How are redox reactions involved in corrosion?
The simple answer is
It is trivial to write the oxidation of iron metal to iron (II) oxide:
And this is quite clearly an oxidation reaction. More, and more complex oxidation products are accessible, as iron has a particularly rich redox chemistry. Hydrous oxides of iron(III) are all known:
We've all seen pictures of monumental bridges around the world, in Sydney Harbour, and San Francisco bay, or the Hell Gate bridge in NY. To this day, there would be huge teams of dedicated corrosion engineers inspecting the rust that inevitably develops, and trying to control it.