DE1107043B - Bath and process for anodic glazing of metals and metal alloys - Google Patents

Description

GERMAN

It is known that many metals and metal alloys can be polished by anodic treatment in acid mixtures. Chrome-nickel steel can be z. B. anodically polish in phosphoric acid-sulfuric acid mixtures. Non-alloy carbon steel can be do not shine satisfactorily in this way or in aqueous phosphoric acid. In this particular case it will be z. B. Mixtures of perchloric acid. and acetic acid used, but they have the disadvantage that they are in compliance special security measures must be operated, since when a certain Bath temperature there is a risk of explosion. Chromic acid, also proposed for carbon steel containing acid mixtures change their composition rapidly during operation, and their regeneration is difficult.

The use of mixtures of sulfuric acid and hydrofluoric acid for polishing various steels, especially chromium-nickel steels, is also known. As tests have shown, these can be polished to a certain extent in a known electrolyte with the composition 45% H ₂ SO ₄ , 13% HBF ₄ (26%) and 42% water at 60 to 75 ° C. However, no polishing effect whatsoever could be achieved on carbon steel in the same bath, although the temperature and the current density were varied within wide limits.

It has now surprisingly been found that mixtures of phosphoric acid and hydrofluoric acid are also excellently suited for polishing carbon steel. Furthermore, with metals and metal alloys at a low temperature, preferably at 30 to 40 ^° C., a higher gloss effect is achieved. It is noteworthy that the content of hydrofluoric acid can be varied within wide limits without the polishing effect being impaired. For example, a very good effect was found at a level of 1.1 g / l and a good effect at a level of 200 g of borofluoric acid per liter. In contrast, both pure phosphoric acid and pure hydrofluoric acid are completely ineffective for polishing.

The water content of the bath can be 50 to 250 g / l, particularly favorable results are achieved with 150 to 200 g / l water.

The baths according to the invention form during electrolysis a stable foam blanket, which is not observed with pure phosphoric acid.

The baths can be produced in a simple manner by mixing the commercially available acids. Phosphorus pentoxide can optionally also be added to adjust the desired water content.

The operation of the baths according to the invention is completely harmless and not harmful to health.

Bath and procedure

for anodic shining of metals
and metal alloys

Applicant:

Siemens-Schuckertwerke

Corporation,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str, 50

Dr. phil. Heinz Grüß, Berlin-Wannsee,

Willi Gillwald, Nuremberg,

Dr. habil. Artur Kutzelnigg, Erlangen,

and Dipl.-Ing. Hans Laub, Nuremberg,

have been named as inventors

The following working example is intended to illustrate the invention:

Bath preparation 37 ml HBF ₄ solution at 27 ° Βέ

963 ml H ₃ PO ₄ , ^ = 1.75

Composition .. .25 g / l HBF ₄ , 206 g / l water

Current density 20 to 50 A / dm ² , preferably 30

up to 40 A / dm ²

Bath voltage 10 volts

Temperature 20 to 50 ⁰ C, preferably 30 to

4O ⁰ C.

Further bath compositions and working conditions are listed in the table.

The bath according to the invention is particularly useful for anodic polishing of carbon steel as well as inter alia. Also suitable for chrome-nickel steel, copper, brass, aluminum and light metal alloys.

109 607/369

3 Further composition
in g / l H ₂ O Current density 4th Polishing effect
for carbon steel H ₃ PO ₁ d = 1.75 approach
HBF ₄ solution
27 ° Be additions HBF ₄ 560 A / dm ² temperature ml ml 672 1070 40 ° C missing (black 1000 1040 108 30 to 40 Surface) 438 grams of P ₂ O ₅ 200 1086 220 40 Well 560 298 50 1117 206 30 to 40 30 to 40 very good 925 75 - 25th 1126 196 30 to 40 30 to 40 very good 963 37 "- 7th 1127 193 30 to 40 30 to 40 very good 990 10 - 1.1 1128 193 30 to 40 30 to 40 very good 998.4 1.6 - 0.55 193 30 to 40 30 to 40 good ¹ 999.2 0.8 - 0.27 1128 30 to 40 30 to 40 small amount 999.6 0.4 1128 193 30 to 40 (blank, veil ² ) - 0.07 193 30 to 40 missing 999.9 0.1 - - 30 to 40 30 to 40 missing 1000 - 30 to 40

^% ) Permanent foam cover.
*) Start of foam formation.

Claims (3)

Patent claims: 1. Bath for anodic shining of metals and the like Metal alloys, in particular carbon steel, characterized in that it is made of water-containing Phosphoric acid with an addition of 1 to 200 g of hydrofluoric acid per liter. 2. Bath according to claim 1, characterized in that it consists of aqueous phosphoric acid with a water content from 50 to 250 g, preferably 150 to 200 g / l. 3. A method for anodic brightening of metals and metal alloys, in particular carbon steel, using a bath according to claims 1 and 2, characterized in that at current densities of 20 to 50 A / dm ² , preferably 30 to 40 A / dm ² , and Temperatures of 20 to 50 ° C, preferably 30 to 40 ⁰ C, is used. Considered publications:
ÜSA. Patent Nos. 2,740,755, 2,542,779. © 109 607/36 »9.6t