DE2045301B2 - Bath for the galvanic deposition of three-layer nickel coatings - Google Patents

Description

A. SOj-RSR ₁ -CN

B. "SO ₃ -RSR ₁ -C-NH,

C. "SO ₃ -RSR ₁ - (CN) ₂

wherein R is an alkyl group with 2 to 4 carbon atoms and R _{1 is} either an alkyl group with 2 to 6 carbon atoms or an alkylaryl group of the structure

R,

in which R _{2 is} an alkyl group with 2 to 4 carbon atoms. means.

3. Bath according to claim 2, characterized in that it is the thiosulfonate in an amount of Contains 0.01 to 0.4 g of I.

4. Bath according to claim 3 for producing the middle layer, characterized in that it contains the thiosulfonate in an amount from 0.03 to Contains 0.1 g / l.

5. Bath according to claim 3 for producing the upper layer, characterized in that it contains the thiosulfonate in an amount of 0.01 to 0.04 g / l.

6. Bath according to claim 3, characterized in that it is the reaction product as the thiosulfonate contains of mercaptopropane sulfonate and butanedinitrile.

7. Bath according to claim 3, characterized in that it is the reaction product as a thiosulfonate contains of mercaptopropane sulfonate and acrylonitrile.

The invention relates to a bath for the galvanic deposition of a three-layer, firmly adhering nickel coating on a corrosion-prone metal surface with a content of at least one sulphurous iron Amide or nitrile.

Sulfur-containing amides and sulfur-containing nitriles have already been used as additives in nickel baths, together with other brighteners. The sulphurous amides act as gloss-ίο more real. With a bath. which contains a conventional brightener and a silicone amide, a certain degree of gloss can be achieved. Add a sulphurous nitrile. this creates fully shiny nickel coatings. Coatings with high rust protection properties are not achieved with these bath additives, however, in de · '., "SA Thickness, whereby the intermediate layer has a higher sulfur content than the neighboring two layers and the upper nickel layer has a significantly higher sulfur content than the lower one. Various inorganic and organic sulfur-containing compounds are then added to the electroplating baths for the middle and upper nickel layers to achieve the desired Sulfur-containing compounds that can be used are / B. thiosulfates, sulfites, bisulfites, hyposulfites, hydrogen sulfites, sulfoxylates, sulfinates, thiocyanates, sulfoxides, sulfinic acids, mercaptoaromatic acids, thiourea, isothiourea, sulfde, thiohydantoin Sulfonyl halides de. Sulfones and the like - Although this is described in this patent. Process gives a much better protection against corrosion, even with a much thinner total thickness of the nickel coating than has been possible up to now. have when operating under this Vei drive certain difficulties shown When the Sweats ^r - "i; iltigen bath additives are used, are the bathrooms, as has been found against air agitation and high temperature sensitive about the speed at with which the deposition run In addition, the electrolytic removal of metallic impurities in the bath, such as zinc, copper and lead, cannot be effected without wetting the sulfur-containing additives through oxidation. This means that after these metals have been deposited, the sulfur-5 " containing additives in the galvanic baths must be replaced. This is both time consuming and costly.

The object of the invention is therefore to provide an improved electroplating bath for depositing a three-layer bath To create nickel coating, with which greater deposition rates are possible and from which metallic impurities are removed without destroying the sulphurous additives in the bath can be.

The object is achieved by a bath for depositing a three-layer, firmly adhering nickel coating on a corrosion-prone metal surface with a content of at least one sulfur-containing Amide or nitrile, the lower firmly adhering nickel layer having a thickness of 3.81 to 38.1 μm and an average sulfur content below 0.03%, the middle layer a thickness of 0.127 to 5.08 μm and an average sulfur content

chi one to 38.1:. '. m and one through

- u η r. and the upper nickel shows examples of compounds used in the designation

!, to U., un. Average cemälien baths can be used are d.e

D ^icke c °, huefel "ehalt have ο 12:02 to 00:15 ° following: • io-ib-re durchschniti- lower layer a

• ^d Ä -M-'ehall has as the minier layer and? HHHH

* ^Hen hher'n al <de lower layer, characterized NC CC -CC-CN _(1,

O ^{nen h} l ^ _cl is. that it. at least for the Ab- HHH

middle layer, at least one tino- ^

<sulphurous nitrile or amide>

ic Is- riiij

' ¹ C ¹¹ Ut <- ■>; ■ - it has been found that when using _

^ES Thi; Cu ^: phonates of nitriles or amides an ^ h

! ⁰ J ₁ , der'schulfelhaltigen compounds, such as si ·.

I ° V de-.sulfur-capable compounds, as they are in

f ¹ ^ SA- ^ ent step 3 090 73? are disclosed. d ·, _H £ ._. £ _ _CN C)

^{It is} heated up and heated to higher temperatures .5 '

l ^id ti ■:} -n can, what a sneaky Abgehe: ^H

d dl tlliche Ververcmi ^ m

lt i ■:} -n can what a sc
* ^Ti 7 - <vht and dali metallic ^

^dUng , vi '/ -k copper and lead. removed from the bath
^ρη -, 2Ι V ^ en without the sulfur-containing compound- ^{| C} "^

jo% s' L ¹ --h Oxvdation must be destroyed. 20 _

^dU S: i of nitriles or armden becomes SO ₃

^^ at least in the galvanic construction

i ^ i of the middle nickel-containing eye, eht. ,,

ii in the galvanic baths for the HC-C-C-NH,

Niklhiht ndet the z ₅

, "R'Uiisweise m to ^ .. ui ..-> -.-" ^ - ^ _

.r - '. ind the upper nickel layer. used. Of the :? _H

^ V-erlt the middle nickel layer lies \ or- '

^k '. "." i- in the range from about 0.05 to 0.3 ",. in the

upper'dWn in the range from about 0.02 to (Urv _c

In other words, the thiosulfonates of the NUr ₁ U ^D Z vide the ealvanic bath for generation 30

t r ^ iiere-. Layer in amounts ranging from about ^

_u ^e ₀ \ ^m _b , s0.4 _£ l, vorzngswe ^ 0.03b.s0.1gl. and to _H

iScuXna of the upper layer in amounts in the range HC-C-CN i ⁴ '

from en 0 01 to 0.04 g I is used. S., Stverstandl.cn Set the eenaue amount on the used each 3> V "b ndun ^ s. So that they in some _n s bales in S outside the ranges specified above

S'e ^ en are so that the desired amount of sweat _; -

In you particular nickel sheet is obtained. _s

The thiosulfonates of nitriles or amides present in the bath _{according to the invention are represented by HHHHH}

to reproduce the formulas below. _NC _ _C _ _C -CCCC-CN O)

H H Ϊ H H H

A. "SO ₃ -RSR ₁ -CN 4

O (CH ₂ I ₃

B. 'SO ₂ -RSR ₁ -C-NH ₂ SO ₃ "

O O

C. -SO ₃ -RSR ₁ - (CN) ₂ HH

H ₂ NCCCCCC-NH ₂ 16)

HlHH

wherein R is an alkyl group with 2 to 4 carbon atoms and 55 S

R _{1 is} either an alkyl group with 2 to 6 carbon atoms i

or an alkyl-aryl group of the structure (CH ₂ ) ₃

SO ₃ -

( VCC-CN

K) ^H ι

in which R _{2 is} an alkyl group with 2 to 4 carbon atoms N / S means. 65

In general, these compounds can be replaced by (CH ₂ ) ₃

Implementation of a mercapto-alkyl sulfonate with a |

Nitrile or an amide. SO ₃ "

Particularly good results are achieved with the conversion product of mercapto-prop; insulphonate with butandinitri! or acrylonitrile.

During the production of the three-layer nickel coating You can use a Watts nickel bath for matt-finished coatings and to form the lower layer a bath for matte, semi-gloss or glossy nickel plating is used to form the top layer ., provided that the upper one has higher sulfur content than the lower layer.

Although increased corrosion protection is achieved with this three-layer nickel coating, in In many cases the top nickel layer is finished with a thin, usually shiny or micro-cracked finish or microporous chrome layer, expediently a thickness of about 0.00012? until 0.00508 mm - »see. In general it has been found to be useful that the lower Nickeischichi is thicker than the above: the preferred ratio is between about 50:50 and 80:20 for best ductility de >> to achieve coating. However, it opens up the ductility does not matter in the first place, so are Thickness ratios of about 40:60 are common. This is an excellent protection against corrosion keep the basic metal surface.

It should be noted that the nickel layers contain small amounts of other components besides sulfur may contain as you would tvpisch for such coatings are. ζ. Β carbon, selenium, tellurium. Zinc, cadmium. Iron and the like. In addition, they can also contain cobalt. z. B. in amounts up to at least 50%. contain. Often, however, it has proven to be useful that the lower nickel layer, if possible, consists of pure nickel.

Accordingly, the lower nickel layer can consist of a Watts nickel bath, a fluoborate, a with a high chloride content, a sulphamate nickel bath or a largely sulfur-free semi-gloss nickel bath be generated. The bath from which the middle nickel layer is deposited can be made of the same Kind of like the one used to deposit the bottom layer, or an alkaline nickel bath or a nickel bath with high sodium, ammonium lithium im- or magnesium content. Likewise, the galvanic baths that make up the top layer deposited will be the same as that. which are used to create the middle layer. Of course, the concentration of sulfur compounds is lower than in the baths for them middle layer. If a decorative plating is desired, the top layer of nickel is made of a bright nickel bath in which one or more of the organic sulfo-oxy compounds, those in Table II of U.S. Patent 2,512 ^ 80 and in Table II of U.S. Patent 2,800,440 Listed are the compounds are also preferably with unsaturated compounds or Amines used to get smoothness and gloss / - are used.

These galvanic baths can also contain other components, such as wetting agents to prevent hydrogen pores, buffers such as boric acid, formic acid. U citric acid, acetic acid, fluoboric acid. Like. The baths Vönnen example, at temperatures ranging from room temperature, ie about 20 ⁰ C, to be operated at least about 85 ⁰ C and at pH values in the range of 1 to 6 c.//a . R USA.- Patent 3,090,733 to produce the - described layered Nickelül'crzuacs: These electroplating baths can be eearbeitet as ir in the same way!. It has been found jt vh. that when the sulfur-containing compounds according to the invention are used, shorter deposition rates are possible because air agitation and higher temperatures are possible and metal impurities are possible. like zinc. Copper and lead can easily be removed without first having to destroy the organic sulfur compounds. Thus, the bath according to the invention can be used to create the three-layer nickel coating on SuIi !. Aluminum. Zinc. Magnesium. Brass and similar corrosion-sensitive base metals are used.

In the following examples, percentages and parts are given. unless otherwise stated, also weight; based.

Example 1

Steel plates were provided with a three-layer nickel coating as indicated below:

15μηι a sulfur-free, semi-glossy nickel layer with a sulfur content of 0.003 "... 1.5: in a high-sulfur nickel deposit! with a sulfur content of 0.143%. obtained by a concentration of 0.05g 1 a reaction product of butanedinitrile and mercaptopropane sulfonate (I) in an air-stirred nickel bath at a temperature of 63 C.

! Ομηι a glossy nickel layer with a sulfur content of 0.05%.

Thereon a thin chrome coating was applied with a thickness of 0.25 micron, and then the accelerated Corrodkote test performed. After 16 hours there was a missing point (rust spot), whereas the same panels without the high-sulfur intermediate layer had more than 25 missing spots (rust spots).

Example 2

A coating was produced as described in Example 1, with the exception that the concentration on the thiosulfonate of dinitrile was increased to 0.1 g of 1. The sulfur content of the intermediate layer was thereby increased to 0.22%. The chrome plated three layer nickel plating was essential better than a coating of the same thickness, which leaves the high-sulfur intermediate layer undone

Example 3

Plates were coated with three layers of nickel provided as follows:

10 rim of a sulfur-free, semi-glossy nickel layer with a sulfur content of 0.003%,

!, 75 µm of a high-sulfur nickel layer with a sulfur content of 0.16%. At C ¹ UTCh, a concentration of 0.09 g 1 of the reaction product of propane nitrile and mercaptopropane sulfonate in an air-stirred nickel bath at a temperature of 6O ⁰ C is maintained,

10 μΐη of a shiny nickel layer with a sulfur content of 0.05%.

This coating was provided with a chrome layer 0.25 µm thick, followed by the Subject to CASS test. After 20 hours the base metal had not penetrated anywhere, whereas the same panels without the high-sulfur intermediate layer have more than 14 defects (rust spots) showed.

Example 4

Plates were provided with a three-layer nickel coating and a chrome top coating, as described in Example 1, with the exception that the high-sulfur layer (1) consists of a Non-air-agitated nickel bath according to Watts at a temperature of 46 ° C using 0.2 g / l Benzenesulfinate (U.S. Patent 3,090,733) and (2) from a Watts air-stirred nickel bath a temperature of 63 ° C using 0.045 g / l of the reaction product of butanedinitrile and mercaptopropane sulfonate had been applied.

After the panels were exposed to the accelerated Corrodkotc test for 32 hours, showed the plates with the high sulfur layer made using Bcnzenesulfinal had been 100 missing points (rust spots) while the plates covered with the high sulfur layer using the reaction product of butanedinitrile and mercaptopropane sulfonate had been showing about 25 missing points (rust spots)

Example 5

15 comparative tests with regard to the stability of the bath additives in example 4 (1) and 3 in hot nickel solutions resulted in:

1. after a nickel solution 16 hours on one pH 1.5 and maintained at 57.2 ° C was 47% of that Benzene sulfonate oxidizes while

2. No loss of the dinitrile thiosulfonate after 24 hours under the same conditions had occurred.

307537

Claims (2)

Patent claims: 1. Bath for the galvanic deposition of a three-layer, adherent nickel coating on a corrosion-prone metal surface with a content of at least one sulfur-containing Amide or nitrile. the lower nickel layer having a thickness of 3.Xi to 3S.1 µm and an average sulfur content below 0.03 ° o. the middle nickel layer has a thickness of 0.127 to 5.08: i.m and an average Sulfur content from 0.05 to 0.3 "and the top nickel layer a thickness of 5.08 to 38.! J.m and an average sulfur content of 0.02 to 0.15 ° o and the upper layer a lower average Schvefc'content has as the middle layer and one higher than the lower layer, characterized that it. at least for the deposition of the middle layer, at least one thiosulfonate a sulfur-containing nitrile or amide. 2. Bath according to claim 1, characterized in that that it contains a compound of the following general formulas as thiosulfonate: