Abrasion- and Peel-Resistant Sol-Gel Coating on Aluminum and Method for Producing a Coating of This Type

Abstract

Provided herein is an aluminum surface having an abrasion- and peel-resistant sol-gel coating. To obtain the coating, the aluminum surface is treated with an aqueous, oxidizing solution, such that said surface provides a suitable base for the subsequent sol-gel coating.

Claims

1. A method for providing a base for a directly following sol-gel coating on an aluminum surface with a natural oxide layer, comprising treating the aluminum surface with an aqueous oxidizing agent, selected from the group consisting of peroxides, persulfates, perchlorates and perborates, wherein a pH value of the aqueous oxidizing agent is in a range of 3 to 8, and wherein the oxidizing agent is used at a concentration of 5 to 50 g/l.

2. The method according to claim 1, wherein the treatment with the aqueous oxidizing agent is carried out at ambient temperature for a period of at least 2 minutes.

3. The method according to claim 2, wherein the ambient temperature is 15 C. to 25 C.

4. The method according to claim 1, wherein the treatment with the aqueous oxidizing agent is carried out over a period of 5 to 10 minutes.

5. (canceled)

6. A method for producing an abrasion-resistant aluminum surface, comprising: a) pretreating an aluminum surface by the method according to claim 1: b) rinsing the pretreated surface and then optionally drying the surface; and subsequently c) applying a sol-gel coat and hardening the sol-gel coat.

7. The method according to claim 6, wherein the sol-gel coating on the aluminum surface has a coat thickness of 0.5 to 5.0 m.

8. An aluminum surface with an abrasion- and peel-resistant sol-gel coating obtained according to a method according to claim 6.

Description

EXAMPLES

[0043] In the following examples, various aluminum surfaces with a bright surface of AlMg 4.5 were first degreased, rinsed and dried. A natural oxide layer had already formed previously on these sheets before the surface was treated further and provided with a sol-gel coating.

Example 1

[0044] Two aluminum sheets of AlMg 4.5 with a surface polished with grain 240 were degreased, rinsed, dried and treated as follows:

[0045] A sol-gel coating was applied by spraying to one sheet without further pretreatment and was then baked for a period of 30 minutes at 240 C. in air. After cooling, the sheet was bent around a radius of 10 d by 90. The sol-gel coat became cracked in the process and flaked off in the area of the bending.

[0046] The second sheet was immersed for a period of 10 minutes in an aqueous solution with 10% by weight hydrogen peroxide, then rinsed with water and dried. Then an identical sol-gel coating was applied by spraying and baked at a temperature of 240 C. for a period of 30 minutes in air. After cooling the sheet was bent with a radius of 2 d by 180. The coating remained free of cracks, homogeneous and firmly adhering in the area of the bending.

Example 2

[0047] Two aluminum sheets of AlMg 4.5 with a bright surface were degreased, rinsed, dried and treated as follows:

[0048] A sol-gel coating was applied by spraying to one sheet without further pretreatment and was then baked for a period of 30 minutes at 240 C. in air. After cooling, the sheet was bent with a radius of 10 d around an angle of 90. The sol-gel coat became cracked in the process and flaked off in the area of the bending.

[0049] The second sheet was sprayed for a period of 10 minutes with an aqueous solution with 10% by weight, then rinsed and dried. Then an identical sol-gel coating was applied by spraying and baked at a temperature of 240 C. in air. After cooling the sheet was bent with a radius of 2 d around an angle of 180. The coating remained free of cracks, homogeneous and firmly adhering in the area of the bending.

Example 3

[0050] Two aluminum sheets of AlMg 4.5 with a bright surface were degreased, rinsed and dried.

[0051] A sol-gel coating was applied by spraying to one sheet without further pretreatment and was then baked for a period of 30 minutes at 240 C. in air. After cooling, the sheet was bent with a radius of 10 d around an angle of 90. The sol-gel coat became cracked and flaked off in the area of the bending.

[0052] The second sheet was sprayed for a period of 5 minutes with an aqueous solution containing 40 g/l of potassium persulfate at pH 4, then rinsed and dried. Then an identical sol-gel coating was applied and baked at a temperature of 240 C. in air. After cooling the sheet was bent with a radius of 2 d around an angle of 180. The coating remained free of cracks, homogeneous and firmly adhering in the area of the bending.