Many metal roofs are made out of galvanized metal which is a type of metal that has been covered with hot zinc in order to protect it from the weather.
Galvanized zinc roof.
Galvanized g90 g90 is not a galvanizing specification.
Zinc coating weights are measured in ounces per square foot and range from g90 to g60 g40 and g30 galvanized steel.
Before the introduction of galvalume to the metal roofing industry in the late 20th century using galvanized sheet and coil was a common practice.
Galvanized and galvalume steel will forgo that aging for a couple of decades.
Metal wall and roof panels in galvanized g90.
It is a coating thickness designation in the galvanizing specification astm a653.
However paint on metal roofs often peels or rusts in which case it is time to repaint it.