WO2008025498A1

WO2008025498A1 - Method for coating components with a lacquer

Info

Publication number: WO2008025498A1
Application number: PCT/EP2007/007476
Authority: WO
Inventors: Rainer Holder; Jochen Holder
Original assignee: Rainer Holder; Jochen Holder
Priority date: 2006-08-31
Filing date: 2007-08-25
Publication date: 2008-03-06
Also published as: EP2056972A1; DE102006042632A1; EP2056972B1

Abstract

The invention relates to a method for lacquering components, especially for lacquering metallic components (52) using a lacquer containing zinc. According to said method, the components (52) are pre-treated, then placed on a holding system (54), plunged into a coating bath (50), rotated about a rotational axis (56) in alternating rotary directions inside the coating bath (50), and removed from the coating bath (50). The components (52) are then centrifuged by rotation in alternating rotary directions and the lacquer is baked onto the components.

Description

Process for coating components with a paint

The invention relates to a method for coating components with a lacquer, in particular for the coating of metallic components with a zinc-containing lacquer.

Complexly shaped components made of metal, which are widely used in the automotive industry, but also in other industries, often have to be reliably and permanently protected against corrosion. For example, components that are cast structures, weldments or otherwise manufactured components, which in particular have a cavity, such as Achsträger assemblies, must be provided with a permanent corrosion protection. It is important that not only the outer surface but also the inner surface of the It is uniformly coated to prevent blistering and to avoid undesirable buildup of paint on functional surfaces such as fittings and the like. In addition, the weight of the coating should on the one hand be kept as low as possible, on the other hand, the coating used must provide the necessary long-term protection even under the most adverse environmental conditions, such as salt, moisture, heat, cold and the like.

Previously, axle subassemblies are provided with hot-dip galvanizing, galvanic coatings, cathodic dip-paint coatings (ie with a so-called cathodic dip-coating) and / or various varnishes. A method for electrocoating a car body is known e.g. known from DE 196 43 082 C2.

With the known coating methods, however, only a relatively uneven application and in particular insufficient corrosion protection can be achieved with hollow parts in the interior. Also, paint accumulation can not be avoided, so that the requirements for a particularly high-quality corrosion protection with the known methods are not met.

For coating connecting parts, such as screws, it is in principle also known in the prior art to carry out a treatment with zinc flake lacquer by dip-spin coating.

However, only parts by mass in the form of bulk material are treated here. However, a treatment of larger components to be coated inside and outside with such a method is not known.

From DE 10 2004 062 753 Al a method for bulk material-Sprühlackie- tion damage-sensitive small parts is also known, the parts to be coated are mixed as bulk material in a mixture together with rounded packing in a device for spray painting in motion, the During this process, workpieces are sprayed with varnish and then separated again from the random packings.

Against this background, the invention has for its object to provide a method for coating components with a paint, with which a high-quality coating with a long-term protective effect in complex shaped components is made possible, which are designed as hollow parts, and wherein a uniform coating as possible the inner surfaces and the outer surfaces possible without Lackanhäufungen is possible.

This object is achieved by a method for coating components with a lacquer, in particular for lacquering metallic components with a zinc-containing lacquer, with the following steps:

(a) pretreating the component;

(b) picking up the component on a holder;

(c) immersing the component in a coating bath;

(d) rotating the component in an alternating direction of rotation about an axis of rotation;

(e) extending the component from the coating bath;

(f) centrifuging the component by rotating it with alternating direction of rotation and

(g) baking the paint.

According to the invention, a particularly uniform layer thickness is ensured by working in a dip-spinning process with a changing direction of rotation both during dipping and when the component is being spun off.

In this way, blistering and Lackanhäufungen can be avoided. Likewise, a uniform coating of both the inner surfaces and the outer surfaces can be achieved. Components that have functional surfaces, such as threads or the like, can be reliably protected in this way against corrosion, without the functioning of the functional surfaces, such as Possibility of receiving a screw in a thread of the component is impaired.

In particular, when using a zinc-containing paint, such as a zinc flake paint, can be achieved in this way, a particularly high-quality corrosion protection in a uniform coating thickness both inside and outside hollow parts.

In a preferred embodiment of the invention, the component in step (d) at its greatest distance (x) from the axis of rotation at a peripheral speed of at least 10 m / min, preferably of at least 20 m / min, more preferably of at least 30 m / min, more preferably rotated at least 50 m / min.

According to a further embodiment of the invention, the component is particularly preferred in step (f) at its greatest distance on the axis of rotation at a peripheral speed of at least 50 m / min, preferably at least 100 m / min, more preferably at least 200 m / min rotated by at least 300 m / min.

These measures can be a particularly uniform coating achieve, which is particularly high quality.

According to a further embodiment of the invention, the component is at least in step (d) or (f) rotated several times alternately in different directions of rotation.

This measure also supports a particularly uniform coating.

In addition, in step (d), the component can be pivoted back and forth about an axis of rotation that is angled at an angle, preferably at right angles. By this measure, a particularly uniform coating is guaranteed even in geometrically very unfavorable conditions in interiors of hollow parts.

As already mentioned, the method according to the invention is particularly advantageous for coating components which are designed as hollow parts which communicate with their outer surfaces via a plurality of openings, and wherein the coating takes place both on the outer surface and on the inner surface of the components ,

Furthermore, the method according to the invention is particularly suitable for coating components which have a length of at least 500 mm in the direction of their greatest longitudinal extent.

Since the respective components are individually received on a holder or possibly several parts are fastened simultaneously to a holder, according to the invention, very large components can be uniformly coated on the inner and outer surfaces.

In a preferred development of the invention, a zinc flake lacquer is used for this purpose.

With a zinc flake varnish, which contains in particular zinc flakes, aluminum flakes, binders, solvents and other inorganic paint components, a particularly high-quality long-term corrosion protection can be guaranteed. By the application method according to the invention in this case the necessary edge parameters, such as uniform coating, no Lackanhäufungen, freedom from bubbles, etc., complied with. In a further embodiment of the invention, a basecoat film is first applied according to steps (a) to (g), and then at least one further film, in particular a topcoat, is applied.

This is preferably done by immersing the component in a coating bath, rotating the component with alternating direction of rotation about an axis of rotation, extending the component out of the coating bath, spinning off the component by turning with alternating direction of rotation and baking the paint.

By applying several layers in a dip-spin process with changing direction of rotation even higher demands on the durability of the coating can be realized in this way.

To move the component, a robot or a handling device is used in an advantageous embodiment of the invention.

In this way, a coating can take place in a fully automatic process. Alternatively, the movement of the component can also be achieved during the dip-spin method by a stationary device for rotating or possibly tilting drive of the component and by raising or lowering the immersion bath. It is understood that, conversely, of course, the rotary drive or tilting drive can be raised or lowered and the immersion bath can be formed stationary.

In a further preferred embodiment of the invention, the step (a) of the pretreatment comprises a degreasing in an immersion bath.

Preferably, the degreasing comprises first a hot degreasing and then a degreasing with ultrasound support in a dipping bath.

In this case, preference is given to alkaline degreasing in an immersion bath or only slightly acidic degreasing. By these measures, the effect of the subsequent treatment steps is supported and by dispensing with acid degreasing or by at best slightly acidic degreasing disadvantages in terms of corrosion protection can be avoided.

After degreasing is preferably carried out first a rinse and then a pickling followed by a rinse.

In this case, the pickling is preferably carried out with ultrasound support in a dipping bath.

According to a further embodiment of the invention, the pickling and rinsing is followed by an activation followed by a phosphating, preferably a zinc phosphating.

Preferably, the phosphating is first followed by rinsing, drying and cooling before starting the dip coating in step (c).

These additional treatment steps further improve the corrosion protection is achieved with only very thin layers.

It is understood that the features mentioned above and the features to be mentioned below can be used not only in the respectively specified combination, but also in other combinations or in isolation, without departing from the scope of the invention.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. Show it: Fig. 1 is a schematic representation of a system for carrying out the method according to the invention and

2 is a schematic representation of the diving station according to FIG. 1.

An apparatus for carrying out the method according to the invention is shown in FIG. 1 and designated overall by the numeral 10.

The apparatus of FIGS. 1 and 2 is used for painting of complex shaped components, which are designed as hollow parts, with a zinc-containing paint, in particular with a zinc flake paint.

The method according to the invention will be described in more detail below with reference to an example for coating components in the form of axle carrier components.

It is understood that the description of this coating method is merely exemplary in nature and that corresponding adaptations may be made within the scope of the appended claims to meet the process of other component geometries, other component materials, or other quality requirements of the particular coating.

In the present case, the component is a support for a front axle of a car, which has a number of functional surfaces for connection of attachments, such as strut mountings, stub axles and the like. More. This is a tubular construction in the basic shape of a rectangle with corresponding surfaces and functional surfaces, the construction is hollow and has a number of openings. The extension in the direction of the maximum longitudinal extent is about 85 cm, the extension in the direction of the maximum transverse extent about 60 cm and the height about 13 cm. It is a welded tubular steel construction. Such a component is coated internally and externally by the method according to the invention. With the method according to the invention, it is possible to avoid air bubbles and lacquer accumulations in the interior and to achieve a uniform coating thickness with a low total weight of the coating. Also Lackanhäufungen be avoided at Verschraubungsflächen.

The components are coated with a base coat of a zinc flake varnish from Magni type B95 and a topcoat from the company Magni type P35.

The entire coating system is preferably fully automated.

According to FIG. 1, an automatic removal of the components from charge carriers, in which they are delivered, first takes place at a loading station 12. The components can be automatically clamped to a suitable holder and pass through the coating system 10. Optionally, before or after passing through one or more stations, a repositioning or suspension on another holder done.

From the loading station 12, the components first pass into a hot degreasing station 14 for carrying out an alkaline degreasing. After the hot degreasing station 14, the components undergo ultrasonic assisted alkaline degreasing in the station 16.

This is followed by a rinsing in a multiple rinsing cascade with city water, in the station 18. This is followed by an ultrasound-assisted pickling in a pickling station 20. Bath temperature and component movement take place as before in the stations 14 and 16 according to the recommendations of the manufacturer of the chemicals for degreasing or stain.

After pickling, flushing with city water occurs in a triple flush cascade at station 22. This is followed by phosphating in the form of a zinc phosphating, for which purpose an activation in an activation station 24 first takes place.

In the subsequent phosphating station 26, a zinc phosphating is carried out in a zinc phosphate bath with an average layer weight of the phosphating of 5 g / m ² .

This is followed again by a rinsing station 28 with a triple flush cascade, in which first a flush with city water and then a rinse with demineralized water (deionized water) takes place from a subsequent rinsing station.

Subsequently, a drying and dehumidifying at about 6O ⁰ C in a drying station 30. The components then pass in the completely dried state in a dipping station 32 in FIG. 2.

In the dipping station 32, components 52 which are received on a holder 54 are coated with a zinc flake varnish in a special dip-and-spin method.

For movement of the components 52, a robot 58 may be used. Alternatively, a fixed suspended device for rotation and possibly tilting drive of the components 52 may be provided and the treatment bath 50 may be formed vertically movable, as indicated by the double arrow 68. It is understood that the treatment bath 50 can also be designed to be stationary and a corresponding movable drive for rotating or pivoting the components 52 can be provided instead of a robot.

In the embodiment according to FIG. 2, the robot 58 has a robot arm 62, on which a rotary drive 60 is provided, by means of which a holder 54 clamped to a receptacle 64 can be driven about an axis of rotation 56 with alternating direction of rotation, as by the double arrow 68 is indicated. In addition, can the rotary drive 60 is pivoted back and forth about a pivot axis 61, which is perpendicular to the axis of rotation 56, as indicated by the double arrow 63. In this way, the clamped on the holder 54 components 52 can be rotated about the axis of rotation 56 with changing direction of rotation and thereby, if desired, in addition to about a horizontal pivot axis 61 back and forth swung.

In this case, the components 52 are preferably, as far as symmetrical components are concerned, clamped to the holder 54 approximately in the middle of their longitudinal extent.

The components 52 are first rotated with a first direction of rotation at about 25 revolutions / minute or a peripheral speed of about 65 m / min within the dip bath 50 about the axis of rotation 56 and after a short time, for example after three revolutions with the reverse direction and the same peripheral speed driven , It can e.g. be raised to speed within 8 seconds, then left rotated for up to 60 seconds. Then slow down again and turn right again with 8 to 60 seconds.

The specified peripheral speed refers here to the maximum distance of the outermost component extension from the axis of rotation 56, which is designated in Fig. 2 by x. It is understood that the respective components 52 in the region of their outermost longitudinal extent in the relevant outer walls 70 corresponding outlet openings 74, so that the coating bath can enter the cavity 72 of the component 52 and can flow out of this again.

After the movement, which is alternately once clockwise and anti-clockwise, for example at 25 rpm, the component is moved up out of the coating bath 50 either by the robot 58, as indicated by the arrow 66, or alternatively the coating bath 50 lowered down (arrow 68). Subsequently, a spin-off takes place above the dip bath 50 again by a first rotary movement clockwise (or vice versa) followed by reverse rotation. For this purpose, a significantly higher rotational frequency is used, which is for example at about 150 U / min. This corresponds to a circumferential speed at the greatest distance x from the axis of rotation 56 of about 400 m / min.

The spin-off occurs e.g. counterclockwise for 8 to 120 seconds and then clockwise for 8 to 120 seconds.

This is followed by predrying in a predrying station 34 at about 100 ^° C. for 10 minutes, followed by firing according to the manufacturer's instructions, for example for 20 minutes at 250 ^° C., in a stoving station 36.

Subsequently, the components 52 are cooled in a cooling station 38 to about 30 to 40 ⁰ C and now coated in a subsequent dipping station 50 in the same manner as before in the dipping station 32 with a topcoat of the type P35 Magni. Again, an alternating clockwise and counterclockwise rotation with the parameters given above takes place. Both in the base coat coating and the top coat at a temperature control of the plating bath 50 is carried out according to the manufacturer, for example at 27 ⁰ C.

Subsequently, in a subsequent predrying station 42, first a pre-drying and then, in a stoving station 44, a stoving according to the manufacturer's instructions, eg 20 min at 200 ^° C.

Thereafter, the components are passed through a cooling station 46 and cooled to 30 to 40 ⁰ C and finally discharged via an unloading station 48 again in suitable carrier.

Claims

claims

Claims 1. A method for coating components (52) with a lacquer, in particular for lacquering metallic components (52) with a zinc-containing lacquer, comprising the following steps:

(a) pretreating the component (52);

(b) receiving the component (52) on a support (54);

(c) immersing the component (52) in a coating bath (50);

(d) rotating said member (52) in a rotating direction about an axis of rotation (56);

(e) extending the component (52) from the coating bath (50);

(F) centrifuging the component (52) by rotating with alternating direction of rotation and

(g) baking the coating.

2. The method of claim 1, wherein the component (52) in step (d) at its greatest distance (x) from the axis of rotation (56) with a peripheral speed of at least 10 m / min, preferably of at least 20 m / min, more preferably at least 30 m / min, more preferably at least 50 m / min is rotated.

3. The method of claim 1 or 2, wherein the component (52) in step (f) at its greatest distance (x) from the axis of rotation (56) with a peripheral speed of at least 50 m / min, preferably of at least 100 m / min, more preferably at least 200 m / min, more preferably at least 300 m / min is rotated.

4. The method according to any one of the preceding claims, wherein the component (52) at least in step (d) or (f) is rotated several times alternately in different directions of rotation.

5. The method according to any one of the preceding claims, wherein the component (52) in step (d) in addition to an axis of rotation (56) angularly, preferably at right angles, extending pivot axis (61) is pivoted back and forth.

A method according to any one of the preceding claims for coating components (52) formed as hollow members communicating with their outer surfaces via a plurality of apertures (74), and wherein the coating is on both the outer surface and the inner surface the components (52) takes place.

7. The method according to any one of the preceding claims for the coating of components (52) having a length of at least 500 mm in the direction of its greatest longitudinal extent.

8. The method according to any one of the preceding claims, wherein a zinc flake varnish is used for coating.

9. The method according to any one of the preceding claims, wherein initially according to the steps (a) to (g), a base layer (basecoat) is applied and then at least one further layer, in particular a topcoat (topcoat) is applied.

10. The method of claim 9, wherein the order of a further layer according to steps (c) to (g) is carried out.

11. The method according to any one of the preceding claims, wherein the movement of the component (52) is a robot (58) or a handling device is used.

12. The method according to any one of the preceding claims, wherein the step (a) of the pretreatment comprises a degreasing in a dip bath (14, 16).

13. The method of claim 12, wherein the degreasing comprises a hot degreasing and then a degreasing with ultrasonic assistance in a dip bath (14, 16).

14. The method of claim 12 or 13, wherein step (a) comprises an alkaline degreasing in a dip bath (14, 16).

15. The method of claim 12, 13 or 14, wherein after the degreasing, a rinse and then a pickling followed by a rinse is performed.

16. The method of claim 15, wherein the dressing takes place with ultrasound support in an immersion bath (20).

17. The method according to claim 15 or 16, wherein after the pickling and rinsing an activation followed by a phosphating, preferably a Zinkphosphatierung performed.

18. The method of claim 17, wherein after the phosphating, first a rinsing, drying and cooling is carried out before starting with step (c).