Composition including an additive to sulphamate electrolytes for depositing hard nickel layers and method of using same

There is added to sulphamate electrolytes for depositing hard nickel layers based on nickel sulphamate an additive comprising of boric acid, nickel chloride and a surface-active substance which represents a derivative of sulphamoylbenzoic acid with the general formula ##STR1## in which X and Y are hydrogen, halogen, ##STR2## alkyl radical or a mixture of these compounds in a concentration from 0.1 to 4 g/l. These hard nickel layers are used in the manufacture of matrices for different work-pieces.

The invention relates to a composition including an additive to sulphamate 
electrolytes for depositing hard nickel layers used in the manufacture of 
matrices for processing plastics, printing blocks, securities, cylinders 
or wall-paper printing, carpets, screen printing, cutting and press tools, 
workpieces for instrumental design, fine mechanics and optics, etc. The 
invention also includes the method of using such composition. 
Electrolytes based on nickel sulphamate, boric acid, nickel chloride and an 
antipitting additive are known, in which, in order to obtain layers with 
high hardness there are added to the electrolyte saccharin (1), 1, 3, 
6-naphthalenetrisulphonic acid (2), coumarin etc. (3) See (1) U.S. Pat. 
No. 3,990,955, (2) U.S. Pat. No. 4,049,509, and (3) Dams B, Rolf R., 
Metalloberflache, No. 35/1981/10. 
However, along with high hardness, these additives diminish considerably 
the plasticity of the layers obtained, and very often cause internal 
tensile stresses which is undesirable in depositing coatings with a 
thickness of several mm. Other drawbacks of these additives are their high 
initial concentrations, their great consumption, their complicated and 
expensive synthesis, as well as the fact that they are carcinogenic 
(coumarin). The insertion of considerable amounts of sulphur in the layer 
in using these additives causes an increased brittleness of the layer at 
high temperatures and a corrosion instability. 
The object of the invention is to provide a surface-active additive to the 
electrolytes for sulphamate nickeling which ensures the obtaining of 
nickel with a high hardness which is uniformly distributed all over the 
item, with a minimal sulphur content, which has high plasticity, and has 
internal stresses which are close to zero. 
According to the invention this object is attained by adding to the 
sulphamate electrolytes an additive in concentrations from 0.1 to 4 g/l, 
representing a derivative of sulphamoylbenzoic acid with the general 
formula 
##STR3## 
in which X, Y can be hydrogen, halogen, 
##STR4## 
alkyl radical, or a mixture of these compounds.

The technological flow-sheet of preparing the additive is easily feasible 
and the yields are high. The initial, intermediate and end products are 
not toxic or carcinogeric. The additive dissolves entirely and rapidly in 
amounts considerably surpassing its operational concentration, so that its 
several times overdosing does not deteriorate the quality of the layer. 
The layers thus obtained have a Vickers hardness from 470 to 550 
kg/mm.sup.2, internal streses from +0.5 to -4.5 kg/mm.sup.2, a plasticity 
measured according to the method of Rolfi-Damas of over 7%, and there are 
no visual defects. The invention is illustrated by the following examples: 
EXAMPLE 1 
An electrolyte with the following composition is used: 
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g/l 
______________________________________ 
nickel sulphamate 350 
boric acid 36 
nickel chloride 3 
alkylethersulphate 0.1 
2, 4 dichloro-5 sulphamoylbenzoic 
0.75 
acid 
______________________________________ 
The layer is prepared at pH 4.4, a temperature of 43.degree. C., and with a 
current density of 10 A/dm.sup.2. The layer thus obtained has a hardness 
of 515 kg/mm.sup.2, a plasticity of 10.5%, and internal stresses of 40.5 
kg/mm.sup.2. 
EXAMPLE 2 
The electrolyte composition is the same as in Example 1, while the additive 
is used in a concentration of 1.5 g/l. 
The layer is prepared at pH 4.4, a temperature of 49.degree. C., and a 
current density of 5 A/dm.sup.2. It has a hardness 500 kg/mm.sup.2, a 
plasticity of 9.5% and internal stresses of 4.5 kg/mm.sup.2. 
EXAMPLE 3 
An electrolyte with the following composition is used: 
______________________________________ 
g/u 
______________________________________ 
nickel sulphamate 350 
boric acid 36 
nickel chloride 3 
nonylphenolether 0.1 
2, 4 dichloro-5-sulphamoyl-6-furanylbenzoic acid 
1.5 g/l. 
______________________________________ 
The layer is prepared at pH 4, a temperature of 49.degree. C., and a 
current density 15 A/dm.sup.2. The coating thus obtained has a hardness of 
545 kg/mm.sup.2, a plasticity of 6.5%, and internal stresses of 0.6 
kg/mm.sup.2. 
Although the invention is described and illustrated with reference to a 
plurality of embodiments thereof, it is to be expressly understood that it 
is in no way limited to the disclosure of such preferred embodiments but 
is capable of numerous modifications within the scope of the appended 
claims.