Process for phosphating metal surfaces

• US 4,944,813 A
• Filed: 01/13/1989
• Issued: 07/31/1990
• Est. Priority Date: 01/14/1988
• Status: Expired due to Fees

• Current Assignee: Gerhard Collardin GmbH
• Original Assignee: Gerhard Collardin GmbH
• Inventors: Hosemann, Kurt, Opitz, Reinhard
• Primary Examiner(s): Silverberg, Sam
• Application Number:
  US07/297,155
• Time in Patent Office: 564 Days
• Field of Search: 148/246, 148/263, 148/260, 72/42
• US Class Current: 148/260
• CPC Class Codes: C23C 22/22 containing alkaline earth metal cations
• CPC Class Codes: C23C 22/367 containing alkaline earth metal cations

Abstract

The present invention relates to a process for phosphating metal surfaces, and more specifically of surfaces of iron, zinc, and aluminum and the alloys thereof as a pretreatment for cold working wherein the surfaces without previous activation are contacted in a temperature range of from 30° C. to 70° C. with an aqueous solution containing

(a) from 10 to 40 g/l of Ca²⁺ ions,

(b) from 10 to 40 g/l of Zn²⁺ ions,

(c) from 10 to 100 g/l of OP₄^3- ions

and, as accelerator,

(d) from 10 to 100 g/l of NO₃^- ions and/or

(e) from 0.1 to 2.0 g/l of organic nitro compounds,

said solution exhibiting a pH value in the range of from 2.0 to 3.8 and a ratio of free acid to total acid of from 1:4 to 1:100.

Claims

1. In a process comprising cleaning and phosphating metal surfaces, the improvement wherein the surfaces without previous activation are contacted in a temperature range of from 30°

C. to 70°

C. with an aqueous solution consisting essentially of;

(a) from about 10 to about 40 g/l of Ca²⁺ ions,

(b) from about 10 to about 40 g/l of Zn²⁺ ions,

(c) from about 10 to about 100 g/l of PO₄^3- ions,

(d) an accelerator selected from the group consisting of

(i) about 10 to about 100 g/l of nitrate ions and

(ii) about 0.1 to about 2.0 g/l of organic nitro compounds,

(e) up to about 10 g/l of Ni²⁺ ions, and

(f) up to abut 10 g/l of simple, complex, or mixed simple and complex fluoride ions,

said solution having a pH value in the range from about 2.0 to about 3.8, a ratio of free acid to total acid from about 1;

4 to 1;

100, and a ratio by weight of Zn⁺² ions to Ca⁺² ions of about 1;

0.5 to about 1;

1.5;

said process producing on the metal surfaces a phosphate layer containing scholzite in an areal density between about 3 and about 9 g/m².

2. A process according to claim 1, wherein the phosphating solution comprises Ni²⁺ ions in an amount of at least about 0.01 g/l.

3. A process according to claim 2, wherein the phosphating solution comprises simple, complex, or mixed simple and complex fluoride ions in an amount of at least about 0.01 g/l.

4. A process according to claim 3, characterized in that the metal surfaces are phosphated at temperatures between about 50°

C. and about 70°

C.

5. A process according to claim 2, characterized in that the metal surfaces are phosphated at temperatures between about 50°

C. and about 70°

C.

6. A process according to claim 1, characterized in that the metal surfaces are phosphated at temperatures between about 50°

C. and about 70°

C.

7. A process according to claim 6, wherein the metal phosphated is an alloy of iron, zinc, or aluminum.

8. A process according to claim 5, wherein the metal phosphated is an alloy of iron, zinc, or aluminum.

9. A process according to claim 4, wherein the metal phosphated is an alloy of iron, zinc, or aluminum.

10. A process according to claim 3, wherein the metal phosphated is an alloy of iron, zinc or aluminum.

11. A process according to claim 2, wherein the metal phosphated is an alloy of iron, zinc or aluminum.

12. A process according to claim 1, wherein the metal phosphated is an alloy of iron, zinc, or aluminum.

13. A process according to claim 12, additionally comprising cold working the phosphated metal surfaces after reacting these surfaces with an alkali stearate to produce a mixed calcium-zinc stearate on the surfaces.

14. A process according to claim 6, additionally comprising cold working the phosphated metal surfaces after reacting these surfaces with an alkali stearate to produce a mixed calcium-zinc stearate on the surfaces.

15. A process according to claim 3, additionally comprising cold working the phosphated metal surfaces after reacting these surfaces with an alkali stearate to produce a mixed calcium-zinc stearate on the surfaces.

16. A process according to claim 1, additionally comprising cold working the phosphated metal surfaces after reacting these surfaces with an alkali stearate to produce a mixed calcium-zinc stearate on the surfaces.