RU2377344C1 - Electrolyte and method to apply tin-cobalt alloy coats - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to electroplating and can be used in various industries to produce coats with colour characteristics identical to those of chromium. Proposed electrolyte comprises the following components, mol/l, i.e. 0.1 to 0.22 of tin chloride or sulphate, 0.07 to 0.3 of cobalt chloride or sulphate, 0.28 to 0.4 of sodium gluconate, and up to 1 l of water at 3.0 to 5.5 pH. Proposed method comprises preliminary preparation of articles and electrolytic deposition at electrolyte room temperature at cathode current varying from 0.2 to 2.5 A/dm² from above described electrolyte. Tin-cobalt alloy coat produced by above described method on metal or metal-coated surfaces contains 40.0 to 60.0 atomic % of cobalt. Aforesaid electrolyte represents a non-aggressive subacidic solution based on Sn(II) and Co(II) gluconate and hydroxygluconate complex compounds.

EFFECT: produced coats feature minimum colour difference between chromium and tin-cobalt alloy coats.

6 cl, 3 tbl, 1 dwg, 8 ex

Description

The invention relates to the field of electroplating, in particular the electrodeposition of alloys, and can be used in the automobile, machine, ship, aircraft, radio, electronics and other industries, where it is necessary in the manufacture of parts, coating, identical in color characteristics chrome, as well as functional coatings with tin-cobalt alloy.

A number of electrolytes are proposed in the patent literature for the electrodeposition of tin-cobalt alloys. In patents (US No. 3951760 and US No. 4021316) proposed alkaline solutions based on pyrophosphate complex compounds of tin and cobalt. In an alkaline medium, complex tin (II) ions are rapidly oxidized to tin (IV). Several patents describe the compositions of solutions based on tin and cobalt chlorides, which also contain fluoride ions as ligands for tin (II) ions, which makes possible the electrodeposition of tin-cobalt alloys (US 3951760 and US 4021316). These solutions are highly corrosive and toxic due to the presence of fluoride ions. Also known are solutions based on the citrate complexes of tin and cobalt (US 4168223), verification of which showed the absence of cobalt in the coatings (US No. 7309411, IPC C25D 3/18, C25D 3/60, publ. 12/18/2007). In US patent No. 7309411 (IPC C25D 3/18, C25D 3/60, publ. 12/18/2007) describes the electrodeposition of antifriction coatings by tin-cobalt alloy from a solution of gluconate complexes. The cobalt content in electrodeposited coatings is 2-15 wt.%, Which according to US patent No. 4428803 (IPC C25D 3/60, C25D 3/56, publ. 01/31/1984) does not match the color of the chromium coatings. Coatings with a tin-cobalt alloy, the color of which is similar to the color of the chrome coating, have been proposed to precipitate from solutions of gluconate or glucoheptate complexes (UK 1497552).

As a prototype, the closest analogue of the proposed invention was selected for replacing protective and decorative chrome coatings, which is a tin-cobalt alloy coating containing 11-29 wt.% (20-45 at.%) Cobalt, as well as an electrolyte and a method of electrodeposition of tin alloy cobalt disclosed in US 4428803, IPC C25D 3/60, C25D 3/56, publ. 01/31/1984.

The known electrolyte contains, g / l (mol / l): tin ions - 0.5-5 (0.0042-0.042), cobalt ions - 0.5-5 (0.0085-0.085), gluconate or glucoheptonate ions - 1-50 (0.0046-0.229), brightener (N- (2-aminoethyl) ethanolamine, monoethanolamine, N-methyl-diethanolamine, triethanolamine or 3-isopropanolamine, and may also contain tris- (hydroxymethyl) -aminomethane) - 1-20 ml / l and water. The pH of the electrolyte is 8.3-9.0. Preparation of parts before electrodeposition of the alloy is carried out in the usual way. The alloy coating is applied at a temperature of 25-35 ° C, with mechanical stirring at an average speed and cathodic current density of 0.5-1.0 A / DM ² .

Coatings obtained from this electrolyte contain 6-29 wt.% (11-45 at.%) Cobalt and are deposited with a low current efficiency of 27-54% in a narrow range of current densities of 0.5-1.0 A / dm ² (the width of the range of current densities of 0.5 A / DM ² ).

The optimum range of cobalt content in the alloy is determined approximately based on visual comparison of the color of the coatings.

The objective of the invention is to expand the range of domestic electrolytes for electrodeposition of tin-cobalt alloy, which allows to obtain high-quality coatings of tin-cobalt alloys on steel, copper, nickel, brass, bronze, polymer products.

The technical result is the minimum color difference between the chrome coating and the tin-cobalt alloy coating, determining the optimum cobalt content in the tin-cobalt alloy coatings, expanding the range of current densities, increasing the current efficiency.

The specified task and the technical result are achieved in that the electrolyte for coating with tin-cobalt alloy on the surface of metal products or polymer products with a metal coating includes tin and cobalt salts, sodium gluconate and water, while it contains chlorides or tin and cobalt salts sulfates, in the following ratio of components, mol / l:

Tin chloride or sulfate 0.1-0.22 Cobalt Chloride or Sulfate 0.07-0.3 Sodium Gluconate 0.28-0.4 Water up to 1 l pH 3.0-5.5.

The electrolyte may additionally contain not more than 0.40 mol / l of sulfate or sodium chloride to increase electrical conductivity and / or not more than 7.0 ml / l of an alcohol solution of n-dimethylaminobenzaldehyde (n-С ₆ Н ₄ N (СН ₃ ) ₂ СОН, DMAB) (20 g / l) and / or not more than 8.0 g / l TsKN-32 (TU 2299-00940195384-99).

The specified task and the technical result are also achieved by the fact that the method of coating with tin-cobalt alloy to replace the chromium protective and decorative coating on the surface of metal products or polymer products with a metal coating includes preliminary preparation of products and electrodeposition, while electrodeposition is carried out at room temperature of the electrolyte, cathodic current density of 0.2-2.5 A / DM ² from the electrolyte indicated above.

As a result, a tin-cobalt alloy coating was obtained to replace the chrome protective and decorative coating on the surface of metal products or on the surface of polymer products with a metal coating containing 40.0-60.0 at.% Cobalt.

Preparation of metal surfaces includes degreasing, activation in a 10% solution of sulfuric acid, and inter-operative washing. If necessary, a layer of shiny nickel coating is applied to the surface of the products. The surface preparation of polymer products before applying chemical coatings with nickel is carried out according to the technology provided for this polymer. Chemical nickel coatings are applied from any chemical nickel plating solution.

The proposed electrolyte is a non-aggressive, slightly acidic solution based on gluconate and hydroxogluconate complex compounds Sn (II) and Co (II).

The electrolyte is prepared as follows. In a separate container in distilled or deionized water, 1/3 of the total volume of the electrolyte at a temperature of 20-40 ° C, the calculated amounts of inorganic components (tin salt, cobalt salt and sodium sulfate or sodium chloride) are dissolved according to the electrolyte composition. In another container, in the same volume of water, sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of electrolyte is adjusted to a predetermined value with water. The required pH of the electrolyte is adjusted with a solution of sulfuric acid or sodium hydroxide. After preparation, the solution is filtered, an alcoholic solution of p-dimethylaminobenzaldehyde (20 g / l), TsKN-32 is added according to the electrolyte composition and stirred until the additives are completely dissolved.

The limiting current density of the electrodeposition of tin – cobalt alloy coatings was monitored in a 250 ml Hoole cell.

The alloy composition was determined by energy dispersive x-ray analysis.

The color characteristics of the coatings were determined using a spectrophotometer with a spherical measurement geometry — SP62 from X-Rite. As a light source, a daylight lamp D65 was used. The angle between the light source and the receiving photocell was 10 °. The coating applied from a standard solution of chromium plating (g / l) was a reference sample: CrO ₃ - 250; H ₂ SO ₄ - 2.5.

The test sample is placed in the measuring unit of the spectrophotometer, the light source is located above the test surface of the sample. The color measurement results are presented in the CIELAB International Scale (L * a * b *), where L * is the brightness, a * is the red / green color, b * is the yellow / blue color. When comparing the samples relative to the standard, the difference in parameters is used: ΔL *, Δa *, Δb *. A generalized characteristic of the color difference is the quantity ΔE *, calculated by the formula:

The measurement error ΔE * is ± 1.

The results obtained for the tin-cobalt alloy were compared with the results for chromium coatings electrodeposited from a trivalent chromium electrolyte (ΔE * = 6).

Example 1

In accordance with the method described above, the following electrolytes were prepared, of which coatings prepared by the usual method were coated with a thickness of 4-7 μm at a current density of 0.6 A / dm ² , their composition was determined (Table 1) and color difference ( table 1, drawing).

Table 1. Electrolyte components BUT AT FROM D E F G SnCl ₂ × 2H ₂ O 0.2 0.13 0.2 0.15 SnSO ₄ 0.18 0.1 CoCl ₂ × 6H ₂ O 0,07 0.3 CoSO ₄ × 7H ₂ O 0,07 0.2 0.3 0.3 Sodium Gluconate 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Na ₂ SO ₄ 0.2 0.2 0.2 0.2 NaCl 0.4 0.4 0.4 DMAB, ml / l 0 8 0 2 7 2 TsKN-32, g / l 0 2 0 8 2 2 pH 4.0 4,5 4,5 4,5 4,5 5.5 four The cobalt content in the alloy, X _Co , at.% 0 33 49 61 72 79 one hundred ΔЕ * 9,4 6.7 1.9 1.9 9.3 6.7 10.3

The results given in this example show (drawing) that the minimum color difference between chromium coatings and tin-cobalt alloy coatings is observed at a cobalt content of 40-60 at.%, And even less at a content of 45-55 at.% Cobalt. The color of coatings with an alloy containing 40-60 at.% Cobalt is much less different from the color of standard chromium coatings than that of chromium coatings electrodeposited from a trivalent chromium plating electrolyte (drawing).

Example 2. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 29.4 g (0.13 mol) of tin chloride dihydrate and 19.7 g (0.07 mol) of cobalt sulfate heptahydrate are dissolved according to the electrolyte composition. In another container, in the same volume of water, 65.4 g (0.3 mol) of sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4.5) is set with a solution of sulfuric acid or sodium hydroxide. The solution is filtered.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.13 Cobalt sulfate heptahydrate 0,07 Sodium Gluconate 0.3 Sodium Chloride or Sulfate 0 p-Dimethylaminobenzaldehyde, ml / l 0 TsKN-32, g / l 0 pH 4,5

The copper cathode of the Hoole cell, a copper sample for determining the composition of the tin-cobalt alloy, current efficiency, and a steel sample for determining the color of the coatings were degreased, washed with running, then distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. An alloy coating, shiny with a blue tint, was obtained in the range of current densities of 0.8 A / dm ² .

At a current density of 0.6 A / dm ^2, coatings containing tin-cobalt alloy containing 43 at.% Cobalt were deposited in a 1-liter rectangular electrolyzer. The current efficiency of the alloy was 83%. The difference (ΔЕ *) in the color of chromium coatings and electrodeposited coatings by tin-cobalt alloy was 1.95.

Example 3. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 28 g (0.13 mol) of tin sulfate and 16.7 g (0.07 mol) of cobalt chloride hexahydrate and 23.4 g are dissolved according to the electrolyte composition (0.4 mol) sodium chloride. In another container, in the same volume of water, 65.4 g (0.3 mol) of sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4, 5) is established with a solution of sulfuric acid or sodium hydroxide. The solution is filtered.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin sulfate 0.13 Cobalt chloride hexahydrate 0,07 Sodium Gluconate 0.3 Sodium chloride 0.4 p-Dimethylaminobenzaldehyde, ml / l 0 TsKN-32, g / l 0 pH 4,5

The steel cathode of the Hula cell, a copper sample for determining the composition of the tin-cobalt alloy, current efficiency, and a nickel-plated brass sample for determining the color of the coatings were degreased, washed with running, then with distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. An alloy coating, shiny with a blue tint, was obtained in the range of current densities of 0.7 A / dm ² .

At a current density of 0.6 A / dm ^2, coatings containing tin-cobalt alloy containing 41 at.% Cobalt were deposited in a 1-liter rectangular electrolyzer. The current efficiency of the alloy was 86%. The difference (ΔЕ *) in the color of chromium coatings and electrodeposited coatings with tin-cobalt alloy was 1.9.

Example 4. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 50 g (0.22 mol) of tin chloride dihydrate and 50.6 g (0.18 mol) of cobalt sulfate heptahydrate and 28.4 are dissolved according to the electrolyte composition g (0.2 mol) of sodium sulfate. In another container, in the same volume of water, 65.4 g (0.3 mol) of sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4.0) is set with a solution of sulfuric acid or sodium hydroxide. The solution is filtered, add 4 ml of an alcoholic solution of p-dimethylaminobenzaldehyde (20 g / l), 6 g of CCN-32 and mix until the additives are completely dissolved.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.22 Cobalt sulfate heptahydrate 0.13 Sodium Gluconate 0.3 Sodium sulfate 0.2 p-Dimethylaminobenzaldehyde, ml / l four TsKN-32, g / l 6 pH 4.0

The brass cathode of the Hoole cell, a copper sample for determining the composition of tin-cobalt alloy, current efficiency, and a steel sample for determining the color of the coatings were degreased, washed with running, then with distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. An alloy coating in the range of current densities of 4.5 A / dm ² was obtained, semi-brilliant with a blue tint.

At various current densities, coatings with a tin-cobalt alloy were deposited in a 1-liter rectangular electrolyzer. The effect of current density on VT, alloy composition, and the difference (ΔЕ *) in the color of chromium coatings and electrodeposit tin-cobalt coatings are shown in Table 2.

Table 2. The current density, A / DM ² 1,5 2.0 2.5 The cobalt content in the alloy, at.% 40 fifty 59 VT alloy,% 85 92 95 Color Difference (ΔE *) 1.9 1.8 1.87

Example 5. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 22.6 g (0.1 mol) of tin chloride dihydrate and 84.3 g (0.3 mol) of cobalt sulfate heptahydrate are dissolved according to the electrolyte composition. In another vessel in the same volume of water is dissolved, according to the electrolyte composition, 65.4 g (0.3 mol) of sodium gluconate and a solution of sodium hydroxide are adjusted to pH 9-10. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte is adjusted with a solution of sulfuric acid or sodium hydroxide. The solution is filtered, add 2 ml of an alcoholic solution of p-dimethylaminobenzaldehyde (20 g / l), 2 g of CCN-32 and mix until the additives are completely dissolved.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.1 Cobalt sulfate heptahydrate 0.3 Sodium Gluconate 0.3 Sodium sulfate 0 p-Dimethylaminobenzaldehyde, ml / l 2 TsKN-32, g / l 2 pH 3.0 or 5.5

The copper cathode of the Hoole cell, a copper sample for determining the composition of the tin-cobalt alloy, current efficiency, and a brass sample for determining the color of the coatings were degreased, washed with running, then distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. Semi-shiny alloy coatings with a blue tint were obtained in the range of current densities of 0.8 A / dm ² at pH 3.0 and 1.0 A / dm ² at pH 5.5.

At various pH and current density of 0.4 A / dm ^2, coatings with a tin-cobalt alloy were deposited in a 1-liter rectangular electrolyzer. The effect of pH on BT, alloy composition, and the difference (ΔE *) in the color of chromium coatings and electrodeposit tin-cobalt coatings are shown in Table 3.

Table 3. electrolyte pH 3.0 5,0 The cobalt content in the alloy, at.% 57 60 VT alloy,% 88 97 Color Difference (ΔE *) 1.84 1.93

Example 6. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 22.6 g (0.1 mol) of tin chloride dihydrate and 84.3 g (0.3 mol) of cobalt sulfate heptahydrate and 11 are dissolved according to the electrolyte composition 7 g (0.2 mol) of sodium chloride. In another vessel, in the same volume of water, 87.2 g (0.4 mol) of sodium gluconate are dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4.5) is set with a solution of sulfuric acid or sodium hydroxide. The solution is filtered, add 2 ml of an alcoholic solution of p-dimethylaminobenzaldehyde (20 g / l) and mix until the additives are completely dissolved.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.1 Cobalt sulfate heptahydrate 0.3 Sodium Gluconate 0.4 Sodium chloride 0.2 p-Dimethylaminobenzaldehyde, ml / l 2 TsKN-32, g / l 0 pH 4,5

The copper cathode of the Hoole cell, a nickel sample for determining the composition of tin-cobalt alloy, current efficiency, and a bronze sample for determining the color of the coatings were degreased, washed with running, then with distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. Semi-shiny alloy coatings with a blue tint were obtained in the range of current densities of 0.6 A / dm ² .

At a current density of 0.4 A / dm ^2, coatings containing tin-cobalt alloy containing 60 at.% Cobalt were deposited in a 1-liter rectangular electrolyzer. The current efficiency of the alloy was 98%. The difference (ΔЕ *) in the color of chrome coatings and electrodeposited coatings with tin-cobalt alloy was 2.0.

Example 7. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 50 g (0.22 mol) of tin chloride dihydrate and 50.6 g (0.18 mol) of cobalt sulfate heptahydrate and 28.4 are dissolved according to the electrolyte composition g (0.2 mol) of sodium sulfate. In another container, in the same volume of water, 65.4 g (0.3 mol) of sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4.0) is set with a solution of sulfuric acid or sodium hydroxide. The solution is filtered, add 7 ml of an alcoholic solution of p-dimethylaminobenzaldehyde (20 g / l), 2 g of CCN-32 and mix until the additives are completely dissolved.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.22 Cobalt sulfate heptahydrate 0.13 Sodium Gluconate 0.3 Sodium sulfate 0.2 p-Dimethylaminobenzaldehyde, ml / l 7 TsKN-32, g / l 2 pH 4,5

The nickel cathode of the Hoole cell, a copper sample for determining the composition of tin-cobalt alloy, current efficiency, and a sample of polyvinyl chloride, previously metallized in a chemical nickel plating solution, were degreased to determine the color of the coatings, washed with running, then with distilled water, and activated in a solution of sulfuric acid (10 %) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. An alloy coating, shiny with a blue tint, was obtained in the range of current densities of 1.8 A / dm ² .

At a current density of 1.2 A / dm ^2, coatings containing tin-cobalt alloy containing 55 at.% Cobalt were deposited in a 1-liter rectangular electrolyzer. The current efficiency of the alloy was 94%. The difference (ΔЕ *) in the color of chromium coatings and electrodeposited coatings by tin-cobalt alloy was 1.93.

Example 8. In a separate container in distilled or deionized water with a volume of 300 ml at room temperature, 50 g (0.22 mol) of tin chloride dihydrate and 50.6 g (0.18 mol) of cobalt sulfate heptahydrate and 28.4 are dissolved according to the electrolyte composition g (0.2 mol) of sodium sulfate. In another container, in the same volume of water, 65.4 g (0.3 mol) of sodium gluconate is dissolved according to the electrolyte composition and the pH of this solution is adjusted to 9-10 with a sodium hydroxide solution. Then, a solution of inorganic salts is poured into a container with a solution of sodium gluconate with stirring, and the volume of the electrolyte is adjusted to 1 liter with water. The required pH of the electrolyte (4.0) is set with a solution of sulfuric acid or sodium hydroxide. The solution is filtered, add 2 ml of an alcohol solution of p-dimethylaminobenzaldehyde (20 g / l), 8 g of CCN-32 and mix until the additives are completely dissolved.

The prepared electrolyte has the following composition and concentration (mol / l) of the components:

Tin Chloride Dihydrate 0.22 Cobalt sulfate heptahydrate 0.13 Sodium Gluconate 0.3 Sodium sulfate 0.2 p-Dimethylaminobenzaldehyde, ml / l 2 TsKN-32, g / l 8 pH 4,5

The copper cathode of the Hoole cell, a copper sample for determining the composition of the tin-cobalt alloy, current efficiency, and a steel sample for determining the color of the coatings were degreased, washed with running, then distilled water, activated in a solution of sulfuric acid (10%) and washed again with distilled water. The electrodeposition in the Hoole cell was carried out at room temperature and a current strength of 1 A for 5 min. An alloy coating, shiny with a blue tint, was obtained in the range of current densities 4.0 A / dm ² .

At a current density of 1.5 A / dm ^2, coatings containing tin-cobalt alloy containing 56 at.% Cobalt were deposited in a 1-liter rectangular electrolyzer. The current efficiency of the alloy was 83%. The difference (ΔЕ *) in the color of chromium coatings and electrodeposited coatings by tin-cobalt alloy was 1.84.

As can be seen from the above examples, the proposed electrolyte is a non-aggressive, slightly acidic solution based on gluconate and hydroxogluconate complex compounds Sn (II) and Co (II). Electrodeposited from an electrolyte in a wide range of current densities and with a high current efficiency, tin-cobalt coatings provide the minimum color difference between the chromium coating and tin-cobalt coating.

Claims (6)

1. The electrolyte for coating tin-cobalt alloy on the surface of metal products or polymer products with a metal coating, including tin and cobalt salts, sodium gluconate and water, characterized in that it contains chlorides or sulfates as salts of tin and cobalt in the following ratio components, mol / l:
tin chloride or sulfate 0.1-0.22 cobalt chloride or sulfate 0.07-0.3 sodium gluconate 0.28-0.4 water up to 1 l
pH 3.0-5.5. 2. The electrolyte according to claim 1, characterized in that it further comprises not more than 0.40 mol / l of sulfate or sodium chloride. 3. The electrolyte according to claim 1 or 2, characterized in that it further comprises not more than 7.0 ml / l of an alcohol solution of p-dimethylaminobenzaldehyde (20 g / l). 4. The electrolyte according to claim 1, characterized in that it additionally contains no more than 8.0 g / l TsKN-32. 5. The method of coating with a tin-cobalt alloy on the surface of metal products or polymer products with a metal coating, including preliminary preparation of products and electrodeposition, characterized in that the electrodeposition is carried out from the electrolyte according to any one of claims 1 to 4 at room temperature, electrolyte, cathode density current 0.2-2.5
A / dm ² . 6. Coating with tin-cobalt alloy to replace the chrome protective and decorative coating on the surface of metal products or on the surface of polymer products with a metal coating, characterized in that it contains 40.0-60.0 at.% Cobalt and obtained by the method according to p. 5.

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