Galvanized G90 is a cold rolled steel sheet that is hot dip coated with a durable protective coating of zinc. To break it down, the “G” stands for galvanized zinc coating, and the number 90 depicts the weight of the zinc on the surface of the steel. Therefore, G90 represents 0.90 oz/ft2 of zinc total for both sides.
G90 is intended for situations where rust and corrosion are in consideration. It is often used on exterior applications for frames and doors as well as openings in pool areas due to exposure of salt and chemicals. Why is zinc used? Zinc is the choice of coating material because as zinc reacts with the elements (oxygen, moisture, and carbon dioxide) it eventually forms zinc carbonate. This is a very resilient and stable layer that adheres firmly to the metal below acting as a protective barrier. This barrier prevents air and moisture from contacting the metal below the zinc coating which further prevents corrosion and deterioration. Keep in mind that contact with lead or copper must be avoided as it can accelerate corrosion of G90 material.