An aqueous passivation composition for the treatment of zinc or zinc alloy coatings, said composition having a pH of less than 3 and comprising: i) phosphoric acid; ii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein said polyphosphonic acid is selected from the group consisting of: aminotris(methylene phosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP); diethylenetriamine penta(methylene phosphonic acid); diethylenetriamine penta(methylenephosphonic acid (DTPMP); and, mixtures thereof; iii) at least one divalent metal cation (M 2+ ) selected from the group consisting of: Mg 2+ ; Ca 2+ ; Mn 2+ ; Co 2+ ; Ni 2+ ; Sr 2+ ; Ba 2+ ; and, Zn 2+ comprising Mg 2+ , wherein the total concentration of divalent metal cations (M 2+ ) is in the range from 0.01 to 1 moles/litre; and iv) at least one water-soluble or water-dispersible fluoroacid or a salt thereof, wherein said fluoroacid is defined by the following general empirical formula (II): H p T q F r O s (II) wherein: p is 1 or 2; q is 1; r is 2, 3, 4, 5 or 6; and, s is 0, 1, or 2; and, T represents an element selected from the group consisting of Ti, Zr, or Si, wherein the molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) is in the range from 1.75:1 to 1.25:1 and comprising fluoroacid in an amount such that the molar ratio of phosphoric acid (H 3 PO 4 ) to the metal (T) of said fluoroacid is in the range from 20:1 to 2:1. i) phosphoric acid; ii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein said polyphosphonic acid is selected from the group consisting of: aminotris(methylene phosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP); diethylenetriamine penta(methylene phosphonic acid); diethylenetriamine penta(methylenephosphonic acid (DTPMP); and, mixtures thereof; iii) at least one divalent metal cation (M 2+ ) selected from the group consisting of: Mg 2+ ; Ca 2+ ; Mn 2+ ; Co 2+ ; Ni 2+ ; Sr 2+ ; Ba 2+ ; and, Zn 2+ comprising Mg 2+ , wherein the total concentration of divalent metal cations (M 2+ ) is in the range from 0.01 to 1 moles/litre; and iv) at least one water-soluble or water-dispersible fluoroacid or a salt thereof, wherein said fluoroacid is defined by the following general empirical formula (II): H p T q F r O s (II) wherein: p is 1 or 2; q is 1; r is 2, 3, 4, 5 or 6; and, s is 0, 1, or 2; and, T represents an element selected from the group consisting of Ti, Zr, or Si, wherein the molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) is in the range from 1.75:1 to 1.25:1 and comprising fluoroacid in an amount such that the molar ratio of phosphoric acid (H 3 PO 4 ) to the metal (T) of said fluoroacid is in the range from 20:1 to 2:1. p is 1 or 2; q is 1; r is 2, 3, 4, 5 or 6; and, s is 0, 1, or 2; and, T represents an element selected from the group consisting of Ti, Zr, or Si, wherein the molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) is in the range from 1.75:1 to 1.25:1 and comprising fluoroacid in an amount such that the molar ratio of phosphoric acid (H 3 PO 4 ) to the metal (T) of said fluoroacid is in the range from 20:1 to 2:1. <EOS>