Scale - layers of iron oxide which build up on steel at high temperatures - is normally unwanted, so it is removed through pickling.

Brushing removes scale too, but with an important difference: SCS brushing fully removes the top layers of scale - hematite and magnetite - plus most of the wustite layer. But it leaves a microns-thin layer of wustite bonded to the base steel.

This layer has attractive properties, the most important being it actually inhibits rust ! SCS samples over two years old, with no surface treatment, show no signs of rust. Brushing also leaves the wustite layer clean and smooth - a bright cold-rolled surface - ready for fabricating or painting with little or no pre-treatment.