Pronunciation: [mˈɪl skˈe͡ɪl] (IPA) 
The spelling of the word "mill scale" is phonetically pronounced as /mɪl skeɪl/. The first syllable "mill" is pronounced as /mɪl/ with a short "i" sound followed by a double "l" consonant. The second syllable "scale" is pronounced as /skeɪl/ with a long "a" sound and the "s" sound at the beginning is pronounced as /s/, not /z/. Mill scale is a flaky surface layer of iron oxide that forms on steel during the hot rolling process.
Mill scale refers to the flaky surface formed on the outermost layer of iron and steel products during their production process in mills. It is a highly adherent and tightly packed oxide layer that forms on the surface of hot rolled steel and is typically black in color. This oxide layer is mainly composed of iron oxides, such as hematite and magnetite, along with other impurities and compounds.
Mill scale is formed due to the oxidation of iron when it is exposed to air and moisture during the hot rolling or forging process. It is a byproduct of steel production and is often considered as a waste material. However, mill scale has various uses and applications in different industries.
In some instances, mill scale is utilized as a raw material in the production of iron-based products. It can be recycled and processed to extract iron, which is then used in the production of steel. Mill scale can also be used as a raw material for the manufacture of cement clinker and as a pigment in paints and coatings due to its dark color.
Furthermore, mill scale is often utilized as a source of iron oxide in the production of ferric chloride, a chemical compound used in water treatment processes and various industrial applications. It can also be used as a filler material in various products, including rubber and asphalt.
Overall, mill scale is a residue material with diverse uses, offering opportunities for recycling and repurposing in various industries to reduce waste and increase the efficiency of resource utilization.
The word "mill scale" derives from the combination of two terms: "mill" and "scale".
- Mill: The term "mill" originally referred to a building or complex where mechanical processes were used to grind grain into flour. Over time, the term expanded its meaning to include any industrial facility that processes raw materials such as metal, wood, or textiles.
- Scale: In this context, the word "scale" refers to an iron oxide coating that forms on the surface of iron or steel during hot-working processes like rolling, forging, or heat treatment. It is a hard, flaky material that is usually a mixture of iron oxides, mainly magnetite and hematite.
Putting the two terms together, "mill scale" refers to the iron oxide coating that is found on steel or iron products as a result of the hot-working processes that occur in a steel mill or industrial facility.
