DE1144073B - Galvanic nickel bath - Google Patents

Description

GERMAN

PATENT OFFICE

C23508VIb / 48a

REGISTRATION DATE: FEBRUARY 27, 1961

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL: FEBRUARY 21, 1963

The invention relates to a new bath liquid for electrolytic nickel plating, which neither boron still contains carbon and the production of pore-free nickel coatings of high purity and Uniformity is allowed and especially for the nickel plating or the production of firmly adhering Nickel coatings on rods made of uranium are intended as they are used in nuclear reactors.

Up to now, electrolytic nickel plating has generally been carried out using bath liquids, the main components are nickel salts, such as especially nickel sulfate, chloride, fluoborate or -sulfamate, occasionally also contain double salts of nickel and ammonium. Usually there a chloride is added, which results in a good electrolytic attack of the bath on the anode target. A strong concentration of nickel salts is usually used. One can also use the conductivity add an increasing salt such as sodium sulfate; this can, however, be large Quantities may be necessary.

It is also necessary to add a buffer substance to the components of the bath mentioned so far, mostly Boric acid to be added.

A substance that reduces surface tension, preferably sodium lauryl sulfate, is also frequently used added in amounts of about 0.1 to 0.5 g / l so as to allow the formation of porous areas and holes in exclude the nickel plating. Such baths result when the process is carried out properly uniform and dense or coherent nickel deposits.

It is also known to use soluble aluminum salts as buffer substances, which are contained in aqueous solution are hydrolyzed. In this case it is absolutely necessary to move the cathode and to add chlorides in high concentration (more than 30 g of chlorine per liter).

The aforementioned technical measures of the known nickel-plating processes result in coatings good quality; however, these coatings contain more or less large proportions of boron and / or Carbon.

In certain applications of nickel plating, in particular in coating or sheathing of uranium rods for nuclear reactors, the presence of the substances mentioned, even if they are only present in traces, undesirable. The elimination of the boron alone has already been planned and the boric acid is replaced by another buffer substance. The most commonly used in this case Buffer substances are the ammonium-galvanic nickel bath

Applicant: Commissariat a l'Energie Atomique, Paris

Representative: Dipl.-Ing. R. Beetz

and Dipl.-Ing. K. Lamprecht, patent attorneys,

Munich 22, Steinsdorfstr. 10

Claimed priority: France of March 22, 1960 (No. 822 062)

Louis Facquet, Vaucresson, Seine-et-Oise,

Jacques Daboval, Clichy, Seine, and Guy Chauvin, Fontenay-aux-Roses,

Seine (France) have been named as inventors

salts that are only used in baths, which have a very strong reduction in surface tension Product contain, because the ammonium salts favor the formation of holes or leaks Places in the nickel deposit. Mixtures of acetic acid and sodium acetate are also available or other acids such as citric acid and tartaric acid are used.

It should be noted, however, that the majority of buffer substances and substances that reduce are added to the surface tension - as far as they are mentioned above -, Contain carbon or may only be used in connection with substances that in turn Contain carbon; the carbon goes, at least in part, into the nickel deposit or -Cover with a.

The invention has the particular purpose of providing a new bath liquid for electrolytic nickel plating to create that results in a flawless, very pure nickel coating that does not have any imperfections or Has holes and contains neither boron nor carbon.

The new bath liquid is characterized in that it is made of nickel sulfate or nickel sulfate— Nickel chloride with a content of less than 15 g / l chlorine ions and potassium or sodium alum consists.

309 510/335

According to the invention, the alum to be used is preferably a potassium alum [(SO ₄ ) ₄ A1 ₂ K ₂ · 24H2O] and the nickel salt is the sulfate of the formula SO ₄ Ni · 7H2O. The use of potassium or sodium alum brings the following advantages which cannot be achieved simultaneously by using a single product: the alum plays the role of a buffer substance because of the aluminum salts it contains; such that they have no abnormal internal stress; their physical and mechanical properties corresponded to the nickel coatings which can be obtained using conventional methods.

As a result, these nickel coatings are ideally suited for a wide range of uses, especially for coating or sheathing uranium rods. The nickel just described

Like those products that contain no chloride, the alum acts to reduce the risk of

the occurrence of holes or imperfections, the formation of imperfections in the cathodic coating

prevent, and indeed as a result of the potassium salts, to avoid, but only allows you to work with one

which it contains; relatively small amperage and can after a

the alum shows a passivation of the

pischen crystallized form, which give easily soluble 15 anode of nickel, if no special

is, and is therefore very easy to use; special measures are taken against it.

the alum contains neither carbon nor boron and can therefore also be used for manufacture of nickel coatings on uranium rods.

The quantities of alum must be more than 15 g / l be of the crystallized salt; On the other hand, they cannot be greater than the solubility limits of the Alums as they are set under the given conditions.

The nickel sum can also be completely or partially due to one or more other nickel salts can be replaced, and it can be used in all concentrations customary in the nickel-plating technique will.

Finally, the simultaneous presence of chlorine within the bath liquid acts in the Meaning that a passivation of the anodes is prevented, which would otherwise be after a certain usage

Example 2

Another composition of the bath, which contains a small amount of chloride, corresponds of the following composition:

Nickel sulfate (SO ₄ Ni · 7H ₂ O) 280 g / l potassium alum

[(SO ^ ₄ Al ₂ K ₂ · 24H ₂ O] 70 g / l

Nickel chloride (Cl ₂ Ni · 6H ₂ O) 3 to 6 g / l

corresponding to 0.9 to 1.8 g / l of chlorine ion

Temperature from 40 to 6O ⁰ C

PH 3 to 3.5

Current density 1.5 to 2 A / dm ²

This bath is much easier to run than the one that did not contain chloride and can with it

duration of the bath and the otherwise a 35 of a much higher current density and within special treatment for elimination or a much longer period of time are carried out, Would require renewal of the electrodes. Which occurs without passivation of the anodes; upper limit of the permissible amount of chlorine ion, the nickel coatings obtained show the same quality which one can still exploit without risking, as in the previous case, and it has run that defects, breakthroughs or pores 40 surprisingly showed that the presence occur after the cathodic precipitate, there are no defects in the coatings because of the chloride close to 15 g / l of the bath liquid. That caused. lower limit is theoretically zero. she comes

practically out of the question, on the one hand in consideration of example 3

the rapid passivation of the electrodes and on the other hand because of the low usable current density, which is due to the fact that one with the reduction in the amount of in the bath liquid contained chlorine ions also the charge carriers. With a further increase in the bath content in the case of chlorine there is a third composition, which is an excellent anodic attack guaranteed and thus a passivation of the

or reduces the conductivity of the bath. 50 excludes anodes, so that the

In the following, the invention will not apply to some of the bath's settling during its use

changes; the bath gives coatings of normal quality, which are also uniform and without imperfections. This Bath corresponds to the following composition:

Nickel sulphate (SO ₄ Ni · 7H ₂ O) ... 280 g / l nickel chloride (Cl ₂ Ni · 6H ₂ O) ... 35 g / l corresponding to 10.5 g / l

Examples explained:

example 1

A first test bath without the addition of chloride or chlorine ion was made with the following composition and tested under the specified working conditions:

Nickel sulphate (SO ₄ Ni · 7H ₂ O) 280 g / l

Potassium alum

[(SO ₄ ^ Al ₂ K ₂ · 24H ₂ O] 70 g / l

Temperature from 40 to 6O ⁰ C

pH 3 to 3.5

Current density 1 A / dm ²

So

Chlorine ion
Potassium alum

[(SO ^ ₄ Al ₂ K ₂ · 24H ₂ O] 70 to 90 g / l

Temperature from 40 to 6O ⁰ C

PH 3 to 3.5

Current density 2 to 5 A / dm ²

6 ₅ The current density could be increased up to 10 A / dm ² when the parts to be treated had nickel deposits. They had no imperfections and the bath liquid was vigorously agitated or stirred, and it turned out to be surprising.

Claims (1)

5 6 Example 4 and its preparation is carried out with a special favorable power yield. The baths are light To run a fourth bath used for experimental purposes and correspond in this respect to the contains a low concentration of alum, the well-known classic nickel-plating baths. they are is close to the specified minimum (15 g / l); 5 excellent for the production of this bath corresponds to the following combination of electrolytic deposits on uranium rods, Settlement: the previously necessary treatments for Nickel sulphate iSOiNi 7 Η, ΟΪ 280 σ / 1 Cleaning and preparation of the surfaces ΓτΓ w iXr S '■■ fin had to keep. The bathrooms also issue Kaiumalum '"'" ¹⁰ drawn deposits on all other metals, [(SO ₄ ) 4A1pKo · 24H ₂ O] 18 g / l ίΖ ™ * ^ otherwise in the usual nickel-plating Temperature "" 50 ⁰ C bath provided with nickel plating. Value . 2 25 ^ * ^e Ρκ values of the baths, as in the examples c? ^^ • "ü + J ι 'uio τ λ M "2 are given and are between 3 and 3.5, Current density 1 to 2 A / dm ^, .., ■, .. _o j ι ι · ι j · wt <. 15 can be noticeably larger or smaller than these values RfMcmVI S ^sem > ^and the specified temperatures that ^{D p} between 40 and 6O ⁰ C can also be A fifth, according to the present level, may be smaller or higher than these values. Yet bath contains a strong one, which must be increased when the temperature is increased, in particular Concentration of alum, and moreover the in 20 special, even with a higher pn value, make sure that in this case alum used a sodium alum; that the temperatures do not rise to values the bath has the following composition: at which the hydrolysis temperatures of the alums Nickel sulphate (SO ₄ Ni -7H ₂ O) .. 280 g / l reached ^{under the} respective working conditions Nickel chloride (Cl ₂ Ni ■ 6H ₂ O) .. 35 g / l _a ^are · Sodium alum ²⁵ [(SO ₄ ^ Al ₂ Na ₂ · 24H ₂ O] 460 g / l PATENT CLAIM: Temperature 50 C Galvanic nickel bath, especially for removing c? α üi c'l. in * i4 9 separate nickel coatings on uranium rods, Current density 5 to 10 A / dm * _{3o ifl nuclear reactors} are used, thereby The specified bath compositions characterized in that it is made of nickel sulfate or equip the manufacture of excellent nickel-nickel sulfate-nickel chloride with a grade coatings without defects; the coatings contain less than 15 g / l chlorine ions and potassium neither boron nor carbon, they are perfect or sodium alum in a concentration of dense, have no porous or other imperfections, 35 contains more than 15 g / l of crystallized salt. © 309 510/335 2. 63