Mill scale is the product of oxidation which takes place during hot rolling. The oxidation and scale formation of steel is an unavoidable phenomenon during the process of hot rolling which involve reheating of steel in a reheating furnace, multi-pass hot rolling and air-cooling in the inter-pass delay times and after rolling. Mill scale is usually removed by process water used for descaling, roll and material cooling, and by other methods. It is subsequently separated by gravity separation techniques.