Disclosed is a system for maintaining a pretreatment bath containing a pretreatment comprising a Group IVB metal. The system comprises an aqueous reducing agent comprising a metal cation and a latent source of sulfate which, upon reaction with a contaminant in the pretreatment bath, forms a metal sulfate. The contaminant comprises a nitrite source. The metal sulfate salt has a pKsp of 4.5 to 11 at a temperature of 25 C. Also disclosed is a method for maintaining a pretreatment bath containing a pretreatment composition comprising a Group IVB metal. The method comprises supplying the reducing agent to the pretreatment bath in an amount sufficient to reduce a pollution ratio of the pretreatment bath to less than 1:1. Also disclosed are substrates with a pretreatment bath maintained according to the system and method.

Provided herein is a method for pretreating aluminum materials, particularly aluminum wheels, wherein an aluminum material is successively i) cleaned and subsequently rinsed, ii) optionally subjected to alkaline pickling and subsequently rinsed, iii) optionally contacted with an aqueous composition comprising at least one mineral acid, iv) optionally rinsed and v) contacted with an acidic aqueous composition comprising a) at least one compound selected from the group consisting of titanium, zirconium and hafnium compounds and b) at least one linear terpolymer prepared by controlled radical polymerisation and comprising vinylphosphonic acid monomeric units, hydroxylethyl- and/or hydroxylpropyl-(meth)acrylate monomeric units and (meth)acrylic acid monomeric units, vi) optionally rinsed, vii) optionally contacted with another aqueous composition, viii) optionally rinsed and ix) optionally dried. Further provided herein is a corresponding composition as well as the use of the materials treated according to the method.

Provided herein is a method for pretreating aluminum materials, particularly aluminum wheels, wherein an aluminum material is successively i) cleaned and subsequently rinsed, ii) optionally subjected to alkaline pickling and subsequently rinsed, iii) optionally contacted with an aqueous composition comprising at least one mineral acid, iv) optionally rinsed and v) contacted with an acidic aqueous composition comprising a) at least one compound selected from the group consisting of titanium, zirconium and hafnium compounds and b) at least one linear terpolymer prepared by controlled radical polymerisation and comprising vinylphosphonic acid monomeric units, hydroxylethyl- and/or hydroxylpropyl-(meth)acrylate monomeric units and (meth)acrylic acid monomeric units, vi) optionally rinsed, vii) optionally contacted with another aqueous composition, viii) optionally rinsed and ix) optionally dried. Further provided herein is a corresponding composition as well as the use of the materials treated according to the method.

The present invention relates to an acidic aqueous composition for treating of zirconium-pretreated metal-based substrate surfaces such as steel metals or aluminium surfaces, a process for treating the substrate surfaces with the composition and the use of the composition as post-treatment of zirconium-pretreated metal-based substrate surfaces for subsequent electrocoating of the surfaces to increase corrosion resistance of said metal-based surfaces prior to electro-coating (e-coat) applications and increases detergent and chemical resistance of treated surfaces used in the white goods industry. The acidic aqueous composition comprises trivalent chromium ions; and hexafluorozirconate ions; characterized in that the source of trivalent chromium ions is a trivalent chromium nitrate salt.

The present invention relates to an acidic aqueous composition for treating of zirconium-pretreated metal-based substrate surfaces such as steel metals or aluminium surfaces, a process for treating the substrate surfaces with the composition and the use of the composition as post-treatment of zirconium-pretreated metal-based substrate surfaces for subsequent electrocoating of the surfaces to increase corrosion resistance of said metal-based surfaces prior to electro-coating (e-coat) applications and increases detergent and chemical resistance of treated surfaces used in the white goods industry. The acidic aqueous composition comprises trivalent chromium ions; and hexafluorozirconate ions; characterized in that the source of trivalent chromium ions is a trivalent chromium nitrate salt.

The present invention relates to a method for the anti-corrosion treatment of components produced from aluminum, in particular casting parts such as vehicle rims, comprising a pretreatment stage and subsequent coating, wherein the pretreatment stage in turn includes a pickle on the basis of sulfuric acid aqueous solutions containing water-soluble compounds of the element Ti and at least one a-hydroxycarboxylic acid which is carried out upstream of an acidic conversion treatment on the basis of an acidic aqueous solution containing water-soluble compounds of the elements Zr and/or Ti.

The present invention relates to a method for substantially nickel-free phosphating of a metallic surface, wherein a metallic surface is treated one after the other with the following compositions: i) with an alkaline, aqueous cleaner composition which comprises at least one water-soluble silicate, and ii) with an acidic, aqueous, substantially nickel-free phosphating composition which comprises zinc ions, manganese ions and phosphate ions.

The invention also relates to the above cleaner composition itself and also to a metallic surface phosphate-coated by the above method, and to the use of said surface.

A composite can include a substrate and a conversion coating overlying the substrate and comprising at least one of a zirconium oxide, a hafnium oxide, or a combination thereof. The conversion coating can be formed from a zirconia or hafnia-based complex obtained by reacting at least one of a zirconium ion source, a hafnium ion source, or a combination thereof, with a chelating compound in a reaction and another chelating compound in another reaction.

A composite can include a substrate and a conversion coating overlying the substrate and comprising at least one of a zirconium oxide, a hafnium oxide, or a combination thereof. The conversion coating can be formed from a zirconia or hafnia-based complex obtained by reacting at least one of a zirconium ion source, a hafnium ion source, or a combination thereof, with a chelating compound in a reaction and another chelating compound in another reaction.

This chemical conversion-treated steel sheet (10) has a chemical conversion treatment coating (12) upon a plating layer (17) of a steel sheet (11). The chemical conversion treatment coating (12) contains a fluororesin, a base resin which is a resin other than a fluororesin, metal flakes (13), and a chemical conversion treatment component. The content of the fluororesin in relation to the total quantity of resins is 3.0 mass % or more in terms of fluorine atoms, the content of the base resin in relation to 100 parts by mass of the fluororesin is 10 parts by mass or more, and the content of metal flakes (13) in the chemical conversion treatment coating (12) is more than 20 mass % but at most 60 mass %.