Method for treating surfaces of aluminum containing substrates
Described herein is a method for treatment of at least one surface of a substrate at least partially made of aluminum and/or an aluminum alloy, including at least a step of contacting said surface with an acidic aqueous composition (A) including one or more metal compounds (M) selected from the group of titanium compounds, zirconium compounds, and hafnium compounds and one or more linear polymers (P) containing (m1) N,N-dimethyl (meth)acryl amide, (m2) vinylphosphonic acid, and (m3) (meth)acrylic acid in form of their polymerized monomeric units, the one or more linear polymers (P) being included in the acidic aqueous composition (A) in an amount of 50 to 5000 ppm. Also described herein is an acidic aqueous composition (A), a master batch to produce the acidic aqueous composition (A), a method of using the acidic aqueous composition (A) for treating surfaces, and substrates comprising the treated surfaces.
1. A method for treatment of at least one surface of a substrate, wherein said surface is at least partially made of aluminum and/or an aluminum alloy, comprising at least a step (1) of contacting said at least one surface with an acidic aqueous composition (A), the acidic aqueous composition (A) comprising
(a) one or more metal compounds (M) selected from the group consisting of titanium compounds, zirconium compounds, hafnium compounds, and mixtures thereof, and
(b) one or more linear polymers (P) prepared by controlled radical polymerization containing
(m1) N,N-dimethyl (meth)acryl amide,
(m2) vinylphosphonic acid, and
(m3) (meth)acrylic acid
in a form of their polymerized monomeric units,
said one or more linear polymers (P) being comprised in the acidic aqueous composition (A) in an amount of 50 to 5000 ppm, based on a total weight of the acidic aqueous composition (A).
2. The method according to claim 1 , characterized in that the surface of the substrate consists of aluminum or an aluminum alloy.
3. The method according to claim 1 , characterized in that the acidic aqueous composition (A) has a pH in a range of 0.5 to 6.5.
4. The method according to claim 1 , characterized in that the one or more metal compounds (M) are comprised in the acidic aqueous composition (A) in a concentration in a range of 50 to 5000 ppm, based in each case on titanium, zirconium, and/or hafnium as metal.
5. The method according to claim 1 , characterized in that the one or more metal compounds (M) present as component (a) are complex fluorides of titanium, zirconium, and/or hafnium.
6. The method according to claim 1 , characterized in that the one or more linear polymers (P) are terpolymers containing only polymerized monomeric units of (m1) N,N-dimethyl (meth)acryl amide, (m2) vinylphosphonic acid, and (m3) (meth)acrylic acid.
7. The method according to claim 1 , characterized in that the one or more linear polymers (P) are comprised in the acidic aqueous composition (A) in a concentration in a range of 100 to 4000 ppm.
8. The method according to claim 1 , characterized in that the one or more linear polymers (P) have a number average molecular weight in a range of 15,000 to 50,000 g/mol.
9. The method according to claim 1 , characterized in that the acidic aqueous composition (A) comprises free fluoride in a concentration in a range of 1 to 250 ppm.
10. The method according to claim 1 , characterized in that the method comprises an additional coating step of applying at least one coating composition to the surface of the substrate obtained after the contacting step (1) to form a coating layer upon the surface, wherein optionally after step (1) a rinsing step (2) is carried out prior to said coating step.
11. A substrate comprising at least one surface, wherein said surface is at least partially made of aluminum and/or an aluminum alloy, wherein said at least one surface has been treated according to the method as defined in claim 1 .