area. As long as there is zinc present on the surface of the iron it will provide some protection.





The zinc is sacrificial to iron (it will corrode first, thereby protecting the iron).