DE1246349B - Bath for the galvanic deposition of silver-antimony alloys - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number:
File number:
Registration date:
Display day:

C23b

German class: 48 a -5/44

Sch34943VIb / 48a
April 10, 1964
3rd August 1967

The invention relates to a bath for the galvanic deposition of silver-antimony alloys, especially for the production of hard and shiny silver coatings.

The silver precipitates that can be deposited electrolytically from the known and commonly used cyanide baths have a relatively low hardness. It is known to add various substances to the electrolytes, which enable the deposition of harder and also shiny deposits ίο. The substances used as brighteners not only increase the gloss, but to a certain extent also the hardness of the silver deposits. With most of these substances, hardnesses of up to about 120 kp / mm ^{a are} achieved under normal conditions. As is also known, silver coatings with higher hardness values (up to over 200 kp / mm ² ) can be produced from electrolytes containing antimony. These silver layers retain their high hardness even after prolonged storage or when heated to higher temperatures (100 to 200 ^° C.), which is not the case with most of the electrolytically deposited silver precipitates.

The introduction of antimony into the cyanide silver baths is associated with certain difficulties. In principle, it is possible to introduce the antimony in the form of alkali (III) antimonate, but it must a good deal of water and alkali hydroxide are added to the bath, because the antimonates are only stable and only sparingly soluble in a strongly alkaline solution. The constant supply of the highly alkaline antimony solution can be used in practice Do not operate because the electrolyte is enriched in an impermissible degree in alkali hydroxide and its volume becomes larger and larger due to the additives. There are therefore various organic compounds. ' used, which form more or less stable complexes with antimony and keep it in solution. as Complexing agents have been used here: Oxy acids, ζ. B. tartaric acid, or amino acids, straight-chain aliphatic polyoxy compounds, e.g. B. ethylene glycol, glycerin or sorbitol, also aromatic Dihydroxy compounds, e.g. B. Pyrocatechol-3,5-disulfonic acid.

However, these complexing agents have the disadvantage that they have an unfavorable influence in higher concentrations on the silver deposition and also harmful decomposition or reaction products in the electrolysis to build.

To overcome these disadvantages, it has already been proposed to use amino alcohols as complex-forming solvents for antimony hydroxide or bath for electrodeposition
of silver-antimony alloys

Applicant:

Schering Aktiengesellschaft,

Berlin N 65, Müllerstr. 170/172

Named as inventor:

Dr. Hubert Offermanns, Solingen-Merscheid;

Dr. Willy Skaliks, Berlin

To use antimony oxide. However, the antimony compounds are only available with considerable effort to bring into solution with amino alcohols, so that ζ. B. even the relatively readily soluble, freshly precipitated antimony oxide hydrate Must be heated to 160 ° C for about 1 hour with triethanolamine in order to achieve a solution to obtain.

It has now been found that complex compounds of an alkanolamine with antimony trichloride are very good are soluble and are particularly suitable as hardeners and brighteners in galvanic silver baths. as Alkanolamines are e.g. B.-particularly suitable where appropriate substituted tri- and dialkanolamines, such as triethanolamine, tripropanolamine, tri-iso-propanolamine, Tributanolamine, tri-isobutanolamine, tripentanolamine, tri- (a-ethylpropanol) -amine, trihexanolamine, Methyl diethanolamine, ethyl diethanolamine, methyldipropanolamine, ethyldipropanolamine, propyldiethanolamine and n-butyl diethanolamine.

The complexes are produced in the simplest possible way by mixing the components with one another. For this purpose, carries antimony trichloride with stirring into an excess of alkanolamine, which may contain some water and, where appropriate, has been heated to initiate the reaction conveniently at about 4O ⁰ C. ' The formation of the complex compound now takes place exothermically, the temperature rising to a greater or lesser extent depending on the conditions. It is not necessary to isolate the excellently soluble complexes; their solution can be added directly to the silver bath. It has proven to be useful if the antimony content of this solution is about 5 percent by weight. The exact composition of the complex compound is not yet known. However, this is irrelevant, since only the presence of the two components in the form of a soluble complex is required for the effect.

709 619/553

I 246

The content of antimony can in d, en according to the invention Baths in a range from about O, Ol to 10 g / l, but preferably this is kept in a range of about 0.2 to 3.0 g / l.

Shiny silver coatings with excellent properties, in particular with great hardness, can be deposited from silver baths which contain the complexes described; will. ., Besopders ^ behave advantageously., The invention. Baths in terms of gloss formation, if ^! % ie - also contain compounds of bivalent selenium. For example, electrolytes with about 30 g / l silver and about 100 g / l free alkali metal cyanide, to which the antimony complex salt solution was added, with current densities between about 0.2 and 1.5 A / dm ² and with electrolyte movement, semi-glossy silver precipitates with a hardness of Vikkers about 160 to 220 fcp '/ mm ² . If potassium or sodium selenocyanate, for example about 0.001 g / r, is added to the electrolyte as a brightening agent, then in the range of about ^{0.1 to 2.5 A / dm 2,} at least deposit the same high hardness.

The following are some examples "of the invention Silver baths listed, which. Animal complexes of Alkanolamine!} as a hardening and glazing agent contain. "'"' ".:" _ ". '." _.

Example! "■

Silver as sodium silver cyanide 30.0 g / l

Free sodium cyanide 110.0 g / l

- .. · Sodium carbonate ... '25.0 "g / l

«- Antimony, as a solution-of - ----- ■ -. - - - ".-"'"-. SbCl ₃ in.triethanolamine.'. 0.5 g / l"

Example 2

Silver as potassium silver cyanide 35.0 g / l

Free potassium cyanide,. 120.0 g / l

: - potassium carbonate 30.0 g / l

Antimony as a solution of

SbCl ₃ in methyl diethanolamine .... 1.0 g / l

Example 3

Silver as potassium silver cyanide .... 30.0 g / l

Free sodium cyanide 100.0 g / l

Sodium carbonate 30.0 g / l

Antimony as a solution of

SbCl ₃ in triisopropanolamine 0.8 g / l

Claims (1)

Patent claims: • 1st bath for the galvanic deposition of silver-antimony alloys with a vial of at least one Koniplexverbindungen of an alkanolamine, with, an inorganic .Antimony compound ^: dung ^ ^r; characterized in that it contains the complex compound of an alkoxolamine with antimony trichloride. "., .- *, -. ........ 2. Bath according to claim !, in (a Jurch, at a content of Komplexyerbindung · triethanolamine with .Antimontrichiorid .., - 3, Bad nac ^ 'to claims 1 and 2, characterized by a further Geiaalt to Glanzbildnerri, preferably compounds of divalent selenium. Considered. Publications: German Auslegeschrift No. 1182 014 ... .. · .._ .. 709 619/553 7.67 © Bundesdruckerei Berlin