Method for corrosion-protective and cleaning pretreatment of metallic components

Abstract

The present invention relates to a method for the corrosion-protective and cleaning pretreatment of metallic components, produced at least partially from metallic materials from the elements iron, zinc and/or aluminum, with the use of an acid aqueous composition containing, in addition to the water-soluble compounds of the elements Zr and/or Ti causing the conversion of the metal surface, a mixture of an aliphatic diol and an aliphatic saturated polyhydroxy compound. It also comprises a chrome(VI)-free aqueous composition based on the constituents mentioned above which delivers outstanding results in cleaning and simultaneous corrosion-protective conversion of technical metal surfaces in one method step.

Claims

1. A method for cleaning and anti-corrosion pretreatment of a metal component which is at least partially composed of a material that consists predominantly of one or more of the metals iron, zinc and/or aluminum, comprising contacting the metal component with an acidic aqueous composition containing components: a) at least 0.003 wt. % of aliphatic diols having at least 4 carbon atoms but no more than 10 carbon atoms; b) at least 0.01 wt. % of aliphatic saturated polyhydroxy compounds having at least 4 but no more than 8 carbon atoms; c) at least one water-soluble compound of Zr and/or Ti; d) at least one water-soluble source of fluoride ions.

2. The method according to claim 1, wherein the of polyhydroxy compounds of component b) have a ratio by mass to the aliphatic diols of component a) of at least 0.4 and no greater than 20.0.

3. The method according to claim 1, wherein hydroxyl groups of the aliphatic diol according to component a) are interconnected by means of no more than 3 carbon atoms.

4. The method according to claim 3, wherein the aliphatic diol according to component a) is selected from acyclic alkane diols having no more than 8 carbon atoms but at least 5 carbon atoms.

5. The method according to claim 3, wherein the aliphatic diol according to component a) comprises 2-methylpentane-2,4-diol.

6. The method according to claim 1, wherein the polyhydroxy compounds according to component b) have more than three hydroxyl groups, and at least two of the hydroxyl groups are interconnected by means of no more than two carbon atoms.

7. The method according to claim 1, wherein in total at least 0.002 wt. % and no more than 0.2 wt. % of the at least one water-soluble compound of Zr and/or Ti, calculated as an amount Zr, are present in the acidic aqueous composition.

8. The method according to claim 1, wherein the acidic aqueous composition has a pH of below 6.0 and above 2.0 and has a free acid content of at least 1 point.

9. The method according to claim 1, wherein the acidic aqueous composition contains component d) the at least one water-soluble source of fluoride ions in such an amount that the acidic aqueous composition has a free fluoride proportion of at least 10 mg/kg.

10. The method according to claim 1, wherein the acidic aqueous composition additionally contains calcium and/or magnesium ions.

11. The method according to claim 1, wherein the metal component consists at least in part of a ferrous material.

12. The method according to claim 1, wherein the contacting of the metal component with the acidic aqueous composition comprises spraying on or spraying at spray pressure of at least 1 bar.

13. The method according to claim 1, wherein upon contacting the metal component, the acidic aqueous composition has a temperature of less than 40° C. but at least 20° C.

14. The method according to claim 1, wherein, directly after contacting the metal component with the acidic aqueous composition, with or without an intermediate rinsing and/or drying step, regions of the metal component contacted with the acidic aqueous composition are immersion coated or powder coated, at least in part.

15. The method according to claim 1, wherein no wet-chemical cleaning of the metal component directly before the contacting with the acidic aqueous composition.

16. The method according to claim 2, wherein the ratio by mass of the polyhydroxy compounds of component b) to the aliphatic diols of component a) is at least 2.0 and no greater than 6.0.

17. The method according to claim 1, wherein the polyhydroxy compounds according to component b) are selected from erythritol, threitol, xylitol, arabitol, ribitol, mannitol or sorbitol, and combinations thereof.

18. The method according to claim 1, wherein in a total amount of at least 0.005 wt. %, of the water-soluble compounds of Zr and/or Ti, calculated as an amount Zr, are contained in the acidic aqueous composition.

19. The method according to claim 1, wherein the acidic aqueous composition has a pH of below 5.5, but above 3.0.

20. The method according to claim 1, wherein the acidic aqueous composition additionally contains in total at least 0.01 wt. % of calcium and/or magnesium ions.

21. An acidic aqueous chromium(VI)-free and phosphate-free composition comprising: a) 0.003-2 wt. % of aliphatic diols having at least 4 carbon atoms but no more than 10 carbon atoms; b) 0.01-5 wt.% of aliphatic saturated polyhydroxy compounds having at least 4 but no more than 8 carbon atoms; c) 0.002-0.2 wt. % of water-soluble compounds of Zr, calculated as an amount of Zr; d) at least 10 mg/kg of free fluoride ions; and e) optionally 0.01-1 wt. % of calcium and/or magnesium ions.

22. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 21, wherein the aliphatic saturated polyhydroxy compounds of component b) have a ratio by mass to the aliphatic diols of component a) is of at least 0.4 and no greater than 20.0.

23. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 22, wherein hydroxyl groups of the aliphatic diol according to component a) are interconnected by means of no more than 3 carbon atoms.

24. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 22, wherein the aliphatic diol according to component a) is selected from acyclic alkane diols having no more than 8 carbon atoms but at least 5 carbon atoms.

25. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 24, wherein the aliphatic diol according to component a) comprises 2-methylpentane-2,4-diol.

26. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 24, wherein the aliphatic saturated polyhydroxy compounds according to component b) have more than three hydroxyl groups, and at least two of the hydroxyl groups are interconnected by means of no more than two carbon atoms.

27. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 24, wherein the acidic aqueous composition has a pH of below 6.0 and above 2.0 and has a free acid content of at least 1 point.

28. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 24, wherein the ratio by mass of the aliphatic saturated polyhydroxy compounds of component b) to the aliphatic diols of component a) is at least 2.0 and no greater than 6.0.

29. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 28, wherein the aliphatic saturated polyhydroxy compounds according to component b) are selected from erythritol, threitol, xylitol, arabitol, ribitol, mannitol, sorbitol, and combinations thereof.

30. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 29, wherein the water-soluble compounds of Zr and/or Ti, calculated as an amount of Zr, are present in the acidic aqueous composition in an amount of at least 0.005 wt. %.

31. The acidic aqueous chromium(VI)-free and phosphate-free composition of claim 30, wherein the acidic aqueous composition has a pH of below 5.5, but above 3.0 and the calcium and/or magnesium ions are present in the acidic aqueous composition in an amount of at least 0.01 wt. %.

Description

EXAMPLE

(1) Oiled steel sheets (Gardobond® MBS 30, Chemetall GmbH) were subjected to a cleaning conversion treatment. The treatment was carried out in a spray chamber at a spray pressure of 1-2 bar for 60 seconds at 25° C. and a pH of the aqueous conversion solution of 4.6.

(2) The conversion solution contained

(3) TABLE-US-00001 0.16 g/L hexafluorozirconic acid 0.32 g/L magnesium nitrate hexahydrate  0.3 g/L sorbitol  0.1 g/L 2-methylpentane-2,4-diol

(4) In the water rupture test immediately after the treatment, no rupture of the running water film was observed after wetting with city water and, even after ten minutes of the metal sheets being stored in the spray chamber after cleaning conversion treatment having been carried out, no flash rust was detectable.