Scale

Scale is a loose oxide layer on ferrous materials that forms mainly at high temperatures. During forging, welding, hot rolling and heat treatment, the workpieces are heated to high temperatures. Cast workpieces are also very hot when the mould is removed. While the parts are hot and slowly cooling down, oxygen quickly bonds with the material on the surface. The resulting scale layers must be removed mechanically, e.g. by sandblasting, or chemically, e.g. by pickling, before further processing. In steel production, losses due to scale are in the order of 4%. Only stainless steels can be produced and processed without scale. For components that are exposed to high temperatures during operation, the use of scale-resistant stainless steels is recommended.