PREPARATION FOR PRE-TREATING SURFACES BY CHEMICALLY CONVERTING OXIDE LAYERS OF TITANIUM OR TITANIUM ALLOYS

Abstract

A preparation and a process for the surface pretreatment of titanium or titanium alloys containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein the preparation has a pH of at least 12, and preferably 13, and wherein a content of further substances is less than 1 g/l.

Claims

1. A process for a surface pretreatment of articles composed of titanium or titanium alloys, comprising: contacting the articles composed of titanium or titanium alloys with a preparation containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein a content of further substances is less than 1 g/l and a pH of the preparation is at least 12, for 5 to 60 minutes at 20 to 80 C.

2. The process as claimed in claim 1, wherein the pH is at least 13.

3. The process as claimed in claim 1, wherein a fluoride content is less than 0.001% by weight, based on fluoride present in the preparation used.

4. The process as claimed in claim 1, wherein a content of NaOH is 300 to 375 g/l, and a content of MGDA is 30 to 100 g/l.

5. The process as claimed in claim 1, wherein the contacting is effected by immersion.

6. The process as claimed in claim 1, wherein the contacting is effected for 10 to 30 minutes at 40 to 70 C.

7. The process as claimed in claim 1, wherein the contacting is effected for 20 minutes at 60 C.

8. The process as claimed in claim 1, wherein the article has a porous layer at a surface thereof after the contacting step, wherein pores of the porous surface are predominantly open, have a number-average pore size of less than 100 nm.

9. The process as claimed in claim 8, wherein the number-average pore size is 30 to 70 nm.

10. An article composed of titanium or titanium alloys treated using the method as claimed in claim 1.

11. An article composed of titanium or titanium alloys having a porous layer at a surface thereof, wherein pores of the porous surface are predominantly open, have a number-average pore size of less than 100 nm.

12. The article as claimed in claim 11, wherein the number-average pore size is 30 to 70 nm.

13. An aircraft comprising an article composed of titanium or titanium alloys as claimed in claim 11.

Description

EXAMPLES

[0023] The examples show various treatments of various titanium alloys. The conditions are stated in each case. Prior to the treatment, the material samples are washed with isopropanol or with an alkaline degreasing agent (Metaclean T2001, experiments 7 and 8 only). After drying, the samples were treated with the aqueous solutions specified by immersion without movement or stirring. The solutions had a pH of approx. 14. After the treatment, the surface obtained was assessed visually. An iridescent surface indicates a surface modification with characteristic dimensions in the region of the wavelength of light (nanostructured surface).

TABLE-US-00001 NaOH MGDA T T # [g/l] [g/l] [ C.] [min] Evaluation/observation 1 Ti6Al4V 240 30 60 15 ++ green/blue iridescent surface 2 Ti6Al4V 240 60 60 15 ++ iridescent surface 3 Ti6Al4V 350 120 75 15 ++ iridescent surface 4 Ti6Al4V 350 65 15 surface not nanostructured 5 Ti6Al4V 350 30 65 15 ++ iridescent surface 6 Ti6Al4V 450 30 65 15 + yellowish iridescent surface with violet specks 7 Ti6Al4V 200 30 65 15 ++ green/blue iridescent surface 8 CpTi 200 30 65 15 ++ violet/blue iridescent surface 9 Ti6Al4V 350 60 60 15 ++ iridescent surface

[0024] A loss of mass was observed in experiment 5 only.

[0025] SEM images of the surface obtained in experiment 5 show a sponge-like surface structure with pore sizes of 30 to 100 nm. The pore walls are of an open and irregularly network-like configuration.

[0026] The roller peel test in accordance with DIN 2243-2 showed exceptional adhesion compared to untreated titanium sheet: at room temperature there was exclusively failure of the adhesive layer and not detachment of the bond, and at 55 C. there was 95% failure of the bond. (Surface pretreatment by alkaline cleaning followed by treatment with HNO3/HF mixture, then analogous to example 5, Ti peel plate: 300*210*0.4 mm, BR 127 primer (cytec), FM 94 adhesive (cytec); room temperature: 174.9 N (100% cohesive failure); 55 C.: 141.2 N (95% cohesive failure)).

[0027] It is noted that the embodiments described are merely illustrative and are not restrictive.

[0028] While the invention has been illustrated and described in detail in the examples and the preceding description, it is intended that such illustrations and descriptions be merely illustrative or exemplary and not restrictive, so that the invention is not limited by the embodiments disclosed. In the claims, the word having does not exclude other elements and the indefinite article a does not exclude a plurality.

[0029] The mere fact of mentioning certain features in various dependent claims does not restrict the subject matter of the invention. Combinations of these features can also be used to advantage.

[0030] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.