GI is made by melting iron ore and coal together in a furnace. Once the melting is done, it is moved to another furnace to burn of any impurities. It has very low carbon content ranging between 0.5% to 0.25% in weight. GI is not used very often in case of solar PV module mounting. It is usually used in case of not so strong roofs, when there is a need for light weight structures.