WO2022033990A1

WO2022033990A1 - Process and device for the galvanic nickel plating of a fin wall

Info

Publication number: WO2022033990A1
Application number: PCT/EP2021/072079
Authority: WO
Inventors: Ralf Senff-Wollenberg; Johann-Wilhelm Ansey
Original assignee: Standardkessel Baumgarte Gmbh
Priority date: 2020-08-10
Filing date: 2021-08-06
Publication date: 2022-02-17
Also published as: EP4193007A1; DE102021120556A1

Abstract

The invention comprises a process for the galvanic nickel plating of a fin wall (FW), which has at least one wall part (FW') which is formed from a number of tubes R₁, R₂, …, R₅) running alongside one another in a longitudinal direction (LR) and connecting cross-pieces (S₁, S₂, …, S₅) respectively arranged between adjacent tubes (R₁, R₂, …, R₅), in which process the fin wall (FW) is introduced as a cathode (FW) into a galvanic bath (1), in which there is an anode (20) at a distance (aA-FW) from the fin wall (FW). An auxiliary anode arrangement (30, 30a, 30b, 30c) is arranged between the fin wall (FW) and the anode (20). As an alternative or in addition, the anode (20) is adapted on a surface (20f) facing the fin wall (FW) at least in some regions to the form of the surface (O) of the fin wall (FW) that is facing the anode (20). The invention also relates to a device for the galvanic nickel plating of a fin wall (FW).

Description

Process and device for galvanic nickel-plating of a fin wall

The invention relates to a method and a device for the galvanic nickel-plating of a fin wall.

Galvanic or galvanotechnical coating or covering, such as e.g. B. Galvanic nickel plating refers to an electrochemical process for producing a metallic coating on a preferably metallic workpiece using electrolysis. With galvanic nickel plating according to DIN EN ISO 1456, the objects to be nickel plated are immersed in a nickel electrolyte, e.g. B. immersed in a so-called galvanic bath and by applying an electrical voltage, a nickel coating is deposited on the surface of the workpiece. Particularly in the field of steam generators for (waste, hazardous waste or biomass) incinerators or (industrial) power plants for the incineration or disposal of solid, liquid and/or gaseous fuels that may contain pollutants, the workpiece in question is typically what is known as a fin wall or membrane wall. Due to the extreme conditions prevailing there (sometimes over 1200° C) and the requirements of 24/7 continuous operation of the systems, this must be protected against corrosion as sustainably and long-term as possible.

More specifically, under such a finned wall or membrane wall, a wall made of (metal) tubes or evaporator heating surface of a water tube boiler, such as e.g. B. a natural circulation boiler, or the like understood, for example, a furnace or a combustion chamber of the power plant or the (waste) incinerator surrounds. The construction of the fin wall consists of parallel tubes, with a metal bar, the so-called "fin" or "membrane", welded between each two adjacent tubes. This makes the wall smoke-tight and the heat of the smoke gas is conducted to the pipe, through which water flows for energy conversion. Strictly speaking, this structural design of the fin wall is therefore not a planar or flat wall, but rather a wall with relief-like structures that essentially extends in one plane. However, this is precisely where the greatest challenges in electroplating typically lie. The more sharp-edged or uneven the surface to be electroplated, the more difficult it is to even out the surface in question electroplating with a preferably thin metal coating such as nickel. In the case of an uneven surface, ie one that is not uniformly spaced from the anode throughout, the metal ions are deposited on the workpiece at different rates (inhomogeneously) due to the formation of field lines. This problem is currently being worked on in a very complex manner using so-called masks, which locally regulate or change the amount of deposition on the workpiece. The selection of materials also plays a key role. Since this has already been done here, the possibilities must be left out.

The invention is based on the object of specifying a method for galvanic nickel-plating of a fin wall with which a longer service life, a more uniform layer thickness, hardness and heat conduction of the galvanized fin wall is achieved and also the assembly of the galvanized fin wall is facilitated without reducing the exposure time in the galvanic Having to change the bath accordingly to regulate the layer thickness.

This object is achieved by a method according to claim 1 and a device according to claim 8.

In the method according to the invention (specifically also referred to as a “covering or coating method”, as will be explained below), the fin wall is introduced or immersed in a galvanic bath as a cathode (negative pole or negatively charged electrode) as usual. According to the invention, an anode is located at a distance from the fin wall.

As mentioned above, the fin wall or membrane wall comprises at least one wall part which is formed from a plurality of tubes running next to one another in a longitudinal direction and connecting webs arranged between adjacent tubes. The fin wall can preferably be made of metal, in particular iron. In this case, for example, metal webs or metal connecting webs can be welded between metal tubes and thus form a fin wall extending essentially in one plane.

A galvanic or electrolytic bath is a container in the relevant discipline, i.e. electroplating or electroplating, in which an electrochemical Deposition of metallic deposits, i.e. coatings on substrates (objects) takes place. The aim here is usually to coat or cover a metallic substrate body with a further metallic layer in order to protect it better against corrosion.

When current is passed through the galvanic bath, the metal ions (cations), here nickel, on the anode (positive pole or positively charged electrode) migrate or flow to the cathode or to the object to be coated, i. H. in the context of the invention z. B. the fin wall. By means of the electric current, metal deposited on the wall of the fin, e.g. B. receive nickel. The longer the object is in the bath and the higher the current, the thicker the metal layer (e.g. nickel layer) on the object. The current density and the distance between the anode and the cathode influence the hardness and the fine-grainedness of the columnar substrate, which is why it can be advantageous, depending on the galvanic process used, to select the settings in such a way that the hardness of the substrate has a value of approx. 240 - 280 HV 10 does not exceed.

Furthermore, according to the invention, an auxiliary anode arrangement is arranged between the fin wall and the anode. An auxiliary anode arrangement can have at least one auxiliary anode, preferably a plurality of auxiliary anodes arranged in series or a group. Within the scope of the invention, an “auxiliary anode” or “auxiliary anode arrangement” is to be understood in a first variant as a conductor which represents a path with low or low electrical resistance in the galvanic bath, but which is then not directly connected to a current source of the galvanic bath is connected, but is charged bipolar by the current flow through the electrolytic liquid in the galvanic bath and thus acts as a local "current flow compressor" or "current density increaser", as will be explained below.

In a second preferred variant, however, an auxiliary anode or auxiliary anode arrangement can also be directly or indirectly electrically coupled or connected to the anode, ie. H. be contacted.

Alternatively or additionally, according to the invention, the surface facing the fin wall is at least partially adapted to the shape of the surface facing the anode of the fin wall to be electroplated. A device according to the invention for galvanic nickel-plating of a fin wall comprises a galvanic bath, for example with an electrolytic solution, which has already been explained above.

The electroplating bath comprises an anode extending essentially in a plane or surface, in order to arrange the fin wall as a flat cathode also extending essentially in one plane at a defined cathode position at a distance from the anode in the electroplating bath.

The device also includes a current source or voltage source which is connected to the anode at one pole and can be connected to the fin wall (cathode) at another pole in order to generate or induce a current flow from the anode to the cathode. In other words, the two components or electrodes (anode wall and fin wall) are polarized by applying a DC voltage. As mentioned, since they are in a conductive liquid, current flows between the anode and cathode, i. H. the positive cations or metal ions move to the cathode, take up electrons and are deposited as a metal layer on the cathode.

Furthermore, the device according to the invention comprises an auxiliary anode arrangement which, in normal operation, is arranged between a fin wall arranged in the galvanic bath and the anode. According to a first variant, the auxiliary anode arrangement can be arranged at a distance from the anode, but spatially directly in front of it.

According to a second variant, the auxiliary anode arrangement can also be electrically connected or coupled to the anode. For this purpose, as a possibility, the auxiliary anode arrangement can also be mechanically coupled directly to the anode, in particular welded, and particularly preferably form so-called “auxiliary anode fins”, as will be explained in more detail later.

Alternatively or additionally, the anode is adapted according to the invention, at least in regions, to the shape of the surface of the fin wall to be electroplated or to be coated with a layer of metal using electrolysis on a surface of the anode pointing to the intended cathode position of the fin wall, which surface faces the anode during operation. In the simplest case, "adapted" means a very rough adaptation, ie it can, for example Elevations and / or depressions may be formed in the anode surface. For example, in the area opposite the fins or connecting webs of a fin wall, the anode can have anode fins protruding in the form of webs relative to the fin wall. B. can be welded or part of the anode. These ensure a local change in the electrical field during electroplating in the electrolytic bath. The more precise design of the anode fins is explained further below.

If - as mentioned above - the auxiliary anode is also directly mechanically connected to the anode, z. B. is welded to this as a part, this can also be seen as an overall anode, which in a certain way is also adapted in shape to the surface of the surface of the fin wall facing the anode during operation. i.e. the transition from the first variant, in which the electric field is influenced by auxiliary anodes, to the second variant, in which the electric field is shaped by the design of the surface of the anode, is fluid in certain design variants.

With the inventive construction of the object of the invention it is achieved that the fin wall to be coated or at least the relevant coated wall part of the fin wall can be coated with a uniform thickness along the planar extent or the surface. On the one hand, this ensures that the fin wall conducts heat evenly, which increases the efficiency of the evaporator during operation. On the other hand, this achieves a uniform hardness of the fin wall, which is preferably below a value of 280 HV10, as a result of which subsequent deformability of the fin wall can be ensured. Overall, this also extends the life of the fin wall, since the fin wall thus has no stronger or weaker areas (weak points) that corrode to different degrees. Next is achieved with the method according to the invention that a usually necessary rework of the fin wall, z. B. at the edges etc. is reduced to the smallest possible extent by the coating process according to the invention. The process is also simpler than the currently known methods, since everything can be carried out in one operation without masks or covers.

Further, particularly advantageous refinements and developments of the invention result from the dependent claims and the following description, with the independent claims of a claim category also analogous to the dependent claims and exemplary embodiments of another claim category can be further developed and, in particular, individual features of different exemplary embodiments or variants can also be combined to form new exemplary embodiments or variants.

As already mentioned, in a preferred variant of the invention, an auxiliary anode arrangement is used. There are different possibilities for designing the auxiliary anode arrangement.

The auxiliary anode arrangement can preferably comprise at least one group of rod-shaped, preferably elongate, auxiliary anodes or auxiliary anode rods. These auxiliary anode rods or auxiliary anodes can each be assigned to a connecting web of the fin wall and each run parallel to a longitudinal extent of the connecting web at a distance in front of the respective connecting web, ie in the middle between two tubes.

In principle, the cross section of an auxiliary anode rod can be arbitrary, e.g. B. round, square, oval, or the like, with symmetrical cross-sections are preferred. Auxiliary anode rods with a symmetrical cross section can then preferably be arranged such that in a state in which the auxiliary anode rods are coupled to the fin wall, the associated axis of symmetry running through the cross section is oriented perpendicular to the surface of the connecting web centrally between the tubes of the fin wall. The contour of the cross section determines the course of the electric field lines and thus the amount of deposit of the application on the relevant section of the fin wall.

There are various options for selecting a suitable material for an auxiliary anode of the auxiliary anode arrangement.

Preferably, an auxiliary anode of the auxiliary anode arrangement can comprise at least one of the following materials or an alloy of different of these materials: platinized titanium, titanium, nickel, tungsten, inconel, incoloy, zircon, zircaloy.

The auxiliary anode arrangement can preferably be electrically insulated from the power source already mentioned above, ie potential-free, ie not itself conducting. When the auxiliary anodes of the auxiliary anode assembly are placed between the anode and the cathode two poles form in the cross section of each auxiliary anode due to the course of the electric field lines, namely a positive pole on the side of the cross section through the auxiliary anode pointing to the fin wall and a negative pole on the opposite side of the cross section pointing to the anode or anode wall through the auxiliary anode. Consequently, each auxiliary anode is polarized in a bipolar manner.

In principle, the auxiliary anodes of the auxiliary anode arrangement could be positioned or coupled individually, for example coupled in an electrically insulated manner to maintain a defined distance at the anode or cathode.

Alternatively, as mentioned, the auxiliary anode assembly may preferably be electrically connected to the anode, e.g. H. be current-carrying and arranged spatially immediately in front of it or directly welded on or as part, e.g. B. as mentioned be designed as an auxiliary anode fin. At this point, it should be pointed out that gas or vapor is actually always generated during electroplating, for which extraction is usually used. However, in order to reduce the degree of gas or vapor development as much as possible, a platinized auxiliary anode made of titanium can preferably be used, which is electrically connected to the anode. Experiments have shown that when using an auxiliary anode which is electrically connected to the anode, less chlorine vapors are produced than when using a platinized auxiliary anode which is electrically insulated from the anode.

The auxiliary anode assembly, like the anode, can be constructed to partially dissolve, i. H. go from her nickel ions in the galvanic bath in solution to deposit on the cathode. For this purpose, the auxiliary anode assembly, for example, made of solid material such. B. pure nickel can be formed.

Alternatively, the auxiliary anode arrangement - like the anode - have a fillable grid or mesh body made of titanium, which is coated with nickel, z. B. in the form of nickel balls or so-called "nickel coins" is filled, whereby nickel can be continuously tracked in order to keep the grid or mesh body sufficiently full.

Alternatively, the auxiliary anode can only consist of material that remains, ie z. B. - as described later - include auxiliary anode fins made of titanium. With the exception of the tip of the fin, the auxiliary anode fins can preferably be coated with a non-conductive coating in order to prevent or limit the surface influence of the entire fin.

Preferably, at least one group of the auxiliary anodes of the auxiliary anode arrangement can be mechanically connected to one another, e.g. H. also with each other. Particularly preferably, the group of auxiliary anodes of the auxiliary anode arrangement can be coupled in an electrically insulated manner, so that there is in any case no direct current flow between the auxiliary anodes and the cathode and/or the anode.

There are various possibilities for attaching or fastening the auxiliary anode arrangement relative to the cathode.

The device according to the invention can preferably comprise a holding device in order to couple the auxiliary anode arrangement to the component or workpiece to be electroplated, ie here the fin wall. Particularly preferably, the holding device can be connected to the fin wall to be electroplated in a mechanically but electrically insulated manner. For example, the holding device can also comprise a non-conductive material, e.g. e.g. plastic. A "forced flow" can be generated in the electroplating bath to remove gases such as hydrogen, which are usually produced during electroplating. The mounting device can preferably be designed in such a way that vibration of the auxiliary anode arrangement when the bath flows through does not impair the electroplating process.

In order to minimize, for example, flow-related oscillations of the anode, auxiliary anodes and fin wall (and possibly prevent the components from clashing as a result), it is advantageous to keep the rod-shaped auxiliary anodes located between the anode and fin wall under tensile stress (in the longitudinal direction). During the electroplating process, local temperature differences in the electroplating bath can also cause the fin wall to expand to different extents compared to the auxiliary anodes, particularly in the longitudinal direction. The mounting device can therefore preferably have tensioning elements with resilient properties, in order in particular to compensate for such temperature differences and thus a different expansion of the auxiliary anodes relative to the fin wall or to the mounting device. In addition, the auxiliary anode arrangement can particularly preferably be introduced, embedded or immersed in the electroplating bath with this holding device (arranged at a desired distance to match the anode).

Advantageously, a distance (of the plane) of the auxiliary anode arrangement from the (plane of) the fin wall can be adjusted by means of the holding device. For this purpose, the holding device can be designed, for example, with slots or the like for the controllable or adjustable introduction of the auxiliary anode rods, as will be explained further below.

The mounting device can preferably have at least one coupling element for coupling to the fin wall. The coupling element can particularly preferably comprise a plug which can be inserted into one end of a tube of the fin wall and clamped there or braced in the tube. This can particularly preferably at the same time seal the tube tightly at this end, so that at least at this end of the tube no liquid can get into the tube, ie no material can be deposited on the inside of the tube.

The mounting device can preferably comprise at least two coupling elements, each with at least one plug or pipe plug. When used as intended, two of the plugs (also known in practice as shut-off discs or pipe plugs) can be arranged relative to one another in such a way that they can be inserted into opposite ends of the same pipe. The auxiliary anode arrangement can be arranged in such a way that the rod-shaped auxiliary anodes are held in a longitudinal direction of the tube running parallel to the tube between the two coupling elements at a defined distance from the fin wall.

The mounting device can preferably have adjustment elements in order to be able to adjust or set the distance between the auxiliary anode arrangement and the fin wall. Particularly preferably, the mounting device can be slotted for this purpose, ie it can include slot cutouts for the previously described coupling element, by means of which the auxiliary anode arrangement is mounted so as to be displaceable overall in a direction towards or away from the fin wall. In this way, the distance between the auxiliary anode arrangement or a row/group of auxiliary anodes and the fin wall can be adjusted, as has already been mentioned above. Preferably, there can be at least one tube, particularly preferably at least two, more preferably three, most particularly preferably four tubes (without a direct connection to the mounting device) between two other tubes on which the fin wall is connected to the stopper of the mounting device at the tube end . The relevant number of tubes between the two lateral tubes held on the top and bottom of the mounting device can each be provided with a tightly sealing, preferably conical, blind plug, in particular without a connection to the mounting device. It can thus be ensured that the respective two ends of the relevant number of tubes are sealed as required, so that as little material as possible gets into the interior of the tubes and is deposited there or coats the interior of the tubes.

In a second variant of the invention, a contour in a sectional plane of the anode, i.e. perpendicularly through the plane of the anode and the fin wall, on a surface facing the fin wall can be essentially adapted to a contour of a surface of the fin wall facing the anode. Particularly preferably, the contour of the anode on a surface facing the fin wall in the area opposite a connecting web can correspond to the surface of the fin wall facing the anode.

Such a device for galvanic nickel-plating of a fin wall is also advantageous independently of the already mentioned idea according to the invention, an auxiliary anode arrangement between the fin wall and the anode. This also ensures that the metal ions are deposited more evenly on the fin wall, i. H. especially in the area of the inner corners at the transition between the tubes and the connecting bars. However, combinations of the ideas described are also possible in order to achieve an optimal application of the coating.

The anode fins already mentioned above can preferably comprise two webs spaced apart from one another, which z. B. are arranged parallel next to each other essentially perpendicularly projecting from the anode wall on the anode wall opposite a fin or a connecting web of the fin wall. Together, the bridges form a double bridge, so to speak. With the exception of the tip of the fin, the anode fins can particularly preferably be coated with a non-conductive coating in order to prevent or limit the surface influence of the entire fin.

The invention, d. H. in particular the mounting device, the auxiliary anode arrangement and/or the anode wall, should preferably be designed or dimensioned in such a way that at least the following usual dimensions of such membrane walls can be electroplated with it:

The invention can preferably be designed in such a way that the tube diameter or the wall thickness of a tube can be 60.3×5.0 or 5.6 mm, particularly preferably 57.0×5.0 or 5.6 mm.

Preferably, the invention can further be designed in such a way that the wall thickness of the connecting webs can measure 5 mm, particularly preferably e mm.

In addition, the invention can preferably be designed in such a way that the division, i. H. the average distance between the centers of two tubes can be 90 mm, particularly preferably 80 mm.

Delivery sizes for membrane walls in terms of length and width are currently determined, at least in Germany, by the sensible transport sizes in road traffic. Accordingly, membrane walls of this type for new installation—if they are transported as usual on the road—can preferably be made up in sections of a maximum length of 12 m and a width of 3.6 to 5 m and particularly preferably of a maximum length of 6 m and a width of 0.9 m. However, the invention can preferably also be suitably dimensioned for this. For the repair or replacement of damaged wall parts of membrane walls, the membrane walls can usually be made up, limited by the transport sizes in the respective plant, preferably in sections of at most 6 m in length and 1.5 m in width.

However, the invention is not limited to being able to electroplate workpieces with the stated dimensions. At the request of the customer, such membrane walls can also have special dimensions, which in particular can also be larger can be than the stated dimensions. The invention can preferably also be suitably dimensioned for such special dimensions.

The invention is explained in more detail below with reference to the attached figures using exemplary embodiments. The same components are provided with identical reference numbers in the various figures. As a rule, the figures are not to scale and should only be understood as a schematic representation. Show it:

FIG. 1 shows a perspective overall view of a device for galvanic nickel-plating of a fin wall according to a first exemplary embodiment of the invention, looking into a galvanic bath,

FIG. 2 shows an enlarged, perspective view of a section of the exemplary embodiment from FIG.

3 shows an enlarged, perspective side view of a section of the exemplary embodiment from FIG.

FIG. 4 shows a partial longitudinal section of an enlarged detail through the device according to FIG. 1, with focus on a coupling element of a holding device between fin wall and auxiliary anode,

FIG. 5 shows a schematic representation of the course of the electric field lines between a section of an anode wall and a fin wall in electroplating according to the prior art, in plan view,

Figure 6 shows a schematic representation of the course of the electric field lines between the anode wall and a wall part of the fin wall in a first embodiment of the invention with the arrangement of a first variant of an upstream auxiliary anode in the area between two tubes at the level of a connecting web of the tubes of the wall part, in plan view, FIG. 7 shows a further schematic representation according to FIG. 6, with a second variant of the upstream auxiliary anode, in plan view,

FIG. 8 shows a further schematic representation according to FIG. 6, with a third variant of the upstream auxiliary anode, in plan view,

FIG. 9 shows a schematic representation of a further exemplary embodiment of the device according to the invention with an anode wall which is essentially adapted to the wall of the fin and is modified relative to FIG. 5, also in plan view,

FIG. 10 shows a section according to FIG. 2, but this time with auxiliary anodes electrically coupled to the anode,

FIG. 11 shows a schematic representation of a further exemplary embodiment of the device according to the invention, with anode fins mechanically coupled to the anode wall on a surface facing the fin wall and protruding in the form of webs, in plan view.

Figure 1 shows an overall view of a first exemplary embodiment of a device according to the invention for galvanic nickel-plating of a fin wall FW, with a view of a wall part FW of a fin wall FW which is immersed in a galvanic bath 1 completely below a liquid surface F (or liquid level F) and which is shown connection to the surrounding galvanic bath 1 is held in position.

At this point it should be pointed out that the liquid level F can advantageously be selected within the scope of the invention such that at least the fin wall FW or here a wall part FW of the fin wall FW is completely covered by the liquid in the electroplating bath 1 .

Such a fin wall FW consists of tubes Ri, R2, . . Si, S2, ..., S5 are welded together. The cuboid galvanic bath 1, which is rectangular in plan, comprises four tank walls 2 and a correspondingly rectangular tank floor 3 on the reverse side Cover rest, which is not shown here. In order to provide a better support surface for such a cover for the galvanic bath 1, for example, the basin edge 4 in the sections of the galvanic bath 1 shown in Figures 2 and 3 protrudes on the outside at the upper edges of the basin walls 2 beyond the basin walls 2.

Several retaining brackets 21 that reach over the pool edge 4 are hung along at least one pool wall 2 on this pool edge 4 . These retaining brackets 21 hold an anode wall 20 or anode 20, which extends in a plane 20E (see Figure 3) and is at least predominantly immersed in the electroplating bath 1, in a position parallel to and at a desired distance from the tank wall 2. The anode, on or in which is the substrate (preferably nickel here without loss of generality) before the electroplating process can—as is generally known—be designed, for example, in the form of a basket, sieve or the like with a grid or as a perforated tube or sieve tube or as expanded metal. The anode or anode wall can thus z. B. as a so-called “anode basket” (e.g. made of titanium) extending in a plane 20E, which guides or contains the substrate for the cathode to be coated. i.e. the anode basket can, for example, with nickel z. B. in the form of nickel balls or nickel pellets, "nickel coins", nickel discs or nickel crowns etc., which nickel then passes through the porous surface of the anode basket through the galvanic bath through oxidation into solution and from there, to put it simply, again deposited by reduction at the cathode.

In addition, a partially permeable anode bag, e.g. B. a textile bag made of natural or man-made fibers or the like can be placed or pulled over in order to intercept or filter the anode sludge that forms on the anode wall during electroplating, which otherwise sometimes causes contamination of the galvanically applied coating on the fin wall FW or responsible for it.

Further in the direction away from this pool wall 2 to the opposite pool wall 2, i.e. in the perpendicular direction, so to speak, to the plane 20E or In the direction of spacing (perpendicular to the two other directions LR, QR) inwards, the fin wall FW already mentioned extends at a desired constant spacing 3A-FW essentially parallel to the plane 20E of the anode wall 20 (see FIG. 3). This position of the fin wall FW (or here a wall part FW of a fin wall FW, which is to be nickel-plated with the method or coating method according to the invention, for example) is defined below as a cathode position P or fin wall position P.

The wall part FW in question of the fin wall FW has a length L and a width B (here, for example, with five tubes Ri, R2, ..., R5 with the associated connecting webs Si, S2, ..., S5), the preferred dimensions of which are given above have already been explained. In FIGS. 1 and 2, the length L designates the dimension of the wall part FW of the fin wall FW in the vertical longitudinal direction LR, the width B corresponds to the dimension in the horizontal transverse direction QR or, for short, the transverse direction QR.

At this point, within the scope of the invention, it should be pointed out that the invention is not limited to the wall part FW shown here. The wall part could, for example, also start with a connecting web and end with a tube or end with connecting webs on both sides or with tubes on both sides. Equally, at least the length of the outer connecting webs can also be selected as desired within the scope of the invention.

FIG. 3 shows an arrangement of the immersed components of the device rotated by 90° to the tank floor 3 of the electroplating bath 1, so that the longitudinal direction LR and the transverse direction QR are also rotated accordingly there. In this orientation, an auxiliary anode arrangement 30, 30a, 30b, 30c and a holding device 40, which will be explained later, or an auxiliary anode frame 40 (not shown here in FIG. 3) are also rotated through 90°. The retaining brackets 21 of the anode wall 20, like the associated anode wall 20, remain on the upper edge of the tank walls 2 on the tank edge 4, since the anode wall 20 was not rotated for this purpose.

The auxiliary anode arrangement 30, 30a, 30b, 30c here comprises four rod-shaped auxiliary anodes 30, 30a, 30b, 30c arranged parallel to one another. At a distance 3A-HA to the anode wall 20, the aforementioned auxiliary anode arrangement 30, 30a, 30b, 30c, more precisely the rod-shaped auxiliary anodes 30, 30a, 30b, 30c, runs vertically, parallel to the longitudinal direction LR of the wall part FW of the fin wall FW, in particular the tubes Ri, R2, R5 of the shown wall part FW of the fin wall FW.

The (auxiliary anode) rods 30, 30a, 30b, 30c, which are not connected here to a power source, represent a path with low or low electrical resistance in the galvanic bath 1 and therefore behave like a bipolar anode, i. H. they form a negative pole on a side pointing to the anode wall 20 and a positive pole on a side pointing to the workpiece, here the fin wall FW. From the resulting negative pole at a reduced distance from the fin wall FW, the cations or metal ions then flow more specifically in a straight line to the wall part FW of the fin wall FW and are deposited there, as will be explained in more detail below.

For this purpose, the auxiliary anodes 30, 30a, 30b, 30c are clamped in the longitudinal direction LR of the auxiliary anodes 30, 30a, 30b, 30c by means of the aforementioned mounting device 40 or the auxiliary anode frame 40 and so-called clamping elements 31, so that they are at as fixed a distance as possible from the wall part FW' of the fin wall FW are held and vibrate as little as possible (wobbling). The auxiliary anode frame 40 (which is located below the liquid surface F in Figures 2 and 4 by way of example without loss of generality) holds the wall part FW of the fin wall FW with the aid of coupling elements 45 (more detailed explanation follows later) at the correct height in the galvanic bath 1. This For this purpose, coupling elements 45 are arranged in at least some of the end faces or tube ends REIA, REIB, . In the pipe ends RE2A, RE2B, RESA, RESB, RESA, RESB of the other pipes R2, R3, R5, simple blind plugs 45' can also be sufficient to seal the respective pipe end RE2A, RE2B, RESA, RESB, RESA, RESB as required (so that no liquid gets into the interior of the tube), as shown, for example, by means of the two middle tubes R2, R3 in FIG. These blind plugs 45' act as a kind of sealing "cork" without a holding function.

At this point it should be pointed out that depending on the size of the wall part FW of the fin wall FW relative to the load - which can carry a certain number of such coupling elements 45 as a supporting interface to the auxiliary anode frame 40 - preferably the proportion of tubes Ri, R4, which are connected by means of the coupling elements 45 are held and sealed, can also be increased. A modified auxiliary anode frame 40 can then be used for this, which has a correspondingly increased number of protruding retaining lugs 40f with adjusting elements 43, designed here as slot recesses 43 or slots 43 (explanation follows later), in order to also accommodate the further coupling elements 45.

In order to offer the necessary stability itself, the auxiliary anode frame 40 described above consists of at least two strips running along the transverse direction QR of the wall part FW of the fin wall FW, which are just above at the height of the (here upper in Figure 4) first tube end REIA and just below the (Here in Figure 4 lower) second pipe end RE are arranged. At least at the ends, these strips are stably connected or braced to one another via the longitudinal struts 41, which longitudinal struts 41 can be seen in FIG. 1, for example. Depending on the dimensions of the wall part FW of the fin wall FW, further transverse struts 42 can be inserted parallel to the said strips for stiffening purposes. In Figure 1, two such cross braces 42 are indicated, for example. As can be seen particularly well in Figure 4, these are designed in such a way that they are very thin and the auxiliary anodes 30, 30a, 30b, 30c only grip on a rear side facing away from the fin wall FW, so that they facilitate the process of Electroplating of the fin wall FW not significantly disturb, but provide additional stability. In addition, they are made of a suitable insulating material that does not significantly affect the field lines.

In particular, Figure 1 also shows that the auxiliary anode frame 40 has retaining tabs 40f that protrude (or continue) from the strips to the fin wall FW, in which, as can be seen for example in Figures 1 and 2, slot recesses 43 are elongated in the direction of spacing (in the width suitable for below-mentioned coupling elements 45, in particular coupling rods 46) are recessed. These slot recesses 43 serve to mount coupling elements 45, in particular coupling rods 46 of the coupling elements 45, in such a way that the distance between the auxiliary anode arrangement 30, 30a, 30b, 30c and the fin wall FW can be adjusted and fixed. For locking or clamping at a desired fixed distance, the coupling elements 45 mounted in the slot recesses 43, in particular the coupling rods 46 of the coupling elements 45, have so-called clamping sleeves 47, which can be seen enlarged in FIG. 2 or schematically in longitudinal section in FIG. The clamping sleeves 47 have here, without loss of generality, an internal thread 47g which engages in an external thread 46g of the coupling rods 46 formed at least partially along the coupling rods 46 . The clamping sleeves 47 could also be designed here without an internal thread 47g, ie be fixed to the coupling rod 46 in a purely non-positive manner, as is the case, for example, in principle with quick-release clamps, quick-release or spring locks, dumbbell locks or clamps or collars and the like. is known for securing weight plates on weight bars.

As can be seen in Figure 4 by way of example using a longitudinal section through a tube Ri - in which longitudinal section the holding device 40 is shown partially in section and the auxiliary anode arrangement 30, the clamping elements 31 and the cross braces 42 are not shown in longitudinal section - the aforementioned extend Coupling rods 46 of the coupling elements 45 from above (or below) the auxiliary anode frame 40 through the slit recesses 43 in the retaining tabs 40f and into the first upper tube end REIA (or the second lower tube end RE) of the relevant tube Ri. A first, hollow-cylindrical, sealing stopper 48 is arranged in an outermost part of the pipe ends REIA, RE, and has an opening in the middle, through which the coupling rod 46 runs. Two spacer rings 50 (e.g. made of metal or the like) and two sealing rings 49 (e.g. made of rubber or the like) are arranged alternately within these plugs 48. The two sealing rings 50 are shown here in a “broadly pressed” or pressed state, in which they doubly seal the pipe Ri on the inside of the pipe. Radially on the inside around the coupling rod 46, the pipe-inner sealing ring 50 also seals against the flange of the coupling rod 46 by contact pressure (in the longitudinal direction LR outwards to the respective pipe end REIA, REIB, i.e. from below or above), so that no liquid can get to the inside of the Coupling rod 46 along an at least partially existing external thread 46g of the coupling rod 46 or beyond the external thread 46g can seep into the interior of the pipe.

The contact pressure can preferably, as shown here, be generated by bracing the coupling rod 46 against one another against the plug 48 or the auxiliary anode frame 40 . Specifically, the flange, which has an outer diameter essentially adapted to the inner diameter of the pipe Ri, is pulled outward against the sealing rings 49 or spacer rings 50 at the end of the coupling rod 46 inside the pipe. The sealing rings 49 are compressed or shortened in the longitudinal direction LR of the pipe Ri by means of the spacer rings 50 and thus widened at the same time in the radial direction, so that they seal the pipe Ri (the same applies to the fourth pipe R4 or any multiple thereof) on the inside of the pipe Seal the inside and at the same time hold it in place as required. Figure 10 shows (auxiliary anode) rods 30, 30a, 30b, 30c which, in contrast to the above description, are electrically connected or contacted to the anode 20 by means of a connecting frame 60 and thus represent anodes adapted to the fin wall FW, which consequently during "dissolve" the electroplating. In order to avoid complete dissolution, they consist of a z. B. nickel balls filled perforated tube or screen tube made of titanium (not shown in detail), in which continuously nickel balls are tracked. The (auxiliary anode) rods 30, 30a, 30b, 30c could also be provided with differently shaped, e.g. B. the above-mentioned nickel substrates are filled or alternatively z. B. consist entirely of a solid tube of pure nickel, which would completely dissolve over time and is therefore typically renewed from time to time to achieve consistent results when plating a cathode.

The advantages of the construction according to the invention of the first exemplary embodiment (FIG. 6) with further slightly modified variants (FIGS. 7 and 8) and a second exemplary embodiment (FIG. 9) compared to the prior art (FIG. 5) are shown schematically below with reference to FIGS explained.

FIG. 5 first shows a roughly schematic plan view of a construction according to the prior art, in which it can be seen how a wall part FW opposite an anode wall 20 of a fin wall FW (as cathode FW) was electroplated. For the sake of simplicity, the wall part FW consists, without restricting the invention thereto (as in the following illustrations), representatively only of an "nth" pipe R _n , which has an "nth" connecting web S _n with a further "n+ 1st" pipe R _n + i is connected or welded. In the operating situation shown, a current flows, as usual, between the anode wall 20 and the wall part FW of the fin wall FW through the liquid, which is not shown here. The electric field E forms the electric field lines E, indicated here schematically, which symbolize the (particle or) ion flow or current flow from the anode wall 20 to the wall part FW. This flow of ions leads to the wall part FW of the fin wall FW being coated, since the particles are deposited there.

Since the surface O of the wall part FW facing the anode wall 20, in particular the tube R _n , the connecting web S _n and the further tube R _n +i, does not run exactly parallel to the fin wall FW at a continuously constant distance 3A-FW to the anode wall 20, the distance and thus the density of the electric field lines E, starting from the two pipe crests (i.e. the most protruding ones). Points) of the tubes R _n , R _n +i observing toward the middle to the connecting web S _n , which in turn runs parallel to the anode wall 20 .

On the one hand, due to the different current densities of the electric field lines E with the same exposure duration, different material deposits (separation or deposition of the metal ions) occur on the wall part FW' of the fin wall FW and thus different layer thicknesses in the area of the tubes R _n , R _n + i or the connecting bridge S _n . On the other hand, the electric field lines E, which leave the anode wall 20 at the level of the connecting web S _n , are slightly curved towards the respective tube R _n , R _n +i, since the electric field E passes through the protruding semicircular tube profiles of the tubes R _n , R _n +i is influenced or distracted accordingly. As a result, more metal ions are deposited or precipitated on the tubes R _n , R _n +i than on the connecting web S _n located between them. As has been shown by tests and practical experience, this different layer thickness also has a corresponding effect on the distribution of hardness, thermal conductivity and the service life of the fin wall FW in operation.

As already described above, according to the preferred first exemplary embodiment of the invention, an auxiliary anode 30 is positioned between the anode wall 20 and the wall part FW of the fin wall FW at the level of each connecting web S _n (see FIGS. 1 to 4). As a variant of this auxiliary anode 30, FIG. 6 shows a rod-shaped auxiliary anode 30a with a round cross section. First of all, as already mentioned above, this ensures a shortened distance of the electric field lines E, since the metal ions flow or flow in bundles or increasingly starting at the respective position of the auxiliary anode 30a (after reaching the auxiliary anode 30a) to the wall part FW of the fin wall FW. In addition, the current density also changes, as a result of which the electric field lines E of the electric field E run much more straight and more evenly both to the two lateral tubes R _n , R _n +i and to the middle connecting web S _n . This achieves a more uniform deposition over the entire wall part FW of the fin wall FW.

In a second alternative variant of the first exemplary embodiment according to FIG. 7, a further auxiliary anode 30b with an oval cross section is shown. This auxiliary anode 30b is arranged in such a way that the large semi-axis of the elliptical or oval cross section of the auxiliary anode 30b is perpendicular to the connecting web S _n or the transverse direction QR of the fin wall FW. The doing perpendicular from a short side of the oval of the Auxiliary anode 30b to the wall part FW' of the fin wall FW electric field lines Eb also run slightly curved or arc-shaped to the wall part FW' of the fin wall FW due to the curved surface. The shape of the cross section of the auxiliary anode 30b is therefore already slightly based on the surface O of the wall part FW facing the anode wall 20, so that the metal ions are more evenly separated or deposited on the wall part FW of the fin wall FW, since the opposite surfaces run parallel to each other in a first approximation.

In order to further match the opposing surfaces to one another, the auxiliary anode 30c in a third alternative variant of the first exemplary embodiment according to FIG. 8 has a somewhat elongated octagonal (or octagonal) cross-section. At least the contour of the side facing the wall part FW′ of the fin wall FW (preferably both sides symmetrically, as shown in FIG. 8) of the auxiliary anode 30c is essentially adapted to the contour or the surface O of the wall part FW of the fin wall FW. As shown here in Figure 8, the two edges of the auxiliary anode 30c (pointing to the curved tube walls of the tubes R _n , R _n +i) run in a straight line, i.e. only essentially or in a first approximation parallel to the curved tube walls of the tubes R _n , R _n +i. Preferably, these two edges of the auxiliary anode 30c can be concave between the corners, ie arcuately following the course of the tube parallel to the curved tube walls of the tubes R _n , R _n +i of the wall part FW′ of the fin wall FW.

According to a second exemplary embodiment of the invention according to FIG. 9, the construction according to the invention is designed without an auxiliary anode 30, 30a, 30b, 30c. In this case, the anode wall 20 itself is designed in relief, ie it comprises a relief or a contour 20f protruding positively in sections from the plane 20E of the anode wall 20 . The surface 20f of the anode wall 20 facing the wall part FW′ of the fin wall FW essentially corresponds to the surface O of the wall part FW facing the anode wall 20, in particular of the tube R _n , the connecting web S _n and the further tube R _n +i , the fin wall fw In other words, the surface 20f (i.e. the positive relief) of the anode wall 20 could be inserted or pushed into the surface O (i.e. the negative relief) of the wall part FW of the fin wall FW in a form-fitting manner if the two walls 20, FW were pushed together. By means of the walls 20, FW or surfaces 20f, O of the walls 20, FW, which thus run at a constant distance 3A-FW from one another the distance of the electric field lines E, Ed is the same everywhere along the common, opposite course of the wall. This results in almost identical layer thicknesses along the course of the wall shown here in the transverse direction QR of the wall part FW. However, the same also applies to the course of the wall in the longitudinal direction LR of the wall part FW (see FIG. 1 downwards or in FIG. 9 into the plane of the drawing).

Contrary to the exemplary embodiment shown, the dimensions of the relief or the contour 20f of the anode wall 20, ie in particular its depth perpendicular to the transverse direction QR, are not adjusted to the exact depth of the fin wall FW, ie the distance from the apex of the tube to the connecting web S _n , within the scope of the invention. limited. Rather, it can also be sufficient to form the anode wall 20 with a smaller scaled relief in a mirrored form of the fin wall FW.

Another possible variant of how the surface of the anode wall 20 can essentially be adapted to the wall part FW′ of the fin wall FW is shown in FIG. In this case, on the anode 20 on a surface facing the fin wall FW, two spaced-apart perpendicular, web-like protruding anode fins 22 are attached, here z. B. welded. The anode fins 22 are each arranged in such a way that they each protrude into a central area between adjacent tubes R _n , R _n +i during the galvanic nickel-plating of the wall part FW of the fin wall FW. The two anode fins 22 can also be seen here essentially as a double web 22 which, viewed as a whole, is located essentially in the middle opposite the connecting web S _n between the adjacent tubes R _n , R _n +i.

As already mentioned above, the electric field in the galvanic bath B is controlled by the anode fins 22, in particular in the areas on the face side of the anode fins 22 at the inner corners between a web S _n and a respective adjacent tube R _n , R _n + i, influenced in such a way that the nickel substrate spreads and deposits more uniformly along the wall part FW' of the fin wall FW on the fin wall FW. Specifically, the electrical field in the galvanic bath B is slightly increased locally in the area of the inner corners, so that, viewed overall, an even more uniform coating can be achieved.

Finally, it is pointed out once again that the devices described in detail above are merely exemplary embodiments can be modified in various ways by those skilled in the art without departing from the scope of the invention. In particular, a combination of the exemplary embodiments described is also possible, ie a contour adaptation of the anode with the additional use of an auxiliary anode arrangement. Furthermore, the use of the indefinite article "a" or "an" does not rule out the possibility that the characteristics in question can also be present more than once.

Reference List

1 galvanic bath

2 pool walls

3 pelvic floor

4 pool edge

20 anode / anode wall

20E plane of the anode wall

20f surface facing the fin wall / contour of the anode

21 anode retaining bracket

22 anode fins / double bridge

30, 30a, 30b, 30c auxiliary anode arrangement / auxiliary anode(s)

31 clamping element

40 fixture/auxiliary anode frame

40f retaining tabs

41 longitudinal struts

42 cross braces

43 adjustment elements / slot cut-outs / slots

45 coupling element

45' blind plug

46 coupling bar

46g external thread

47 collet

47g internal thread

48 plugs

49 sealing rings

50 spacers

60 Connection frame auxiliary anode - anode

3A-FW Distance fin wall - anode / anode wall

3A-HA distance anode - auxiliary anode

B Width of the wall part of the fin wall

E, Ea, E , Ec, Ed electric field / electric field lines

F Liquid surface / liquid level

FW fin wall / cathode

F wall part of the fin wall

Length / height of the wall part of the fin wall LR Longitudinal / Longitudinal Extension

O Shape of the surface of the fin wall facing the anode

P cathode position / fin wall position

QR transverse direction/direction of transverse extension Ri, R2, R5, Rn, Rn+1 tubes

REIA, RE2A, RESA first tube ends

REIB, RE2B, ■ ■ ■ , RESB second tube ends

Si , S2, , S5, Sn connecting bridges

Claims

26 patent claims

1. A method for the galvanic nickel-plating of a fin wall (FW) which has at least one wall part (FW) consisting of several tubes (Ri, R2, ..., R5) running next to one another in a longitudinal direction (LR) and between adjacent tubes ( Ri, R2, ..., R5) arranged connecting webs (Si, S2, ..., S5) is formed, in which the fin wall (FW) as a cathode (FW) in a galvanic bath (1) is introduced, in which an anode (20) is located at a distance (3A-FW) from the fin wall (FW), an auxiliary anode assembly (30, 30a, 30b, 30c) being disposed between the fin wall (FW) and the anode (20), and /or wherein the anode (20) on a surface (20f) facing the fin wall (FW) is at least partially adapted to the shape of the surface (O) of the fin wall (FW) facing the anode (20).

2. The method according to claim 1, wherein the auxiliary anode arrangement (30, 30a, 30b, 30c) comprises at least one group of rod-shaped auxiliary anodes (30, 30a, 30b, 30c), these auxiliary anodes (30, 30a, 30b, 30c) each having one Connecting web (Si, S2, ..., S5) of the fin wall (FW) are assigned, and in each case at a distance in front of the respective connecting web (Si, S2, ..., S5) parallel to the longitudinal direction (LR) of the connecting web (S1 , S2, ... , S5).

3. The method according to claim 1 or 2, wherein the auxiliary anode arrangement (30, 30a, 30b, 30c) is coupled to the fin wall (FW) by means of a holding device (40) and is introduced with this into the galvanic bath (1).

4. The method according to claim 3, wherein a distance of the auxiliary anode arrangement (30, 30a, 30b, 30c) to the fin wall (FW) is adjusted by means of the holding device (40).

5. The method according to any one of the preceding claims, wherein at least one group of the auxiliary anodes (30, 30a, 30b, 30c) of the auxiliary anode arrangement (30, 30a, 30b, 30c) is mechanically coupled to one another.

6. The method according to any one of the preceding claims, wherein a contour (20f) in a sectional plane of the anode (20) on a surface (20f) facing the fin wall (FW), preferably in the area opposite a connecting web (Si, S2, S5) of

Fin wall (FW), is adapted essentially to a contour (O) of an anode (20) facing surface (O) of the fin wall (FW).

7. The method according to any one of claims 1 to 6, wherein web-like protruding anode fins (22) are attached to the anode (20) on a surface facing the fin wall (FW), preferably perpendicularly, the anode fins (22) are particularly preferably arranged in such a way that they each protrude into a central region between adjacent tubes (Ri, 2, . . . , 5) during the galvanic nickel-plating of a fin wall (FW).

8. A device for galvanic nickel-plating of a fin wall (FW), comprising a galvanic bath (1) with an essentially in a plane (20E) extending anode (20) to the fin wall (FW) as a cathode (FW) at a defined To arrange the cathode position (P) at a distance (3A-FW) from the anode (20) in the galvanic bath (1), and with a power source which is connected at one pole to the anode (20) and at another pole to the Fin wall (FW) can be connected in order to generate a current flow from the anode (20) to the cathode (FW), the device comprising an auxiliary anode arrangement (30, 30a, 30b, 30c) which, in normal operation, is placed between a galvanic bath ( 1) arranged fin wall (FW) and the anode (20), and/or the anode (20) of the device is arranged on a surface (20f) of the anode (20) pointing to the intended cathode position (P) of the fin wall (FW) at least in some areas to the shape of the anode (20) during operation facing surface (O) of the fin wall to be electroplated (FW) is adapted.

The device of claim 8, wherein an auxiliary anode (30, 30a, 30b, 30c) of the auxiliary anode assembly (30, 30a, 30b, 30c) comprises at least one of the following materials or an alloy of different ones of these materials: platinized titanium, titanium, nickel , Tungsten, Inconel, Incoloy, Zircon, Zircaloy.

10. The device according to claim 8 or 9, wherein the auxiliary anode arrangement (30, 30a, 30b, 30c) is electrically insulated from the current source or current flows through it.

11. Device according to one of claims 8 to 10, comprising a mounting device (40) to couple the auxiliary anode arrangement (30, 30a, 30b, 30c) to the fin wall (FW) to be electroplated.

12. The device according to claim 11, wherein the mounting device (40) has at least one coupling element (45) for coupling to the fin wall (FW), wherein the coupling element (45) preferably comprises a plug (45) which in one end (REIA, REIB, RE2A, RE2B, ... , RESA, RESB) of a tube (Ri, R2, ... , R5) of the fin wall (FW) can be inserted and clamped there and the tube (Ri, R2, .. . , R5) tightly closed at this end (REIA, REIB, RE2A, RE2B, ..., RESA, RESB).

13. The device according to claim 12, wherein the mounting device (40) comprises at least two coupling elements (45), each with at least one plug (45), wherein the plugs (45) are arranged relative to one another when used as intended such that they are in opposite ends (REIA , REIB, RE2A, RE2B, ..., RESA, RESB) of the same tube (Ri, R2, ..., Rs) can be inserted, the auxiliary anode arrangement (30, 30a, 30b, 30c) being arranged such that the rod-shaped Auxiliary anodes (30, 30a, 340b, 30c) running in a longitudinal direction (LR) of the tube (Ri, R2, ..., Rs) parallel to the tube (Ri, R2, ..., Rs) between the two coupling elements ( 45) are held.

14. The device according to claim 12 or 13, wherein the mounting device (40) comprises adjusting elements (43), preferably slot recesses (43), for the coupling element (45), by means of which the auxiliary anode arrangement (30, 30a, 30b, 30c) overall in one Direction to or away from the fin wall (FW) is slidably mounted.