RU2248410C1 - Method for steel treatment before enamel coating - Google Patents

Abstract

FIELD: steel enamel coating, in particular surface treatment of steel products before direct-on enamel coating.

SUBSTANCE: claimed method includes nickel film plating and additional copper film plating. Method of present invention makes it possible to avoid insufficient purity of deposited metal, coat embrittlement, insufficient enamel adhesive strength with steel surface, and is useful in manufacturing of enameled steel articles of various applications and multiply configuration.

EFFECT: method characterized by conventional metal treatment, decreased reagent consumption; coating of improves mechanical properties.

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Description

The invention relates to the field of steel enameling, and in particular to a method for surface treatment of steel products before applying groundless enamels, and can be used in the manufacture of enameled steel products for various purposes and various configurations.

Known methods of processing steel before groundless enameling - nickel plating (Enameling of metal products / Ed. By V.V. Vargin. L.: "Mechanical Engineering", 1972, 496 S.). A layer of metallic nickel with a thickness of 0.2-0.5 μm is deposited directly on the steel before enameling, but this method does not sufficiently increase the adhesion strength of the enamel to steel, the coatings are brittle, and there are small amounts of pin pins.

A known method of chemical deposition of Nickel on the surface of the steel (Kelman E.Ya., Temkina B.Ya. Chemical nickel plating. - M .: CBTI, 1960. - P.10, table 3, composition 2). The composition of the solution, g / l: nickel chloride 14-20, sodium acetate (pH = 3.7-5.5) 5.0-11.0, calcium hypophosphite 8.0-10.0. The temperature of the solution is 85-90 ° C, pH = 4-5, the rate of coating formation is 8-10 μm / h.

The disadvantages of this invention include: the inability to accurately control the thickness and time of applying a nickel film, insufficient purity of the deposited metal, high consumption of reagents, laborious preparation of metal, low mechanical properties of the coating, brittleness of the coating, insufficiently high adhesion strength of the enamel to the metal and the presence of enameled on the surface defect products ("pinpricks").

Closest to the claimed method of processing steel before enameling is the method of electrolytic deposition of Nickel on the surface of the steel (Yampolsky AM Copper plating and nickel plating. - L .: Mashinostroenie, 1971. - P.76). The electrolyte composition, g / l: NiSO ₄ · 7H ₂ O 200-300, N ₃ BO ₃ 25-30, NaF 4-6, NaCl 3-15, disulfonaphthalenic acid 2-4, formalin 1-1.5. Operating temperature 20-30 ° C, pH 5.8-6.3, current density 1-2 A / dm ² , current efficiency 95-96%.

However, the disadvantages of this invention include the fragility of the Nickel film and the lack of leveling effect, as well as the presence of a small number of "pin counts" and the value of the adhesion strength of the enamel coating 2-3 points (GOST 24405-80).

The objective of this invention is to provide such a method of surface treatment of steel before applying a single-layer enamel, which would avoid such disadvantages as insufficient degree of purity of the deposited metal, high consumption of reagents, laborious preparation of metal, low mechanical properties of the coating, brittleness of the coating, insufficiently high enamel adhesion strength with metal, etc.

The problem is solved in that a layer of copper (0.2 μm) is deposited in the same manner on a layer of electrochemically deposited nickel film (0.3 μm). The copper plating of the steel surface before enameling is a fundamentally new way, previously not found in literary sources. The deposition of a copper layer on a nickel layer can significantly increase the adhesion strength of enamel with metal up to 5 points (GOST 24405 -80) and avoid defects.

Electrolyte solutions for copper plating and nickel plating were made up of reagents of the following grades: H, ChP, ChDA. The solution of Nickel electrolyte has the following chemical composition, g / l:

NiCl ₂ · 6H ₂ O 250-300,

NiSO ₄ · 7H ₂ O 6-10,

H ₃ BO ₃ 25-35,

the rest is water.

Temperature

electrolyte 20-22 ° C,

pH 0.5-1.5

current efficiency 96%.

To prepare a nickel electrolyte, all components were dissolved in water at a temperature of 40-60 ° C and adjusted to pH = 0.5-1, and then the solution was cooled to a temperature of 20-22 ° C.

The copper plating electrolyte has the following chemical composition, g / l:

CuSO ₄ · 5H ₂ O 210-245,

H ₂ SO ₄ 50-60,

C ₂ H ₅ OH 3-6,

Temperature

electrolyte 18-22 ° C,

pH 3-4,

current output 100%.

The copper plating electrolyte was prepared as follows: copper sulfate was dissolved in water at a temperature of 40-60 ° C and sulfuric acid and ethyl alcohol were slowly poured, after which the electrolyte was cooled to a temperature of 18-22 ° C.

Steel samples (08 kp) were preliminarily subjected to the following treatment before electrolytic deposition: degreasing (treatment of the steel surface with Viennese lime), washing in running water, washing in distilled water, etching in a solution of hydrochloric acid (Hcl: H ₂ O = 1: 1) 3-5 minutes, washing in running water, washing in distilled water. Samples thus prepared were placed in a solution of nickel electrolyte. The current density is 1.0 A / dm ² , the voltage is 180-220 V, the size of the samples is 60 × 60 mm, the film thickness is 0.2-0.4 microns, the application time is 17 minutes. Next, the sample was washed in distilled water and placed in a copper plating electrolyte solution. Its parameters: current density 1.5 A / dm ² , voltage 180-220 V, sample size 60 × 60 mm, film thickness 0.1-0.3 μm, application time 3 min. Before the samples were immersed in the bath, a current was turned on, after which the samples were lowered and swayed so that no air bubbles remained in the deepened areas. Then, the samples were again washed in distilled water, dried and a single-layer enamel coating was applied by spraying. The next step was drying the samples in an oven at a temperature of 100-150 ° C and firing at a temperature of 750 ° C for 3 minutes.

Example 1

To obtain a Nickel electrolyte used the following composition, g / l:

NiCl ₂ · 6H ₂ O 250;

NiSO ₄ · 7H ₂ O 6;

H ₃ BO ₃ 25;

water the rest;

electrolyte temperature 20 ° C;

pH 0.5 coating thickness 0.2.

The solution was prepared by dissolving the reagents in water at a temperature of 40-60 ° C and constantly stirring until complete dissolution, and then cooled to a temperature of 20 ° C.

Steel samples, type 0.8 kp, were degreased with Viennese lime, washed with running water, then distilled and etched in a hydrochloric acid solution (1: 1). Then it was again washed in running and distilled water and suspended in a galvanic bath. Electrolysis modes: current density 1.0 A / dm ² , temperature 20 ° C, solution pH 0.5, deposition time 17 minutes. After coating, the samples were washed in cold distilled water from electrolyte residues and dried with filter paper.

Then applied a copper coating of copper plating electrolyte composition, g / l:

(CuSO ₄ · 5H ₂ O 210;

(H ₂ SO ₄ ) 50;

(C ₂ H ₅ OH) 3;

electrolyte temperature 18 ° C;

pH of solution 3;

coating thickness 0.3.

A copper plating electrolyte was prepared as follows: copper sulfate was dissolved in water at a temperature of 40-60 ° C and sulfuric acid and ethyl alcohol were slowly poured, after which the electrolyte was cooled to a temperature of 18 ° C. Before immersion of the samples in the bath, a current was turned on, after which the samples were lowered and rocked so that no air bubbles remain in the recessed areas. Coating time 3 minutes, current density 1.5 A / DM ² .

Then, the samples were again washed in distilled water, dried and a single-layer enamel coating was applied by spraying. The next step was drying the samples in an oven at a temperature of 100-150 ° C and firing at a temperature of 750 ° C for 3 minutes.

Using this method of surface treatment of steel and its further enameling under these conditions, single-layer glass-enamel coatings were not as fragile as with nickel plating, the mechanical properties improved, but the coating quality was satisfactory, with minor defects and insufficiently high adhesion strength of 4 points (GOST 24405 -80).

Example 2

To obtain a Nickel electrolyte used the following composition, g / l:

NiCl ₂ · 6H ₂ O 275;

NiSO ₄ · 7H ₂ O 8;

H ₃ BO ₃ 30;

water the rest;

electrolyte temperature 21 ° C;

pH 1.0;

coating thickness 0.3.

The solutions were prepared by dissolving the reagents in water at a temperature of 40-60 ° C and stirring constantly until complete dissolution, and then cooled to a temperature of 21 ° C.

Steel samples, type 0.8 kp, were degreased with Viennese lime, washed with running water, then distilled and etched in a hydrochloric acid solution (1: 1). Then it was again washed in running and distilled water and suspended in a galvanic bath. Electrolysis modes: current density 1.0 A / dm ² , temperature 21 ° C, solution pH 1.0, sedimentation time 17 minutes. After coating, the samples were washed in cold distilled water from electrolyte residues and dried with filter paper.

Then applied a copper coating of copper plating electrolyte composition, g / l:

CuSO ₄ · 5H ₂ 0 225;

H ₂ SO ₄ 55;

C ₂ H ₅ OH 4.5;

electrolyte temperature 20 ° C;

solution pH 3.5;

coating thickness 0.2.

A copper plating electrolyte was prepared as follows: copper sulfate was dissolved in water at a temperature of 40-60 ° C and sulfuric acid and ethyl alcohol were slowly poured, after which the electrolyte was cooled to a temperature of 20 ° C. Before immersion of the samples in the bath, a current was turned on, after which the samples were lowered and shook so that no air bubbles remain in the recessed areas. Coating time 3 minutes, current density 1.5 A / dm ² .

Then, the samples were again washed in distilled water, dried and a single-layer enamel coating was applied by spraying. The next step was drying the samples in an oven at a temperature of 100-150 ° C and firing at a temperature of 750 ° C for 3 minutes.

The obtained samples, in contrast to the example described above, have several advantages: high adhesion strength - 5 points (GOST 24405-80), the absence of brittleness, burnouts and coating defects, the presence of a leveling effect.

Example 3

To obtain a Nickel electrolyte used the following composition, g / l:

NiCl ₂ · 6H ₂ O 300;

NiSO ₄ · 7H ₂ O 10;

H ₃ BO ₃ 35;

water the rest;

electrolyte temperature 22 ° C;

pH 1.5;

coating thickness 0.4.

The solutions were prepared by dissolving the reagents in water at a temperature of 40-60 ° C and constantly stirring until complete dissolution, and then cooled to a temperature of 22 ° C.

Steel samples, type 0.8 kp, were degreased with Viennese lime, washed with running water, then distilled and etched in a hydrochloric acid solution (1: 1). Then it was again washed in running and distilled water and suspended in a galvanic bath. Electrolysis modes: current density 1.0 A / dm ² , temperature 22 ° C, solution pH 1.5, deposition time 17 minutes. After coating, the samples were washed in cold distilled water from electrolyte residues and dried with filter paper.

Then applied a copper coating of copper plating electrolyte composition, g / l:

CuSO ₄ · 5H ₂ O 245;

H ₂ SO ₄ 60;

C ₂ H ₅ OH 6;

electrolyte temperature 22 ° C;

solution pH 4;

coating thickness 0.1.

A copper plating electrolyte was prepared as follows: copper sulfate was dissolved in water at a temperature of 40-60 ° C and sulfuric acid and ethyl alcohol were slowly poured, after which the electrolyte was cooled to a temperature of 22 ° C. Before immersion of the samples in the bath, a current was turned on, after which the samples were lowered and rocked so that no air bubbles remain in the recessed areas. Coating time 3 minutes, current density 1.5 A / dm ² .

Then, the samples were again washed in distilled water, dried and a single-layer enamel coating was applied by spraying. The next step was drying the samples in an oven at a temperature of 100-150 ° C and firing at a temperature of 750 ° C for 3 minutes.

A higher degree of purity of the deposited metal, higher mechanical properties than the coating with one deposited nickel, but the coating also has various types of defects: burnouts, low adhesion strength - 3 points (GOST 24405-80).

Claims (1)

A method of processing steel before enameling, comprising electrochemical deposition of a nickel film, characterized in that an additional layer of copper film is electrochemically applied.