DE959242C - Bath for the galvanic deposition of antimony or antimony alloys - Google Patents

Description

ISSUED FEBRUARY 28, 1957

G 11878 VI j 48 a

is used

The invention relates to the galvanic deposition of antimony or antimony alloys, for example Pb-Sb, from a solution of an antimony compound.

Normally, antimony cannot be electroplated in a smooth, shiny and firmly adhering form deposit as required for most purposes.

It has been proposed to add colloidal substances to galvanic baths, for example Diethylenediamine (U.S. Patent 2,195,454), polyether (British Patent 595,148) and the additions mentioned by Fanhauser in "Galvanotechnik", 1949, Vol. i, pp. 865, 866. These substances are knocked down at the same time as the metal, but only result in a certain amount Grain refinement and, especially in the case of antimony, are not satisfactory.

U.S. Patent 2,474,092 suggests adding citrates or Rochelle salt to lead baths before, but in this way only inadequate coarsely crystalline and non-adherent Manufacture coatings. Better results are obtained from U.S. Patent 2,474,092

only occurred through the use of tar (or salts of similar hydroxy acids) together with certain complex betaines containing long chain alkyl substituents. These However, connections are known to be very expensive and difficult to represent.

German patent specification 731 102 suggests the galvanic deposition of sub-group metals, namely copper, nickel, cobalt, zinc ίο and cadmium, to make from a bath liquid, which contains the metal to be deposited in the form of ethylene diamine tetra acetate.

It is well known that antimony differs fundamentally chemically from the subgroup metals. In its compounds, antimony behaves primarily as a non-metal; it does not form complex cyanides, as is typical for the transition _{elements (for example K 2} [Cu (CN) ₄ ] etc.), nor does it form complexes with ammonia, which are also characteristic of the subgroup elements. Furthermore, there is no simple antimony salt which is so stable that it can be used directly in electroplating baths. For example, the sulfate Sb ₂ (SO ₄ ) 3 and the chloride Sb Cl ₃ (in contrast to the corresponding compounds of copper, nickel, cobalt, zinc and cadmium) separate out basic salts when dissolved in water, for example SbOCl. But if you add acid to stabilize the salt solutions, you get completely unusable antimony deposits, such as the well-known "amorphous" antimony from Sb Cl 3-H Cl solutions. Given this situation, it is by no means to be assumed that antimony would form a complex ion with ethylenediamine-tetra-acetic acid, so that the use of this compound in the deposition of antimony seems to be excluded from the outset by itself. It is all the more surprising to find that, despite the special properties of antimony, the addition of ethylene-diamine-tetra-acetic acid has a beneficial effect on the deposition of antimony. So far it has not been possible to explain and theoretically prove the surprising effect of ethylene-diamdn-tetra-acetic acid, namely the production of a smooth, shiny and firmly adhering coating.

According to the invention, an electroplating bath intended for electroplating contains an alkali salt of ethylene-diamine-tetraacetic acid, which is abbreviated in the following is referred to as an "additive".

The tetra-, tri-, di- or mono-sodium salt of ethylene-diamine-tetraacetic acid can be used as an additive or use the appropriate potassium compound.

The additive can be acidic or alkaline baths until a solubility ' Product can be added in any amount. However, these amounts are preferably in a range that is characterized on the one hand by a ratio of at least 2V2: 1 between the Additive and the antimony dissolved in the bath liquid, on the other hand through the solubility of the additive is limited.

Antimony or antimony alloys can be electrodeposited in any thickness will.

For decorative layers and corrosion-resistant protective coatings Layer thicknesses of up to 0.005 mm or more are preferably used, are typical 0.0038 mm. On the deposited layer of antimony or antimony alloy can still a chromium layer can be deposited galvanically.

To illustrate this, the following is an example of a good antimony bath: 80 to 200 g / l dibasic ammonium citrate, 10 to 80 g / l potassium antimonyl tartrate, 30 to 60 g / l Tetra-sodium salt of ethylene-diamine-tetra-acetic acid.

For the deposition of an alloy of antimony and lead, 10 to 25 g / l lead oxide are added to the bath or a corresponding amount of lead acetate is added. Likewise, instead of dibasic Ammonium citrate, citric acid and ammonia can be used. When a lead-antimony alloy should be knocked down, which consists mainly of antimony, the bath can contain 40 to 80 g of potassium antimonyl tartrate and contain 20 g of lead oxide or lead acetate per liter of water. Lower concentrations of Potassium antimonyl tartrate are used for the galvanic deposition of antimony-lead alloys, in which lead is the predominant component. is. Such antimony alloys with high Lead contents are very ductile and harder and whiter than lead and form a good base for lead alloys with high antimony content.

Advantageously voltages used by 1 to ioo 4 volts and current densities from 54 to 540 Amp./m ^2, while the bath temperatures between room temperature (and below) and 52 ⁰ C (or higher) may fluctuate. The _pH value of the electrolyte should be between 4 and 5 (preferably 5) Hegen.

For the deposition of an alloy, which consists mainly of antimony and a smaller one Amount of copper, 0.4 to 2 g of copper sulfate are added to the antimony bath described last added per liter of water. In this way, deposits of extraordinary sheen can be produced. "

For galvanic deposition of antimony-tin alloys, 20 cm ^{3 of} tin (II) fluorate (46% solution) per liter of water can be added to the antimony bath described above.

For the galvanic deposition of antimony-cadmium alloys, the above-described About 10 iao to 25 g of a soluble cadmium compound were added to the antimony bath per liter be e.g. B. cadmium sulfate or cadmium chloride.

For the galvanic deposition of antimony-indium alloys, the above-described Antimony bath about 10 per liter

to 40 cm ³ of a 5 ° ⁰ / ° ig ^e are added N solution of indium chloride in water.

The anodes can consist of pure antimony; in the case of electrodeposition of antimony alloys, however, one can also use anodes made of an alloy of antimony and the metal to be deposited together with antimony.

Antimony or alloys of antimony can be electroplated to any of the usual cathodes used metals are deposited, for example on iron or steel, copper, Lead, tin, nickel, cadmium, indium, zinc, etc.

When electroplating casting molds made of steel, brass or mainly zinc exist, one uses the rule with good success:

1. Create a thin coating of lead in an alkaline lead bath;

2. deposit a lead-antimony coating (an alloy with a high lead content);

3. Separate an antimony-lead coating (an alloy with a high antimony content) or an antimony-copper coating (an alloy with a high antimony content).

A thin indium or tin coating can be deposited in place of the lead coating. If copper is used as an intermediate layer, it is preferred (because of the possibility of a Reaction between copper and antimony) a thin coating of lead, indium or a lead-antimony alloy The high lead content is applied over the copper before the high antimony alloy is deposited.

Claims (4)

PATENT CLAIMS: 1. Bath for the galvanic deposition of antimony or antimony alloys, thereby characterized in that it is an alkali salt of ethylene-diamine-tetra-acetic acid, preferably the tetra sodium salt contains. 2. Bath according to claim 1, characterized by a content of potassium antimonyl tartrate. 3. Bath according to claim 1 and 2, characterized in that that it contains the following substances dissolved in water: dibasic ammonium citrate 80 to 200 g / l tetra-sodium salt of the ethylene diamine-tetra-acetic acid 30 - 60 g / l Potassium antimonyl tartrate 10 - 80 g / l 4. bath for electrodeposition of an antimony-lead alloy according to claim I and 2, characterized in that it contains the following components dissolved in water: dibasic ammonium citrate 80 to 200 g / l tetra-sodium salt of the ethylene diamine-tetra-acetic acid 30 - 60 g / l Potassium antimonyl tartrate 10 - 80 g / l Lead oxide or lead acetate 10-25 g / l Considered publications: German Patent No. 731,102;
British Patent No. 595 148;
U.S. Patent Nos. 2195454, 2474092; Galvanotechnik (formerly Pfanhauser), 1949, Vol. I, pp. 865, 866. © 609 617/439 8.56 (609 809 2.57)