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.

Abstract: A method is shown for surface-treating a protectively coated substrate (1), more particularly steel strip, for the purpose of enhancing the strength of adhesion with an adhesive (10), where the at least partly multi-phase protective coat (2) comprises at least zinc and magnesium. In order to provide a particular suitability for adhesive bonding, it is proposed that the protective coat (2) be subjected to a pickling treatment, directed substantially at at least one intermetallic Zn—Mg phase (4) of the protective coat (2), with acidic pickle, more particularly acid.