What Is Scale?

Scale

Scale on steel, often referred to as mill scale, is a layer of iron oxides that forms on the surface of steel during the hot rolling process. This flaky, bluish-gray coating initially provides a protective barrier against corrosion, but it is brittle and can detach from the steel surface over time. Because of this, mill scale is often removed before further processing or coating through pickling or other methods to ensure better adhesion and longevity of additional protective coatings.