Abstract: A method for improving the adhesive capacity of a protectively coated steel sheet is proposed, in which, in a continuous process, a protective coating based on Zn—Al—Mg is applied to the steel sheet and, in a further step, the protective coating undergoes a surface treatment in which an aqueous composition is applied in order to modify the natural oxide layer, which contains Al2O3 and MgO, without pickling this natural oxide layer as a result. In order to significantly increase adhesive capacity of the protectively coated steel sheet, the invention proposes skin-pass rolling the protectively coated steel sheet and then reacting the natural oxide layer with an aqueous fluoride-containing composition, reducing its MgO content in order to thus modify the natural oxide layer.

Abstract: A method for improving the adhesive capacity of a protectively coated steel sheet is proposed, in which, in a continuous process, a protective coating based on Zn—Al—Mg is applied to the steel sheet and, in a further step, the protective coating undergoes a surface treatment in which an aqueous composition is applied in order to modify the natural oxide layer, which contains Al2O3 and MgO, without pickling this natural oxide layer as a result. In order to significantly increase adhesive capacity of the protectively coated steel sheet, the invention proposes skin-pass rolling the protectively coated steel sheet and then reacting the natural oxide layer with an aqueous fluoride-containing composition, reducing its MgO content in order to this modify the natural oxide layer.