Method for pretreating aluminum materials, particularly aluminum wheels
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.
1. A method for pretreating aluminum materials, 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 copolymer soluble in the aqueous composition, the copolymer being a linear terpolymer prepared by controlled radical polymerisation and comprising:
vinylphosphonic acid monomeric units m1 and
hydroxyethyl- and/or hydroxypropyl-(meth)acrylate monomeric units m2 and
(meth)acrylic acid monomeric units m3, and
vi) optionally rinsed,
vii) optionally contacted with another acidic aqueous composition,
viii) optionally rinsed, and
ix) optionally dried.
2. The method according to claim 1 , wherein step iii) is performed and the at least one mineral acid is sulfuric acid and/or nitric acid.
3. The method to claim 1 , wherein the composition in step iii) additionally comprises a titanium and/or zirconium compound.
4. The method according to claim 1 , wherein the pH value of the composition in step v) is in the range of 2.0 and 6.0.
5. The method according to claim 1 , wherein the concentration of component a) in the composition in step v) is in the range of 0.015 and 0.5 g/l, calculated as metal, and the concentration of component b) is in the range of 0.01 and 1 g/l, calculated as solid addition.
6. The method according to claim 1 , wherein the component a) of the composition in step v) is at least one complex fluoride selected from the group consisting of the complex fluorides of titanium, zirconium, and hafnium.
7. The method according to claim 1 , wherein the at least one copolymer of component b) of the composition in step v) is a terpolymer that contains vinylphosphonic acid monomeric units m1, present in the copolymer at a molar content of 5 to 50% based on the whole copolymer, hydroxyethyl- and/or hydroxypropyl-(meth)acrylate monomeric units m2, which are present in the copolymer at a molar content of 5 to 70%, typically 20 to 55% based on the whole copolymer and (meth)acrylic acid monomeric units m3, which are present in the copolymer at a molar content of 25 to 85%, typically 40 to 70% based on the whole copolymer.
8. The method according to claim 1 , wherein the at least one copolymer of component b) of the composition in step v) is a terpolymer that contains 2-hydroxyethyl-(meth)acrylate and/or hydroxypropyl-(meth)acrylate, wherein the latter is 2-hydroxypropyl-(meth)acrylate, 3-hydroxypropyl-(meth)acrylate or a mixture of 2-hydroxypropyl-(meth)acrylate and 3-hydroxypropyl-(meth)acrylate, as monomeric units m2.
9. The method according to claim 1 , wherein the component b) of the composition in step v) includes at least one copolymer selected from the group consisting of (meth)acrylic-acid-hydroxyethyl(meth)acrylate-vinylphosphonic-acid-terpolymers, and (meth)acrylic-acid-hydroxypropyl(meth)acrylate-vinylphosphonic-acid-terpolymers.
10. The method according to claim 1 , wherein the composition in step v) additionally contains at least one poly(meth)acrylic acid having a number averaged molecular weight of at least 28,000 g/mol.
11. The method according to claim 1 , wherein the composition in step v) additionally comprises c) at least one compound selected from the group consisting of organoalkoxysilanes, organosilanoles, polyorganosilanoles, organosiloxanes, and polyorganosiloxanes.
12. The method of claim 11 , wherein the component c) is at least one organoalkoxysilane, organosilanole, polyorganosilanole, organosiloxane, and/or polyorganosiloxane, each comprising at least one amino group, urea group, imido group, imino group, and/or ureido group per organoalkoxysilane/organosilanole unit.
13. The method according to claim 1 , wherein the composition in step v) additionally comprises d) at least one type of cation selected from the group consisting of cations of the metals of the groups IA, IIA, IIIA, VB, VIB, and VIIB of the periodic system of the elements, of lanthanides as well as of bismuth and of tin, and/or at least one corresponding compound.
14. The method according to claim 13 , wherein the composition in step v) contains lithium cations.
15. The method according to claim 13 wherein the component d) is at least one of a molybdenum and/or a vanadium compound, having a concentration in the range of 1 to 400 mg/l, calculated as metal.
16. The method according to claim 1 , wherein the composition in step v) additionally comprises a component e) which is at least one compound selected from the group consisting of substances affecting the pH value, organic solvents, water-soluble fluorine compounds, and nanoparticles.
17. The method according to claim 1 , wherein the total fluorine content in the composition in step v) is in the range of 1.5 to 500 mg/l.
18. The method according to claim 1 , wherein the composition in step v) contains ammonium ions and/or corresponding compounds.
19. The method according to claim 1 , wherein the rinsing steps vi) and/or viii) are carried out.
20. The method according to claim 1 , wherein the aluminum material is vi) rinsed and vii) contacted with an aqueous composition containing at least one linear terpolymer prepared by controlled radical polymerisation and comprising:
vinylphosphonic acid monomeric units m1, and
hydroxyethyl- and/or hydroxypropyl-(meth)acrylate monomeric units m2, and
(meth)acrylic acid monomeric units m3, and
wherein step viii) is omitted.
21. The acidic aqueous composition according to step v) of claim 1 , wherein the acidic aqueous composition comprises:
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 m1, and
hydroxyethyl- and/or hydroxypropyl-(meth)acrylate monomeric units m2, and
(meth)acrylic acid monomeric units m3.
22. A concentrate, wherein the composition of claim 21 can be prepared from the concentrate by diluting and optionally adjusting the pH value.
23. A conversion-coated aluminum material obtainable by the method according to claim 1 .
24. A method of using an aluminum material treated with the method according to claim 1 , the method comprising using the aluminum material in automotive construction, vehicle construction, aircraft construction and facade construction, particularly for wheels, edgings and other mounting parts, cans, beverage cans, tubes, films, profiles and housings, in the field of aluminum finishing, and for architectural construction elements made of aluminum or aluminum alloys in indoor and outdoor areas, in particular in window, facade, and roof construction.
25. The method according to claim 1 , wherein the aluminum materials comprise aluminum wheels.
26. The method according to claim 1 , wherein the concentration of component b) in the composition in step v) is in the range of 0.004 to 1.8 g/l, calculated as solid addition.