Preparation method of composite coating on surface of steel and iron material

Abstract

The invention belongs to the technical field of steel and iron material surface treatment, and particularly relates to a steel and iron material surface composite coating preparation method which comprises the following steps: adding a main salt, a water repellent agent and a nanotube material loaded with a low-surface-energy substance into a deep eutectic solvent to prepare a plating solution; the composite coating with the hydrophobic performance is prepared on the surface of a steel material in a pulse electrodeposition mode through a one-step method. The method has the advantages that the deep eutectic solvent plating solution system is adopted for preparing the composite coating, and the defects that a traditional aqueous solution electroplating system is narrow in process window, inflexible in coating composition regulation and control and the like are overcome while the plating solution has the remarkable environment-friendly characteristic. Compared with direct-current electrodeposition, the pulse electrodeposition process can remarkably improve the dispersing capacity of the plating solution, inhibit concentration polarization of the plating solution and improve the quality of a plating layer; according to the preparation method of the composite coating, doping of the hydrophobic agent and the tubular nanometer material loaded with the low-surface-energy substance in the coating can be achieved in one step, and therefore the surface of a steel material is endowed with the super-hydrophobic function.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel material surface treatment, and particularly relates to a steel material surface composite coating preparation method. BACKGROUND

[0002] The economic loss caused by metal corrosion is up to hundreds of billions of yuan each year. As the most widely used metal material in the national economy, the corrosion protection of steel materials is of great significance. Preparing various coatings on the surface of steel materials is an important anti-corrosion technology, which can also endow the surface of steel materials with special functions such as hydrophobicity, wear resistance, etc. Hydrophobicity can bring practical effects such as corrosion prevention, drag reduction, and anti-fouling, so the hydrophobicity of the coating has attracted widespread attention. Currently, some research has been carried out in this field. Patent No. CN104746118A discloses a method for preparing a super-hydrophobic coating on a steel substrate by Fe-based nano-composite electro-brush plating. The method uses nano-composite electro-brush plating iron process and blackening treatment of the coating to prepare a super-hydrophobic coating with a contact angle greater than 150° and a rolling angle less than 3° on the surface of a steel substrate, which consists of the following steps: (1) preparation; (2) process flow for preparing a micro-nano rough structure on the surface of steel by nano-composite electro-brush plating iron; (3) electrocleaning → activation → plating of a base layer → plating of a nano-Cu / Al2O3 composite coating → soaking in alkali solution, rinsing with water after each process to prevent contamination of the next process; blackening treatment of the coating; (4) modification of the rough surface with a low surface energy material. This method constructs a super-hydrophobic surface by electro-brush plating iron on the metal surface, followed by blackening treatment and then hydrophobic modification. However, this method is complex and cannot achieve the preparation of a super-hydrophobic coating in one step, which is not conducive to practical application. Patent No. CN116590767A proposes a laser texturing method for preparing a super-hydrophobic coating on the surface of a mining equipment alloy, which includes the following steps: (1) pretreatment of a 65 manganese steel substrate; (2) preparation of a Ni-Co-P composite plating solution; (3) preparation of a Ni-Co-P nano-composite coating by spray electrodeposition; (4) laser texturing of the surface of the Ni-Co-P nano-composite coating; (5) low surface energy treatment of the textured coating surface. This invention combines spray electrodeposition technology with laser texturing technology, uses laser texturing technology to construct array bump and pit topographies on the surface of the Ni-Co-P nano-composite coating, and finally performs low surface energy treatment on the textured Ni-Co-P nano-composite coating surface to obtain a super-hydrophobic coating. However, the spray electrodeposition and laser texturing steps of this method need to be carried out on special equipment, and subsequent low surface energy treatment is still required after texturing, which also cannot achieve the preparation of a super-hydrophobic coating in one step.Patent publication number: CN114959818A, discloses a method for preparing super-hydrophobic coating by one-step electrodeposition in deep eutectic solvent, the specific steps are as follows: preparation of deep eutectic solvent, mix choline chloride and ethylene glycol according to 1:1-1:4 molar ratio, heat and stir at 60-80℃ until a colorless transparent liquid is formed; preparation of electroplating solution: add 1-20g / L of concentrated nickel chloride hexahydrate and 6-50g / L of stearic acid into the deep eutectic solvent in step A and stir to obtain the electroplating solution; electrodeposition: use carbon steel as cathode and platinum sheet as anode, immerse the cathode and anode electrodes into the electroplating solution, connect the direct current power supply, adjust the current to 0.01-0.5A, the electrodeposition temperature is 60-80℃, and the deposition time is 10-120min; post-plating treatment: after electrodeposition, take out the cathode plated sheet, rinse with deionized water, and blow dry for storage. This method can make the carbon steel surface deposit into a super-hydrophobic coating in one step, but the coating formed by the reaction product of stearic acid and nickel ions is prone to hydrolysis in alkaline environment, resulting in a decrease in hydrophobicity. Patent publication number: CN102199783A, discloses a nickel electroplating solution and a method for preparing super-hydrophobic nickel coating using the nickel electroplating solution. The nickel electroplating solution uses choline chloride-based ionic liquid as solvent and NiCl2·6H2O or NiCl2 as solute, with a molar concentration of 0.1-3 mol / L. The method for preparing super-hydrophobic nickel coating using the nickel electroplating solution is as follows: use pure nickel as anode and the workpiece to be electroplated as cathode, and perform electroplating in the nickel electroplating solution with a temperature of room temperature-200℃ and a voltage of 0.2-2V during electroplating. The obtained nickel coating has super-hydrophobic properties with a contact angle greater than 160° and a rolling angle less than 2°. However, the hydrophobicity of such coating solely depends on the special microstructure of the coating without introducing hydrophobic substances, and since the hardness of the nickel-plated layer is not high, once the microstructure is damaged by external force or covered by contaminants, the hydrophobic performance will significantly decrease. Similarly, patent publication number: CN113174617A, discloses a method for preparing super-hydrophobic Zn-Fe alloy coating by electrodeposition in deep eutectic ionic liquid. The electrolyte is prepared by dissolving zinc source, iron source, solubilizer, viscosity reducer, and pH adjuster in deep eutectic ionic liquid with choline chloride and ethylene glycol as hydrogen bond acceptor and donor. The electrodeposition process is carried out at a constant current of 10-500mA / cm for 10-60min at 40-90℃ to obtain super-hydrophobic Zn-Fe alloy coating with good corrosion resistance. The super-hydrophobic Zn-Fe alloy coating contains 1-20wt% of iron, has a water contact angle of ≥160° and a rolling angle of ≤4°, showing good hydrophobicity and corrosion resistance. However, this method still solely depends on the special microstructure of the coating without introducing hydrophobic substances, and since the hardness of the coating is not high, once the microstructure is damaged by external force or covered by contaminants, the hydrophobic performance will significantly decrease. 2 Summary Summary

[0003] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide a steel material surface composite coating preparation method, through a eutectic solvent plating solution system, combined with pulse electrodeposition process, realizing the synchronous doping of hydrophobic agent and nanotube material loaded with low surface energy substance in the coating, and obtaining the persistent and stable super-hydrophobic performance of the steel surface.

[0004] In order to achieve the above-mentioned purpose, the present application realizes the following technical scheme: A steel material surface composite coating preparation method, in which a eutectic solvent is added with main salt, hydrophobic agent and nanotube material loaded with low surface energy substance to prepare a plating solution, and a composite coating with hydrophobic performance is prepared on the surface of the steel material by one-step pulse electrodeposition.

[0005] The eutectic solvent is a mixture of choline chloride and hydrogen bond donor, and the molar ratio of choline chloride to hydrogen bond donor is 1:2-1:3, and the hydrogen bond donor is ethylene glycol or glycerol.

[0006] The main salt is nickel sulfate or nickel chloride, and the addition amount of the main salt is 12-28 g / L. The main salt is the source of nickel element in the coating.

[0007] The hydrophobic agent is a fatty acid, and the addition amount of the hydrophobic agent is 10-25 g / L. The hydrophobic agent migrates to the inside and surface of the coating during electrodeposition and plays a hydrophobic role.

[0008] The fatty acid is one or two of dodecanoic acid, tetradecanoic acid and hexadecanoic acid.

[0009] The addition amount of the nanotube material loaded with low surface energy substance is 1.2-5.0 g / L, and the length of the nanotube material loaded with low surface energy substance is 2-5 μm, and the inner diameter is 10-20 nm.

[0010] The low surface energy substance is one or two of polydimethylsiloxane, trimethylchlorosilane and perfluorodecyltriethoxysilane. The low surface energy substance is loaded in the tubular nanomaterial and co-deposited in the coating with the tubular nanomaterial. When the coating is mechanically damaged, the low surface energy substance is released from the tubular nanomaterial and plays a hydrophobic role, hindering the transmission of corrosion medium to the steel substrate. The low surface energy substance can also make up for the decrease in hydrophobic performance caused by the hydrolysis of the fatty acid hydrophobic agent.

[0011] The preparation method of the nanotube material loaded with low surface energy substance is as follows: 20~35g / L of low surface energy substance is dissolved in anhydrous ethanol to form a solution, and then nanotube material is added to the solution, the amount of nanotube material added is 1.0%~1.5% of the mass of the solution, stirring at a speed of 3000~5000r / min under a pressure of ≤5000Pa for 60~90min, and then drying at 40~50℃ under negative pressure for more than 12h after filtration; the nanotube material is halloysite nanotube or carbon nanotube.

[0012] The preparation method of the plating solution is: adding choline chloride into a hydrogen bond donor, stirring at 60~80℃ for 24~48h to obtain a eutectic solvent; adding a host salt and a hydrophobic agent into the eutectic solvent, stirring at 60~80℃ for 12~24h, and then adding nanotube material loaded with low surface energy substance, dispersing the nanotube material in the eutectic solvent by ultrasonic method at 30~50℃, and the ultrasonic time is 30~60min.

[0013] The parameters of the pulse electrodeposition are: square wave pulse current, frequency is 500~1000Hz, duty cycle is 50%~70%, current density is 10~20mA / cm 2 , electrodeposition time is 40~60min; the plating solution is stirred by magnetic stirring, the stirring speed is 300~500r / min; the pure nickel sheet is the anode, and the steel sample is the cathode, the distance between the cathode and the anode is 2~5cm; the temperature of the plating solution is 60~70℃. Compared with the traditional aqueous solution electrodeposition, the viscosity of the eutectic solvent system plating solution is higher, the mass transfer is slower, and the concentration polarization is easy to occur, thereby affecting the electrodeposition efficiency and the quality of the coating. The pulse electrodeposition can effectively inhibit the concentration polarization, improve the dispersion ability of the plating solution, and overcome the adverse effects of the high viscosity of the eutectic solvent system.

[0014] Compared with the prior art, the beneficial effects of the present application are: 1. The present application uses a eutectic solvent plating solution system to prepare a composite coating, the plating solution has the characteristics of being environmentally friendly, and overcomes the shortcomings of the traditional aqueous solution electroplating system, such as narrow process window and inflexible coating composition regulation. The pulse electrodeposition process overcomes the disadvantage of high viscosity of the eutectic solvent plating solution, and compared with direct current electrodeposition, can significantly improve the dispersion ability of the plating solution, inhibit the concentration polarization of the plating solution, and improve the quality of the coating; 2. The present application uses a one-step electrodeposition process to introduce a hydrophobic agent and nanotube material loaded with low surface energy substance into the plating solution, which can realize the preparation of a hydrophobic coating by one-step electrodeposition, the contact angle of the coating can be more than 150°, and the super-hydrophobic state is realized; the coating sample does not rust under neutral salt spray test conditions for 2000 hours, and shows good corrosion protection performance. The preparation of the coating does not require complex special equipment and is easy to implement. DETAILED DESCRIPTION

[0015] In order to better illustrate the present application, the content of the present application is described below in combination with specific examples. However, the content of the present application is not limited to the examples.

[0016] The process parameters for preparing the composite coating on the surface of the steel material are shown in Table 1, and the technical effects of the examples and comparative examples are shown in Table 2.

[0017] Table 1: Examples and Comparative Examples Table 2: Effects of Examples and Comparative Examples Note: (1) The contact angle is the contact angle of water with the surface of the sample; (2) The neutral salt spray test is carried out in accordance with GB / T1771, and "O" indicates that there are no rust spots on the surface of the sample, and "X" indicates that rust spots appear on the surface of the sample.

[0018] The implementation effects of each example show that the composite coating preparation method can impart good hydrophobicity and corrosion resistance to the steel substrate. Compared with Examples 1-7, the molar ratio of choline chloride to hydrogen bond donor in Comparative Example 1 is too high, resulting in too large viscosity of the plating solution; the content of the main salt in Comparative Example 2 is too low; the above factors affect the thickness and uniformity of the coating, resulting in poor hydrophobicity and corrosion resistance. Compared with Examples 1-7, the content of the hydrophobic agent in Comparative Example 3 is too low, the addition amount of the nanotubular material in Comparative Example 4 is too low, and the addition amount of the low surface energy substance in Comparative Example 5 is too low; the above factors all result in too low content of the hydrophobic and low surface energy substances in the coating, resulting in poor hydrophobicity. Compared with Examples 1-7, the content of the hydrophobic agent in Comparative Example 3 is too low, the addition amount of the nanotubular material in Comparative Example 4 is too low, and the addition amount of the low surface energy substance in Comparative Example 5 is too low; the above factors all result in too low content of the hydrophobic and low surface energy substances in the coating, resulting in poor hydrophobicity. Compared with Examples 1-7, the distance between the anode and the cathode in Comparative Example 6 is too large, resulting in decreased electrodeposition efficiency, leading to poor hydrophobicity and corrosion resistance of the coating. Compared with Examples 1-7, the pulse frequency in Comparative Example 7 is too high, resulting in decreased electrodeposition efficiency, which is prone to form defects in the structure of the coating, leading to poor hydrophobicity and corrosion resistance. Compared with Examples 1-7, the duty cycle in Comparative Example 8 is too high, so that the concentration polarization cannot be effectively alleviated, resulting in decreased electrodeposition efficiency, which is prone to form defects in the structure of the coating, leading to poor hydrophobicity and corrosion resistance. Compared with Examples 1-7, the current density in Comparative Example 9 is too low, resulting in decreased electrodeposition efficiency, which is prone to form defects in the structure of the coating, leading to poor hydrophobicity and corrosion resistance. Compared with Examples 1-7, the electrodeposition time in Comparative Example 10 is too short, resulting in too thin coating, which further leads to poor hydrophobicity and corrosion resistance.

Claims

1. A method for preparing a composite coating layer on a steel material surface, characterized by, The plating solution is prepared by adding host salt, hydrophobic agent and nanotubular material loaded with low surface energy substance into the eutectic solvent, and the composite coating with hydrophobic property is prepared on the surface of steel material by one-step pulse electrodeposition.

2. The method according to claim 1, wherein the method is characterized by: The eutectic solvent is a mixture of choline chloride and hydrogen bond donor, and the molar ratio of choline chloride to hydrogen bond donor is 1:2-1:3, and the hydrogen bond donor is ethylene glycol or glycerol.

3. The method according to claim 1, wherein the method is characterized by: The host salt is nickel sulfate or nickel chloride, and the addition amount of host salt is 12-28 g / L.

4. The method according to claim 1, wherein the method is characterized by: The hydrophobic agent is fatty acid, and the addition amount of hydrophobic agent is 10-25 g / L.

5. The method for preparing a composite coating on the surface of steel materials according to claim 4, characterized in that, The fatty acid is one or two of dodecanoic acid, tetradecanoic acid and hexadecanoic acid.

6. The method for preparing a composite coating on the surface of steel materials according to claim 1, characterized in that, The addition amount of nanotubular material loaded with low surface energy substance is 1.2-5.0 g / L, and the length of nanotubular material loaded with low surface energy substance is 2-5 μm, and the inner diameter is 10-20 nm.

7. The method according to claim 1, wherein the method is characterized by: The low surface energy substance is one or two of polydimethylsiloxane, trimethylchlorosilane and perfluorodecyltriethoxysilane.

8. The method according to claim 1, wherein the method is characterized by: The preparation method of nanotubular material loaded with low surface energy substance is as follows: 20-35 g / L of low surface energy substance is dissolved in anhydrous ethanol to form a solution, and then nanotubular material is added into the solution, and the addition amount of nanotubular material is 1.0%-1.5% of the mass of the solution, and the solution is stirred at a speed of 3000-5000 r / min under a pressure of ≤5000 Pa for 60-90 min, and then filtered and dried under negative pressure at 40-50 ℃ for more than 12 h; the nanotubular material is halloysite nanotube or carbon nanotube.

9. The method according to claim 1, wherein the steel material is a steel material having a surface layer of a coating layer of zinc, zinc alloy, aluminum, aluminum alloy, or a combination thereof. The preparation method of the plating solution is as follows: choline chloride is added into hydrogen bond donor, and the mixture is stirred at 60-80 ℃ for 24-48 h to obtain eutectic solvent; host salt and hydrophobic agent are added into the eutectic solvent, and the mixture is stirred at 60-80 ℃ for 12-24 h, and then nanotubular material loaded with low surface energy substance is added, and the nanotubular material is dispersed in the eutectic solvent by ultrasonic method at 30-50 ℃, and the ultrasonic time is 30-60 min.

10. The method for preparing a composite coating on the surface of steel materials according to claim 1, characterized in that, The parameters of the pulse electrodeposition are: square wave pulse current, frequency of 500-1000 Hz, duty cycle of 50%-70%, current density of 10-20 mA / cm 2 , electrodeposition time of 40-60 min; the plating solution is subjected to magnetic stirring, stirring speed of 300-500 r / min; the pure nickel sheet is used as an anode, and the steel sample is used as a cathode; the distance between the cathode and the anode is 2-5 cm; and the plating solution temperature is 60-70 DEG C.

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