Galvanized steel, which was developed over 100 years ago, has served as the standard anti-corrosion metallic coating, and both Galvalume and galvanized steels are metallic-coated sheet steels. But the coating on galvanized steel is essentially 100% zinc, while the coating on Galvalume steel is an alloy of 55% aluminum and 45% zinc, by weight. It is, therefore, much more like an aluminum coating rather than a zinc coating. It provides excellent galvanic or sacrificial protection to the steel base at scratches and cut edges, and good overall protection in many outdoor environments. In comparative atmospheric corrosion tests between Galvalume and galvanized steels made around the world over the past 30 years, Galvalume demonstrated a significantly longer life than galvanized steel with an equivalent coating thickness. Based on these tests, the roofs are expected to last 30 to 40 years before requiring any major maintenance, such as field painting.