Cast iron
Cast iron is made from pig iron, which is the product of smelting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting.
Corrugated galvanised iron
Corrugated galvanised iron or steel (colloquially corrugated iron (near universal), wriggly tin (taken from UK military slang), pailing (in Caribbean English), corrugated sheet metal (in North America) and occasionally abbreviated CGI) is a building material composed of sheets of hot-dip galvanised mild steel, cold-rolled to produce a linear corrugated pattern in them. Although it is still popularly called "iron" in the UK, the material used is actually steel (which is iron alloyed with carbon for strength, commonly 0.3% carbon), and only the surviving vintage sheets may actually be made up of 100% iron. The corrugations increase the bending strength of the sheet in the direction perpendicular to the corrugations, but not parallel to them, because the steel must be stretched to bend perpendicular to the corrugations. Normally each sheet is manufactured longer in its strong direction.