DE1053275B - Process for the joint separation of lead and indium by electrolysis of an aqueous bath - Google Patents

Description

The use of certain agents to inhibit the normal reactions of metal ions in solutions is known in electroplating. In particular, it is known that in this way the precipitation of magnesium and to prevent calcium compounds in water softening. It has been suggested use these agents to reduce the activity of unwanted metal ions in solutions for the preparation of metal coatings, so that one obtains relatively pure metal deposits can, even if small amounts of other metals are present, otherwise contaminate the deposit would.

In British Patent 737 713 it is proposed to carry out the electrodeposition of lead or lead alloys or of antimony or antimony alloys from a solution which contains an alkali metal salt of ethylenediaminetetraacetic acid in order to obtain an even, smooth and shiny metal deposit. In the galvanic deposition of lead-indium alloys from such a solution, particularly good results are obtained if a cathode current density of 0.01 to 0.02 A / cm ² is used in the bath,

The invention aims to provide an advantageous method for the electrolytic deposition of lead and indium alloys, especially at higher cathode current density, e.g. B. up to 0.12 A / cm ² .

It is already known that the co-deposition of indium and lead is relatively balanced proceeds when substances are present in the bath, which are referred to in the following as "regulating agents" are designated. Such a regulating agent is e.g. B. ethylenediaminetetraacetic acid, which in the is referred to as "Enta" for abbreviation in the following description. Other regulatory agents used in the mentioned context can be used, are z. B. Propylenediaminetetraacetic acid and cyclohexane-1,2-diammotetraacetic acid,

The baths in which these regulating agents are used are preferably neutral or almost neutral, with the regulating agents then as salts are present, e.g. B. as sodium, potassium or ammonium salts or .as mixtures of these salts.

If in baths that contain regulating agents, dissolvable anodes are used and if the anode power is higher than the cathode power, especially at high current densities, the proportion of M et all ions increases as a result of the difference between the Anode and cathode output constantly on. This increase not only causes changes in the composition the deposition, it also makes the whole process cumbersome and expensive because of the electrolyte Processes for joint deposition are withdrawn at certain time intervals of lead and indium by electrolysis

an aqueous bath

Applicant:
Vandervell Products Limited, London

Representative: Dipl.-Ing. W. Cohausz

and Dipl.-Ing. W. Florack, patent attorneys,

Düsseldorf, Schumannstr. 97

Claimed priority:
Great Britain December 2, 1955

William John Waterman, Cookham, Berkshire,

and Vincent Ernest Gripp, Stoke Poges,

Buckinghamshire (UK),

have been named as inventors

must and the metal values must be reset. But if to change the metal concentration in To keep the electrolyte sufficiently low, indissoluble anodes are used, one occurs Oxidation of the regulating agent, with formaldehyde and certain nitrogen compounds be generated. These substances have a cathode-inhibiting effect on the deposition of indium. The usage indissoluble anodes therefore causes destruction of the regulating agent and considerable Reduction of the indium content of the alloy.

The invention is based on the knowledge that the oxidation of the regulating agent, which occurs when using indissoluble anode occurs, can be significantly degraded if the electrolyte additionally contains hydrazine. So z. B. in a solution, the ethylenediaminetetraacetic acid (Enta) contains, through an indissoluble anode, above all the hydrazine is oxidized, so that the decomposition of the enta can largely be avoided. It is also advantageous that the hydrazine decomposition products are harmless are in contrast to the sole oxidation of the enta. Hydrazine also destroys some

809 770/408

Claims (1)

3 4 Existing formaldehyde components that would otherwise become an indissoluble anode (and expedient would continuously collect in the electrolyte, also a dissolvable anode) is used and a temperature despite the considerably delayed oxidation of the enta. temperature of approx. 45 to 70 ° C is maintained. A tem- It is therefore preferred by adding hydrazine to the temperature of 60 ° C. The current density Electrolytes possible, the metal ion concentration 5 is expediently in the order of magnitude from 0.06 to by periodic: use of indissoluble anodes 0.12 A / cm ² . The deposited lead-indium alloy to keep at the desired value without a contains about 7 to 10% indium, the proportion of particular loss of regulating agents due to the process conditions in detail. Oxidation occurs. So z. B. if the temperature of the in- In practicing the invention, it is advantageous io diumanteil remove the deposited alloy, that in the bath, as is known, citric acid at increasing p _H values takes either the indium or tartaric acid is present to a good anode of the alloy, as well as even with an increase in resolution. In addition, one becomes, especially current density. If the hydrazine concentration is increased by adding a small amount of gelatin to the bath at high anode current densities, as is also known to be the case during the process. The deposits from a freshly prepared bath apart from lead and indium only occasionally in electrolytes of the composition mentioned need to be added in small proportions. The decomposition, however, is generally not as balanced as that of the regulating agent is slight,
is required even if gelatin is present. In order to maintain the metal content in the bath - This case occurs especially at high current densities 20, it is advisable to use dissolvable anodes; it is therefore to use for making more balanced, along with indissoluble. The more dense deposits on the cathode, expediently, detachable anodes can be added from pure indium or a small amount of triethylenetetramine, from pure lead or suitable indium-lead alloys, diethylenetriamine or ethylenediamine. exist. The indissoluble anodes are made up of graphite. Improve instead of adding ammonium chloride together. Connection of dissolvable and indissoluble Electrolytes, which come in handy when applying the er- anodes to the bus bars of the cells during are used, therefore contain lead and the whole process can also have very good results. Individual connections, one of the regulating acts mentioned, can be obtained if dissolvable and non-dissolvable the agent, and hydrazine. Preferably, the 30 detachable anodes are alternately connected for a short period of time. Baths also include citric acid (or tartaric acid), one to be included. For this purpose, a rotating small amount of gelatin, triethylenetriamine (or render or other suitable adjustable commu- Diethylenetetramine or Ethylenediamine) and Ammotator are used, so that the times in which nium chloride added. the anodes in question are connected, and also As an example, let the following composition 35 change the frequency of the switchover an electrolyte for the co-deposition of can in order to achieve the desired metal balance Indium and lead serve: to maintain the bath. TDi, · / 1 c] 1 -JN on / 1 The method according to the invention is particular τ j / ι η ι -j \ ■ <ο r / 1 advantageous in the manufacture of bearings by Indium (as chloride) 12.5 g / l. _Λ1 ,., Τ j · j t> i ■ r “, *: ,,, .. '· 40 simultaneous deposition of indium and lead Enta (ethylenediaminetetraessig- ^ - ■ ,. R 11 ι · · au u -j .. ^v , ^J ° 100/1 a suitable basis, being a deposition ". '' .. '''- ^ ° 1. the alloy is made at the front of the bearing. _TT,. λ λ η η Βεΐ application of the invention one obtains plane, Hydrazine 11.0g / l, ·. . ,,, _Λ, ·, ·, _r ·· ~ - \ .. λ η η dense and solid deposits of more uniform Gelatine 1.0 g / l ~,,,.?, .. ^{,, ö} ~. , ^& , “... ^ ₁ ,,, ■ e η it 45 composition and constant thickness Trietylenetetramine 5.0 g / l, empty area Ammonium chloride 20.0 g / l of the storage tray. The amounts of the ingredients in the bath can be can be varied within certain limits. Proven patent claims: have the following quantities: 50 • ßj j j5 I ₃ J ₅ 25 g / l 1. Process for the joint separation of Indium 10 'to 15 s / l lead and indium by electrolysis of an aqueous jr _n ta §ς _D j _s U5 „- / ι bath, the compounds of the two metals and Citric acid '.'. '.'. '.'. '. '.'. '.'. '.'. '. 45 to 55 g / l a regulating agent from the group of Hydrazine 9 5 to 62 5 g / l ⁵⁵ ethylenediaminetetraacetic acid, propylenediamine Ammonium chloride ". '.'. '.'. '.'. '.'. 5 to 30 g / l tetraacetic acid or cyclohexane-l ^ -diamine tetra- Gelatine contains 0 2 to 2 0 g / l acetic acid, characterized in that Triethylentetramine ''.'.'.'.'.'.'.'.'. 1 to 10 g / l ^ m. Bath when using an insoluble anode Hydrazine, is added. If tartaric acid is used instead of citric acid. is applied, this is expediently drawn in proportions that the bath hydrazine in one proportion about 35 to 45 g / l added, lead and indium can be added from 9.5 to 62.5 g / l, the electrolyte as hydroxide, sulfate, acetate, 3. The method according to claim 1 or 2, in which Chloride or carbonate can be added. As a regulating agent, a sodium, potassium Also use lead and indium nitrates, but 65 or ammonium salt or mixtures of these are used it is expedient to use the nitrate ion from the electrolyte salts, characterized in that excluded, because it in the elimination of that Has bath to a _pH value of 5.0 to 7.0 Indium has a cathode-inhibiting effect. is set. The bath is VXM to a _pH value from about 5.0 to 4. The method according to claim 1 to 3, characterized 7.0 set. A _pH value of 6.0 is preferred. 70 marked that the bath additionally tri- 5 6 Ethylenetetramine or diethylenetriamine or Ethy- 6. The method according to claim 5, characterized in that Lenediamine is added. draws that the soluble and the insoluble anode 5. The method according to any one of claims 1 to 4, are switched on alternately. characterized in that the concentrations of lead and indium in the bath legally obtained, in addition to a un- ^Contemplated publications: soluble anode or use a soluble anode. German Patent Nos. 731 102, 959 242; will be. British Patent No. 737 713. ι 809 770/408 3. 59