The primary difference lies at its coating layer. For the galvanized sheet, a layer of zinc material is averagely distributed on the surface of galvanized sheet, playing as a positive sheet protective to the base metal, in another word, zinc works as substitute for corrosive-proof protecting the base metal until it is torn off.
While the galvalume sheet's surface is a coating layer consisting of 55% aluminium, 43.5% zinc and other few elements, which appears a honeycomb structure under microscopic observation. Aluminium honeycomb wraps the zinc.Under such circustances, even though the coating of galvalume also plays its protective role as positive sheet, however, such protection decrease sharply due to declining content of zinc and no easily electrolysis when zinc wrapped by aluminium.
Therefore, once the galvalume sheet is cut open, the verge of cut would be generally losing its protector and quickly go rusting. So we should cut as less as possible, once cutting happen, use anti-rusting paint or zinc-rich paint for protecting the verge, extending its lifespan.