DK147237B - BATHROOM FOR ELECTRIC NICKLING OF METAL AND METAL ALLOYS, SPECIFICALLY ALUMINUM AND ALUMINUM Alloys, AND PROCEDURE FOR STRUCTLESS NICKLING USING THE BATH - Google Patents

Description

147237

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a bath for electroless nickel plating of metal and metal alloys, in particular aluminum and aluminum alloys, of nickel salt, complex salts, sodium hypophosphite, an accelerating addition in the form of a water-soluble polyhydroxy derivative of benzene and a water-soluble copper salt as a stabilizing agent.

Baths for powerless nickel plating, especially high power baths with high excretion rate, are under certain conditions, e.g. local overheating, excessive concentration of reducing agent by addition of supplementary solution, prone to instability, i.e. to a more or less rapid self-destruction. This is evidenced by an ever-increasing "wild separation" of nickel, especially on the bottom and the walls of the bathtub. The elimination of nickel leads to increasing chemical consumption, to the formation of flawed, rough coatings and to the need for frequent cleaning of the bathtub. In extreme cases, by instability of the bath, a spontaneous self-degradation of the bath is induced, which necessitates an immediate interruption of operation.

German Commonly Available Patent Application 2,253,491 discloses baths for electroless nickel-plating of metal, plastics and ceramics which, to increase the rate of excretion, contain a certain amount of a water-soluble polyhydroxybenzene which may contain at least one additional functional group and as stabilizing agent possibly copper in the form of a water-soluble copper salt. Such baths are particularly suitable for the electroless nickel plating of steel, copper and copper alloys, also in production companies. They are also well suited for the electroless nickel plating of aluminum and aluminum alloys in the case of smaller volumes and smaller production volumes. However, with larger baths and / or larger amounts of aluminum nickel-plated parts, difficulties occur, which are mainly contingent on the poor stability of the bath.

The object of the invention is to provide baths for electrically nickel-plating metal and metal alloys, in particular aluminum and aluminum alloys, which are also suitable for a production-electroless nickel plating at high production rates. Furthermore, the stability of the baths must be ensured while maintaining a high excretion rate.

This problem is solved with a bath containing nickel salt, complex salt, sodium hypophosphite, an accelerating addition in the form of a water-soluble polyhydroxy derivative of benzene and a water-soluble copper salt as a stabilizing agent, which bath is characterized by the fact that the bath is - 3 - 147237 (a) contains 30-150 g / l of at least one complexing agent, (b) has a content of 10-50 g / l sodium hypophosphite and 5-10 g / l of accelerant, (c) has an increased content of stabilizer using a nickel complex salt -supplement solution containing 1-5 g / l copper (II) sulfate (CuSOitSI 2 O) and (d) during operation has a nickel content of not less than 7 g / l.

The baths of the invention are characterized by excellent bathing stability while maintaining a high excretion rate. You get shiny nickel coatings, even in larger thicknesses. On the nickel intermediate layers which are streamlessly produced with the baths according to the invention, particularly well-adhered galvanic coating of e.g. silver on aluminum. A very significant advantage of the baths of the invention also lies in the fact that they can be used at lower temperatures of 80-94 ° C while maintaining the high excretion rate. In that case, the odor gene due to ammonia is very poor. Also, with the baths according to the invention, in a rational workflow, streamless thick nickel plating of approx.

50um, such as e.g. is required for flanges for refrigerant pumps or pressure regulators or for impellers in annulus compressors.

The invention also relates to a method for electrically nickel-plating metal and metal alloys, in particular aluminum and aluminum alloys, using a bath according to claims 1 and 2, and the method is characterized by the characterizing part of claim 3.

For many applications, it is of particular advantage that the most diverse parts of aluminum castings and kneading alloys, which must be provided with a galvanic coating, for example silver, are nickel-plated in advance. With the nickel intermediate layer, a good corrosion protection is achieved and a particularly good adhesion of the galvanic coating. Furthermore, copper-coated wires or wire connections which have been electrically nickel-plated in a bath according to the invention can be bonded particularly well with a semiconductor.

A particularly suitable accelerating agent is 3,4-dihydroxybenzoic acid.

As the supplementary solution, nickel complex salt solutions, preferably consisting of nickel sulfate, lactic acid, ammonium sulfate, dihydroxybenzoic acid and copper (XI) sulfate, are used.

Suitable complexing agents are citric acid, glycolic acid, acetic acid and succinic acid, malonic acid, malic acid, propionic acid or the alkali salts of these acids. Lactic acids and lactates have proved particularly suitable.

The baths of the invention are used with particular advantage for nickel plating of the various parts of aluminum casting and kneading alloys, e.g. antenna parts, satellite parts, cable plug housings, etc. In many cases, especially for high frequency parts, the electrically nickel-plated aluminum parts are then further galvanized silver to achieve a high surface conductivity. The baths according to the invention are also well suited for the electroless nickel plating of transistor feet. Also, the baths according to the invention can advantageously be used in the electroless nickel plating with subsequent galvanic silvering of aluminum contact blades for high current fuses. Thick nickel flanges for refrigerant pumps and pressure regulators as well as impellers for ring compressors have shown excellent properties.

The invention is further explained in the following by means of some examples.

Example 1

The objects of metal, e.g. of copper or copper alloys are electrically nickel-free after a standard treatment in the electroplating technique, in a nickel bath of the following composition:

Nickel sulphate NiSOi,. * 6Η20 35 g / l tri-sodium citrate 0585 ^307 * 5.5Η20 100 g / l

Ammonium sulphate (NH₂SOifF 25 g / l

Sodium hypophosphite NaPH 2 O 2 H 2 O 20 g / l 3.4-dihydroxybenzoic acid (HO) 205 µg 6 g / l

Copper (II) Sulfate CuSO 4 * 5H 2 O 0.05 g / l pH 7.2-7.5

Temperature 88-94 * C Separation rate 20-25 µm / h 2

Surface loading of the bath up to 2 dm / 1 2 3

Every 10 minutes is added to the bath per minute. dm product surface 10 cm of an ammonia nickel complex salt solution (supplementation solution A) 3 147237 - 5 and 5 cm reduction solution (supplementation solution B).

The supplement solutions have the following composition: 1. Nickel complex salt solution (supplement solution A)

Nickel sulphate 190 g / l tri-sodium citrate 75 g / l

Ammonium sulphate 30 g / l 3,4-dihydroxybenzoic acid 6 g / l

Copper (II) sulfate 2 g / l

Ammonia 350 g / l 2. Reduction solution (supplement solution B)

Sodium Hypophosphite 395 g / l As soon as a certain bathing density has risen, a portion of the electrolyte volume is discarded and replaced with water so that the bathing density is kept within 3 3 for certain limits (1,051 g / cm - 1,262 g / cm at operating temperature).

Example 2

The articles of aluminum or aluminum alloys are nickel-plated in a nickel bath of the following composition:

Nickel sulphate NiSO 3 eHgO 35 g / l Lactic acid CH 3 CHOHCOOH 50 g / l

Ammonium sulphate (NH 1) SO 50 50 g / l

Sodium hypophosphite NaPH202 * H2O 20 g / l 3,4-dihydroxybenzoic acid (HO) 2CeHitCXDOH 6 g / l

Copper (II) Sulfate CuSO 1 S0 O 0.05 g / l pH 7.2-7.5 Temperature 88-94 * C Separation rate 25-35 µm / h 2

Plate loading of the bath up to 2 dm / 1 2 3

Every 10 minutes is added to the bath per minute. dm product surface 10 cm of an ammonia nickel complex salt solution (supplement solution A) 3 and 5 cm reduction solution (supplement solution B).

The supplement solutions have the following composition: - 6 - 147237 1. Nickel complex salt solution (supplement solution A)

Nickel sulphate 190 g / l Lactic acid 50 g / l

Ammonium sulphate 30 g / l 3,4-dihydroxybenzoic acid 6 g / l

Copper (IX) sulfate 2 g / l

Ammonia 350 g / l 2. Reduction solution (supplement solution B)

Sodium Hypophosphite 395 g / l As soon as a certain bathing density has risen, part of electrolyte volund.net is discarded and replaced with water so that the bathing density is kept within 3 3 for certain limits (1,051 g / cm - 1,262 g / cm at operating temperature).

Example 3

The articles of cast aluminum are nickel-plated seamlessly after a common pre-treatment in the gal-vanot technique. The bath used for this has the following composition:

Nickel sulphate ΝΐβΟι / β ^ Ο 35 g / l

Sodium glycolate HOCH2 "000 Na 50 g / l

Ammonium sulphate (NHi ^ SOi, 50 g / l

Sodium Hypophosphite NaPI ^C ^'O 20 g / l 2,3-dihydroxybenzoic acid (ΗΟ ^ ΟβΗ ^ ΟΟΟΗ 6 g / l

Copper (II) sulphate CuSOi / SI ^ O 0.05 g / l pH 7.2-7.5 Temperature 88-94 * 0 Separation rate 25-35 μιη / h 2

Surface loading of the bath up to 2 dm / 1 2 3

Every 10 minutes is added to the bath per minute. dm product surface 10 cm of an ammonia nickel complex salt solution (supplement solution A) 3 and 5 cm reduction solution (supplement solution B).

The supplement solutions have the following composition: - 7 - 147237 1. Nickel complex salt solution (supplement solution A)

Nickel sulfate 190 g / l

Sodium glycolate 50 g / l

Ammonium sulphate 30 g / l 2,3-dihydroxybenzoic acid 6 g / l

Copper (II) sulfate 2 g / l

Ammonia 350 g / l 2. Reduction solution (supplement solution B)

Sodium Hypophosphite 395 g / l As soon as a certain bathing density has risen, a portion of the electrolyte volume is discarded and replaced with water so that the bathing density is kept within 3 3 for certain limits (1,051 g / cm - 1,262 g / cm at operating temperature).

The 50 mm thick nickel-plated aluminum parts have excellent corrosion resistance to water and alkaline solutions.

Example 4

Aluminum objects must be silver plated to become superconducting in terms of high frequency current. To obtain a silver-coated coating, the parts are pre-electrically nickel-plated.

The nickel intermediate layer is applied by electrically nickel-plating in an electrolyte having the following composition:

Nickel sulphate NiSOi ^ e ^ O 35 g / l

Sodium acetate CH3COO Na 50 g / l

Ammonium sulphate (NH4 SO2 * 25 g / l

Sodium hypophosphite NaPH 2 O 2 H 2 O 20 g / l 2,5-dihydroxybenzoic acid (HO 2 CgH 2 COOH 6 g / l

Copper (II) sulphate CuS (V5H20 0.05 g / l pH 7.2-7.5 Temperature 88-94 * C Separation rate 25-35 μιη / h 2

Surface loading of the bath up to 2 dm / 1 2 3

Every 10 minutes is added to the bath per minute. dm product surface 10 cm of an ammonia nickel complex salt solution (supplement solution A) 3 and 5 cm reduction solution (supplement solution B).

The supplement solutions have the following composition: - 8 - 147237 1. Nickel complex salt solution (supplement solution A)

Nickel sulfate 190 g / l

Sodium acetate 50 g / l

Ammonium sulphate 30 g / l 2,5-dihydroxybenzoic acid 6 g / l

Copper (II) sulfate 2 g / l

Ammonia 350 g / l 2 · Reduction solution (supplement solution B)

Sodium Hypophosphite 395 g / l As soon as a certain bathing density has risen, a portion of the electrolyte volume is discarded and replaced with water so that the bathing density is kept within 3 3 for certain limits (1,051 g / cm - 1,262 g / cm at operating temperature).

In the manner described, it is applied over approx. 20 minutes a nickel spacer with a thickness of 10 microns.

The parts thus treated, after decapitation in 10% by volume sulfuric acid and rinsing in running water, are galvanically pre-silvered for 10 seconds at a current density of 6-8A / dm and then silvered at a 2 current density of 1.2A / dm. After 15 minutes, the layer thickness is 10 µm.

In this way, a body of low density and with a surface layer is obtained which, in connection with an excellent pendant, has excellent conductivity for high frequency currents.