Scale

A surface coating on rod or wire that is comprised of oxidized base metal. Three iron oxides are present: ferrous oxide, magnetite and ferric oxide, formed on the rod or wire in that order. Generally oxides are formed during heating, lengthy exposure to certain atmospheric condition or manufacturing processes such as rolling, drawing, forming, heat-treating and storing. There are many mixtures of these oxides that form on the surface of steel at different temperatures and give the steel different colors, such as yellow, brown, purple, blue and red. Oxides must be thoroughly removed from the surface of steel objects that are to be coated with tin, zinc or other metals. 2) In the copper industry, cuprous and cupric oxides are prevalent in the manufacturing processes. The rate of cooling has a great influence on the thickness and structure of scale. Being abrasive in nature, the oxide must be removed from the surface prior to further processing. See Descaling and Pickling.