SELF-LUBRICATING ELECTROLYTICALLY DEPOSITED PHOSPHATE COATING

Abstract

The present disclosure relates to a self-lubricating, electrolytically deposited phosphate coating on metal workpieces, comprising stabilized solid lubricants incorporated into the phosphate coating and to a method for the production thereof.

Claims

1. An electrolytically deposited phosphating layer comprising at least the elements zinc and phosphorous on a metallic workpiece, wherein the phosphating layer comprises solid lubricant particles stabilized by hydrocolloids, wherein the stabilized solid lubricant particles are at least partially embedded in the phosphating layer.

2. The phosphating layer according to claim 1, wherein the hydrocolloid is a nitrogen-containing hydrocolloid.

3. The phosphating layer according to claim 1, wherein the hydrocolloids are selected from the group consisting of polyamines, polyimines and their quaternary salts, polyvinyl pyrrolidones, polyvinyl pyridines, collagen, gelatin, chitosan hydrolyzate, keratin hydrolyzate, casein hydrolyzate, amidopectines as well as copolymers and/or mixtures thereof.

4. The phosphating layer according to claim 1, wherein the hydrocolloid is gelatin having a molecular weight of greater than or equal to 1,000 Da and less than or equal to 100,000 Da.

5. The phosphating layer according to claim 1, wherein the solid lubricant particles are selected from the group consisting of metal and ammonium salts of saturated fatty acids, MoS.sub.2, h-BN, WS.sub.2, graphite, oxidized and fluorinated graphite, PTFE, Nylon, PE, PP, PVC, PS PET, PUR, clay, talc, TiO.sub.2, mullite, CuS, PbS, Bi.sub.2S.sub.3, CdS or mixtures thereof.

6. The phosphating layer according to claim 1, wherein the solid lubricant particles consist of MoS.sub.2 and have a platelet-shaped geometry.

7. A method for producing a phosphating layer comprising stabilized solid lubricant particles at least comprising the steps of: a) providing a metallic workpiece; b) immersing the metallic workpiece in an aqueous electrolyte solution comprising at least zinc, phosphate ions, solid lubricant particles and hydrocolloids; c) passing an electric current through the metallic workpiece to deposit a phosphating layer on the workpiece; and d) optionally post-treating the electrolytically deposited phosphating layer.

8. The method according to claim 7, wherein the hydrocolloids are selected from the group of nitrogen-containing hydrocolloids.

9. The method according to claim 7, wherein the phosphating layer comprising stabilized solid lubricant particles is deposited on a workpiece which on the surface has a phosphating layer comprising the elements ZnXP, wherein X is selected from the group including Fe, Ni, Ca, Mn.

10. The method according to claim 7, wherein the current-carrying contact time of a surface element of the workpiece with the aqueous electrolyte solution is greater than or equal to 1 second and less than or equal to 100 seconds.

11. The method according to claim 7, wherein the basis weight of the deposited phosphating layer comprising stabilized solid lubricant particles determined according to DIN EN ISO 3892 is greater than or equal to 0.5 g/m.sup.2 and less than or equal to 10 g/m.sup.2.

12. The method according to claim 7, wherein the aqueous electrolyte solution further comprises an anionic, cationic, amphoteric or non-ionic wetting agent in a concentration of greater than or equal to 0.1 and less than or equal to 10 g/l.

13. The method according to claim 7, wherein the metallic workpiece consists of a low alloy steel, iron, aluminum, titanium, copper, nickel, an alloy including iron, aluminum, titanium, copper or nickel or a hot zinc dipped material.

14. The method according to claim 7, wherein the workpiece is a workpiece obtained by draw-peeling.

15. The method according to claim 14, wherein the surface of the workpiece is pretreated mechanically or electrochemically, in particular activated, prior to the coating process.

Description

EXAMPLES

Example 1

[0038] A phosphated cold heading wire is produced, wherein a steel wire having a diameter of 10 mm is pulled for about 10 seconds through a phosphating solution of the following composition:

TABLE-US-00002 Zinc: 40 g/l Phosphate: 40 g/l Acid ratio free acid:total acid: 7.5 pH value: 1.2 Gelatin 0.2 g/l (hydrocolloid) Wetting agent (BASF 0.2 g/l Crafol AP 261) Molybdenum disulfide 6.0 g/l particles (5 m)

[0039] The temperature of the bath is about 55 C. and the strength of the direct current is approximately 12 A/dm.sup.2. A phosphating layer having an average thickness of 4-8 g/m.sup.2 is deposited which comprises embedded molybdenum sulfide particles. The phosphated cold heading wire is rinsed with water and subsequently drawn at a rate of 0.06 m/s in one step to a diameter of 7 mm. The drawing process is carried out without the addition of another lubricant. The wire can be drawn at a constant final diameter without any problems and no tearing of the wire or other loss of quality occurs.

Example 2

[0040] A phosphated cold heading wire is produced, wherein a cold heading wire having a diameter of 10 mm is pulled for approximately 2 seconds through a phosphating solution of the following composition:

TABLE-US-00003 Zinc: 45 g/l Phosphate: 40 g/l Acid ratio of free 6.5 acid:total acid: PH value: 1.2 Polyethyleneimine G 0.1 g/l 35 BASF (hydrocolloid) Wetting agent (BASF 0.5 g/l Lutensol ON 110) Boron nitride particles 5.5 g/l 1 m (Hebofill 410)

[0041] The other bath parameters correspond to those of Example 1. A phosphating layer with an average thickness of 6 g/m.sup.2 is deposited, which comprises embedded boron nitride particles. The phosphated cold heading wire is rinsed with water and subsequently drawn in one step to a diameter of 7 mm. The drawing process is carried out without the addition of a further lubricant. The wire can be drawn at a constant final diameter without any problems and no tearing of the wire or other loss of quality occurs.

[0042] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.