SU540946A1 - Electrolyte for steel plating - Google Patents

Description

The invention relates to the field of electrochemistry and can be used for applying, for example, protective and decorative electroplated coatings in mechanical engineering, building design, automotive industry, etc.

The compositions of electrolytes for galvapic copper plating of steel containing complex copper ions, including acetic acid, erythroles, acid, tartrate, ammonia, are known. However, they did not cause industrial use, since they give brittle sediments, which form a weak adhesion to steel.

Lime also pyrophosphate electrolytes for electroplating of steel. However, their use is associated with technological difficulties arising from the need to apply pre-copper plating in a low-concentration and pyrophosphate electrolyte, anodic pre-treatment, and the use of a "current shock."

In the most widely used pyrophosphate electrolyte, the cathode current efficiency is 75-80%, the scattering power is much lower than that of cyanide, and the copper coating has a weak adhesion to steel. To increase its strength, it is necessary to give a “current shock for 30-60 seconds, which improves adhesion, but leads to inevitable roughness of coatings. In addition, when

The copper plating of steel products should be suspended under current in order to avoid the release of contact copper.

When finishing household products, such as lighting electrical fittings, electrolytes based on amino-derivatives, in particular ethylenediamine, have become widespread at present. They also require a "shock" at the beginning of the process in order to avoid peeling of the copper coatings. However, even in this case, satisfactory coatings can only be obtained on products subjected to turning or careful blowing with quartz sand. On stamped parts, after etching or rough sanding, it was not possible to obtain high-quality copper coatings. Significant electrolyte deficiencies are: the need to hang the parts under current, large

The initial increase in current density is 3-5 times against the given and the professional harm of ethylenediamine is known, which together makes it a very incomplete substitute for cyanide baths.

An electrolyte for the electroplating of copper steels is also known, which is an aqueous alkaline solution containing copper sulphate and citric acid. This technical solution is the closest to the invention in its technical nature.

The aim of the invention is to increase the adhesion strength of the copper coating to the base and increase the scattering ability of the electrolyte.

This goal is achieved due to the fact that aluminum sulphate and sodium phosphate are added to the electrolyte for the galvapic medchip of steel, which is an aqueous solution containing copper sulphate and citric acid at the following concentrations of components, g / l: Copper sulfate 50-100

Citric acid84-168

Aluminum sulphate 133-266 Sodium phosphate 20-60

AlkaliUp pH 8-9.3

Preparation of electrolyte.

Weights of citric acid, copper sulphate, aluminum sulphate and sodium phosphate are dissolved in water and the pH is adjusted to 8-9 with a solution of concentrated alkali. The resulting solution is diluted to the required volume.

The following are examples of bath formulations and electrolysis modes, in which dense, fine-crystalline coatings are obtained, providing very high adhesion strength both with the steel base and with subsequent metal layers. The anodic and cathodic current outputs in all examples are 100%.

Example 1. The electrodeposition of copper on steel cathodes was carried out from an electrolyte of the following composition:

Copper sulfate 0.2 m / l (50 g / l)

Citric acid 0.4 m / l (84 g / l)

Aluminum sulphate0.2 m / l (133 g / l)

Sodium phosphate 20 g / l

,five; temperature - 20 ° C.

At about 0.2 a / dm, Z) a 0.05 a / dm, a coating 3 microns thick is deposited in 60 minutes.

Example 2. The electrodeposition of copper on steel cathodes was carried out from an electrolyte of the following composition:

Copper sulfate 0.2 m / l (50 g / l)

Citric acid 0.4 m / l (84 g / l)

Aluminum sulphate0.2 m / l (133 g / l)

Sodium phosphate 20 g / l

. Temperature - 40 ° C.

At, 4 a / dm, Da 0, l a / dm, a coating 3 microns thick is deposited in 30 minutes.

Example 3. The electrodeposition of copper on steel cathodes was carried out from an electrolyte of the following composition:

Copper sulfate

0.3 m / l (75 g / l) Lemon citrate 0.6 m / l (126 g / l) Aluminum sulphate, 3 m / l (200 g / l) 5 Sodium phosphate 40 g / l pH-9. Temperature - 25 ° C. At 1k 0.4 a / dm, Da 0, a / dm, a coating with a thickness of 3 microns precipitates in 30 / 1Ш ".

Example 4. The electrodeposition of copper on 0 steel cathodes was carried out from the electrolyte of the following composition: Copper sulfide 0.3 m / l (75 g / l)

Citric acid 0.6 m / l (126 g / l)

Sulphate alyumiNII0, 3 m / l (200 g / l)

Sodium phosphate 40 g / l

pH 9, 3. Temperature - 40 ° C. With A., 6 a / dl, Da 0, l5 a / dm, a coating of thickness 3 Л1КЛ1 precipitates in 20 minutes. J.

Example 5. The electrodeposition of copper on steel cathodes is carried out from an electrolyte of the following composition:

Sulfuric acid copper 0.4 m / l (100 g / l)

5 Citric acid 0.8 m / l (168 g / l)

Aluminum sulphate0, 4 m / l (266 g / l) Sodium phosphate 60 g / l, 3. Temperature is -40 ° C. 0 At Ah 0.8 a / dm, Ots 0.2 a / dm, a coating with a thickness of 3 liters {km precipitates in 16 minutes.

At a / dm, Da 0.25 a / dm, a coating of 3 microns thick is deposited in 13 minutes.

Electrolyte properties.

The dispersing ability of the electrolyte was measured in a Field cell measuring 145 x X75X50, which was thermostatically controlled. Calculations were also made according to the Field formula:

MB

/ SL1d

g100%

fk +

K - ratio of the distance from the anode

where to the far cathode to the distance from the anode to the near cathode (in experiments);

Me, M,

the gain of the near and far electrode during the experience, respectively.

Electrolysis time - 15 min. The table shows data on the scattering ability of the electrolyte according to the invention.

Claims (1)

Invention Formula Electrolyte for electroplating of steel, which is an aqueous alkaline solution containing copper sulphate and citric acid, characterized in that it does not increase the adhesion strength of the copper coating to the base and enhance the scattering ability of the electrolyte. it additionally contains aluminum sulphate and sodium phosphate at the following component concentrations, g / l: Sulfate copper50-100 Citric acid84-168 Aluminum sulphate 133-266 Sodium phosphate 20-60 AlkaliUp pH 8-9.3