Method for producing a flat steel product having a protective zinc-based metal layer and a phosphating layer produced on a surface of the protective metal layer and flat steel product of this type

A method for producing a flat steel product having a protective zinc-based metal layer and a phosphating layer produced on a surface of the protective metal layer, comprising at least the following method steps which are carried out in a continuous process:

• a) providing a flat steel product, wherein a protective metal layer formed from a Zn—Al alloy consisting of Zn and 0.1-0.5 weight percent (wt. %) Al and unavoidable impurities, a Zn—Mg alloy, or a Zn—Mg—Al alloy containing in total up to 8 wt. % Mg and Al by hot dip coating is present on at least one side of the flat steel product;
• b) at least partly removing a native oxide layer present on the surface of the protective metal layer by wetting this surface with an acidic solution having a pH of 1-3.5 for a wetting period of 1-60 seconds, wherein, for the acidic solution, an acid selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, phosphoric acid, phosphonic acid, nitric acid, formic acid, oxalic acid, acetic acid, citric acid, malic acid, tartaric acid, nitrous acid and hydrofluoric acid is used;
• c) optionally, rinsing the surface of the protective metal layer wetted with the acidic solution with an aqueous rinsing solution;
• d) activating the surface of the protective metal layer by applying an aqueous activation solution to the surface of the protective metal layer;
• and
• e) phosphating the activated surface of the protective metal layer by applying an aqueous phosphating solution to the activated surface of the protective metal layer for a wetting period of 10 s or less.