Steel sheet protected against corrosion and process for its production

摘要

A process for producing of corrosion-resistant thin steel sheet, in which a zinc-contg. coating (5) of at least 80 wt. % Zn is produced upon carbon-deficient thin steel sheet (1) by electrolytic means or immersion in a metal melt, is novel in that one or more metals (4) apart from Zn, or a metal alloy not contg. Zn is deposited by vacuum coating on the zinc-coated thin metal sheet, and then, without exposing it to an oxidising atmosphere, the sheet is heat treated in an inert gas atmosphere. The metal or metals or metal alloy not contg. zinc is produced by electron beam evaporation or magnetron sputtering. The corrosion-resistant thin steel sheet is subjected to ion bombardment or is heated to 150-400[deg]C, pref. 220[deg]C before the vacuum coating. The heat treatment following the vacuum coating is carried out at an inert gas pressure of 10-100 kPa, pref. 80 kPa for max. 100 seconds, pref. 0 seconds at 300-400[deg]C.