Question

Why is zinc better than sn in protecting iron from corrosion?

Answer 1

My understanding of these two metal coatings is that zinc is a sacrificial anode when applied to steel, while tin is not, though both provide corrosion protection under ideal circumstances. Point being, if the surface is scratched, the zinc will still (generally) corrode before the steel does. With tin, once the surface is scratched, the steel will corrode much more quickly as the tin no longer protects the area scratched.

One thing to keep in mind is that zinc is not necessarily “better” overall. It’s just that from a cost / performance perspective, zinc may be the better option in a larger number of applications, while tin still has some advantages in other applications. Zinc is presently a lot less expensive than tin, so cost/performance likely leads a lot of industries to choose galvanizing of some sort (zinc) over tin.