A method for post-treatment of a chromium finish surface to improve corrosion resistance comprising a) providing a substrate having a chromium finish surface, and at least one intermediate layer between the chromium finish surface and the substrate, selected from the group consisting of nickel, nickel alloys, copper and copper alloys, wherein the chromium finish surface is a surface of a trivalent chromium plated layer, obtained by electroplating the substrate, having the at least one intermediate layer, in a plating bath, the plating bath comprising chromium (III) ions; b) contacting the chromium finish surface with an aqueous solution, comprising a permanganate, at least one compound which is selected from a phosphorus-oxygen compound, a hydroxide, a nitrate, a borate, boric acid, a silicate, or a mixture of two or more of these compounds; c) forming a transparent corrosion protection layer onto the chromium finish surface during step b.

Described herein is a method for treatment of at least one surface of a metal containing substrate including at least contacting the surface with an aqueous acidic Ni-free composition (A) including at least zinc cations, manganese cations, and phosphate anions to form a conversion coating on the surface and contacting the formed coating with an aqueous Ni-free composition (B) including one or more linear polymers (P) containing at least vinyl phosphonic acid, (meth)acrylic acid, and hydroxyethyl- and/or hydroxypropyl (meth)acrylate in form of their polymerized monomeric units. Also described herein is the composition (B), a master batch to produce the composition (B), a kit-of-parts including both compositions (A) and (B), a kit-of-parts including respective master batches to produce both compositions (A) and (B), and a coated substrate obtainable by the method described herein.

A grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes a grain-oriented magnetic steel sheet and an insulating tension coating containing a phosphate salt and silica on a surface of the grain-oriented magnetic steel sheet, the coating further including a crystalline compound represented by the general formula (1): M.sup.II.sub.3M.sup.III.sub.4(X.sup.VO.sub.4).sub.6 . . . (1). A method for producing a grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes applying an insulating tension coating liquid to a surface of a finish annealed grain-oriented magnetic steel sheet, the coating liquid including colloidal silica, a phosphate salt and a metal element M-containing compound in a specific ratio, and heat treating the steel sheet at least one time at a temperature of not less than 900° C. in an atmosphere including a non-oxidizing gas and having a dew point of not more than 0° C.

A grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes a grain-oriented magnetic steel sheet and an insulating tension coating containing a phosphate salt and silica on a surface of the grain-oriented magnetic steel sheet, the coating further including a crystalline compound represented by the general formula (1): M.sup.II.sub.3M.sup.III.sub.4(X.sup.VO.sub.4).sub.6 . . . (1). A method for producing a grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes applying an insulating tension coating liquid to a surface of a finish annealed grain-oriented magnetic steel sheet, the coating liquid including colloidal silica, a phosphate salt and a metal element M-containing compound in a specific ratio, and heat treating the steel sheet at least one time at a temperature of not less than 900° C. in an atmosphere including a non-oxidizing gas and having a dew point of not more than 0° C.

A solution for forming an insulation coating of grain-oriented electrical steel sheet includes an aqueous solution prepared by mixing a phosphate solution and colloidal silica. Chromium is not added to the aqueous solution. The colloidal silica includes silica particles surface-modified by an aluminate or is prepared by adding an aluminate to colloidal silica such as conventional colloidal silica.

A solution for forming an insulation coating of grain-oriented electrical steel sheet includes an aqueous solution prepared by mixing a phosphate solution and colloidal silica. Chromium is not added to the aqueous solution. The colloidal silica includes silica particles surface-modified by an aluminate or is prepared by adding an aluminate to colloidal silica such as conventional colloidal silica.

A method for phosphating metal surfaces in a layer-forming manner using a colloidal aqueous solution as an activation stage containing a dispersed particulate constituent, the particulate constituent containing dispersed inorganic compounds of phosphates of polyvalent metal cations; plus polymeric organic compounds as dispersing agents, which are composed at least partially of styrene and/or an α-olefin having no more than 5 carbon atoms and are composed at least partially of maleic acid, its anhydride and/or its imide, the polymeric organic compounds additionally comprising polyoxyalkylene units. In the activation stage of the method according to the invention, the addition of condensed phosphates can be dispensed with such that the content of dissolved condensed phosphates in the colloidal aqueous solution is less than 0.25, based on the phosphate content in the particulate constituent thereof, in each case based on the element P.

An insulation layer formation method comprises: a first step in which a surface treatment is applied to a base material to form thereon a high-resistance layer having high electric resistivity; a second step in which metal plating parts are formed on the base material that has undergone the first step in such a manner as to allow a high-resistance layer to be formed thereon; and a third process in which a high-resistance layer is formed on the base material that has undergone the second step.

The present patent application relates to an aqueous composition for coating grain oriented steel, comprising aluminium cations, manganese cations, dihydrogen phosphate, hydrogen phosphate and/or phosphate anions, colloidal silica and optionally iron cations, wherein the aluminium cations, expressed as Al.sub.2O.sub.3, manganese cations, expressed as MnO, dihydrogen phosphate, hydrogen phosphate and/or phosphate anions, expressed as P.sub.2O.sub.5, colloidal silica, expressed as SiO.sub.2, and optionally iron cations, expressed as FeO, which are present in the composition, give the sum formula of (Al.sub.2O.sub.3).sub.2(MnO).sub.1,8-2,4(FeO).sub.0-0,2(P.sub.2O.sub.5).sub.5-7(SiO.sub.2).sub.≥30.

The present patent application relates to an aqueous composition for coating grain oriented steel, comprising aluminium cations, manganese cations, dihydrogen phosphate, hydrogen phosphate and/or phosphate anions, colloidal silica and optionally iron cations, wherein the aluminium cations, expressed as Al.sub.2O.sub.3, manganese cations, expressed as MnO, dihydrogen phosphate, hydrogen phosphate and/or phosphate anions, expressed as P.sub.2O.sub.5, colloidal silica, expressed as SiO.sub.2, and optionally iron cations, expressed as FeO, which are present in the composition, give the sum formula of (Al.sub.2O.sub.3).sub.2(MnO).sub.1,8-2,4(FeO).sub.0-0,2(P.sub.2O.sub.5).sub.5-7(SiO.sub.2).sub.≥30.