Provided is a surface treated steel sheet for a fuel tank, the surface treated steel sheet including: a Zn plated layer or a ZnNi alloy plated layer which is formed on at least a surface of the steel sheet to be an inner surface of the fuel tank; and a chromate-free chemical conversion coating layer containing a water-and-oil repellent, the chromate-free chemical conversion coating layer being placed over the Zn plated layer or the ZnNi alloy plated layer on the surface to be the inner surface of the fuel tank. A water contact angle on a surface of the chromate-free chemical conversion coating layer is more than or equal to 70 degrees and an n-hexadecane contact angle on the surface of the chromate-free chemical conversion coating layer is more than or equal to 30 degrees and less than or equal to 70 degrees.

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.

A steel sheet for a fuel tank according to the present invention includes: a ZnNi alloy plated layer placed on one surface or each of both surfaces of a base metal; and a chromate-free chemical conversion coating film which is placed over the ZnNi alloy plated layer. The ZnNi alloy plated layer has a crack starting from an interface with the chromate-free chemical conversion coating film and reaching an interface with the steel sheet, the chromate-free chemical conversion coating film consists of an organosilicon compound consisting of a condensation polymer of a silane coupling agent, a phosphoric acid compound and/or a phosphonic acid compound, a vanadium compound, and a titanium compound and/or a zirconium compound, and a concentration of a total of amounts in terms of metal, per surface, of the phosphoric acid compound and/or the phosphonic acid compound+the vanadium compound+the titanium compound and/or the zirconium compound, is 5 mass % to 20 mass %.

A steel sheet for a fuel tank according to the present invention includes: a ZnNi alloy plated layer placed on one surface or each of both surfaces of a base metal; and a chromate-free chemical conversion coating film which is placed over the ZnNi alloy plated layer. The ZnNi alloy plated layer has a crack starting from an interface with the chromate-free chemical conversion coating film and reaching an interface with the steel sheet, the chromate-free chemical conversion coating film consists of an organosilicon compound consisting of a condensation polymer of a silane coupling agent, a phosphoric acid compound and/or a phosphonic acid compound, a vanadium compound, and a titanium compound and/or a zirconium compound, and a concentration of a total of amounts in terms of metal, per surface, of the phosphoric acid compound and/or the phosphonic acid compound+the vanadium compound+the titanium compound and/or the zirconium compound, is 5 mass % to 20 mass %.

A steel sheet for a fuel tank includes: a ZnNi alloy plated layer which is placed on one surface or each of both surfaces of a base metal and formed on at least one surface; and an inorganic chromate-free chemical conversion coating film which is placed over the ZnNi alloy plated layer. The ZnNi alloy plated layer has a crack starting from an interface between the ZnNi alloy plated layer and the inorganic chromate-free chemical conversion coating film and reaching an interface between the ZnNi alloy plated layer and the steel sheet, and a water contact angle on a surface of the inorganic chromate-free chemical conversion coating film is more than or equal to 50 degrees.

A steel sheet for a fuel tank includes: a ZnNi alloy plated layer which is placed on one surface or each of both surfaces of a base metal and formed on at least one surface; and an inorganic chromate-free chemical conversion coating film which is placed over the ZnNi alloy plated layer. The ZnNi alloy plated layer has a crack starting from an interface between the ZnNi alloy plated layer and the inorganic chromate-free chemical conversion coating film and reaching an interface between the ZnNi alloy plated layer and the steel sheet, and a water contact angle on a surface of the inorganic chromate-free chemical conversion coating film is more than or equal to 50 degrees.

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.

Described herein is an aqueous, chromium-free composition for a pretreatment of aluminum surfaces, which includes at least one water-soluble phosphorus compound, at least one water-soluble zirconium compound, at least one water-soluble titanium compound, and at least one water-soluble molybdenum compound, a phosphorus compound content being in a range from 15 to 50 mg/l (calculated as phosphorus), a zirconium compound content being in a range from 400 to 600 mg/l (calculated as metal), a titanium compound content being in a range from 85 to 400 mg/l (calculated as metal), and a molybdenum compound content being in a range from 40 to 150 mg/l (calculated as metal). Also described herein are a corresponding method and a correspondingly pretreated component or strip.

Described herein is an aqueous, chromium-free composition for a pretreatment of aluminum surfaces, which includes at least one water-soluble phosphorus compound, at least one water-soluble zirconium compound, at least one water-soluble titanium compound, and at least one water-soluble molybdenum compound, a phosphorus compound content being in a range from 15 to 50 mg/l (calculated as phosphorus), a zirconium compound content being in a range from 400 to 600 mg/l (calculated as metal), a titanium compound content being in a range from 85 to 400 mg/l (calculated as metal), and a molybdenum compound content being in a range from 40 to 150 mg/l (calculated as metal). Also described herein are a corresponding method and a correspondingly pretreated component or strip.