Passivation composition based on mixtures of phosphoric and phosphonic acids

Patent metadata

Field	Value
Publication number	US-12428733-B2
Application number	US-202117244152-A
Country	US
Kind code	B2
Filing date	Apr 29, 2021
Priority date	Dec 5, 2018
Publication date	Sep 30, 2025
Grant date	Sep 30, 2025

Abstract

The present invention provides an aqueous passivation composition for the treatment of zinc or zinc alloy coatings, comprising:
i) phosphoric acid; ii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, iii) at least one divalent metal cation (M 2+ ); and, iv) at least one water-soluble or water-dispersible fluoroacid or a salt thereof, wherein said fluoroacid is defined by the following general empirical formula (II):

H p T q F r O s   (II)

wherein: each of q and r represents an integer from 1 to 10;
each of p and s represents an integer from 0 to 10; and, T represents an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge, and B.

First claim

What is claimed is:

1. An aqueous passivation composition for the treatment of zinc or zinc alloy coatings, said composition having a pH of less than 3 and comprising:
i) phosphoric acid;
ii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein said polyphosphonic acid has a general formula (I):

in which:
n is at least 2; and,
Z is a connecting organic moiety having an effective valency of n,
said polyphosphonic acid being characterized in that at least two phosphonic groups are separated by an alkylene bridge having 1 or 2 carbon atoms (C 1 -C 2 alkylene), wherein the composition has a molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) in a range from 2:1 to 1:1;
iii) at least one divalent metal cation (M 2+ ); and,
iv) at least one water-soluble or water-dispersible fluoroacid or a salt thereof, wherein said fluoroacid is defined by general empirical formula (II):
H p T q F r O s   (II)

wherein: each of q and r represents an integer from 1 to 10;
each of p and s represents an integer from 0 to 10; and,
T represents an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge, and B.

2. The composition according to claim 1 , wherein in general formula (I) n is an integer from 2 to 5.

3. The composition according to claim 1 , wherein said polyphosphonic acid is selected from the group consisting of: aminotris(methylene phosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP); diethylenetriamine penta (methylene phosphonic acid); diethylenetriamine penta (methylenephosphonic acid (DTPMP); and mixtures thereof.

4. The composition according to claim 3 , wherein said polyphosphonic acid comprises 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP).

5. The composition according to claim 1 wherein the composition has a molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) in a range from 1.75:1 to 1.25:1.

6. The composition according to claim 5 wherein the molar ratio of phosphonate groups to phosphoric acid (H 3 PO 4 ) is in a range from 1.6:1 to 1.4:1.

7. The composition according to claim 1 , wherein said at least one divalent metal cation (M 2+ ) is selected from the group consisting of: Mg 2+ ; Ca 2+ ; Co 2+ ; Ni 2+ ; Sr 2+ ; and Ba 2+ .

8. The composition according to claim 7 comprising Mg 2+ .

9. The composition according to claim 1 , wherein the composition has a total concentration of divalent metal cations (M 2+ ) in a range from 0.01 to 1 moles/litre.

10. The composition according to claim 9 , wherein the total concentration of divalent metal cations (M 2+ ) is in a range from 0.01 to 0.5 moles/litre.

11. The composition according to claim 1 , wherein in formula (II):
T is selected from Ti, Zr, or Si;
p is 1 or 2;
q is 1;
r is 2, 3, 4, 5 or 6; and,
sis 0, 1, or 2.

12. The composition according to claim 1 , wherein said at least one fluoroacid is selected from the group consisting of fluorotitanic acid (H 2 TiF 6 ); fluorozirconic acid (H 2 ZrF 6 ); fluorosilicic acid (H 2 SiF 6 ); fluoroboric acid (HBF 4 ); fluorostannic acid (H 2 SnF 6 );
fluorogermanic acid (H 2 GeF 6 ); fluorohafnic acid (H 2 HfF 6 ); fluoroaluminic acid (H 3 AlF 6 ); and
combinations thereof.

13. The composition according to claim 12 , wherein said at least one fluoroacid is selected from the group consisting of fluorotitanic acid (H 2 TiF 6 ); fluorozirconic acid (H 2 ZrF 6 ); and, fluorosilicic acid (H 2 SiF 6 ); and combinations thereof.

14. The composition according to claim 1 , wherein said at least one fluoroacid is present in an amount such that the composition has a molar ratio of phosphoric acid (H 3 PO 4 ) to the element (T) of said fluoroacid in a range from 20:1 to 2:1.

15. The composition according to claim 1 further comprising at least one α-hydroxycarboxylic acid represented by the general formula (III):
R 1 CH(OH)COOH  (III)

wherein:
R 1 represents a hydrogen atom, a C 1 -C 4 alkyl group, a C 2 -C 6 alkenyl group, a C 1 -C 6 alkoxy group, a C 3 -C 6 cycloalkyl group or a C 6 -C 10 aryl group.

16. The composition according to claim 1 being substantially free of peroxide and persulphate compounds.

17. The composition according to claim 1 , wherein said at least one fluoroacid is present in an amount such that the composition has a molar ratio of phosphoric acid (H 3 PO 4 ) to the element (T) of said fluoroacid in a range from 10:1 to 4:1.

18. A process for imparting a passivate film to a substrate comprising at least one zinc or zinc alloy coated surface, comprising: contacting the at least one zinc or zinc alloy coated surface of the substrate with the aqueous composition of claim 1 at a temperature ranging from 20° C. to 90° C. for a period of time sufficient to form a passivate film thereon.

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Jadhav Aditi
• Kumar Girdhari
• Vijay Meenu

Classifications

• C23C22/83

  Chemical after-treatment · CPC title

• C23C22/42

  containing also phosphates · CPC title

• C23C22/368 Primary

  containing magnesium cations · CPC title

• C07C59/01

  Saturated compounds having only one carboxyl group and containing hydroxy or O-metal groups · CPC title

• C23C22/361 Primary

  containing titanium, zirconium or hafnium compounds · CPC title