SU1236018A1 - Solution for electrochemical treatment of titanium and its alloys - Google Patents

Description

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The invention relates more to electroplating, in particular to the electrochemical treatment of titanium and its alloys, and can find application in various industries related to the processing of titanium and its alloys.

The purpose of the invention is to increase the uniformity of etching the scale and reduce the toxicity of the electrolyte.

The positive effect is achieved due to the fact that the electrolyte contains sodium fluoride as a source of fluorine ions and additionally contains an oxalic acid salt and hydroxycarboxylic acid.

The treatment process is carried out in a potentiostatic mode with an ex. SII 5-8 V, current density 5-20 A / dm. The treatment time is 20 minutes.

When the salt of oxalic acid with hydroxycarboxylic acid is displaced, a solution with a strongly pronounced buffering effect is obtained, which during the long-term operation stabilizes the acidity of the electrolyte, which ensures uniform removal of scale and eliminates corrosion corrosion. In addition, the specified mixture

binds titanium ions into the solution in complexes of different composition, which helps to divert the product of anodic dissolution from the reaction zone and thereby intensifies the etching process. p} ard with this mixture of hydroxycarboxylic acid and oxalic acid salt contributes to the formation of a 1-in in the initial period on the surface of titanium and its alloys, a barrier oxide film that prevents the base metal from penetrating and dissolving in it the hydrogen released in the process reaction.

The concentration of sodium fluoride below 2% reduces the removal rate of metal oxides and worsens the degree of processing; the concentration of sodium fluoride in an amount of 4% corresponds to the limit of electrolyte solubility under given conditions. The introduction of sodium fluoride into the proposed electrolyte in an amount of 2–4% allows one to automatically maintain its concentration in the solution.

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The introduction of less than 5% oxycarboxylic acid into the electrolyte reduces the activity of the electrolyte, impairs the quality of the workpieces. Concentration of acid over 10% does not affect the quality of the treated surface.

When the concentration of B1-salt of the acid is below 0.5%, the leveling effect decreases and the surface treatment speed decreases, and with an increase in this salt content of 1%, oxalates are adsorbed on the surface of the parts, which leads to shielding of the surface.

 The treatments in the electrolyte according to the invention, the surface of the parts made of titanium and its alloys are obtained bright and glossy.

Experimental data obtained using the electrolyte according to the invention, are given in table 1.

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 ABOUT

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- To determine the adhesion strength of nickel EGC coatings with titanium, a grid of scratches is laid on the surface of the controlled coating with a steel hole at a distance of 2 from each other. to break.

Anodic treatment is subjected to samples of titanium 1 grades W 1-0, W 1 - and alloys W 3 - W 5, W 8, W 9,

35 W 22, FROM 4 FROM 4-1.

As can be seen from the table, the electrolyte according to the invention provides a uniform etching of rust while maintaining a high purity class of the surface, and the electrolyte is less toxic due to mixing. hydrofluoric acid to sodium fluoride. Electrochemical treatment in the electrolyte according to the invention leads to the adhesion of the adhesion of the coating to the titanium of the nickel coating.

Table 2 shows the treatment mode and the rate of scale of electrolyte compositions, scale.

After treatment of titanium and its alloys from the electrolyte according to the invention, it is possible to directly apply coatings, for example, nickel.

0.7

Rest

0.7

20

0.7

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tagging. In experiments 1–9, it is possible that the alnis oblgaiov is applied before applying glpanipsyx:; sr.tiy, and in experiments 10 to use it for further use of an inverse need for actinisyroilia on the surface of the film, which is covered with a passive film.

Table I

0.068

0.1

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Peeling of coatings was not observed.

ZON O 20

0.12

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The coating is peeled off

table 2

7% H ,,, 0, + 3% NaF + 1% Na, DM 7% H ,, 0 + 3% NaF + 1.5%

Continuation of table 2

60 60 60 60

0.09 0.05

Claims (1)

SOLUTION FOR ELECTROCHEMICAL TREATMENT OF TITANIUM AND ITS ALLOYS, containing fluoride ions, characterized in that, in order to increase the uniformity of etching of the scale and reduce the toxicity of the electrolyte, it additionally contains oxalic acid salt and hydroxycarboxylic acid, and sodium fluoride as a source of fluoride ions in the following ratio, wt.%: Sodium fluoride 2-4 Oxycarboxylic acid 5-10 Oxalic acid salt Water ί