Method for pretreating aluminum materials, particularly aluminum wheels

Abstract

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.

Claims

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.

Description

EXAMPLES

(1) The following examples further illustrate the invention but are not to be construed as limiting its scope.

(2) 1. Acidic Aqueous Compositions

(3) 1.1 Polymer (P1) as component b) has been used, which is a terpolymer obtained by a controlled radical polymerization of a monomer mixture consisting of 4 to 25 mole-% of vinylphosphonic acid, 30 to 60 mole-% of hydroxypropyl (meth)acrylate and 30 to 60 mole-% of (meth)acrylic acid, wherein the sum of all monomeric units present in polymer (P1) adds up to 100 mole-%, having a number averaged molecular weight M.sub.n between 12,000 and 15,500 and a weight averaged molecular weight M.sub.w between 21,000 and 25,000. The polymer (P1) is prepared by a controlled radical polymerization using O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate as a control agent.

(4) 1.2 A number of aqueous solutions (each made by use of deionized water) containing an amount in the range of from 0.75 to 5.5 g/L of the commercially available product Gardobond® X 4707 (available from Chemetall GmbH) or containing an amount in the range of from 0.75 to 5.5 g/L of the commercially available product Gardobond® X 4742 (available from Chemetall GmbH) have been placed in a beaker. Gardobond® X 4707 is an acidic aqueous solution, which contains titanium compounds and zirconium compounds as component a). Gardobond® X 4742 is an acidic aqueous solution, which contains zirconium compounds as component a).

(5) To the above mentioned aqueous solution containing Gardobond® X 4707 an aqueous solution of polymer (P1) containing (P1) has been added in different amounts ranging from 0.1 g/L to 10 g/L.

(6) To the above mentioned aqueous solution containing Gardobond® X 4742 an aqueous solution of polymer (P1) containing (P1) has been added in different amounts ranging from 0.1 g/L to 10 g/L.

(7) 1.3 A further series of aqueous solutions (each made by use of deionized water) have been prepared from Oxsilan® 9801 and Oxsilan® additive 9900. Oxsilan® 9801 and Oxsilan® additive 9900 are commercial products available from Chemetall GmbH.

(8) To the above mentioned aqueous solutions an aqueous solution of polymer (P1) containing (P1) has been added in different amounts ranging from 0.1 g/L to 10 g/L.

(9) 1.4 A number of further comparative aqueous solutions (each made by use of deionized water) containing an amount in the range of from 0.75 to 5.5 g/L of the commercially available product Gardobond® X 4742 (available from Chemetall GmbH) have been placed in a beaker. To the above mentioned aqueous solution containing Gardobond® X 4742 an aqueous solution of a commercially available poly(meth)acrylic acid has been added in different amounts ranging from 0.1 g/L to 10 g/L.

(10) 2. Inventive Method

(11) 2.1 Aluminum wheels (AlSi7) have been used as substrate, which are available from the company Ronal (Switzerland).

(12) In a cleaning step i) these substrates have been cleaned by making use of the commercial product Gardoclean® S 5086 (Chemetall GmbH) (60° C., 10 minutes) followed by treatment with a mineral acid in a step iii). The treatment was performed by making use of one of the commercial products Gardacid® P 4325 (Chemetall GmbH) or Gardobond® X4717 (Chemetall GmbH) (90 seconds). After performance of step iii) rinsing with tap water is performed in a step iv) (30 seconds).

(13) 2.2 After performance of the steps as outlined in item 2.1, contacting step v) is carried out, i.e. the surfaces of the substrates are contacted with an inventive or comparative acidic composition in order to form a conversion coating layer on the substrate. The contacting step is performed for 45 seconds.

(14) After having performed said contacting step v) the resulting substrate bearing a conversion coating layer due to carrying out the contacting step is subjected to a rinsing step vi) with deionized water.

(15) Following the rinsing step a drying step ix) is performed (10 minutes at 80° C.). Afterwards, at least one further coating layer is applied onto the substrates. In alternative 1) a polyester powder coating (commercial product PT1005BR999F, available from the company Freilacke; in the following referred to as “PE”) is first applied onto the substrate, curing is performed at 180° C. and then an acrylic clear coating composition (commercial product K01853LRA999, available from the company Freilacke; in the following referred to as “AC1”) is applied onto the cured PE coat. Curing is performed at 190° C. In alternative 2) a commercial powder coating (commercial product PO1857BR999A, available from the company Freilacke; in the following referred to as “KSP”) is first applied onto the substrate, curing is performed at 180° C. and then an acrylic clear coating composition (commercial product KO1853LRA999, available from the company Freilacke; in the following referred to as “AC1”) is applied onto the cured KSP coat. Curing is performed at 190° C. In alternative 3) a commercial clear coating composition (commercial product PY1005, available from the company Freilacke; in the following referred to as “AC2”) is applied onto the substrate and curing is performed at 200° C. The dry layer thicknesses of these coatings obtained are in the range of 10-120 μm.

(16) 2.3 The experiments performed are summarized in the following Tables 1, 2 and 3 as well as 4:

(17) TABLE-US-00001 TABLE 1 Experiments of Series 1 Further coating Aqueous acidic applied according Product used composition used to alternative No. in step (iii) in step (v) 1), 2) or 3) B1a Gardacid ® Gardobond ® X 4707 alternative 1) P 4325 (5 g/L) + aq. solution of polymer (P1) (1 g/L) B1b Gardacid ® Gardobond ® X 4707 alternative 2) P 4325 (5 g/L) + aq. solution of polymer (P1) (1 g/L) B1c Gardobond ® Gardobond ® X 4707 alternative 1) X 4717 (5 g/L) + aq. solution of polymer (P1) (1 g/L) B1d Gardobond ® Gardobond ® X 4707 alternative 2) X 4717 (5 g/L) + aq. solution of polymer (P1) (1 g/L)

(18) TABLE-US-00002 TABLE 2 Experiments of Series 2 Further coating Aqueous acidic applied according Product used composition used to alternative No. in step (iii) in step (v) 1), 2) or 3) B2a Gardacid ® Gardobond ® X 4742 alternative 1) P 4325 (0.75 g/L) + aq. solution of polymer (P1) (1 g/L) B2b Gardacid ® Gardobond ® X 4742 alternative 2) P 4325 (0.75 g/L) + aq. solution of polymer (P1) (1 g/L) B2c Gardobond ® Gardobond ® X 4742 alternative 1) X 4717 (0.75 g/L) + aq. solution of polymer (P1) (2 g/L) B2d Gardobond ® Gardobond ® X 4742 alternative 2) X 4717 (0.75 g/L) + aq. solution of polymer (P1) (2 g/L)

(19) TABLE-US-00003 TABLE 3 Experiments of Series 3 Further coating Aqueous acidic applied according Product used composition used to alternative No. in step (iii) in step (v) 1), 2) or 3) B3a Gardacid ® Oxsilan ® 9801 (5.5 g/L) + Oxsilan ® alternative 3) P 4325 additive 9900 (4.5 g/L) + aq. solution of polymer (P1) (2.0 g/L) B3b Gardacid ® Oxsilan ® 9801 (5.5 g/L) + Oxsilan ® alternative 3) P 4325 additive 9900 (4.5 g/L) + aq. solution of polymer (P1) (2.0 g/L)

(20) TABLE-US-00004 TABLE 4 Experiments of Series 4 Aqueous acidic Further coating Product used composition used applied after No. in step (iii) in step (v) drying step ix) C1a Gardacid ® Gardobond ® X 4742 alternative 3) P 4325 (0.75 g/L) + aq. solution of poly(meth)acrylic acid) (1 g/L)
3. Properties of the Coated Substrates

(21) 3.1 A number of properties of the coated substrates obtained by the inventive method described in item 2. has been investigated. These properties were determined according to the test methods described hereinbefore. The results are displayed in the Tables below.

(22) TABLE-US-00005 TABLE 4a Crosscut Crosscut after after Crosscut Crosscut condensation condensation after after clima test clima test water water according to according to Crosscut storage storage DIN EN ISO DIN EN ISO Example after at 63° C. at 63° C. 6270-2 CH 6270-2 CH CASS test no. preparation for 1 h for 24 h for 1 h for 24 h 240 h B1a 0 0 0 0 0 nd B1b 0 0 0 0 nd 2 B1c 0 0 0 0 0.5 nd B1d 0 nd nd 0 nd 0.5 nd = not determined

(23) TABLE-US-00006 TABLE 4b Crosscut Crosscut after after Crosscut Crosscut condensation condensation after after clima test clima test water water according to according to Crosscut storage storage DIN EN ISO DIN EN ISO Example after at 63° C. at 63° C. 6270-2 CH 6270-2 CH CASS test no. preparation for 1 h for 24 h for 1 h for 24 h 240 h B2a 0 0 0 0.5 0.5 nd B2b 0 0.5 0.5 0 nd 1.9 B2c 0 0 0 1.0 0.5 nd B2d 0 0.5 0.5 0 nd 0.8 C1a nd 5 5 5 nd nd nd = not determined

(24) TABLE-US-00007 TABLE 4c Example no. CASS test 240 h FFC, MU 672 h B3a 0.5 1.4 B3b 0.9 1.4