Pretreating zinc surfaces prior to a passivating process

The invention relates to a wet-chemical pretreatment of zinc surfaces prior to applying a corrosion-protection coating. The wet-chemical pretreatment produces a deposition of a thin inorganic coating which substantially consists of oxide and/or metallic iron. An iron layer structure which is applied according to the invention, hereinafter referred to as steeling, improves the achievable corrosion protection of wet-chemical conversion coatings known from the prior art on zinc surfaces. Furthermore, the steeling process causes both a reduction of the contact corrosion of joined metal components which have zinc and iron surfaces as well as a reduction of corrosive coating migration on cut edges of galvanized steel strips with coating layer structures. In particular, the invention relates to an alkali composition for steeling purposes, said composition containing an iron ion source, a reducing agent based on oxoacids of the elements nitrogen and phosphorus, and water-soluble organic carboxylic acids with an amino group at the α, ß, or γ position with respect to the acid group and/or the water-soluble salts thereof.