RU2805024C1 - Method for making optically black hybrid coating on steel - Google Patents

Abstract

FIELD: technical electrochemistry.

SUBSTANCE: invention can be used in chemical engineering, electronics and automotive industries, and heat engineering. The method involves deposition of a hybrid coating on steel grade 08kp at a voltage of 15 V from an aqueous electrolyte solution containing nickel sulphate, citric acid, salts of molybdenum, cobalt, iron, boric and polyacrylic acids, with a ratio of average cathode and anodic currents over the period of 1.1 :1-1.4:1; pH 4-5, temperature 65°C at the following ratio of components (g⋅l ^-1):

EFFECT: increasing the emissivity (degree of emissivity) of the resulting coatings.

1 cl, 4 ex

Description

The invention relates to the field of technical electrochemistry and can be used in chemical engineering, electronics and automotive industries, and heat engineering.

There is a known method for producing an optically black oxide-ceramic coating on the surface of aluminum and its alloys by the authors Zh.I. Bespalova, I.N. Panenko [Pat. RU No. 2459890, IPC C25D 11/14, C25D 15/00, publ. 08/27/2012, Bulletin. No. 24. A method for producing an optically black oxide-ceramic coating on the surface of aluminum and its alloys], including microplasma oxidation in aqueous electrolyte solutions. The coating is applied in a pulsed anodic-cathode mode with a duration of anodic pulse trains of 50 ms, cathodic pulses of 40 ms, pauses between them of 10 ms, a ratio of average anodic and cathodic currents of 1.1:0.9 from aqueous electrolyte solutions with sequential oxidation for 10 min in three solutions containing sodium hydroxide (NaOH), sodium metasilicate (Na ₂ SiO ₃ ⋅9H ₂ O), sodium tetraborate (Na ₂ B ₄ O ₇ ⋅10H ₂ O), potassium bichromate (K ₂ Cr ₂ O ₇ ), sodium tungstate (Na ₂ WO ₄ ⋅2H ₂ O), ammonium paramolybdate ((NH4) ₆ Mo ₇ O ₂₄ ⋅4H ₂ O), tungsten oxide (WO ₃ ), at different concentrations of the first two components. As a result of oxidation under microplasma discharge conditions, a uniform, intense black coating is formed on the surface of the aluminum alloy, having absorption (α) and emission (ε) coefficients, respectively, determined in a wide range of light waves of 95.8 and 87.0%.

The disadvantage of this method is the need to use complex equipment, as well as the need to use a three-stage synthesis to obtain coatings, which increases the labor intensity of the process.

There is a known method for producing a coating that increases the emissivity of a metal surface by the authors Yu.V. Bogdanov, A.S. Knyazev, V.I. Kuzevanov, L.G. Steiner [Pat. RU No. 2368702, IPC S23S 24/00, S23S 20/06, B05D 1/02, publ. 09/27/2009. Bull. No. 27. A coating applied to a metal surface that increases its emissivity, and a method of applying it], including spraying the coating material onto the metal surface. The coating material is sprayed in the form of a suspension obtained by mixing a mineral filler and a source of mineral SiO ₂ - binder in the form of a concentrated aqueous sol of silicic acid at a ratio of binder and filler in the suspension of 10-50 and 90-50 wt. % respectively. In this case, the metal surface is heated to a temperature of 100-350°C before spraying the suspension.

The disadvantage of this method is the proposed coating application method - pneumatic spraying, which does not allow obtaining coatings that are uniform in thickness.

The closest method of production is the method of producing selective coating described by the authors Zh.I. Bespalova, V.A. Klushin, A.S. Dyachishin [Pat. RU No. 2393275, IPC C25D 11/10, F24J 2/48, publ. 06/27/2010. Bull. No. 18. Method for producing selective coating], using alternating asymmetric current, which consists in applying a coating of an electrolyte containing aluminum sulfate, nickel sulfate, formaldehyde and citric acid, with an average cathode to anodic current ratio of 1.5:1 and a voltage of 8 to 15 V , at a temperature of 25±5°C.

The disadvantage of this production method is the need to use a toxic compound - formaldehyde and the low emissivity of the coating (ε = 6%).

The invention is aimed at increasing the emissivity (degree of emissivity) of the resulting coatings.

The task is achieved by deposition of an optically black hybrid coating on steel grade 08kp at a voltage of 15 V from an aqueous electrolyte solution containing nickel sulfate, citric acid, additionally containing salts of molybdenum, cobalt, iron, boric and polyacrylic acids, with the ratio of the cathode and anodic currents averaged over the period 1.1:1 - 1.4:1; pH 4-5, temperature 65°C, electrolysis time 70-100 min at the following ratios of electrolyte components (g-l ^-1 ):

Oxides of molybdenum, nickel, cobalt and iron are characterized by a wide range of optical properties due to the incomplete d-shell of metals, which is a common feature of this group.

Nanosized particles of transition metal oxides embedded in various matrices, including polymer ones, are of great interest due to their controlled optical and physical properties, which are caused by both classical and quantum size effects.

Polyacrylic acid is an anionic polymer and has the ability to form complexes with d-metal ions. The introduction of polyacrylic acid into the coating composition ensures its dullness and higher uniformity of distribution of metal oxides over the surface, as well as their stability.

The use of alternating asymmetric current makes it possible to obtain coatings based on metal oxides, including molybdenum oxides, of non-stoichiometric composition, capable of continuously absorbing in the IR range, which leads to high values of not only the absorption coefficient, but also the emission coefficient.

The proposed method for producing an optically black hybrid coating on steel made it possible to:

- to form a hybrid coating based on oxides of molybdenum, cobalt, nickel, iron and polyacrylic acid on the surface of 08 kp steel;

- achieve an increase in the thermal radiation coefficient (emissivity);

- ensure uniform distribution of metal oxides in the polyacrylic acid matrix.

The formation of optically black hybrid coatings was carried out on the surface of steel grade 08kp, previously prepared according to standard methods, with polarization by an alternating asymmetric current of industrial frequency, representing two half-sine waves of different amplitudes from an electrolyte containing salts of molybdenum, nickel, cobalt, iron, citric and boric acids, polyacrylic acid . Macroelectrodes made of 08kp 40×40×1 mm (on both sides) were used as the working electrode. Cobalt served as the counter electrode.

To experimentally test the proposed method, optically black hybrid coatings on steel were obtained.

The method for producing an optically black hybrid coating on steel is as follows:

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition at a voltage of 15 V from an aqueous electrolyte solution containing nickel sulfate, citric acid, salts of molybdenum, cobalt, iron, boric and polyacrylic acids, at a ratio of average period of cathode and anode currents 1.1:1 - 1.4:1; pH 4-5, temperature 65°C and electrolysis time 70-100 min with the following ratio of components (g-l ^-1 ):

The determination of solar radiation absorption coefficients (a _s ) was carried out by the relative method on a solar reflectometer "RS-K" using reference samples, and the determination of emissivity coefficients (ε) was carried out by the relative method on an infrared reflectometer "RI-K". The absorption coefficient (a _s ) was 0.89-0.95; the emissivity (ε) was 0.90-0.95.

If the confidence interval of the concentrations of the electrolyte components is not observed, the technical result is not achieved, namely, an increase in the thermal emission coefficient (emissivity) is not achieved.

Let's consider an example of the implementation of the method with specific values of the electrolyte components and electrolysis modes.

Example 1.

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition from an electrolyte, with the following component ratio (g⋅l ^-1 ):

The electrolysis time was 70 minutes, the density of the average cathode current over the period j _K =0.17 A⋅dm ^-2 , the anodic current j _A =0.12 A⋅dm ^-2 , electrolysis temperature 65°C. The absorption (α) and emissivity (ε) coefficients were 0.90 and 0.90, respectively.

Example 2.

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition from an electrolyte, with the following component ratio (g⋅l ^-1 ):

The electrolysis modes differ from Example 1 in the density of the cathode current averaged over the period j _K =0.15 A⋅dm ^-2 , the anodic current j _A =0.12 A⋅dm ^-2 . The absorption (α) and emissivity (ε) coefficients were 0.89 and 0.90, respectively.

Example 3.

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition from an electrolyte, with the following component ratio (g-l ^-1 ):

The electrolysis modes differ from Example 2 in the density of the cathode current averaged over the period j _K =0.17 A⋅dm ^-2 of the anodic current j _A =0.12 A⋅dm ^-2 , as well as the electrolysis time of 80 minutes. The absorption (α) and emissivity (ε) coefficients were 0.95 and 0.95, respectively.

Example 4.

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition from an electrolyte, with the following component ratio (g⋅l ^-1 ):

An optically black hybrid coating was obtained on the surface of 08kp steel with dimensions of 40×40×1 mm by electrodeposition from an electrolyte, with the following component ratio (g⋅l ^-1 ):

The electrolysis mode differs from Example 3 with an electrolysis time of 100 minutes. The absorption (α) and emissivity (ε) coefficients were 0.92 and 0.91, respectively.

Claims (2)

A method for producing an optically black hybrid coating, which consists in deposition of a hybrid coating on steel grade 08kp at a voltage of 15 V from an aqueous electrolyte solution containing nickel sulfate, citric acid, characterized in that the electrolyte additionally contains salts of molybdenum, cobalt, iron, boric and polyacrylic acid , with the ratio of the average cathode and anodic currents over the period being 1.1:1–1.4:1; pH 4-5, temperature 65°C and electrolysis time 70–100 min, with the following ratio of components (g⋅l ^-1 ): Cobalt (II) sulfate (CoSO ₄ ⋅7H ₂ O) 90-110 Cobalt (II) chloride (CoCl ₂ ⋅6H ₂ O) 10-16 Boric acid (H ₃ BO ₃ ) 15-30 Iron (II) sulfate (FeSO ₄ ⋅7H ₂ O) 6-12 Nickel (II) sulfate (NiSO ₄ ⋅7H ₂ O) 20-30 Ammonium heptamolybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ ) 30-50 Citric acid (C ₆ H ₈ O ₇ ) 3-5 Polyacrylic acid ((C ₂ H ₃ COOH) _n ) 2