
What exactly is Mill Scale and what is done about it
Mar 05, 2022 · 2005. A. Mill scale consists primarily of magnetite, Fe 3 O 4, of characteristic bluegray "steely" color. An extremely thin outer film of hematite, Fe 2 O 3, is invisible to the naked eye. The inner portion of the magnetite contains fine metal grains and sometimes, residual black FeO (see below), which contribute to the roughness of descaled metal.