SU742493A1 - Solution for electrochemical polishing of metals - Google Patents

Description

(54) ELECTROCHEMICAL POLISHING SOLUTION The invention relates to the electrochemical machining of metals, in particular to the polishing of carbonaceous (Art. 3, Art. 45) and alloyed (HVSG) steels. The known solution for electrochemical polishing of carbonaceous and alloyed steels, containing a mixture of sulfuric and phosphoric acids and organic additives 1. Such a solution makes it possible to obtain a high-quality surface, but the use of sulfuric and phosphoric lobes makes the solution very aggressive. The closest to the invention in terms of the composition of the components is the solution for electrochemical polishing of metals / containing pyrophosphoric acid and water 2. However, this solution provides high quality polishing only for non-ferrous metals and alloys and when it is polished in various steel grades surface area. The purpose of the invention is to increase the class of purity of the surface of steel products.

METALS For this, the solution additionally contains potassium dichromate and acetothioamide in the following ratio of components, wt.%: Pyrophosphoric acid 82-83 Potassium dichromate 12-12.5 Acetothioamide 0.4 - 0.6 Water Rest. The polishing process is carried out at 5060 ° C, anodic current density of 4060 A / dm for 3-5 minutes. The solution is prepared as follows. Potassium bichromate and water are introduced into the pyrophosphoric acid. The solution is heated until the potassium dichromate is completely dissolved, and only after that is acetothioande (thioacetic acid, ethanethionamide, thioacetamide) is added. Potassium dichromate in an acidic environment serves as an oxidizing agent. The redox potential in the course of the reaction is +1.33 V. With this positive value of the potential, all the impurities in the steel are oxidized. Acetothioamide, as a surfactant, provides a higher grade of purity of its processing.

protects against point and local surface corrosions, as well as from the etching of individual areas.

The content of pyrophosphoric acid in the solution is maintained within 82-83 wt.%. A decrease in acid concentration leads to a deterioration in the quality of polishing. Increasing the content of pyrophosphoric acid above 83% increases the viscosity of the solution, which in turn reduces the conductivity of the solution and impairs the quality of polishing (uneven polishing on the surface is observed).

The composition of the solution and the polishing mode are given in Table 1 and 2.

In all examples, the surface cleanliness is increased by 2-3 classes (Ra 0.16 µm) in comparison with the initial 5 (purity class з 8).

Thus, the proposed solution allows polishing of both carbon and alloyed steels, is simple to prepare, and does not contain explosive or harmful substances in its composition.

Table 1

Composition Pyrophosphoric Acid

Potassium dichromate

Acetosnoamid

Water

82 828283

12121212,5

0.4 0.60.5 0.5

5,6 5,45,5 3,0

Table

Claims (1)

Claim A solution for electrochemical polishing of metals containing pyrophosphoric acid and water, with the exception that in order to improve the cleanliness class of the surface of steel products, it additionally contains potassium dichromate and acetythoamide in the following ratio of components , weight.%: Pyrophosphoric acid 82-83 Potassium dichromate 12-12.5 Acetothioamide 0.4-0.6 45 Water The rest.