EP1979506A1

EP1979506A1 - Chromium(vi)-free composition for protection of a galvanized metal surface against corrosion, process for producing it and pulley

Info

Publication number: EP1979506A1
Application number: EP06830602A
Authority: EP
Inventors: Bertram Haag; Sergej Vogelsang
Original assignee: Schaeffler KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2006-01-16
Filing date: 2006-12-13
Publication date: 2008-10-15
Also published as: KR20080093990A; WO2007082613A1; CN101360847A; DE102006002224A1; US20100160102A1; JP2009523909A

Abstract

The present invention relates to an arrangement for protecting a substrate against corrosion, comprising a substrate, in particular a metallic substrate, and an electrically conductive corrosion protection layer applied to the substrate to protect the substrate against corrosion, which layer has a zinc-containing layer which has been applied to the substrate and has a passivation layer which has been applied to the zinc-containing layer for passivating the zinc-containing layer and contains many particles of hard material which have such a nature that the particles of hard material increase the coefficient of friction on a free surface of the passivation layer compared to a conversion layer without particles of hard material but leave the electrical conductivity of the passivation layer essentially unchanged. The invention further relates to a process for producing such an arrangement and a pulley.

Description

Arrangement for protecting a substrate against corrosion, method for its production and pulley

The present invention relates to an arrangement for protecting a substrate from corrosion, a method for producing such an arrangement and a pulley.

Steel or alloy steel components are typically subject to corrosion especially in an elevated temperature environment, such as in the engine compartment. To protect against corrosion, such components made of steel or steel alloy are therefore usually coated with a corrosion protection layer of zinc or a zinc alloy. Since this zinc-containing layer can also corrode, a so-called passivation layer or conversion layer is applied for further passivation on the surface of this zinc layer or zinc alloy. This usually consists of a chromate coating, which may contain, for example, chromium (III) or chromium (VI). However, it is also possible to use corrosion protection layers based on, for example, Zr or Ti.

To further protect the passivation layer, it may be coated with a so-called topcoat, a polymer compound, for example polyacrylate or polyethylene, or an organic or inorganic paint.

In the following, the invention and the problem underlying the invention with reference to a generator freewheel pulley will be explained, but without limiting the invention thereto. When operating a generator via a generator freewheel pulley, a belt of polymeric material passes over the generator freewheel pulley and drives it. During this process, the frictional contact between the belt and the pulley can lead to electrostatic charging. This charge can damage any electrical or electronic parts in the vicinity of a more or less spontaneous, uncontrolled discharge. There is therefore a need to remove this electrostatic charge in a controlled manner. However, removal of the electrostatic charge is only possible via electrically conductive regions of the generator freewheeling pulley, so that the generator freewheeling pulley is electrically conductive as far as possible in the region of the surface in frictional contact with the belt.

When operating a generator freewheeling pulley, it is also important that there is a relatively high friction between the generator freewheeling pulley and the corresponding belt. This makes it possible to reduce the slip between the pulley and the belt and thus to achieve a better entrainment behavior of the belt with constant belt tension or a same entrainment behavior with reduced belt tension. A reduced belt tension with the same driving behavior results in a longer life of the belt. Overall, this leads to a lower cost in the provision and operation of the generator freewheel pulley.

However, it is problematic that the coatings usually applied to improve the corrosion protection or the frictional resistance, such as topcoat or paint coating, are electrically nonconductive and thus can not dissipate electrical charges. The use of all-plastic components as an alternative does not allow discharge of the charges.

There is therefore a need for a surface coating for a generator freewheel pulley, which is both electrically conductive and at the same time also has a good frictional resistance at the surface.

It is the object of the present invention to provide a coating which is electrically conductive and has an increased frictional resistance.

According to the invention, this object is achieved by a coating having the features of claim 1, by a pulley having the features of claim 10 and / or by a method for producing such a coating having the features of claim 12. According to a first aspect (claim 1), the present invention relates to an arrangement for protecting a substrate against corrosion, comprising a substrate, in particular a metallic substrate, with an applied on the substrate, electrically conductive corrosion protection layer for protecting the substrate from corrosion, the one on the substrate having deposited zinc containing layer having a passivation layer provided on the zinc containing layer for passivating the zinc containing layer having a plurality of hard material particles arranged such that by the hard material particles frictional resistance on a free surface of the passivation layer in the Compared to a passivation layer is increased without hard particles, but the electrical conductivity of the passivation layer is substantially retained.

Hereinafter, a zinc-containing layer or a zinc-containing material is understood to mean a layer or a material of zinc or a zinc alloy. Also, when referring to a zinc layer, a layer of a zinc alloy should be included. The terms passivation layer and conversion layer are used in the same application in this application.

The idea underlying the present invention is to increase the frictional resistance of the passivation layer to polymer materials such as V-belts or rubber rollers by the use of hard material particles in a passivation layer. At the same time, the wear of both the passivation layer and the contacting polymer materials can be reduced. In addition, the electrical conductivity of the surface, in particular of the passivation layer, can be maintained in order to be able to dissipate electrostatic charging occurring in the friction between the passivation layer and the polymer material. The use of hard material particles in the passivation layer accordingly does not affect the electrical properties of the surface or at least negligibly, but improves the stability and in particular the frictional resistance to other materials.

According to a second aspect (claim 10), the present invention relates to a pulley having a metallic body having a hub for snugly receiving a shaft with an outer surface its circumference for receiving a belt made of a polymer material, with an arrangement according to the first aspect of the invention, wherein the substrate of the arrangement is at least in the region of the outer surface of the metallic body.

The application of the passivation layer containing hard material particles makes it possible to provide a pulley which exhibits less or no electrostatic charge. The pulley shows due to the increased frictional resistance better entrainment behavior. As a result, the power transmission is increased at the same belt tension or a lower belt tension can be selected in order to achieve the same force transmission as in a passivation layer without hard material particles.

According to a further aspect (claim 12), the present invention relates to a method for producing a passivation layer, in particular for an arrangement according to the first aspect of the present invention, comprising the steps:

(a) providing a passivation bath comprising hard material particles;

(b) providing a substrate on the surface of which a zinc-containing layer is applied;

(c) immersing the substrate in the passivation bath, thereby forming on the surface of the layer a passivation layer comprising a plurality of hard material particles, the passivation layer thus formed being such that the friction resistance at a free surface of the particles is determined by the hard material particles Passivation layer is increased compared to a passivation layer without hard particles, but the electrical conductivity of the conversion layer is substantially retained.

The hard material particles integrated in the conversion layer are incorporated into the conversion layer during the production thereof. Due to the size of the hard material particles, these easily remain suspended in the passivation bath and are integrated into this conversion layer when the conversion layer fails. By means of the method according to the invention, a preferably homogeneous incorporation of the hard material particles into the conversion layer takes place.

Advantageous embodiments, developments and improvements of the invention Dungsgedankens will be apparent from the other dependent claims and from the description with reference to the drawings.

According to a preferred development, the hard material particles are formed as nanoparticles. According to a further preferred development, the size of the nanoparticles is in the range of 1 to 1000 nm, preferably in the range of 2 to 100 nm, more preferably in the range of 8 to 50 nm and in particular in the range of 10 to 20 nm. By the size of the nanoparticles These can be easily introduced into the Passivierungsbad and form a suspension. The size of the particles is preferably less than the thickness of the passivation layer that is to be produced. Thus, a good particle distribution is achieved in the passivation layer. The size of the particles is chosen so that they protrude slightly from the passivation layer. As a result, the surface of the passivation layer is changed in such a way that a better adhesion behavior is produced.

According to a further preferred development, the hard material particles consist of an inorganic hard material. According to yet another preferred development, the hard material particles have a Mohs hardness of at least 5. Preferred materials for the hard material particles are inorganic carbides, oxides, diamonds and / or nitrides, in particular SiO ₂ , SiC, WC, Al ₂ O ₃ and / or BN , or mixtures thereof. However, there are many more materials with the same or similar hardness and these properties conceivable.

According to yet another preferred development, the passivation layer has a thickness of at most 800 nm, preferably in the range of 50 to 500 nm and in particular of 100 to 200 nm. The zinc-containing layer may have a thickness of more than 0.5 μm, preferably more than 100 μm be.

According to a preferred embodiment, the passivation layer is formed as a chromium-containing passivation layer, which therefore contains chromium.

According to a preferred development of the second aspect of the present invention, the pulley is designed as a V-ribbed disk or as a flat disk.

According to another preferred development, the substrate is made of steel or a steel alloy.

According to a preferred development of the third aspect of the present invention, hard material particles are introduced into a passivation solution in order to produce the passivation bath.

According to another preferred development, after the passivation layer has been produced in the passivation bath, the passivation layer is rinsed in a further step (d). The rinsing may take place before or after a drying step according to another preferred development of the present invention. It is also possible to rinse them both before and after a drying step of the passivation layer.

According to a preferred embodiment, the passivation bath contains a chromium-containing passivation solution.

According to another preferred development, the chromating bath is essentially chromium (VI) -free. By using chromium (III) in the passivation bath, it is possible to produce a conversion layer which is essentially chromium (VI) -free. Other possibilities are, for example, by using passivations based on Zr or Ti.

The invention will be explained in more detail below with reference to embodiments with reference to the accompanying figures of the drawings. From the figures show:

1 shows a first general embodiment of an inventive arrangement for protecting a substrate from corrosion.

2 shows in the partial figures a) to d) a method for producing a corrosion protection layer according to the invention;

3 is a perspective view of a generator freewheel pulley.

Fig. 4 is a cross-sectional view of the generator freewheel pulley

Fig. 3 with a corrosion protection layer according to the invention. In the figures of the drawing are identical and functionally identical elements and features - unless otherwise stated - denoted by the same reference numerals.

Fig. 1 shows a first general embodiment of an inventive arrangement for corrosion protection of a substrate. The arrangement is designated by reference numeral 14 here. The assembly 14 includes a substrate 10 having a corrosion protection layer 16 applied thereon. The substrate 10 may be steel or a steel alloy.

On the substrate 10, a zinc-containing layer 1 1 is applied as part of the corrosion protection layer 16. The zinc-containing layer 11 can be deposited galvanically or by hot dip galvanizing, for example. The thickness of the layer 1 1 can be chosen more or less freely. By way of example, the layer thickness of the layer 11 is more than 0.5 μm and preferably a few μm.

On the layer 1 1, a passivation layer 12 is also applied as part of the corrosion protection layer 16. The passivation layer 12 may contain Zr, Ti, chromium (III) or else chromium (VI). According to the invention, the passivation layer 12 contains nanoparticles 13, which may be formed, for example, as SiO ₂ nanoparticles. In further exemplary embodiments, the nanoparticles 13 can consist, for example, of Al ₂ O ₃ or SiC. Some of the nanoparticles 13 pass slightly out of this surface 15 on a surface 15 of the chromating layer 12 and thus of the anticorrosion layer 16, whereby a somewhat roughened surface 15 is formed. As a result, the surface 15 of the corrosion protection layer 16 is changed in such a way that increased friction and, consequently, an improved entrainment effect compared to a polymer material of a belt are achieved.

FIG. 2 shows a method for producing a passivation layer 16 according to the invention.

First, a substrate 10 is provided (FIG. 2a).

- On this substrate 10, a zinc-containing layer 1 1 is applied (Fig. 2b). The assembly thus prepared is immersed in a passivation bath 17. The Passivierungsbad 17 can be heated, for example, to 30 ° C. The passivation bath 17 contains nanoparticles 13. These are incorporated in the conversion layer 12 during the deposition of the conversion layer 12 on the zinc-containing layer 11 in the passivation bath 17 (FIG. 2c).

- Subsequently, the assembly 14 thus prepared is removed from the Passivierungsbad 17, rinsed and dried (Fig. 2d).

A concrete example for generating the conversion layer 12 is shown below.

150 ml / l of the passivating solution Lanthane TR 175 part A and 90 ml / l of the nanoparticle-containing solution Lanthane TR 175 part B of the commercial product from Coventya GmbH & Co. KG in deionized water are prepared in a 5 liter beaker. The pH of the solution was adjusted to pH = 2.0 with HNO ₃ . The temperature of the solution was 30 ⁹ C. In this solution, a freewheeling pulley electroplated with a ZnFe alloy is immersed while stirring the solution for 75 seconds. After several dips in demineralized water, the component is dried at 70 ° C. In this case, a corrosion protection layer 16 provided with nanoparticles is produced.

FIG. 3 shows a perspective view of a generator freewheeling pulley 21, to the disk body 22 of which V-ribs 23 are attached. The V-ribs 23 are designed such that a V-ribbed belt can be deflected over the outer circumference of the generator freewheeling pulley 21. The surface of the V-ribs 23 of the outer periphery of the generator freewheel pulley is provided with a corrosion protection layer 16 according to the present invention.

4 shows the generator freewheeling pulley from FIG. 3 in a cross-sectional view. The mounted on the disk body 22 V-ribs 23 are provided with a corrosion protection layer 16.

Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto but modifiable in a variety of ways. In the foregoing embodiment, the invention has been illustrated with reference to a generator freewheel pulley. However, the present invention should not be so limited but is in many ways modifiable and, of course, may be applied to other systems and applications.

It goes without saying that the quantities, quantities, temperatures, pH values, etc. given can also be varied without deviating from the essence of the invention. It also goes without saying that any passivation baths known in the art can be used. For example, cobalt can be added to the electrolyte solution. Furthermore, it is possible, for example, to add surfactants or protective colloids to the passivation bath without influencing the invention.

LIST OF REFERENCE NUMBERS

10 Substrate 11 Zinc-containing layer

12 passivation layer, corrosion layer

13 nanoparticles

14 Arrangement for protecting a substrate from corrosion

15 Surface of the assembly 14 16 Anti-corrosion layer

17 passivation bath

21 Generator freewheel pulley

22 disk body

23 V-rib

Claims

claims

An assembly (14) for protecting a substrate (10) against corrosion, comprising a substrate (10), in particular a metallic substrate, with an electrically conductive corrosion protection layer (16) applied to the substrate (10) to protect the substrate from corrosion ink jet film comprising a zinc-containing layer (11) applied to the substrate (10), comprising a passivation layer (12) applied to the zinc-containing layer for passivating the zinc-containing layer (11) containing a plurality of hard material particles (13) which are such that by the hard material particles (13) the frictional resistance at a free surface (15) of the passivation layer (12) is increased compared to a conversion layer (12) without hard material particles (13), but the electrical Conductivity of the passivation layer (12) is substantially retained.

2. Arrangement according to claim 1, characterized in that the hard material particles (13) are formed as nanoparticles.

3. Arrangement according to claim 2, characterized in that the nanoparticles have a size of 1-1000 nm, preferably 2-100 nm, more preferably 8-50 nm and in particular 10-20 nm.

4. Arrangement according to one or more of the preceding claims, characterized in that the hard material particles (13) consist of inorganic hard material.

5. Arrangement according to one or more of the preceding claims, characterized in that the hard material particles (13) have a Mohs hardness of at least 5.

6. Arrangement according to one or more of the preceding claims, characterized in that the hard material particles (13) as inorganic Carbide, oxides and / or nitrides are formed, in particular as SiO ₂ , SiC, WC, Al ₂ O _3, diamond and / or BN, or mixtures thereof.

7. Arrangement according to one or more of the preceding claims, characterized in that the passivation layer (12) has a thickness of at most 800 nm, preferably from 50-500 nm and in particular from 100 to 200 nm.

8. Arrangement according to one or more of the preceding claims, characterized in that the passivation layer (12) is formed as a chromium-containing passivation layer (12).

9. Arrangement according to one or more of the preceding claims, characterized in that the substrate (10) comprises steel or a steel alloy tion.

10. Pulley (21)

a metallic body (22) having a hub for accurately receiving a shaft, an outer surface at its periphery for receiving a belt of polymer material,

- With an assembly (16) according to one or more of the preceding claims, wherein the substrate of the assembly (16) at least in the region of the outer surface of the pulley is part of the metallic body (22).

11. Pulley according to claim 10, characterized in that the pulley is designed as a V-ribbed disk or as a flat disk.

12. A method for producing a passivation layer (12), in particular for an arrangement (16) according to one or more of claims 1 to 9, comprising the steps:

(a) providing a passivation bath (17) comprising hard material particles (13); (b) providing a substrate (10) on the surface of which a zinc-containing layer (11) is applied;

(c) immersing the substrate (10) in the passivation bath (17), thereby forming on the surface of the zinc-containing layer (1 1) a passivation layer (12) having a plurality of hard material particles (13) passivation layer (12) formed in such a way that is increased by the hard material particles (13) of the frictional resistance on a free surface (15) of the passivation layer (12) compared to a passivation layer (12) without hard material particles (13), but the electric Conductivity of the passivation layer (12) is substantially retained.

13. The method according to claim 12, characterized in that prior to step (a) a passivation solution is provided, in which for the generation of the passivation bath (17) hard material particles (13) are introduced.

14. The method according to claim 12 or 13, characterized in that the passivation layer produced in step (c) is subsequently rinsed in a further step (d).

15. The method according to any one of claims 12 to 14, characterized in that the passivation layer (12) after step (c) and / or after step (d) is dried.

16. The method according to any one of claims 12 to 15, characterized in that the passivation bath (17) contains a chromium-containing passivation solution.

17. The method according to any one of claims 12 to 15, characterized in that the passivation bath (17) is formed substantially chromium (VI) -free.