DE102010026046A1 - Electrolytic surface coating of components, comprises pretreating the components to be coated, performing main treatment to the resulting components under the use of two different zinc-nickel electrolytes, and post-treating - Google Patents

Abstract

Electrolytic surface coating of components, comprises subjecting components to be coated to at least one pretreatment, a main treatment and a post-treatment, where a zinc-nickel alloy is applied as a coating material. The main treatment comprises at least two process steps, which are performed under the use of two different zinc-nickel electrolytes. The first process step uses a ductile zinc-nickel electrolyte (80-90%), and the second process step uses a semi-ductile zinc-nickel electrolyte (10-20%).

Description

The invention relates to a process for the electrolytic surface coating of components, wherein the component to be coated is subjected to at least one pretreatment, a main treatment and an aftertreatment, and wherein a zinc-nickel alloy is applied as the coating material.

For many technical applications, components are provided with a metal coating by electroplating. Such electrolytic surface coatings primarily aim for better corrosion protection. At the same time, the visual appearance of the components can be improved.

In DE 103 10 071 B3 a device is described in which a component to be coated is picked up individually by a gripper, immersed in a galvanic bath and moved to different positions during diving. Such separate treatments with associated gripper are suitable for components that must not be damaged (frame processing).

Out DE 199 32 524 C1 For example, a device for coating components in a container filled with electrolyte solution is known. The components are arranged in a rotating basket, which has a plurality of small openings on the lateral surface. Such treatments using drum-like assemblies are for large quantities of bulk products, such. As screws or nuts, suitable (drum machining).

In EP 0 060 444 A1 a device for galvanic coating is described, which has at least one pretreatment section, a galvanic section and an aftertreatment section. Here, several trough-shaped containers are provided for each processing section, in which the process medium is located. The components to be coated are manually placed on carrier assemblies and kept fixed in position on this irr the various trough-shaped containers, so that a complete flushing with the respective process medium is guaranteed. Such devices with support assemblies for receiving the components to be coated are particularly suitable for large numbers, the products may also have geometrically demanding shapes with hard-to-reach contours. This is true, for example, in numerous stamped parts for automotive production.

The prior art discloses a multiplicity of coating methods for depositing a wide variety of metal layers on surfaces. In this case, the coating material used is largely independent of the treatment variants with drums, carrier assemblies or the like selected, but in particular taking into account the specific materials and subsequent conditions of use of the components to be coated. In this regard, typical coating materials are, for example, zinc, copper, nickel, chromium, tin or combinations of these materials.

One frequently used variant is the use of zinc-nickel electrolyte for surface coating. Such zinc-nickel alloys are advantageous for corrosion protection. The disadvantage is that significant color variations can result, which are problematic at least for applications in which the component to be coated is later visible on the finished product.

The object of the invention is to provide a technical solution with which a homogeneous surface and a constant (deformable) surface quality can be achieved on components which have been galvanically coated with a zinc-nickel alloy.

This object is achieved in that the main treatment of the component to be coated comprises at least two process steps using two different zinc-nickel electrolytes, initially a ductile zinc-nickel electrolyte (80-90%) and subsequently a semi-ductile zinc-nickel electrolyte. Electrolyte (10-20%) can be used. As a result, a component layer of another electrolyte is again applied to the already fully galvanized upper component layer. Advantageous embodiments are the subject of subclaims, whose technical features are explained in more detail in the embodiment.

By applying the method according to the invention, a homogeneous surface and a uniform surface quality can be ensured for the galvanically coated components with a zinc-nickel alloy irrespective of their geometric contour. At constant nickel incorporation rates, highly ductile zinc-nickel surfaces are achieved with a uniform, glossy appearance.

The proposed two-stage treatment with two different electrolytes combines the benefits of a malleable zinc-nickel surface with safe process control, outstanding optics and effective equipment utilization through the high deposition rates of a non-deformable conventional zinc-nickel electrolyte. In this case, by the selection and arrangement of the coating components a variable and largely optimally adapted to the respective concrete components machining can be realized. Thus, in addition to effective plant utilization, customer-specific and article-dependent flexibility is achieved.

Hereinafter, an embodiment of the invention will be described with reference to the drawings.

The proposed method is designed for the electrolytic surface coating of components, wherein the respective component to be coated is subjected to at least one pre-treatment, a main treatment and an aftertreatment and wherein a zinc-nickel alloy is applied as the coating material. Such a procedure is generally known, so that it is possible to dispense with more detailed explanations here.

However, it is essential in the present case that the main treatment of the component to be coated comprises at least two process steps using two different zinc-nickel electrolytes. First, a ductile zinc-nickel electrolyte (80-90%) is used. Thereafter, the component to be coated is rinsed. Subsequently, a semiductile zinc-nickel electrolyte (10-20%) is used.

The entire process sequence is shown schematically in the drawing. Here, the pretreatment "V" of the component to be coated comprises, as process steps, a decoction degreasing, a pickling, an electrolytic degreasing and a pickling. After each of these four process steps, rinsing takes place before the respective next process step is carried out.

Pretreatment "V" follows the main treatment "H" already described above with the use of a ductile zinc-nickel electrolyte (80-90%) and a semi-ductile zinc-nickel electrolyte (10-20%), between these two process steps a rinse is provided.

The main treatment "H" is followed by the post-treatment "N" of the component to be coated, which includes rinsing and passivation as process steps.

As a final process step, the after-treatment "N" is followed by a drying "T" of the component to be coated.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10310071 B3 [0003]
• DE 19932524 C1 [0004]
• EP 0060444 A1 [0005]

Claims (5)

Process for the electrolytic surface coating of components, wherein the component to be coated is subjected to at least one pre-treatment, a main treatment and an aftertreatment and wherein a zinc-nickel alloy is applied as the coating material, characterized in that the main treatment comprises at least two process steps using two different ones Zinc-nickel electrolyte comprises, first a ductile zinc-nickel electrolyte (80-90%) and then a semi-zinc-nickel electrolytic electrolyte (10-20%) are used. A method according to claim 1, characterized in that the component to be coated is rinsed after treatment with the ductile zinc-nickel electrolyte before it is treated with the semiductile zinc-nickel electrolyte. A method according to claim 1, characterized in that the pretreatment of the component to be coated as process steps comprises a Abkochenentfettung, a pickling, an electrolytic degreasing and a pickling, wherein between each of these process steps, a purging is carried out. A method according to claim 1, characterized in that the aftertreatment of the component to be coated as a method steps comprises rinsing and passivation. A method according to claim 1, characterized in that after the post-treatment drying of the component to be coated takes place.

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