DD205198A1 - ELECTROLYTE FOR ELECTROCHEMICAL POLISHING - Google Patents

Abstract

The invention relates to an electrolyte for electrochemical polishing (gloss bath) of products of pure metals, preferably nickel, cobalt and iron, and their alloys with one another or with chromium as the main alloying constituent. The aim of the invention is an electrolyte which has a substantially higher operating time with constant, electrochemical labor and in which the polishing objects remain observable. The invention is based, to find a suitable additive for the gloss bath, which must be almost free of water the task. According to the invention, the electrolyte, which consists in a known manner of a mixture of sulfuric acid and ethylene glycol, 1 to 10% by mass of organic phosphonic acids or derivatives thereof added. Electrochemically polished objects are widely used, e.g. as cutting tools, cast prostheses in stomatology, as heating conductors for furnaces, implants in medicine or as base materials for metal-ceramic composites.

Description

239791 1

Electrolyte for electrochemical polishing

Field of application of the invention

The invention relates to an electrolyte for electrochemical polishing (gloss bath) of products of pure metals, preferably nickel, cobalt and iron, Bowie their alloys with each other or with chromium as the main alloying ingredient. Such products are widely used, for. B. from Co-Cr alloys or Co-Cr-Mo alloys as cutting tools in the metalworking industry and as cast prostheses in dentistry, from Ni-Cr alloys as a heat conductor for electrically heated ovens or as implants in medicine next the first mentioned alloys, of Ni-Fe-Cr alloys as surgical instruments or of Ui-Cr and Ni-Cr-Mo alloys as base materials for metal-ceramic composites, which are among the most valuable therapeutic agents in dentistry, for example.

Characteristic of the known technical solutions

It is often necessary to provide the surface of products made of these materials with a finer profile or a defined roughness and a higher light reflectance (gloss) than achievable by sandblasting, pickling or other surface treatment methods, for example Composite with ceramics or

1-2MAH932 * 0U9245

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to reduce the retention options for microbial colonization.

Very good for this electrochemical polishing is suitable in which the workpiece is partially dissolved anodically. As electrolysis liquids of different compositions are used, however, all mixtures of inorganic acids or mixtures thereof with mono-, bi- or polyfunctional alkanols, the water content may only be very limited, otherwise the anodic Metallauf- * solution by simultaneously expiring Water electrolysis is impaired ·

However, the known gloss baths have the disadvantage that, in accordance with the formation of anhydrous or only partially hydrated salts, the throwing power of the baths is changed by their crystallization at the cathode material and thus the operating time or its utilization rate is very limited. In addition, the gloss baths get a dark color, which makes it no longer possible to observe the introduced objects.

Object of the invention

The aim of the invention is an electrolyte which has a much longer service life with constant, electrochemical labor and in which the polishing objects remain observable.

Since r l ath the essence of He findunfl

The invention has for its object to find a suitable additive for the luster, which must be almost free of water, through which the absorption capacity for the reaction products formed is substantially increased. According to the invention an electrolyte for electrochemical polishing, in a known manner aue a mixture of

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Sulfuric acid and ethylene glycol, 1 to 10 percent by mass of organic phosphonic acids or their derivatives added, for example, diphosphonoacetic acid or diphosphonodimethyl.

formamide.

Suitable electrolytes are compositions in the following ranges:

70 to 90% by weight of ethylene glycol

15 to 30% by mass of sulfuric acid 1 to 10% by mass of organic phosphonic acid 1 to 5% by mass of water

The polishing conditions depend on the desired final state ·

The polishing times are shorter at higher temperature and in certain cases it may be better to polish the product twice over a short time.

A luster bath of the composition according to the invention retains a light color even during prolonged use, whereby the observability of the objects to be polished is maintained and the degree of utilization of the bath is increased by a factor of five.

embodiments Example 1:

In a shine bath of the composition

75% by mass of ethylene glycol 17% by mass of sulfuric acid

4% by mass diphosphonoacetic acid

4% by mass of water

are sandblasted castings made of an alloy of

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68 "O mass percent cobalt 25» 0 mass percentage chromium

3.5% molybdenum by weight

3 * 5 mass% Mn ₁ G, Si, Al

introduced and edited under the following conditions:

ρ anodic current density: 11-12 A per dm voltage: 6-7 V.

Working temperature: 40 ⁰ C ί 3 K

Polishing time: twice per 5 minutes / workpiece, whereby this is rinsed in the meantime with water and dried

Ratio of the cathode area to the anode area: ^ 2: 1

While about 50 to 60 skeletons of model cast prostheses can be treated with gloss baths of the known composition having a volume of 1000 ml, the solution according to the invention permits the electropolishing of about 300 objects with the same electrochemical workload per object. No disturbing discoloration of the medium is observed here. which occurs in the known gloss baths already at a load factor of 20 to 30 percent and is in a blackening, with parallel formed on the cathode surfaces reaction products are deposited, which adversely affect the throwing power of the bath · This fact does not occur in the proposed solution ·

Example 2:

In a shine bath of the composition

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75% by mass of ethylene glycol oil 17% by mass of sulfuric acid 6% by mass of diphosphonodimethylformamide 2% by mass of water

be cast objects made of an alloy of

70% by mass nickel 16% by mass chromium 5% by mass molybdenum 9% by mass Mn, Al, Si, Fe

introduced and edited under the following conditions:

anodic current density: 8-10 A per dm voltage: 7-8 V

Working temperature: 30 ⁰ C ί 3 K Polishing time: twice 3e 5 minutes / workpiece, intermediate rinse

and drying ratio of the cathode to the anode surface: ^ 2:

While in the previous technology of achieving the metal-ceramic composite, the metallic scaffolds once or several times oxidized at temperatures around 1000 ⁰ O and are subsequently sandblasted again, can be dispensed through the electropolishing these operations. The electrolytic polishing produces a metallically clean surface, the roughness of which is used for the retention of the ceramic firing compound and has a more uniform profile with respect to the sandblasted surface. In both examples, the electrochemical polishing takes place in the stationary bath.

Claims (2)

239 79 1 1 invention claim 1 · Electrolyte for the electrochemical polishing of products of pure metals, preferably nickel, cobalt and iron, and their alloys with each other or with chromium as the main alloying component of sulfuric acid and ethylene glycol, characterized in that 1 to 10 percent by weight of organic phosphonic acids or derivatives thereof are added » 2. Electrolyte according to item 1, characterized in that are used as phosphonic acids, for example diphosphonoacetic acid or diphosphonodimethylformamide ·