EP3064617A1 - Device and method for nickel plating large-area components - Google Patents

Abstract

The invention relates to a device for the electrolytic nickel plating of a large-area component, comprising an electrolysis tank or attachment or conversion elements for forming an electrolysis tank and spaced apart anodes and / or anode groups, wherein planar shielding elements between individual anodes and / or anode groups are arranged, wherein the shielding are arranged such that they form at least partially electrically shielded volume areas for segmental coating of the large-area component.

Description

The invention relates to a device for the electrolytic nickel plating of large-area components and to a method for the electrolytic nickel plating of large-area components.

A problem with the nickel plating of large-area components results from the practical handling. To be nickel-plated components in conventional nickel plating process about 25 different baths, resulting in an immense space requirement. The bathrooms must be comparatively large. Due to the fact that the nickel plating is absolutely free of pores and moreover a drying of the surface to be nickel-plated during the process must be avoided at all costs (water-free), a variety of device and process-related difficulties arise. In particular, the nickel plating of materials problematic in this respect or the inner coating of large-volume containers are associated with particularly great difficulties. Thus, due to the large depth of such containers associated with correspondingly large volumes and the usually different diameters at different depths, a uniform coating is associated with comparatively great problems. Thus, in particular a movement or emptying of such containers, which can easily have a weight of over 100 t, almost impossible.

A corresponding field of application, for an internal nickeling of large-volume containers, falls within the scope of the transport and storage containers for radioactive waste. The containers have a cylindrical and / or square receiving area and a sealing area with different diameters, resulting in special requirements for the formation of a nickel coating.

To avoid the aforementioned problems and to provide a non-porous nickel plating is from the DE 195 02 358 A1 a method has become known in which a large-area component is heated, pickled after the heating, rinsed, dekapiert, coated in an electrolysis and rinsed. Furthermore, from this document a device for carrying out the aforementioned method has become known, the arrival or conversion elements for forming a trough, an anode compartment of a plurality of substantially parallel rod-shaped anodes, which are positioned near the surfaces to be coated, and a traversing device for the anode compartment.

Although the method described above has been proven in practice, there is nevertheless a need for improvement with regard to the precision and the flexibility of the method as a whole. In particular, difficulties have resulted in the deposition of a homogeneous layer thickness of the nickel layer. It has also been found that certain areas of the surface to be coated must withstand greater loads than other areas. For this purpose, it is necessary to deposit different layer thicknesses in these mutually adjoining areas, wherein each area must not, if possible, have any layer differences. In the aforementioned difficulties, the known from the prior art method reaches its limits.

It is therefore the object of the invention to provide a device and method which eliminate the disadvantages known from the prior art.

To achieve the object, a device for electrolytic nickel plating of a large-area component, comprising an electrolysis tank or attachment or conversion elements to form an electrolysis tank and spaced apart anodes and / or anode groups, wherein planar shielding elements between individual anodes and / or anode groups are arranged the shielding elements are arranged such that they form at least partially electrically shielded volume regions for segmental coating of the large-area component.

Due to the configuration according to the invention, it is advantageously possible to coat the surface of large-area components particularly homogeneously by segment-wise nickel-plating. In particular, layers can be produced here in which differences in the layer thickness can be almost completely avoided. It has been found that the arrangement of shielding elements according to the invention between the anode or anode groups required for the coating and the surface segment to be coated results in the formation of particularly homogeneous electric fields. This allows in contrast to those known from the prior art Approaches a virtually trouble-free control of the deposition processes in the individual shielded areas. In shielding-free systems, as has been established in the prior art, the maintenance of a homogeneous electric field extending over the entire surface of the component to be coated is virtually impossible. In particular, the interference fields occurring at the edges of the anodes lead to an undesirable heterogeneity of the electric field as a whole. The deposition of homogeneous layers of the same thickness is therefore possible only to a very limited extent in these systems. In the device according to the invention, in contrast to the prior art, a plurality of spatially limited, relatively small electric fields are constructed, which are easier to handle and less prone to interference. In addition, the formation of interference fields at the edges of the anodes is advantageously prevented by the inventive interposition of the shielding elements according to the invention. The invention thus enables the deposition of a particularly homogeneous nickel layer, which has substantially the same layer thickness at each surface portion of the component to be coated. Substantially the same layer thickness in the sense of the invention means a layer thickness which differs by less than ± 2 μm, preferably by less than ± 1 μm and particularly preferably by less than ± 0.5 μm from the average layer thickness of the nickel coating.

According to the invention the shielding elements are flat. As a result, the shielding elements are advantageously comparatively light and yet form a comparatively large electrically shielded volume region. For this purpose, the shielding elements can be designed in any desired planar form. Preferably, the shielding elements are in the form of plates, sheets, membranes, disks and the like. The preferred shape depends essentially on the strength of the electric field to be shielded. If an electric field with comparatively high field strength is to be shielded, shielding elements with a comparatively large thickness, ie plate-shaped or disk-shaped shielding elements, are preferred. If, on the other hand, an electrical field with comparatively low field strength is to be shielded, shielding elements with a comparatively small thickness, that is to say sheet-like or membrane-shaped shielding elements, are preferred. In the particular case of the inner coating of cylindrical bulky containers, the shielding elements are each preferably formed of circular plates or discs. Particularly preferred here is the design as a perforated disc. In this case, a substantially annular volume region can be formed between two shielding elements, in which a preferably also ring-shaped anode is arranged. It has been found here that any fields present in the interior of the annular anode have no influence on the coating result. Advantageously, the training of the Shielding element as a perforated disk thus to material savings, without negatively affecting the shielding effect in the result.

According to a preferred feature of the invention, the shielding elements are arranged interchangeably within the device. It is thereby possible to replace elements requiring repair or otherwise unusable in a simple manner. As a result, in particular the maintenance of the device is lowered in an advantageous manner overall. It also allows the adaptation of the device according to the invention to the respective requirements, in particular the field strengths to be set. Depending on requirements, shielding elements of different types can be interchanged here. As an example, the exchange of plate-shaped elements against membrane-shaped elements may be mentioned here. In this way, the device according to the invention can be adapted to a large number of possible nickel plating methods and thus has a comparatively broad range of applications. Particularly preferably, it may be provided to use shielding elements of different types for the shielding of different volume areas in parallel. This is particularly advantageous in cases in which anodes or anode groups of different volume ranges are individually controlled and operated with different process parameters. This may be advantageous, in particular, for the case in which some surface segments of the large-area component are to be coated deliberately and simultaneously with different layer thicknesses. It may be provided to provide different field strengths in the individual volume areas. In order to shield the different field strengths, it is preferably provided that the above-mentioned suitable shielding elements are combined with each other in terms of shape and material as a function of the respective field strength.

According to a preferred feature of the invention, the shielding elements are formed of an electrically insulating material. In this case, preference is given in particular to polymeric materials which are stable in the electrolyte used. Particularly preferred are polypropylene (PP), polytetrafluoroethylene (PTFE), polyimides (PI) and polysulfone (PSU). On the one hand, these materials are electrical insulators and on the other hand have excellent resistance to electrolytes typically used in nickel plating. Depending on the setting of the process parameters, it can preferably be provided to use shielding elements made of different materials.

According to the invention either an electrolysis tank or attachment or conversion elements to form an electrolysis tank is provided on the device side. The second variant is used here in particular the inner coating of large-volume containers. Due to the invention or conversion elements of the container to be coated to a Remodeled electrolysis tank. By virtue of this measure, large immersion vessels, as provided according to the first variant, can be dispensed with, since the electrolysis vessel for accommodating the electrolyte is essentially formed by the large-volume vessel to be coated itself. The attachment and conversion elements represent collar, overflow areas, drainage holes or the like and are arranged as needed on the container to be coated.

According to a preferred embodiment of the invention, at least a part of the anodes and / or the anode groups is formed individually controllable. In the context of the invention, individual means in particular that different anode or anode groups can be operated simultaneously but independently of one another. Preferably, the surface segments of the component to be coated on the process side can thereby be coated either with the same deposition characteristics, in particular current density and field strength, or with different deposition characteristics. If the surface segments are coated with the same deposition characteristics, the result is a homogeneous nickel coating according to the invention with essentially the same layer thicknesses. On the other hand, if the surface segments are coated with different deposition characteristics, then individual surface segments may preferably be coated with different layer thicknesses or different speeds. Such a process management can be advantageous where different segments of the large-area component are exposed to different levels of stress and must be coated with a correspondingly greater layer thickness. This possibility, opened up by the invention, of coating different surface segments with different layer thicknesses in one process step permits an extensive simplification of the nickel plating process. In the prior art, the component must go through various baths for this purpose, which on the one hand represents a comparatively large logistical problem and on the other hand leads to inefficient use of resources. The aforementioned problems can be completely avoided by the invention. Preferably, the individual controllability of the anodes and / or the anode groups is realized by the assignment of a separate rectifier. The rectifier and the anodes and / or the anode groups are connected to each other for this purpose control technology.

According to a preferred embodiment of the invention, the anodes and / or the anode groups are formed such that their spatial position and / or their orientation are variable. Preferably, the anodes and / or anode groups are movably received by the device for this purpose. Furthermore, the anodes and / or anode groups are preferably designed to be pivotable. Particularly preferred are the anodes and / or Anode groups both movably received by the device and designed to be pivotable. As a result, the anodes and / or the anode groups can be spatially adapted to the geometry of the surface segment to be coated or their positioning and alignment can be matched to the material to be coated. In practice, surfaces often have to be coated with complex surface textures, which can often result in suboptimal coating results. Due to the spatially flexible configuration of the anodes and / or anode groups can produce high quality nickel layers with the advantages of the invention despite complex surface textures. Preferably, the anodes and / or anode groups are so movably received by the device that they are movable only within the electrically shielded volume space. This avoids that the anodes and / or anode groups are moved out of the electrically shielded area. As a result, the shielding according to the invention and the associated formation of a homogeneous nickel coating is advantageously ensured even when the anodes are moved in an advantageous manner. More preferably, the anodes and / or the anode groups are received only linearly movable by the device. In this scenario, a shielded volume space of at least two shielding elements is limited. Inside the volume space, the anode is arranged. The side of the volume space, which faces the surface segment to be coated in the intended use case, is preferably formed without a screening element. Preferably, this side is designed to be completely open, in order to ensure the necessary for the coating ion flow in the direction of the surface segment to be coated. In this case, the anode is received by the device in the direction of the screening element-free, preferably the completely open side and in the opposite direction linearly movable. In this way it is ensured that the necessary for the formation of a homogeneous nickel layer electric field is always aligned in the direction of the surface segment to be coated, whereby the formation of interference fields is effectively prevented.

According to the invention, the anodes can be shaped as desired. Preferably, the decision is which anode is used, but according to the preferred process parameters, the surface finish of the component to be coated and the desired properties of the resulting nickel coating. With regard to the inner coating of large-volume cylindrical and / or square containers made of ductile iron, for example (GJS-400-15 according to EN 1563), which is particularly difficult to coat, the use of rod-shaped anodes with a round or oval cross-section is particularly preferred. In the event that large-area components with level Surface to be coated, the design of the anodes in plate form is particularly advantageous. In the cases in which a component has surface segments of different surface properties and / or materials, the arrangement of anodes of different geometry in the individual volume regions can preferably be provided with particular advantage. In addition to the arrangement of individual anodes in the volume spaces, it may also be provided according to the invention to arrange anode groups in the anode spaces. Anode groups are preferably formed from at least two, preferably a plurality, anodes of the same type. As a result, comparatively strong electric fields and a high current density can be generated, which is advantageous in particular in the case of a coating with a high layer thickness. Advantageously, the process duration is thereby reduced, which leads to an improvement of the economy on the method side.

In terms of the method, a method for the electrolytic nickel plating of a large-area component is proposed to solve the problem underlying the invention, wherein the surface of the component is coated by means of suitable anodes and a nickel-containing electrolyte with nickel, characterized in that the surface is coated in segments, each surface segment is spatially associated with an anode or an anode group, wherein the anode or the anode group of the respective surface segment is electrically shielded by anodes or anode groups of the remaining surface segments.

The method according to the invention advantageously makes it possible to coat the surface of large-area components particularly homogeneously by segment-wise nickel-plating. In particular, layers can be produced here in which differences in the layer thickness can be almost completely avoided. According to the invention, the effect is due among other things to an almost interference-free control of the deposition processes in the individual shielded areas. In particular, an undesirable formation of interference fields which lead to a detrimental heterogeneity of the electric field as a whole can be advantageously avoided. According to the invention, a plurality of comparatively small, spatially limited electric fields are built up during the process, which are easier to handle and less susceptible to interference than the comparatively large electric fields provided for this purpose by the prior art. The method according to the invention thus makes it possible to deposit a particularly homogeneous nickel layer which has substantially the same layer thickness at each surface section of the component to be coated.

According to a preferred embodiment of the invention, the surface segments are pretreated prior to electrolysis. Such pretreatment may in particular comprise the steps of heating, pickling, rinsing and / or decaping. In such a pretreatment, it is sometimes necessary to apply comparatively large current densities to the surface to be pretreated. By virtue of the configuration according to the invention, these current densities can be set in segments, which is advantageous in terms of the transport of the current required for this purpose.

According to a preferred feature of the invention, the anodes and / or the anode groups are individually controlled for segmental coating of the surface of the component. The individual surface segments of the component to be coated can preferably be coated independently of one another in this case either with the same deposition characteristics, in particular current density and field strength, or with different deposition characteristics. If the surface segments are coated with the same deposition characteristics, the result is a homogeneous nickel coating according to the invention with essentially the same layer thicknesses. On the other hand, if the surface segments are coated with different deposition characteristics, individual surface segments may preferably be coated with different layer thicknesses and / or different speeds. Such a process management can be advantageous where different segments of the large-area component are exposed to different levels of stress and must be coated with a correspondingly greater layer thickness. This possibility, opened up by the invention, of coating different surface segments with different layer thicknesses in one process step permits an extensive simplification of the nickel plating process. In the prior art, the component must go through various baths for this purpose, which on the one hand represents a comparatively large logistical problem and on the other hand leads to inefficient use of resources. The aforementioned problems can be completely avoided by the invention.

According to the invention, the component is coated with nickel. Preferably, nickel is deposited here from an aqueous nickel sulfamate solution. The nickel sulfamate solution contains at least boric acid in addition to nickel sulfamate and water. The nickel sulfamate concentration is preferably adjusted to a value between 60 and 100 g / l, preferably 80 g / l. The boric acid concentration is preferably adjusted to a value between 20 and 50 g / l, preferably 30 g / l. The pH of the electrolyte is preferably adjusted to a value between 3 and 4, preferably 3.2. The electrolyte temperature is preferably set to a value between 35 and 45 C, preferably 40 ° C set. The current density is preferably set to a value between 1 and 20 mA / cm ² , preferably 15 and 18 mA / cm ² . Preferably, it is intended to nickel-plating various surface segments by means of different current densities.

Fig.1

eine erfindungsgemäße Anordnung der Anoden und der Abschirmelemente in schematischer Schnittdarstellung;

The invention will be explained in more detail below with reference to an exemplary embodiment which is not intended to be limiting for the person skilled in the art. It shows

Fig.1

an inventive arrangement of the anodes and the shielding in a schematic sectional view;

Fig.1 shows an inventive arrangement of the anodes 1, 2, 3 and the planar shielding elements 4, 5, 6, 7 in a device according to the invention for the electrolytic nickel plating of a large-area component 8 in a sectional view.

The shielding elements 4, 5, 6, 7 are presently arranged such that they form the electrically mutually shielded volume regions 9, 10, 11 between them. In this case, the anode 1 is arranged in the interior of the volume region 11 in the interior of the volume region 9, the anode 2 in the interior of the volume region 10 and the anodes 3, which together form the anode group 12.

The volume regions 9, 10, 11 are formed on their respective component side 13, 14, 15 shielding element. In the present case, they are designed to be completely open, so that unimpeded ion transport in the direction of the component 8 is ensured.

The arranged in the volume region 9 anode 1 is present rod-shaped and formed with a circular diameter. The anode 2 arranged in the anode region 10 is in the present case plate-shaped. The anode group 12 arranged in the volume region 11 is formed from a plurality of rod-shaped anodes 3 with a circular cross-section. The anodes 1, 2 and the anode group 12 are formed individually controllable in the present case. The arrangement of individually controllable anodes of different types in each of electrically electrically shielded volume regions 9, 10, 11 allows the coating of the respective surface segments 16, 17, 18 with different process parameters. In the present case, this can be used to nickel-coat the surface segments 16, 17, 18 in parallel operation with different layer thicknesses, different speeds and the like. Furthermore, the anodes 1, 2 and the anode group 12 are adapted by their respective shape design to the different geometry not shown here and the partially different material of the individual surface segments 16, 17, 18 in order to optimize the deposition of a homogeneous nickel layer within the respective segment ,

The anodes 1, 2 and the anode group 12 are presently received by the device linearly movable. They are in each case in the direction of the component-side side 13, 14, 15 of the respective volume space 9, 10, 11 movable. In this way, a further adaptation to the surface condition of the respective surface segment 16, 17, 18 is possible. In terms of even further adaptation, the anodes 1, 2 and the anode group 12 are also designed to be pivotable. Preferably, they are pivotable at an angle of up to 20 ° in relation to the respective mid-perpendicular.

The electrolysis tank (not shown) is filled here with an electrolyte for nickel plating of the component 8 to be coated. The electrolyte completely fills the volume regions 9, 10, 11 and ensures permanent wetting of the surface segments 16, 17, 18 of the component 8 to be coated. In the present case, the electrolyte is formed from an aqueous nickel sulfamate solution. The solution contains nickel sulfamate in a concentration of 80 g / l, boric acid in a concentration of 30 g / l. In the process, the pH of the electrolyte is adjusted to a value of 3.2. The electrolyte temperature is set to a value of 40 ° C. In the volume range 9, a current density of 10 mA / cm ^{2 is} set in the present case. In the volume region 10, a current density of 15 mA / cm ^{2 is} set. In the volume region 11, a current density of 18 mA / cm ^{2 is} set. By choosing the aforementioned parameters, the surface segments 16, 17, 18 are nickel plated with different layer thicknesses, with surface segment 16 having a comparatively low layer thickness in the μm range and surface segment 18 having a comparatively high layer thickness in the mm range being nickel plated. Surface segment 17 is nickel plated in comparison with a middle layer thickness.

The shielding elements 4, 5, 6, 7 are in the present case designed as plates. The plates consist entirely of the electrical insulator polytetrafluoroethylene. Furthermore, the material is resistant to the electrolyte used.

Reference number list

1

anode

2

anode

3

anode

4

shielding

5

shielding

6

shielding

7

shielding

8th

component

9

electrically shielded volume range

10

electrically shielded volume range

11

electrically shielded volume range

12

anode group

13

Component-side side of the volume region 9

14

Component-side side of the volume region 10

15

Component-side side of the volume region 11

16

surface segment

17

surface segment

18

surface segment

Claims (15)

Apparatus for the electrolytic nickel plating of a large-area component, comprising an electrolysis tank or attachment or conversion elements for forming an electrolysis tank and spaced-apart anodes and / or anode groups, wherein planar shielding elements are arranged between individual anodes and / or anode groups, wherein the shielding elements are arranged such that they form at least partially electrically shielded volume areas for segmental coating of the large-area component. Apparatus according to claim 1, characterized in that at least part of the shielding elements are plate-shaped. Device according to one of the preceding claims 1 or 2, characterized in that at least part of the shielding elements are membrane-shaped. Device according to one of the preceding claims, characterized in that the shielding elements are exchangeably received by the device. Device according to one of the preceding claims, characterized in that the shielding elements are formed substantially of an electrically insulating material. Apparatus according to claim 5, characterized in that the shielding elements are formed at least partially from a polymer. Device according to one of the preceding claims, characterized in that the anodes and / or the anode groups are formed individually controllable. Apparatus according to claim 7, characterized in that the anodes and / or the anode groups are each connected to a separate rectifier control technology. Device according to one of the preceding claims, characterized in that at least two shielding form a shielded volume region, wherein the shielding elements are arranged opposite to each other and the anode or the anode group is positioned in the interior of the volume region, wherein the volume region is formed on the component side shielding element. Apparatus according to claim 9, characterized in that the anodes or the anode groups are accommodated within the respective volume range in the direction of the shielding element-free side of the respective volume region and in the opposite direction movable from the device. A process for the electrolytic nickel plating of a large-area component, wherein the surface of the component is coated by means of suitable anodes and a nickel-containing electrolyte with nickel, characterized in that the surface is coated in segments, wherein each surface segment is spatially associated with an anode or an anode group, wherein the anode or the anode group of the respective surface segment is electrically shielded by anodes or anode groups of the remaining surface segments. A method according to claim 11, characterized in that the anodes or the anode groups are individually controlled for segmental coating. Method according to one of claims 11 or 12, characterized in that anodes or anode groups, which are assigned to different surface segments are operated at least partially simultaneously. Method according to one of claims 11 to 13, characterized in that at least partially different current densities are set between the surface segments and the respective anode or the respective anode group. Method according to one of claims 11 to 14, characterized in that the surface segments are at least partially coated with different layer thicknesses.

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