ELECTROLYTIC NICKEL PLATING COMPOSITION AND METHOD OF ELECTROLYTIC NICKEL PLATING USING SUCH A COMPOSITION

Abstract

The invention relates to a composition for electrolytic nickel plating. In order to provide an improved composition, it is proposed that it comprises one or a plurality of nickel ion sources and a mono-, di- or tri-hydroxybenzene compound, preferably a hydroquinone compound or the salts thereof or mixtures thereof.

Claims

1. Composition for electrolytic nickel plating, characterised in that it comprises one or a plurality of nickel ion sources in the form of nickel sulfate, nickel chloride and/or nickel sulfamate and a mono-, di- or tri-hydroxybenzene compound, preferably a hydroquinone compound or the salts thereof or mixtures thereof as a complexing agent in a quantity greater than 5 g/L.

2. Composition as claimed in claim 1, characterised in that it comprises an additional sulfoxylate ion source and/or an additional carboxylate ion source.

3. Composition as claimed in claim 2, characterised in that the additional carboxylate ion source comprises a salicylic acid compound.

4. Composition as claimed in claim 3, characterised in that the salicylic acid compound is a 5-sulfosalicylic acid.

5. Composition as claimed in claim 1, characterised in that the mono-, di- or tri-hydroxybenzene compound, preferably the hydroquinone compound or the salts thereof or mixtures thereof, are present in quantities of 5-30 g/L, preferably 10-20 g/L, preferably 15 g/L.

6. Composition as claimed in claim 2, characterised in that the additional sulfoxylate ion source and/or the additional carboxylate ion source, preferably the salicylic acid compound, preferably the 5-sulfosalicylic acid, or mixtures thereof are present in quantities of 2-40 g/L, preferably 5-25 g/L, preferably 10 g/L.

7. Composition as claimed in claim 1, characterised in that it has a pH value of 3 to 7.

8. Method for electrolytic nickel plating on a substrate, characterised in that it comprises: providing the substrate; contacting the substrate with a composition for electrolytic nickel plating as claimed in any one of claims 1 to 7; and applying an electric current to the composition for electrolytic nickel plating and the substrate.

9. Method as claimed in claim 8, characterised in that the strength of the applied electric current is 0.5 to 4 A, preferably 1.5 to 3.5 A, preferably 3 A.

Description

EXAMPLE 1

[0042]

TABLE-US-00002 hydroquinone 15 g/L 5-sulfosalicylic acid 10 g/L

[0043] Completely desalinated water is introduced to the solution to make up 1500 ml.

[0044] The pH value is determined electrochemically by pH measuring chain on a pH-meter (Metrohm 744 pH-Meter). The device is calibrated with corresponding commercial solutions (CertiPUR Buffer Solution for the pH values 1, 4 and 7 by Merck) prior to the measurement. To measure current, a calibrated Fluke 175 True RMS Multimeter is used. The measured pH value is 5.

[0045] The anodes used are solid anodes consisting of solid nickel material (1 cm thick) with sheathings.

[0046] Commercially available brass sheets (Hull-cell sheets, Ossian) are coated with 3 A for 780 min at 55 C. after typical pre-treatment (degreasing, rinsing, activation, rinsing). A magnetic stir core operating at 100 revolutions per minute is used as the electrolyte movement.

[0047] After the coating procedure, the pH value of the electrolyte is likewise measured by means of the method described above. The measured pH value is 5.1.

[0048] Within the scope of examining the smoothing performance, a homogeneous, high-gloss layer was demonstrated from 0.05 A/dm.sup.2 to the upper edge of the Hull-cell sheet, with smoothness at least as good as is the case in the comparative example with boric acid (45 g/L instead of hydroquinone and 5-sulfosalicylic acid).

[0049] The combination of hydroquinone and 5-sulfosalicylic acid thus has a highly inhibitory effect upon layer growth in the high current density range, wherein an extremely homogeneous layer thickness distribution is achieved without any hydrogen development being visible.

EXAMPLE 2

[0050]

TABLE-US-00003 4-phenolsulfonic acid, Na-salt 40 g/L 5-sulfosalicylic acid 5 g/L

EXAMPLE 3

[0051]

TABLE-US-00004 4-phenolsulfonic acid, Na-salt 40 g/L hydroquinone 10 g/L

EXAMPLE 4

[0052]

TABLE-US-00005 4-phenolsulfonic acid, Na-salt 40 g/L hydroquinone sulfonic acid, K-salt 10 g/L

[0053] Examples 2 to 4 are conducted and evaluated in a similar manner to example 1. What is common to all of the examples is that they produce high-gloss, highly smooth and ductile layers.

[0054] Furthermore, even when 4-phenolsulfonic acid is used alone, it is possible to produce a corresponding layer which satisfies all of the requirements of a layer of a gloss nickel bath, with the exception of a low level of burning-on in the high current density range, which in practice is irrelevant for the most part. This limitation at high current densities can be very efficiently corrected with the addition of the secondary substances indicated in the examples, whereby the applicable current density range becomes considerably larger than in the case of corresponding boric acid methods, whilst all other aspects of a gloss nickel layer are retained.

[0055] It is assumed that this extension of the current density range is due significantly to the complexing properties of the additionally introduced, phenolic compounds which are effective specifically in the pH range of the nickel hydroxide formation.