DE1621241A1 - Bath and process for generating particularly hard nickel coatings without electricity - Google Patents

Description

Patent application

the

Company üilectro Chemical Engineering G.m.boH., Zug / Switzerland,

Poststrasse 9

"Bath and process for electricityless generation" in particular hard nickel coatings "

The invention relates to a bath and a method for electroless Nickel plating of metallic and semi-metallic materials, especially l'itan, stainless steel, beryllium, i / .agn & siurn and its alloys, consisting of an aqueous Solution · containing nickel, hypophosphite, complexing agents and surface-active ions and with ammonium hydroxide a certain PH level is set.

The previously known baths and methods for currentless shutdown; idunj; of nickel-phosphorus or nickel-boron alloys work on the principle that reducing agents such as sodium hypophosphite, sodium borohydride, etc., bound to a complexing agent and therefore released in a controlled manner

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ions with the inclusion of components of the fieduktionsmit ^ fcels, such as phosphorus or boron, on surfaces with a kainlytic effect, to be deposited. ·

The main disadvantages of these baths would be that

1. Not all common materials, such as in particular Magnesium and its alloys, stainless steels, titanium etc. could be coated directly with it. If it ever succeeded for one or the other material, they were Adhesion strength and hardness extremely inadequate,

2. They are not stable enough and when regenerating agents are added decompose at working temperatures,

3. The bath control through the necessary large amounts of accelerators, stabilizers, complexing agents and additives and the process engineering application with continuous bath regeneration difficult and expensive the practical, profitable application to achieve more uniform Layers is thereby placed in T-stretcher,

A. by not a single process without subsequent heat treatment .- ■

2 action a hardness of 1,000 kp / mm MHv "can be achieved could. One of the usual heat treatments of 400 ° C is e.g. for aluminum and its alloys, magnesium and its alloys, zinc and its alloys, plastic, etc. not applicable, as these materials are unfavorable influenced or destroyed,

5. It e.g. in the well-known baths with sodium hypophosphite is not possible, the bath liquid without special procedural circumstances, such as cooling, subsequent getre & eniiB metering in separate containers and then

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send reheating to working temperature etc. to regenerate,

6. In the previously known processes, free many Iferkstoffe an under-tinning, under-tinning, under-galvanizing u.B.w. is to be carried out, what see naturally procedurally complicates and makes more expensive and also brings technical high-quality parts with it,

7 · the nickel-plated surfaces obtained were mostly matt and had to be polished,

8. that the treatment temperatures must be selected to be relatively high in order to obtain the necessary deposition rates.

The disadvantages mentioned and others are thereby achieved according to the invention Avoid using a bath which, in addition to nickel, Hypophosphite and complexing agents or the like. Fluoride and / or another surfactant, e.g. * phosphoric acid and phosphorous acid and / or condensed phosphoric acids, boric acid and borates combined with ammonium hydroxide in one PH value of 7 or above, preferably 7 '»0 - 9> 0.

ti s
• a »it in contrast: to the German

Auslegeschrift 1 20J 567 from October 21, 1965 is in which claims it becomes necessary to have a pH below 7.0 is to keep such a bath in solution. The consequence of the Ammonia content and the "specified pH value in this bath but is the high hardness and abrasion resistance as well as with a corresponding movement of the parts that obtained without specialist treatment, mirror-like surface. Due to a high fluoride content excellent adhesive strength is obtained on all metals, semi-metals and alloys. By combining of the substances mentioned (fluoride, ammonium, phosphates) it is possible that the concentration of hypophosphite 10 - 150 g / l can be without a bath decomposition occurs. Through a

I 0 9 8 1 11 1 5 k 9 _{ßAD or}} © ihal

high sodium hypophosphite content will have a greater deposition rate low temperatures.

Due to the extremely high stability of the bath, it is possible to add the regeneration solutions directly to the bath to regenerate in the reaction vessel at working temperature, which saves a lot of equipment and costs.

learners will e.g. in the previously known baths on sodiumh3rpophosph.it- and sodium thurhydride based average

~ ρ

Layer hardnesses of approx. 500 kp / mm -MHV are obtained while with the method according to the invention with greater economic efficiency and easier handling without subsequent heat treatment

treatment 'hardnesses from 950 - 1050 kp / mm MHV and one of the hard ■ chromium the same abrasion resistance can be achieved.

The invention creates a bath that contains as few ions as possible other than just the ions required for the reaction, This makes it particularly reliable and easy to regenerate, and the deposition rate is sufficiently high at temperatures from 40 ° C possesses, which is a very great advantage especially when treating plastics made conductive. · This also has the advantage of great bath stability, so that with the specified amount of reducing agents γ / can be grounded at any temperature without it it is necessary to use special stabilizers. the Deposition rates are far above the usual values at higher temperatures; for example, at 95 ° G 50 my / h deposited. It is particularly surprising, however, that the inventive Procedure hardness and abrasion resistance values of the layers produced can be achieved by none galvanic or currentless Eickelbad were achieved.

A variant of the bath according to the invention is that also other surface adsorptive substances, such as bromides,

"-" 109817/1549 'bad original

Iodides. Or the like, could be used, but that other reducing agents with a RedOxpot flow based on the respective concentration of the reducing agent of 3.1 Yl) Is 0 \ 2 V, 'coupled with the bath fair ingredients mentioned, may be associated with bath decomposition,

Because of the excellent action of the bath components, the working temperature of the bath according to the invention can be between room temperature and the boiling point: it is, however, preferably used at 60-90 ° C. Surprisingly, even at the preferably mentioned low working temperatures can be found , has already reached sufficiently high deposition rates of approx. 20 mj / h .

As has been ascertained, the bath according to the invention leaves the otherwise tedious pretreatments, e.g. copper plating, or even non-platable ketals and semiconductors, e.g. magnesium and its alloy, Jewish steels, 3? itan; silicon and, its /! , nickel-plating without any problems. These metals can according to the invention. can be nickel-plated directly as well as ζ » B, iron and copper. "...""" ■ -:;

In the reduction of nickel II ions by the hypophosphite ion this is automatically oxidized to the phosphite ion. in the Over time, the bath liquid accumulates in this Substance up to its solubility limit> As soon as "this exceeded and the phosphate precipitates, roughness is formed (Fittings.) On the surfaces to be nickel-plated.

In order to avoid this, in some processes a complexing agent is added anyway, which reduces the phosphite ions up to a higher level Maintains concentration in solution ^ Fill other procedures; these Ions in a special container.

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In contrast, it has proven to be particularly economical and: '·:.> Simply proved, the bath solution in the circuit via iron hydroxide or lux mass o.a. "to filter Bath removed without the need for additives and separate Fall facilities need to be installed.

For fully continuous operation of the bath, it is advisable to use the Concentration of the important bath components constantly increasing Hold £. Sine depletion in reducing agents and Hickei would lead to a reduction in the rate of deposition. Therefore, all bathroom components that are continuously consumed and so that are withdrawn from the bath, are continuously added. The interfering decomposition products that form should also be removed.

Attempts to make a suitable regeneration solution showed the following difficulties:

1. If possible, no foreign Ions get into the bath, otherwise the lifespan of the baths is greatly reduced and lifting reactions occur.

. '■ ■

en

2. The volume / of the regeneration solution must be as small as possible

so that no increase in volume of the bath occurs, i.e. the added volume of liquid must be equal to the or under the low evaporation losses on the bath surface lie.

The connections of the nickel, which the demands 1) to are able to fulfill - are like that in water and in the bath solution sparingly soluble that 2) is impossible to meet. But there ~ As a solvent, apart from water, only a consumable component of the bath comes into question, so as not to contain any foreign ions Bringing them into the bath solution were attempted solutions with usable nickel salts in aqueous ammonia solutions

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made. It has been shown, surprisingly, that the compounds which are smearily soluble in water, such as nickel hydroxide, nickel oxide, nickel fluoride, etc., are easily soluble in aqueous ammonia solutions with a concentration of more than 20% and that large amounts of nickel salts are absorbed. When dissolving, for example, nickel fluoride in 25% ammonium hydroxide solution, there was such a good ratio between solvent and dissolved salt that when this solution was added to the bath solution, which was fully used with nickel-plated objects, the ammonia consumed in the ^; the same ratio as the used nickel was replaced by the regeneration solution. The hegeneration volume became so small that it was below the evaporation losses and thus; the demands made were solved in an ideal way. . ".

To ä-ae container volumes for new baths and their storage to spell this kind of solution-making also when preparing ivy instead of e.g. dissolving Nicke 1-darbonat-in Sluösäure can be used. , ·

At the same time, it was surprisingly found that contrary to this the previously usual procedure the Mckelsalz-Regenerungslösung together with the sodium hypophosphite dissolved in it from a single container and through: a single metering device metered in without any disadvantages can be. ,,

The heavy metal salts of lead, chromium, arsenic, antimony, tin, copper and zinc, among others, which are naturally present in traces of impurities in the steomless nickel plating baths, have various influences on the killing process. They act as Eatalysafco.Fgs> ifte and thus influence the deposition rate, prevent nucleation and act

10981 7/1549 bath

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so on the bath stability and the smoothness of the nickel-plated surface a. Since these salts, just like nickel, are deposited on the workpieces to be treated, you get continuously changing and uncontrollable conditions in continuously operated baths. Because these heavy metal salts are preferably present in the nickel salt, come depending on the Purity of the starting product and the added amount of .fiegenerierungslösung different amounts of this catalyst ^ poisons in the solution. To maintain permanently the same ^ Bathing properties, however, require a constant bathroom mirror of these trace substances.

It turned out that when certain larger amounts are added, for example Pb * 'ions of 1 - JO ppm, especially approx. 15 ppm, optimum conditions exist for the aforementioned factors, surface smoothness and deposition rate. This amount can be continuously maintained in the bath by metering in and checking (atomic absorption * spectrophotometer) or, which is much simpler, by the depot effect of a compound. The decay effect is advantageously achieved by adding or storing a larger amount of a poorly soluble lead compound in the L bath, the solubility product of which in the bath corresponds exactly to the amounts given above. PbCrO4 and FbG03, for example, lie within these limits.

To steamer the regeneration solution addition is a permanent Determination of the concentration of the consumed bath components to recommend. This ongoing determination of the concentration by means of chemical analyzes is very complex and too time-consuming tied together. If the analytical result is retained after approx. An additional dosage has long been 30 minutes due to this value Obsolete, as the nickel plating continues in the meantime.

A way has been found to determine this concentration. need to carry out directly in the bathroom. - ■ '-, L

'. - ®ÄO OHlGlNAL

1 0 9 8 1 7/1 5A9

We found out that the continuous steamer of the Fickel concentration and the consumption ratio to it " standing liatric hypophosphite by a flow eolorimeter (Photometer) is possible. The control of the PH value can also be used be done with such a device as the color of the Solution with the pH values diminished.

In fully integrated operation, a partial flow of the bath fluid kept in circulation by one or more pumps is branched off and passed through a tube colorimeter. The concentration ^ fe *? ^ ² controls a dosing pump which, if the value falls below this value, adds regeneration solution until it is reached again · · .. · '""

Which surprisingly split up »has; In the case of the present bath, the phosphite which forms from the sodium hypophosphite during the reaction process also has a special influence on the hardness of the resulting layer. The layers become harder with a high phosphite ion content in the bath than with a low one. Since a high content of phosphite is indicated by a cloudiness of the solution (precipitating hickel phosphite), this value can also be continuously displayed by measuring the turbidity in the long-tube colorimeter. As a result, when a certain, excessively high turbidity diffuse is reached, a pump can be switched on which, in order to remove the phosphite, pumps the bath solution through an iron oxide or hydroxide-containing filter material instead of centrifugal filtration and switches it off again when the second limit value is reached SSA is also possible ^that: to regulate pot reference a centrifuge so that a welding field is generated, in which only the Te union high specific gravity, therefore, the impurities that are deposited, while the almost colloidal _ particles of the completed phosphite in the solution remain. This guarantees a permanent, optimal for increasing the hardness

109817/1549 _{; VBAD} original

Concentration of the phosphite that forms in the bathroom anyway. At the same time, the following becomes more disruptive in "other methods" = Factor kept under control: _ -

ils is known that other, currentless nickel plating processes Eat the phosphite ion up to a certain concentration is enriched. If it starts beyond this concentration, the entire bath solution is usually discarded. In some cases... Attempts have been made to remove these ions by laborious precipitation. By, the method according to the invention results a clear advantage that extends the lifespan of the baths considerably increased and at the same time: the concentration on this component keeps constant.

With the continuous regeneration of a long-term bath it turned out that the initial, strong luster of the educated Hard nickel layers after a long period of operation of the Bath wears off. Tests with different brighteners showed that the most suitable connection is always reflected in the creation

13.3.0x1

Yellowish precipitation, equal to / whichever duration of the bath Is lactic acid.

It is known that in certain electroless nickel plating baths at pH values below 6 lactic acid to accelerate the absorption rate is used. In the present bath, the lactic acid also had a slight effect on the rate of deposition, surprisingly but a particularly high gloss effect, with PH-ifted over 6.0, the concentration of lactic acid being 5-100 g / l.

At the same time, the lactic acid greatly reduced the hydrogen bubble adhesion, which always occurs in ferrous materials and which is visible in the layer formed as a small crater, and completely eliminated it in conjunction with a fluorinated wetting agent, which was present in quantities of 0.001 - 1 g / l bath liquid - - - . r 109817/1549>£> ^

The fully configuring operation, a chemical nickel-plating plant is "best" feasible if certain conditions are met in the execution, the attachment e ^^^

So it was not yet possible to carry out an electroless nickel plating process without cooling the bath solution, regeneration and filtration in the cooled state as well as subsequent reheating to heating temperature., .- / Since this is possible with the Aa bath solution according to the invention , appropriate plant locations could be found that also meet these requirements in terms of equipment.

When the reducing agent and nickel concentration is reduced by the deposition of ulcer on the parts to be nickel-plated, there is usually an undesirable effect due to the formation of finely crystalline precipitates similar to colioids which, on the one hand, undesirably settle on the parts to be nickel-plated and therefore allow rough surfaces to develop, but on the other hand they are also nickel-plated themselves and, due to their relatively large surface, are extremely uneconomical:? has been no lack of _attempts% to filter these precipitates, which is in itself technically easy to solve, but in view of economy a "ehr circuitous route represents iäine filtration of notviendigerwelse hot Iiösuhg is not possible because the Eilterkuchen continue with the solution in contact remains and therefore removes more and more bath constituents from the solution through nickel plating and only "brings advantages with regard to the roughness of the parts to be nickel-plated." Due to certain gelatinous constituents in the solution: which would clog every filter within a few minutes during nitration it is necessary to work either with precoat filters, which were very unprofitable, because germs got into the bathroom as germs through the oleuses of the trier mass and because the very large surface of the filter

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tiönshilfsmittel especially, a lot of nickel-plated surface bot. The second way, a double / .iltration over two different Filter, is extremely cumbersome and in-continuous, Operation not to be used.

One .was therefore previously forced to use the solution to be filtered cool down until their ability to react to one tolerable minimum ', then to filter to Finally, heat up the reading again.

Surprisingly, it has now been found that in the case of a separation the precipitation of the solution with the aid of a centrifuge having a gravity field of at least 100 g, these disadvantages do not occur.

Bs has shown that

1. there is no booster pump that could also be nickel-plated, is required because centrifuges work without pressure,

2. the metallic parts, regardless of the material, the Centrifuge running at high speed even when touched almost not nickel-plated with the hot bath solution and therefore not in undesirable ¥ ice nickel and reducing agents remove from the bath,.

3- the precipitation varies according to the respective work activity remove the bath with the help of a solvent, i.e. clean the centrifuges. = ·

It is known that all substances in a chemical nickel-plating solution at reaction temperature are reduced to shorter or nickel-plating for a longer period of time. Therefore, one of the most difficult foundations of experience is the selection of the appropriate container. and plant parts materiais. After testing all available Materials surprisingly found that in the

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bath solution according to the invention a material of the composition Qr: 10: - ■ / $$%, ELs 50 - 75 ^, Mo: 10 - 18 "'# ■ * - JP ^ -s remainder

has a passive potential, which itself is caused by catholic

Activation currents of 10 ₁ ampere per cm are not permanently activated and automatically return to the PassiVftereiGh. wanders. This makes it possible to manufacture all the attachment parts from metallic material, which results in very large parts. The "gate parts" consist of 1. very easy cleaning of the system parts in nitric acid, while e.g. plastic

¹ Ke—

it is attacked in the long run, 2. in a very favorable thermal conductivity, which is advantageous for the heat transfer in this Terfahren for heating. _: - / ■ '-

Another possibility to use metallic system parts has also been found. Since the usual stainless steels of various compositions are activated and nickel-plated in the present bath, but are much cheaper in price than the above-mentioned material, activation must be avoided for these in order to prevent pitting ".." -. - ■ ".--- ■" -. '., ".- .-. _; : - .. '■; V "" -. "■;""

jjis is known that this can be done by giving up an anOdic »Stromes can reach a height of up to 10 amperes per cm can. Much known, but much simpler and more economical Is that you get the nobler potential through a high but short-term thyristor-controlled pulse current again and again when it has sunk after a long period of time due to the activation process. The effort required to do this is very low. \ - ..- ".". "", ν:

JSs follow examples like && invention for that. Bad and procedure ί "." ■ ^f "-; / ■ ■""■'■-;_.; _

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SAD OBiOiNAL

Example 1 i

In a bathroom, «consisting of -i

.15 g / 1 NIGO ₅ . "

20 ml / l HF 40% ■

15 g / l trisodium nitrate 40 ml / 1 HH ^ OH 25% 25 S / l HaH ₂ PO ₂ ... B ₂ O,

were at a pH of 8.5 and a temperature of 80 G Electron-Broben (Mg-Alloy) nickel-plated. The divorce speed was 30 µm / h. The hardness & the resulting

ρ layers was 990 kp / mm IHT.

Example 2 r

In a bathroom, consisting of:

10 g / l NICO, -

20 ml / 1 HF 40% 50 g / l sodium diphosphate

30 ml / 1 NH ₄ OH 25 ^ ig -

40 g / l lactic acid,

18/8 stainless steel samples were nickel-plated at a pH of 7 · 5 tuid at a temperature of 90 °. The deposition rate was 35 μm / h, the hardness of the layers produced was 1050 kp / mm ² MHT.

Example 3 t '' -

In a bathroom consisting of .:. 4 H ₂ O 20 g / l

Borax, Erist, 40 g / l

NaH ₂ PO ₂ . H ₂ O. 20 g / l

NH.OH to PH 8.0

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A Delrin sample made conductive with PdGIo was nickel-plated at a temperature of 30 ° G. The deposition rate was 10 μm / h, the hardness of the layer 980 kp / mm ² MHV, with good adhesion.

example 4: 5 (PO) ₂ Composition In a bath of , P ₄ O ₇ • 7.H ₂ O "". 20th g / l Ni, JT 20th g / l Na. H ₂ PO ₄ . 5 g / l Fa HO 40 g / l Na

^ up to EH = 9 and at a temperature of about »70 ° G, Al Zn Mg samples were nickel-plated. The deposition rate was 20 µm / h. The hardness of the resulting layers was 900 MV kp / mm ² with a load of 50 g.

. ; BATHROOM QBlGMAL

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Claims (1)

- 16 - ■ "■... 505 3.11.6? Ado P a ten t to sayings ν ■. \ 1. Bath for electroless nickel-plating of metallic and semi- s metallic materials, in particular titanium, stainless steel ,, and magnesium and its alloys, consisting of an aqueous solution containing nickel, hypophosphite and complexing agent ions, characterized in that it contains, in addition to surface-active anions, ammonium hydroxide in such a concentration, that a pH value of 7 or above, preferably 7 »0 - 9» 0 is established. 2. Bath according to claim 1, characterized in that it is as surface-active anions iodides, bromides, borates, phosphates and / or polyhypophosphates, preferably fluorides. 5. Bath according to claim 1-2, characterized in that others .Reducing agent with a redox potential, based on the respective concentration of the or the reducing agent .of 5.1? up to 0 * 200 V, coupled with the bath components mentioned are present without bath decomposition. 4. Method of using the Badea according to claims 1-5, characterized in that the working temperature is between Room temperature and boiling temperature is maintained. 5. The method according to claim 4-, characterized in that the Working temperature is kept at 60 - 95 ° C. 109817/1549 ^ o _neiNAL 6. The method according to claims 4-6, characterized in that that the addition of the regeneration solutions, directly into the Ar · ^ working container takes place. ■ 7. The method according to claim 6, characterized in that the regeneration solutions are added to the working tank at working temperature ». 8. The method according to claimsu4 - 7> characterized in that the treatment with a relative movement of the parts to be nickel-plated opposite; . performed the Vemicklungsbad _*: .. ''_{_;;..} 9. The method according to claims 4-8, characterized in that that the sodium hypophosphite in a 1-concentration of. 10 - 150 g / l is maintained .:; ; 10. The method of claims 4-9 "characterized in DALI for removing the Zersetzungspj Qduktes from the hypophosphites, d» H?. of phosphite ion, iron oxide, iron hydroxide or the like. Is used. 11. The method according to claims 4-10, characterized in that the nickel salt used for regeneration does not contain any foreign anions and is dissolved in an aqueous, concentrated ammonium hydroxide solution of more than 20 % . 12. The method according to claim. _R 11, characterized in that the ITeäansatz electroless iiickelbäder then takes place. 13. The method according to the claims. 11 - 12, dadurcih marked, that the winding salt solution together with; the ^ dissolved therein Reducing agents is added. 14. The method according to claims 1.-13 »daudrch", that this is enough to stabilize and prevent nucleation 109817/1549 put heavy metal, especially lead salt, in one Concentration of T -50 ppm / metal content by an analytical Control device or through a depot one poorly soluble connection of these heavy metal ions is kept constant, whose solubility product in the Bath solution lies between these limit values. 15. Method according to claims 14, characterized in that that the automatic monitoring and control of the bath concentration and the addition of Hegeneration through in the bath circuit built-in analysis devices that control regulators are carried out, e.g. flow colorimeter or atomic absorption spectrophotometer ... 16, method according to claims 1-15 »characterized in that that the phosphite concentration by continuous measurement with a flow turbidity meter (photometer), the one Pump. With filter compound containing iron oxide or hydroxide or controls a centrifuge, is kept constant. ' 17 · Bath according to claims 1 - 3 »characterized in that PH— ■. -. it is in the / range of 6.0 - 12.0 lactic acid as a grlanain indigenous. with a concentration of 5-100 g / l. '. 18. Bath according to claims 1 ~ $ and 17 »characterized in that that it is in addition to the hydrogen bubble disposal and the Elimination of the resulting pores in the layer fluorinated wetting agent in the concentration from 0.001 to 1 g / l contains. 19 · Process according to claims 4--16 and for operating the Bath according to claims 1-3 and 17-18 »characterized in that that the cleaning of the bath from solids \. by centrifuging with one or more centrifuges 109817/1549 of the gravitational field takes place from 100 g. 20. The method according to claims 4-16 and for operating the Bath according to claims 1-3 and 17-19 »characterized in that that all parts of the system that come into contact with the bath fluid are made from a material of the composition 10 - 33 % Cr, 50 - 75% Ni, 10 - 18% Mo, remainder Pe,
"exist. _; .. · '. \ 21. The method according to claims 4-16 and for operating the bath according to claims 1-3 and 17-19, characterized in that that other metallic materials before Nickel plating are protected by a -4
thyristor-controlled pulse current of the high 2 · 10 to —12 '
10 "A / cm, which only starts in the event of activation * can be brought back to the passive potential. BATH 109817/1549