Question

why do we use iron coated zinc for bridges and auto mobile

Answer 1

Hot molten wax coatings areusually used under body components to prevent corrosion. ... Metallic coatings such as zinc, aluminium, zinc-iron are applied on steel parts to prevent corrosion. Powder coating, organic autodeposition also prevents corrosion.

Answer 2

iron is a highly reactive metal it can reach with oxygen and water and acids that make it weak . and can cause damage to the bridges or auto mobiles moreover zinc and iron together provide better strenght