DE2404097A1 - METHOD AND DEVICE FOR APPLYING A FINALLY DISTRIBUTED POWDER CONTAINING COMPOSITE COATING TO OBJECTS - Google Patents

Description

SUZUKI MOTOR COiIPANy LIMITED

300, Takatsuka, Kaminura, Hamana-Gun, Shizuoka Prefecture Japan

Method and device for applying a finely divided Composite coating containing powder on objects

The Toe invention relates to a method and apparatus sun applying a finely divided powder containing it Composite coating on objects using an electroplating process by means of a conventional lethal plating or electroplating bath, in which electrically non-conductive powder is finely divided, is carried out to form a coating containing the powder to train

Fine dispersed silicon carbide (SiO) particles in, for example, a nickel deposit formed by electroplating, improve the abrasion resistance of the finished surface, which is, for example _, desirable for the inner surfaces of internal combustion engine cylinders. Such electroplating is achieved by using the SiO powder evenly and finely distributed in the Uikkelplattierbad, the object to be plated as a cathode in the bath opposite one as an anode

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Berlin office

Telephone: 885 6037/886 2382
Wireword: Invention Berlin

Bank account: W. Meissner, Berliner Bank AG, Depka36 Berlln-Halensee, KurfUrstendamm 130, account no. 95 716

Postal checking account:

W. Meissner, Berlin West 12282

üenenderi 1, 'ickelstab immersed and daiui -siiieii eiits ;; - r c-rush occurred stroa. through, these oillektroden lä.it (see for example lie Ja-Pat.-Publ _o Lr. 3806/1961 ) *

Electroplating in the electroplating bath read in powder contained in a thorough, finely divided state at all times, otherwise Ic will receive an identically designed coating will. To ensure thorough distribution, Various kinds of proposals have been made. These include mechanical rocking or shaking of the plating bath, a vibration of the object to be plated and a stirring of the bath with air bubbles emerging from "at the bottom of the Plating container located, with a plurality of openings provided with air lines emerge. Among these usual Method, the mechanical shaking can distribute the powder, difficult evenly in the plating container, as the container are usually too big. That is why one generally has the mechanical shaking of the bath with a vibration of the object to be plated coupled. This combined process has the disadvantage of low productivity, because a rather voluminous · equipment for the production of the Vibration is required.

For these reasons, the method of stirring has become more popular of the bath with the help of air bubbles, because this does not require large equipment, the initial ones Investment costs are low and the plating bath is stirred evenly. However, the benefits of stirring are available due to air bubbles in some cases disadvantages compared to the oxidation of the surface of the base material to be clad and are based on the consequent reduction in the quality of the plating. Another disadvantage is that the plating bath itself is oxidized by the air bubbles, resulting in an unfavorable change in the bath composition results.

409833/0939 " ³ "

The invention is based on the object, dieee tile parts Procedure to eliminate.

The aim is to create a method and a device for a finely divided powder-containing composite coating, v / obei a powdery material in a circulating Plating solution is evenly finely distributed, with a coating or electroplating container in the circuit of the plating solution is provided, and it is possible to apply a uniform plating layer on a plate in the plating bath or to form a uniform coating while the plating solution is constantly renewed as it circulates around one Avoid consumption or dilution of the ions in the bath. Here, the current density should be able to be increased by one to maintain the highest possible plating efficiency, and the particle size and concentration of the powdery material mixed into the bath, e.g. SiO, in a suitable Wise controllable, so that the quality of the coating and the efficiency can be increased.

Furthermore, the method and the device should be suitable for a composite coating containing finely divided powder at the same time on a number of cylindrical or ring-shaped To apply objects with the aim of high productivity in the plating process.

The stated object is achieved with the means and measures according to the invention specified in the claims and in the following description of exemplary embodiments.

Fig. 1 shows schematically a device according to the invention for applying a composite coating containing finely divided powder.

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2 and 3 show vertical sections through electroplating baths with cylindrical or ring-shaped objects to be plated.

Pig. Figures 4 and 5 are front and side views of a typical facility having a plating and overflow tank.

In the upright, cylindrical coating or electroplating container 1 are an anode 2 and parallel to it an object 3 to be plated in an upright position at a distance from one another arranged. The object 3 is electrically connected to act as a cathode. Around the upper outer circumference of the electroplating container 1 is a liquid-tight return or overflow container 4 with a larger outer diameter attached as the container 1. In the lower part of the electroplating tank 1, a distributor plate 1a is in a horizontal position Layer attached, which consists of a stainless steel grid and serves to the powder in the plating bath as to distribute fine particles evenly. The useful mesh size of the grid can range from 0.1 to 1.1 cm lie.

Storage or storage containers 5, 6, 7 are arranged side by side to container 1, which provide a solution for a pre-nickel plating, contain a composite coating solution and wash water. The composite coating solution in the reservoir 6 contains powder of a very hard material such as silicon carbide (SiG) or tungsten carbide. In addition to such a component can use the composite coating solution for the intended application appropriate other substances may be added, e.g. the oxide or carbide of a metal, e.g. aluminum oxide, Titanium oxide or titanium carbide, which are insoluble in the electrolyte and water, or fine particles of a solid lubricant or an organic polymer such as carbon fluoride,

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Fluorocarbon polymer (fluorocarbon polymer), molybdenum disulfide or synthetic rubber,

The liquids from these containers 5, 6 and 7 are through a preceding operation of the bottom opening 15 of the electroplating container 1 via lines S, 9, 10 and 11. Valves 5a, 6a, 7a are arranged in lines 8, 9, 10. In the line 14 connected to the bottom opening 15 of the container 1 there are a line 14 driven by the motor 13 Feed or circulation pump 12 and a valve 14a.

Each of the liquids, such as the composite coating solution fed to the bottom of the container 1, flows upward and overflows into the overflow or recycle container 4. At the bottom of this container 4 an opening 3a is provided, to which a return line -16 connects, which is branched into three lines 17, 18 and 19, which each lead to the storage containers 5 * 6, 7. In this way, the overflowed liquid is fed back to the storage container 5 "6, 7" In the branch lines 17s 18? 19 mutually independent valves 5b, 6b, 7b are arranged. An auxiliary line 20 and a drain pipe 21 are connected via valves 20a, 21a, "Ms auxiliary line 20 is arranged such that liquid can be supplied from the pump 12 directly to the overflow tank 4 ₀

To regulate the flow rate and the flow rate of the plating solution rising in the container 1, is preferably a variable displacement pump 12 is used. If necessary, it will be fitted with a flow control valve 12a, which replace the existing valve 14a can.

When the object to be coated 3 is selected from a variety of cylindrical or ring-shaped objects 22 (Fig. 2),

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so these are stacked on top of one another, with their axes aligned. A long anode 2a is formed along the center line or axis of the cylindrical hollow body 22a thus formed inserted vertically and electrically connected so that the objects 22 to be plated are the cathodes. To this · Both the inner and outer surfaces of the cylindrical or ring-shaped workpieces 22 can be coated with a composite be provided with a high degree of efficiency

The 3? 3 shows another embodiment of the invention object for the effective plating of ring or cylindrical objects 22, here with "annular Seals 23 are alternately stacked and centered, the seals 23 made of an acid-resistant material, such as silicone rubber. Along the axis or center line of that formed in this way. Hollow body 22a, a long anode 2a is suspended vertically · Sin with the line 14 (Pig. 1) funnel-shaped bottom part 15a to be connected is on the lowermost of the articles 22 in the stack over the lowermost Seal 23 liquid-tight "attached. Since the objects to be plated 22 with the seals in between 23 in one leakproof. Stacked way, serves the cylinder obtained in this way as an electroplating or coating container. The individual objects 22 thus act as the cathodes, and the inner surfaces can be provided with a Yerbund coating at the same time. This embodiment can do so be modified that treated workpieces in the form of flat plates in addition to the objects 22 or in their place can be.

Like the Pig. 4- and 5 show the plating and overflow tanks 1 or 4 can be mounted in a suitable manner on a common support frame 24. The anode 2 and the too Plating objects 3 can also either on the over-

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barrel 4 or be held on the support frame 24 via suitable support means (not shown).

Electroplating generally has the disadvantage of one over other methods such as melt flow plating lower plating speed. To increase this, the application of a high current density must be made possible without giving up any current efficiency. However, since the Bath composition and other operating conditions are constant in many cases, is the range of current density that ei ne good plating quality can be maintained, limited.

In this context it should be noted that the critical current density for electroplating is given by:

_{Ie =} μ

S (1 -

Herein is:

Ie = critical current density [A / dm J

η = valence of the clad metal

P = Faraday's constant [96,500 OJ

D = diffusion coefficient [cm / secj

C = metal residue concentration [mol / cnrj

£ = thickness of the diffusion layer [cm]

q £ = transport number of metal ions

If Ie in equation 1 is to be increased while maintaining the same bath composition, then either D or oC increased or <f decreased because n, P and 0 are constants. Although the diffusion coefficient D and the ion transport number «sC increase with the increase in the bath temperature

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can become larger, the temperature increase has its limit because of the decomposition effect on the bath. It follows from this that the thickness i of the diffusion layer is the only controllable variable.

a laminar flow is assumed, then the strength is the diffusion layer:

= 2.91. x (JiLi.) ^1/2 / (£.) ^1/3 (Eq. 2)

Herein is:

V * kinetic viscosity [ePj

χ = position of the test body in the direction of flow j_ ^cm J μ. = Flow rate of plating solution fcm / sec] D = diffusion coefficient [cm

[cm / secj

If the thickness of the diffusion layer is to be reduced in Equation 2, the flow rate of the plating solution must be taken into account. In equation 2, £ - K. juC 'where K is a constant, and it follows from this that only the flow rate needs to be increased.

As mentioned earlier, the bath composition and other operating conditions are often predetermined for electroplating. Therefore, sufficient care must be taken if these conditions are changed. In order to be able to improve the electrodeposition rate without a noticeable change in any of these conditions, it is important to perform the plating process efficiently with a high current density. In order to increase the current density without affecting the bath composition or any other factor, it is only necessary to increase the flow rate because, as already noted, equations 1 and 2 have the relationship Ie in their composition. cC. K. ^ ' where K is a constant

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is. In view of this, a variety of routes have been developed Increase in flow velocity taken. For example, in the relevant field, the so-called jet flow method for high speed has become a compulsory one Feeding of the plating solution, and the so-called parallel flow method, whereby a plating solution at high speed in a horizontal flow flows to the workpiece, suggested and tried »

The foregoing is based on the assumption that the flow of the plating solution is laminar. However, the method according to the present invention also produces satisfactory results when the bath is in the turbulent flow region. This is shown, for example, by a test of a composite coating, which was carried out with a plating solution containing 150 g / l of silicon carbide powder, a turbulent flow with a Reynolds ¹ see number Re = 28,000 at a flow rate of 60 cm / sec and a current density of 70 A / dm was applied. It was found that the current efficiency achieved was 100 % , that the silicon carbide content of the coating applied was 5% and that the micro Vickers hardness of the coating was 580. It was found that a plating coating having a fine appearance could be obtained in the manner described.

In composite plating in the area of turbulent flow, as in the area of laminar flow, the critical Current density can be increased by increasing the flow rate of the plating solution. In the pail of the turbulent flow the strength of the diffusion view is given by equation 3:

- ₂₇ , a * (X) * ^{/ 5} x. ^1/5 / _(f )

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From equations 3 and 1 it follows *

I 4/5

Ie = K. JJi '

where K is a constant.

In ordinary plating baths it appears that the jet stream and parallel flow processes pose relatively few problems in the plating process. For composite coating solutions that Contain materials that are to precipitate separately and finely divided, as is the case according to the present invention Pail, however, these methods have disadvantages due to uneven stirring or agitation and uneven Distribution of the material to be deposited

These problems are completely eliminated by the method according to the invention eliminated, after which the plating solution can flow upward in the vertical direction. Bs is thus possible, the flow velocity to increase and perform plating at holier speed.

When plating with conventional container arrangements, it is customary to stir the plating bath or the objects to be plated vibrate, as previously mentioned, aiming at high speed plating by reducing the thickness of the diffusion layer in implement the! Eat. For practical purposes, this is the maximum achievable Current density at most a few 10 A / dm. In contrast, the present invention is by a small one Distance of 0.2 to 10.0 cm between the anode and cathode and by an upward current of high speed with 0.4 to 400 cm / sec of the plating solution between and along-the Electrodes characterized, which results in a high current density according to the invention, with conventional container plating processes impossible to achieve »In this way, plating is carried out much faster than before. This

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High speed plating is both laminar as possible in the turbulent flow area.

The process of composite plating is now carried out with the aid of the Device according to the invention "described.

First, all valves are closed and heaters, for example immersion heaters not shown, are placed in the container 5 containing the nickel plating solution and the container 6 containing the composite coating solution. The heater to bring the plating solutions in the containers 5 and 6 at predetermined temperatures, preferably for the plating solution in the container 5 50-3 ⁰ C, and preferably for the solution in the container 6. 57 - 3 ⁰ C "be Then, a pre-treated, The object 3 or 22 to be plated is placed in the electroplating container 1. The object to be plated has been pretreated in order to support the secure adhesion of the composite coating to the surfaces of the base material If the parts are cylindrical or ring-shaped, they are, as shown in Pig. 2 and 3, -stacked into a single object ·

These preparatory steps are followed by a pre-nickel plating or a conventional nickel plating of the object by means of a plating bath that is free of hard particles. This as Plating designated as pre-nickel plating is intended to serve the same purpose as the pretreatment mentioned above, the plating bath is composed:

780 - 46 g / l of a 60% nickel sulfamate solution, 11.7 - 0.7 g / l nickel and 45 - 5 g / l boric acid. At the beginning the valves 5a, 5b, 14a and 20a are opened and the pump 12 is put into operation so that it brings the pre-nickel plating solution into the electroplating tank 1 - from the bottom upwards. Thereafter, the valve 20a is closed again, and it is, either

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the open position of the valve 14a is regulated or the flow control valve 12a, if present, is "actuated in order to control the flow rate of the pre-nickel plating solution in a suitable manner" through the anode 2 and the object 3 "or A current of preferably 2-10 A / dm is allowed to flow for a predetermined period of time (5-20 min) in order to obtain a pre-nickel plating coating. After this Yorplattieren the current flow and the pump 12 are switched off _o Then, the valve 5a is closed while the other valves Ha, 20a and 21a are opened to the remaining Vorvernickelungslösung deducted. The result is a nickel coating of 1 - 20 μ. Starch that has been deposited on the surface of the base material, free of hard particles.

After the pre-nickel plating, the first rinsing process is carried out. The valves 5b and 21a are closed while the valves 7a, 7b opened and the pump 12 started up in this way, water is fed from the container 7 into the electroplating and overflow containers 1 and 4, respectively, whereby the to Plating objects 3 or 22 and also the pipe system are washed. After cleaning, the pump 12 is stopped, the valve 7a is closed and the valve 21a is opened to withdraw the remaining rinse water from the system. Finally the valve 7b is closed

Composite plating is the next step. For this purpose, the valve 21a is closed, the valves 6a, 6b are opened and the pump 12 is started in order to generate an upward flow in the electroplating container 1 for the composite coating solution. The rate of flow of the composite coating solution at 0.4-400 cm / sec is controlled by closing valve 20a and either regulating the opening of valve 14a or by using the flow control valve 12a. The composite coating solution is composed of 826-46 g / l of a nickel sulfamate solution, 15.1 ^± 1.7 g / l nickel chloride, 45 ¹ ½ g / l

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Boric acid, 2.9-0.7 g / l sodium acarine and 150 g / l silicon carbide. No organic hardener is used. Using a current density of 15-300 A / dm for a predetermined time, the article 3 or 22 is completely plated. The plating coating so obtained can range in thickness from about ten to several thousand microns. The thickness of the coating is usually between about 100 and 600 μ. “When the coating is finished, the power supply is interrupted and the pump 12 is put out of operation. Then valve 6a is closed and the other valves 14a, 20a and 21a are opened to withdraw the remaining composite coating solution from the piping system.

The composite coating is followed by a second and final rinse. First the valves 6b, 21a are closed, while the Valves 7a, 7b are opened. Then the pump 12 is started to bring water into the plating and overflow tank 1 or »4 for thorough cleaning of the object provided with a composite coating and the pipe system to promote. After this last flush, the pump 12 is stopped, the valve 7a is closed, and the drain valve 21a is opened to draw off the remaining rinse water. Finally, the valves 14a, 20a and 7b are closed.

The same procedure applies to the embodiments of the Pig. and 3 »where a plurality of cylindrical or annular Objects receive a composite coating at the same time.

Those with a Yorvernickel and a composite coating in Objects provided in the manner described are then removed from the device

Examples of composite coatings made by the method of the invention are given below.

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Examples

(1) Critical current density

If the current density remains the same, the current yield is the ' larger the higher the flow rate of the plating solution isto This relationship is shown in Table 1 in a typical way »

Table 1 Relationship between the flow rate of the plating solution and the current efficiency (current density 20 A / dm ² )

Flow rate (cm / sec) 0.47 1.7 4.2 current efficiency (#) 96 97 100

The current density for a lOOfiige current yield - or the critical current density - is achieved by increasing the flow rate of the plating solution. To use a high current density, a correspondingly increased flow rate is required.
Table 2 shows this relationship.

Table 2 Relationship between critical current density

and flow rate (current efficiency 100 i>)

critical current density (A / dm ² ) 15 20 25 30

Flow velocity _v >42>42>65> 9.0

(cm / sec) ''''.

As can be seen in Table 2, a current density of more than 30 A / dm can be used if the flow rate

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plating solution speed to 9.0 cm / sec or more is increased.

(2) Hardness of the composite coatings

The hardness of the experimentally formed plating coatings was determined with a Vickers micro hardness tester. The hardness the coatings obtained according to the invention is not through the Flow rate of the plating solution but is dictated by the current density applied. That becomes from Table 3 evident.

Table 3 Relationship between current density

and hardness
(Flow velocity 4.2 cm / sec)

Current density (A / dm ² ) 15 20, 25 I 30

Hardness (mHV 0.2) 531 . 559; 573 | 590

If a current density of 20 A / dm is used in the usual container plating, the hardness obtained is about 550, doho, the value is only slightly different from that according to the invention received value. The hardness of the plating coating produced according to the invention, however, depends on that used Current density. Thus, the hardness can be freely or arbitrarily controlled by having a high current density when using a plating coating with a high degree of hardness is desired, or a low current density if only a low degree of hardness is required, applies.

(3) Cathodic current efficiency

The cathodic current yield drops as the current density increases, which is indicative of the precipitation of a greenish substance, obviously

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bar nickel hydroxide on the cathode, this one Waste can be avoided by accelerating the flow of the plating solution. However, this can happen once at the cathode deposited nickel hydroxide or the like. not by increasing the flow velocity at any point of the Plating process are removed; a high flow rate must already be used at the beginning of the plating process will. This means that it is important to increase the flow rate when using a high current density should come, or in other words, that a high current density is applied by increasing the flow rate can be. This relationship is illustrated in Table 4.

Table 4 Effects of flow velocity

and current density ·., on the cathode current efficiency

Cathode current efficiency (%) Current density (A / dm *)

15 20 25 30

Flow velocity: 97 96 93 88 0.47 cm / see 100 100 95 93 4.2 cm / see

(4) Silicon carbide contents of composite coatings

Aluminum objects have been provided with a SiC composite coating and checked for their carbon content. For this purpose, part of the coatings is peeled off and burned in an O ^ stream, so that SiC is consumed, whereby its amount can be measured. 'Then were based on the so determined Values determined the silicon carbide content.

The plating solution, the silicon carbide content of 3 - 4% in the plated coatings for the usual container plating have been found in the present invention in

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Praris was used and similar results were obtained.

As "has been described, the invention allows over conventional Method using a higher current density. This leads to a higher silicon carbide content in the obtained Coating. This allows the silicon carbide content of a composite coating to be adjusted by controlling the current density to be applied will. Table 5 shows this relationship.

Table 5 Relationship between silicon carbide content

and current density
(Flow velocity 4.2 cm / sec)

Current density (A / dm ² ) 15 j 20; 25th

SiO content of the coating (#) 3.0 ^: 3.7 3.7

30 4.0

(5) Dispersibility of silicon carbide in plated coatings

Clad composite coatings were embedded in resin, sanded and polished with emery and buffing. The distribution of silicon carbide particles in the base materials was examined microscopically. In with a composite cover

at current densities of 20 A / dm or less provided test pieces the distribution of silicon carbide particles was easy uneven compared to conventional container plating; some Ückel surfaces showed poor distribution the silicon carbide particles.

Composite coatings formed at current densities of 25 A / dm and above in accordance with the invention exhibited uniformity Distribution of silicon carbide particles in the nickel base materials. This tendency became all the more evident when

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the distribution plate 1a was housed in the lower part of the electroplating tank 1 «. When the composite coating solution is motionless is held, the larger the tendency of the particles, the smaller the particle size of the silicon carbide to accumulate is. For example, in a solution that was left in cows for a few days, the silicon carbide particles were in Accumulated form a mass. Those in the return line for the distribution plate 1a built into the composite coating solution is used to evenly distribute the mass into separate, discrete, fine particles.

Examples of composite coatings with fine particles other than Silicon carbide, namely with tungsten carbide, aluminum oxide, titanium dioxide, Titanium carbide, carbon fluoride, molybdenum disulfide and synthetic rubber, are given below. The Search were carried out under conditions which usually required the use of currents exceeding 20 A / dm allowed.

(6) composite coating with tungsten carbide (WC)

Particle size: 0.1-10 μ.

Concentration: 10 - 150 g / l

Flow velocity: 20-300 cm / sec

Current density: 20 - 300 A / dm ²

(i) Critical current density

As already mentioned, for the same current density, the higher the flow rate of the plating solution, the greater the current efficiency. Taking. If a current yield of $ 100> is assumed, the relationship to the flow velocity is as shown in Table 6.

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Table 6 Relationship between critical

Current density and flow rate of the plating solution (current efficiency 100 fi)

critical current density
! (A / da ² ) ^{20 25 30}

^; Flow velocity

'■■ (cm / sec)> 21.8 > 32.0> 45.0

(ii) Hardness of the composite coating

Unlike plating with silicon carbide, an increased current density does not lead to a correspondingly increased hardness of the plating coating. This is shown in Table 7.

Table 7 Relationship between current density

and hardness (flow velocity 45 cm / sec)

Current density (A / dm ² ) 20 25 30 ' Hardness (mHV 0.2) 546 550 550

(iii) Tungsten carbide content of the composite coating In the same way as silicon carbide, the tungsten carbide content of a composite clad coating tends to increase an increase with an increase in the current density. This relationship can be seen from Table 8.

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Table S ratio swiseiieii current density

and tungsten carbide Mgelialt (Flow velocity 45 cm / seo)

! Current density (A / dm *)

; Flat & egg ^: 3 dss plating

ifbersugs (f £)

Terisuii & uberzug ait Alissain

file size
Concentration:
Flow velocity current density s

(i) Critical current density

Its increased flow rate of a plating solution "brings about a 100% Stroaauslseate and an increased critical Current density-, the relationships are in the! Tables and 10 reproduced »

Table 9 Relationship between flow rate

speed and current yield (current density 20 A / dm ² )

Flow rate 4.2 ^; 6.1 (em / sec)

Current efficiency (#); 98 ^: 100

!
! 20th ; 25 30 3.8 4.0 4.1 CAI ₂ O ₃ ) 0.1 - 10 / * » 25th - 200 g / l - 400 csa / sec 20th - 3G0 A / dm ²

Table 10 Relationship between critical

Current density and flow velocity (current yield 100 ^)

critical current density (A / dm) 20 25 30 flow velocity (cm / sec)> 6.1> 9.2 --13.5

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(Flow velocity 13.5 25th 30] cm / sec) 20th 5.0 5.3 4.8 553 565 550

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(ii) Hardness and Alumina Content of Yerbund Coating The higher the current density, the greater the alumina content of the clad coating, with the result that the hardness of the coating also becomes greater. These relationships are shown in Table 11 _β

Table 11 Relationship between current density,

Hardness and AlpQ-z content

Current density (A / dm)

Al ₉ Q ,, - content of the * ^p coating

Hardness (mHV 0.2)

(8) Composite coating with titanium dioxide (TiOp)

Particle size: 0.1 - 5 jul

Concentration 10 - "100 g / l

Flow velocity! 3 - 300 om / sec

Current density: 20 - 300 A / dm ²

(i) Critical current density

With a current density of 20 A / dm, there is a current efficiency of 100 # if the flow rate Exceeds 3.5 cm / sec · A higher flow velocity becomes accompanied by a greater critical current density. These relationships are shown in Tables 12 and 13

Table 12 Relationship between flow rate

speed and power output

(Current density 20 A / dm ² )

Flow velocity _{Λ o} (Sm / sec) ■ ¹ » ²

Current efficiency (f) \ 96 j 100

I "i -

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Table 13 Relationship between critical

Current density and flow rate (current yield

critical current density 20 25 30 (A / dm ² )

Flow velocity / - 3.5> 5.2 --7.5 (cm / sec)

(ii) Hardness and titanium dioxide content of the composite coating An increase in the current density is not accompanied by an increased titanium dioxide content or increased hardness. This can be seen from Table 14.

Table 14- Relationship between current density,

Hardness and TiOg content

(Flow velocity 7.5cm / see,

Current density (A / dm ² ) 20 25 30

TiGp content of the 2.3 2.1 2.3

Coating (#)

Hardness (mHV 0.2) 520 516 518

(9) Composite coating with titanium carbide (EiC)

Particle size 0.1-1G μ.

Concentration: 10 - 100 g / l

Flow velocity i 7 - 500 cm / sec

Current density: 20 - 300 A / dm ²

(i) Crystalline current density

A current density of 20 A / dm results in a flow velocity of 7.2 cm / sec a 100% current yield. The relationships between the flow velocity and Table 15 shows the critical current density.

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Table 15 Relationship between two critical

Current density and flow rate (Stroiaausfeeute 100 f »)

critical © current tight ©

Flow velocity

(cm / sec) > ⁷ ^ ²

(ix) Hardness and sitanisarbiclgekalt of the V © r "bundüTjerzug

Sin increase in the current density of the SitankarMdgehalts and consequently the hardness of the resulting coating check is accompanied by an increase _o Dae is apparent from Table sixteenth

Table 16 Relationship between current density ₉

Hardness and TiC retention (flow velocity 15 ₉ 6 cm / sec)

Current density (A / dm ² ) 20 25 30!

TiC content of

Coatings (54) 3 ₉ 6 4.0 4.2

Hardness (mHV 0.2) 565 568 580

(10) Verliund coating with carbon fluoride (CF) n

Particle size: 0.1 - 15 μ.

Concentration: 2 - 60 g / l

Flow velocity: 2 - 1000 cm / sec

Current density: 20 - 200 A / dm ²

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(i) Critical current density

The relationships between the flow velocity and the current efficiency as well as between the flow velocity and the critical current density are shown in Tables 17 and 18. If the critical If the current density is to be increased, it is only necessary to use a higher flow rate.

lamella 17 ratio between flow

speed and power output

(Current density 20 A / dm)

\ Flow velocity 0.62 j 2.8: (cm / sec) ^:

Current efficiency (#) 99 100

Table 18 Relationship Between Critical

Current density and flow rate (current yield $ 100)

: critical current density j j

! (A / dm ² ) 20 25 30

f '

Flow velocity

(cm / sec)> 2.8 > 4.1 - 6.0

(ii) Hardness and carbon fluoride content of the composite coating An increased current density is not accompanied by an increased carbon fluoride content; rather is an easy one Determine a decrease in the (CF) n content. In the same way the hardness also shows a slight decrease. This relationship is shown in Table 19

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Table 19

j

^: Current density (A / dnT)

(CF) n content of the coating

■ hardness (mHV 0.1)

Hardness and (CPjn content of Composite coating (Flow velocity 6 cm / sec)

20th

2.4
535

2.4 523

30th

2.1 525

(11) Bonded coating with molybdenum disulfide (MoSp)

Particle size j 0.1 - 10 µ. Concentration: 10 - 100 g / l Flow velocity: 7 - 400 cm / sec Current density: 20 - 300 A / dm ²

(i) Critical current density

The relationships between the flow velocity and the current efficiency as well as between the flow velocity and the critical current density are shown in Tables 20 and 21. In short, the higher the flow velocity, the greater the critical current density.

Table 20

Relationship between flow velocity and current yield (current density 20 A / dm ² )

Flow velocity (cm / sec)

Current yield (? £)

5.2

7.6

100

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409833/0939

Table 21

Relationship between critical current density and flow velocity (Current efficiency 100? £)

critical current density (A / dm ² )

Flow velocity (cm / sec)

20th

> 7.6

30th

> 16.9

(ii) Hardness and molybdenum disulfide content of the composite coating The hardness and molybdenum disulfide content of the clad Composite coatings are not affected by the density of the applied current. These ratios are in Table 22 given.

Table 22

Current density (A / dm)

MoSp content of Coating

Hardness (mHV 0.2)

Hardness and MoSg content of the composite coating (flow rate 16.9 cm / sec)

3.2

526

3.5

518

3.5

520

(12) Composite cover with synthetic rubber SBR-Iatex (Butadiene styrene rubber)

Particle size: 0.01 - 0.3 g / l Concentration: 1 - 100 cm / sec Flow velocity: CVl - 200 L / dnr Current density: 20th - 300 i

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409833/0939

(i) Critical current density

A 100 # current yield is achieved with a low flow rate. As in the case of inorganic Powder becomes one by increasing the flow rate get high critical current density. These relationships are shown in Tables 23 and 24 «,

Table 23

-Relation between flow velocity and current yield (current density 20 A / dm ² )

Flow velocity (cm / sec)

Current efficiency

Table 24

0.80
99

2.0 100

Relationship between critical current density and flow velocity (Current yield $ 100)

critical current density (A / dm ² )

Flow velocity (cm / sec)

20th

> 2.0

3.1

30th

> 4.5 y

(ii) Hardness and latex content of the composite coating The hardness and latex content of the composite silver coating remain unaffected by changes in the current density »This relationship is shown in Table 25 ο

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409833/0939

Table 25

Hardness and latex content of the composite coating (Flow velocity

4.5 cm / sec)

Current density (A / dm)

Latex content of overturning (Ji)

Hardness (mHV 0.2)

20th
1.9

25 1.8

508

30 1.8

505

Examples of composite coatings with base materials other than nickel

Examples of YerTöund plating are given below, the plating baths being based on metals other than nickel, namely copper, zinc and tin. The results can can be summarized in that the following tendencies are generally found in the individual plating operations although the critical current density ranges vary:

a) if the flow velocity is increased, so the critical current density increases.

b) A high current density tends to reduce the silicon carbide content and to increase the hardness of the resulting plating coating.

In each case the powder to be deposited separately and finely divided was a silicon carbide with a particle size of 0.5-3 μLL . The powder was used at a concentration of 150 g / l of each plating bath.

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409833/0939

(13) Copper-based composite plating

The composition of the plating solution and the plating "conditions were the following:

Composition:

Plating temperature: flow velocity: current density:

Copper sulfate 220 ■ - 20 g / l sulfuric acid 47-17 g / 1 30 ± 0.1 - 400 cm / seo 1 - 90 A / dm ²

The relationships between the flow velocity and the critical current density as well as between the current density, the SiO content and the hardness of the plating cover are in the Tables 26 and 27 reproduced.

Table 26

Relationship between critical current density and flow velocity

critical current density
(A / dm ² ) 10 20th j
30th Flow velocity
(cm / sec) > 5. > 20 > 45

Table 27

Current density (A / dm) SiC content of the coating (? £) Hardness (mHV 0.2)

SiC content and hardness of the composite coating

10

3.3 306

20th

3.5

31-8

30th

3.6

325

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409833/0939

(14) VerlBund silver plating on a zinc basis

The composition of the plating solution and the plating conditions were as follows:
Composition:

Plating temperature: flow rate t Current density:

Zinc sulfate 240 g / l Ammonium chloride 15th g / l Aluminum sulfate 30th g / l Soda acetate 15th g / l Glucose 120 g / l 25 ± 5 ^° C 0.1 - 500 cm / sec 1 - 70 A / dm ²

The relationships between the flow velocity and the critical current density as well as between the current density, the SiC content and the hardness of the plating coat are in the Tables 28 and 29 given.

Table 28

Relationship between critical current density and flow velocity

critical current density
(A / dm ² ) 5 10
> 11 15th
^ 25 Flow velocity
(cm / sec) > 2.5

Table 29

SiO content and hardness of the plating material

Current density (A / dm ² ) 5 10
2.8 15th
3.0
150 SiC content of
Cover (? £) 2.6 148 Hardness (mHV 0.2) 132

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409833/0939

(15) Zinc based composite coating

The composition of the plating solution and the plating conditions were the following:

Composition: Tin sulfate 50 g / l sulfuric acid 100 gA Cresol sulfonic acid 100 g / l / 3 - naphtol 1 g / l gelatin 2 g / l Plating temperature: 25-5 ⁰ C Flow velocity: 0.3 - 600 cm / sec Current density: 1 - 50 A / dm ²

The relationships between the flow velocity and the critical current density as well as between the current density, the SiC content and the hardness of the plated coating are in in Tables 30 and 31.

Part 30

Relationship between critical current density and flow velocity

critical current density (A / dm ² )

Flow rate (cm / sec)

10

> 38

15> 83

Table 31

Relationship between SiC content and hardness of the clad Coating

Current density (A / dm) VJl 10 VJI SiC content of
Coating (#) 2.7 2.9 3.1 Hardness (mHV 0.2) 51 53 59

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409833/0939

The method and apparatus for applying a fine Coating containing dispersed powder "offer the following Advantages:

1. The purest container plating process is stirring of the plating bath by blowing introduced air and / or vibrating or shaking the object to be plated is indispensable. According to the invention all falls the work and energy to be expended for this purpose. It is just a circulation pump for the plating solution is necessary, so that there is a great saving in labor.

2β In a sulfamic acid bath (Ni (NHpSO,) ₂ 4HpO) the maximum current density that can be used in practice for normal loads

container plating process 20 A / dm. According to the invention are Current densities greater than 20 A / dm can be used by increasing the flow rate of the plating solution. This shortens the plating time.

3. When the flow rate of the plating solution is the same, the hardness of the composite coating can be controlled by control the current density can be adjusted. In other words, the higher the current density, the harder it gets plating coating obtained because of an increased silicon carbide content of the plating.

4ο With an increase in the flow rate of the plating solution the cathode current efficiency can be improved.

ο The application of a high current density leads to a high Content of fine, hard particles, e.g. made of silicon carbide, which are separated and finely divided in the Verhund coating Precipitation are formed. In addition, the more thoroughly the fine, hard particles are dispersed.

6. As already mentioned, the characteristics of the are in agreement The composite coating formed with the invention is not the least bit among those of coatings produced in conventional Way with ordinary plating containers.

409833/0939

- Patent claims -

Claims (9)

Patent claims: Method for applying a finely divided powder containing Coating on objects, characterized by the insertion of the pretreated and cleaned object (3, 22) into an upright plating container (1) and applying the composite coating to the object Flow of the composite coating solution from the bottom of the container (1) upwards and returning the solution to one with the Plating container (1) connected storage container (6), wherein the composite coating solution is a very hard, powdery Material such as silicon or tungsten carbide or an oxide or carbide that is insoluble in the electrolyte and water Metal or fine particles of a solid lubricant or an organic polymer. 2. The method according to claim 1, characterized in that the object under control of the speed of the circulated and plating solution flowing upward in the container is provided with the composite coating. 3. The method according to claim 1 and / or 2, characterized in that the composite coating solution by one of the Solution containing fine particles dispersing evenly, arranged in the lower part of the plating tank (1) grid-like distribution plate (1a) is guided « 409833/0939 Berlin office 4. The method according to any one of claims 1 to 3, characterized in that that a plurality of cylindrical or ring-shaped objects (22) stacked on top of one another and as Cathodes in the container (1) are used that in the cylindrical formed by these objects (22) Cavity (22a) an anode (2a) is used and that the individual objects (22) simultaneously with one Composite coating are provided. ο Method according to claim 4 »characterized in that the cylindrical or ring-shaped objects (22) with the interposition of ring-shaped sealing washers (23) be joined together to form a cylindrical, a cavity (22a) enclosing, sealed stack, which is of the composite coating solution from below, flows through the inner surfaces of the objects facing the cavity (22a) simultaneously with a composite coating be provided. 6β device for applying a finely divided powder containing Composite coating on objects characterized by an upright, cylindrical plating container (1) through a reservoir (6) containing the plating solution connected to this container withdrawing the plating solution from the storage container (6) and supplying it to the lower part of the plating container (1) as well the solution in this an upward flow giving delivery means (pump 12) and through the from the upper Plating solution flowing over part of the plating container (1) back to the storage container (6) leading devices (4, 16), 7. Device for applying a finely divided powder containing Composite coating on objects, characterized by an upright, cylindrical plating surface - 3 409833/0939 container (1), in which a plurality of cylindrical or ring-shaped, objects to be plated (22) with their axes aligned with the vertical axis of the container (1) are stacked one on top of the other, by an anode (2a) held along the axis, by one with the plating container (1) connected reservoir (6) for the plating solution, through this solution the lower part of the Plating container to and up in this along the outer and inner surfaces to be plated of the stacked Objects (22) conveying means (pump 12) and through the from the upper part of the plating tank (1) overflow Plating solution to the reservoir (6) returning devices (4, 16). 8. Device according to one of claims 6 to 8, characterized in that d ^ 3 the the plating solution from their reservoir (6) to the lower part of the plating container (1) or the stack of objects to be plated (22) conveying means a pump (12) of variable delivery rate or have a flow control valve (12a) * 9. Device according to one of claims 6 to 9, characterized in that. indicates that in the lower part of the plating tank (1) or at the lower end of the objects to be plated (22) formed a stack that evenly finely distributes the powder contained in the composite coating solution Plate (1a) is arranged. , pc Meissner 409833/0939 Blank page