The layer of scale adhering to the hot-rolled strip in Cold Rolling Mill No. 2 is removed in a hydrochloric-acid solution during the so-called pickling process. The resulting iron-chloride solution is then converted into hydrochloric acid and ferric oxide in a thermal process called spray roasting. The iron-chloride solution is chemically cleaned prior to being spray-roasted in order to ensure compliance with the high chemical and physical requirements for ferric oxide. The share of undesirable elements such as silicon, chromium, nickel, copper, titanium and aluminium is reduced.
