What's the difference between galvanized steel coil and galvanized aluminum coil?

The main difference is the coating. There is a very even zinc coating on the galvanized steel coil which protect the coil well. It has great corrosion resistance. Galvanized steel coils are ideal options for constructing strong roofing systems. The coating of galvanized aluminum coil is composed of 55% aluminum, 43.5% zinc and few other elements. Though the coating can protect the coil, its performance is not good as galvanized steel coil because of less zinc. Once the galvanized aluminum coil is cut, the edge around it will be rusted quickly. It should be coated with rustproof paint to prolong its lifespan. So that galvanized aluminum coil is not suitable for cutting process. But the surface of galvanized aluminum coil is more beautiful than galvanized steel coil and it cost much more.