RU1807093C - Process for preparing amorphous alloys - Google Patents

Abstract

Usage: in mechanical engineering, chemical and other industries. The inventive deposition is carried out on a pulsed alternating current with a direct pulse duration of 0.1-10 s and reverse - 0.05-0.2 s from an electrolyte containing, g / l: nickel sulfate 40-60, nickel chloride 30- 50, chromium sulfate 180-200, sodium hypophosphite 20-40. 1 tab.

Description

The invention relates to the field of electroplating and can be used in mechanical engineering, aviation and chemical industries to create protective electrochemical coatings.

The purpose of the invention is to increase the corrosion resistance of an amorphous alloy based on nickel and phosphorus in aggressive environments.

- This goal is achieved by the fact that in the known method for producing an amorphous electrolytic alloy based on nickel and phosphorus, including precipitation by current with a density of 15-25 A / dm from an electrolyte retaining nickel sulfate and chloride, sodium hypophosphite, deposition is carried out on pulsed alternating current with a duration forward pulse 0.1-10 s and reverse 0.05-0.2 s from an electrolyte additionally containing chromium sulfate, in the following ratio of components, g / l:

Nickel sulfate Nickel chloride

40-60 3050

Chromium sulfate 180-200 Sodium hypophosphite 20-40 Distinctive features of the claimed method is conducting deposition on pulsed alternating current with a direct pulse duration of 0.1-10 s reverse - 0.05-0.2 s from an electrolyte, optionally containing sulfate chrome, with the above ratio of components.

- The effectiveness of the proposed method is due to the following. The introduction of Ni-P into an amorphous alloy as a chromium impurity sharply increases the corrosion resistance of the alloy in aggressive environments. In order to obtain a chromium-doped amorphous alloy electrochemically, a soluble chromium salt, e.g. chromium sulfate, is added to the electrolyte. During the deposition process, chromium atoms co-precipitate simultaneously with the main components, causing the doping of the resulting amorphous alloy.

However, if the deposition process is conducted. at a constant current, an increasing enrichment of the surface of the coating is observed.

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These atoms result in passivation of the surface and termination of the deposition process. As a result, it is not possible to obtain a high-quality coating with a large thickness.

To obtain triceps; coating of any thickness, the deposition process must be carried out with alternating pulse current, including deposition pulses and reverse polarity pulses. During the reverse polarity pulse, the passivation layer is destroyed, which causes the resumption of the coating growth process. The duration of this pulse is chosen based on a compromise between the need, on the one hand, for minimal dissolution of the coating and, on the other hand, for a sufficient degree of destruction of the passivating layer. As established experimentally, the optimal pulse duration of the reverse polarity is 0.05-0.2 s. At a shorter duration, the passivation layer is not completely destroyed, and the resulting coating is of poor quality. With a longer duration, the coating quality remains high, however, the performance of the deposition process is markedly reduced.

The duration of the direct deposition pulse is determined by the requirements for obtaining the maximum corrosion resistance of the amorphous coatings while maintaining its high quality. As follows from the experiments, when the deposition pulse duration is less than 0.1 s, the resulting coating is noncorrosion-resistant and has poor quality with a dark coating, and when the duration is more than 10 s, the deposition process is terminated. In connection with this, the duration of the direct pulse, the deposition pulse, is chosen to be 0.1-10 s.

An example of the method.

The invention is carried out as follows. The electrolyte ingredients are dissolved in distilled water in the above ratio.

To improve the stability of the solution, it is worked through. For this, an anlitom Nl-Cr alloy anode and a copper or nickel cathode are placed in the bath. The cathode area is 0.1 anode areas. A constant current density of 10-15 A / dm2 is passed between the cathode and the anode for 1 hour. The electrolyte temperature is 70-90 ° C. After that, the electrolyte is ready for use.

As an iodine, in addition to the NS-Cr alloy, pure nickel can be used.

After working out the electrolyte at the same temperature, a device for mechanically mixing the electrolyte is turned on, coated parts are loaded and current is turned on. Before loading, the surface of the parts is activated and washed; copper parts, as well as parts made of iron and nickel, are activated by electropolishing

8 solution of phosphoric acid in the course of 3ZO-bOS. .

In order to obtain a coating of uniform thickness, it is necessary that the distance between the individual parts is at least 5 cm. For products of symmetrical shape (cylinders, spheres, etc.), the anode is made in the form of a hollow cylinder, for flat products the anodes are in the form of plates.

The amplitude of the deposition pulses was 15–25 A / dm2, the reverse pulses

polarity - 1.5-5 A / dm2. The process of deposition of chelm to obtain a coating of the required thickness,

The corrosion rate was calculated by the value of the corrosion current obtained from potentiodynamic measurements.

The data on the corrosion rate of the resulting 4 amorphous alloy coatings for various process embodiments are shown in the table. Corrosion resistance tests were carried out in two aggressive environments - 1 N hydrochloric acid solution and 5 N sulfuric acid solution.

In addition to the options listed in the table, an amorphous alloy NIP according to the prototype was also obtained. It has been established that it does not possess corrosion resistance in acids (mourn corrosion in 1 N. HCI solution over 2000 mm / year).

As follows from the given options

the implementation of the method, the deposition of an amorphous alloy of Ni-P alloyed with chromium on a pulsed current with a duration of a forward pulse of 0.1-10 s and a reverse pulse of 0.05-0.2 s from an electrolyte containing an additional 180-200 g / l sulfate chromium, allows four orders of magnitude to reduce the corrosion rate of the alloy. This makes it possible to produce highly efficient according to the proposed method.

tread coatings operating in aggressive environments.

Claims (1)

SUMMARY OF THE INVENTION A method for producing an amorphous alloy based on nickel and phosphorus. Preferably, nickel-phosphorus-chromium, including precipitation with a current density of 15-25 A / dm2 from an electrolyte containing nickel sulfate and chloride, sodium hypophosphite, and the like, and in order to increase of corrosion resistance in aggressive environments, deposition is carried out on pulsed alternating current with a forward pulse duration of 0.1-10 s and reverse 0.05-0.2 s from an electrolyte additionally containing sulfate chrome in the following ratio of components, g / l :. Nickel sulfate 40-60 Nickel chloride 30-50 Sulfate chromium 180-200 Sodium hypophosphite 20-40 Effect of the content of chromium salts in the electrolyte and deposition conditions on the corrosion rate of the amorphous Nf-P-Cr alloy