Preparation method of high-performance black zinc-aluminum-magnesium coated steel plate

Abstract

The invention discloses a preparation method of a high-performance black zinc-aluminum-magnesium coated steel plate, which comprises three working procedures of pretreatment, micro-arc oxidation and hole sealing treatment, and comprises the following steps: immersing the activated zinc-aluminum-magnesium coated steel plate into electrolyte for micro-arc oxidation in-situ coloring treatment; and the micro-arc oxidation steel plate is subjected to hole sealing treatment through a hole sealing agent. According to the method, the black zinc-aluminum coated steel plate is prepared by adopting a micro-arc oxidation method without being carried out in a high-temperature and high-pressure closed container, so that the preparation method is simple, the production is safer, the production cost is low, the production efficiency is high and the period is short; the prepared black zinc-aluminum coated steel plate is uniform in blackening, good in decorative effect and good in corrosion resistance and friction resistance; the application field of the zinc-aluminum-magnesium coated steel plate is expanded, and the zinc-aluminum-magnesium coated steel plate has very remarkable social benefits and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-dip galvanized aluminum-magnesium steel plates, and specifically relates to a preparation method of a high-performance black zinc-aluminum-magnesium coated steel plate. Background Art

[0002] As a new type of environmentally friendly and energy-saving steel plate, zinc-aluminum-magnesium coated steel plate has been widely used in photovoltaic, automobile, home appliance and equipment manufacturing. In recent years, black coating has gradually been used as a decorative coating for daily necessities, and is widely favored in the fields of building roof materials, outer packaging materials, home appliances, automobiles, etc. At present, there are few reports on black zinc-aluminum-magnesium coated steel plates at home and abroad. The preparation method of black appearance coated steel plates is mainly based on black paint coating. In order to obtain black coated steel plates with higher blackness values, the coating thickness must be increased to hide the base color of the coated steel plates, resulting in a series of problems such as high coating costs, poor adhesion between coatings and coatings, and easy to fall off. In recent years, with the continuous development of marine, automotive, photovoltaic, and outsourcing materials, higher requirements have been put forward for the corrosion resistance, friction resistance, and decorativeness of coated steel plates.

[0003] The prior art mostly prepares black zinc-aluminum-magnesium coated steel sheets without forming a black coating film and a black conversion film. For example, patent CN201680082619.9 manufactures black coated steel sheets by contacting the coated steel sheets with water vapor inside a sealed container, which includes three steps: first, heating the coated steel sheets arranged inside the sealed container under the condition that there is a gas whose dew point is always lower than the temperature of the coated steel sheets; second, exhausting the ambient gas inside the heated sealed container, and making the pressure of the internal gas of the sealed container reach below 70 kPa; finally, introducing water vapor into the sealed container with an internal gas pressure below 70 kPa, so as to blacken the coating. Patent CN202180086544.2 prepares black coated steel sheets by a constant humidity heat treatment method. Although the distribution of water vapor and the content of blackening promoting elements in the coating can prepare coated steel sheets with uniform blackening and low lightness L*, the above technologies generally adopt a water vapor contact method to prepare black coated steel sheets, and the reaction time is about 210 hours, or even longer. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art, shorten the production time of black coated steel plates, and promote the development of low-carbon green steel, the present invention provides a method for quickly preparing high-performance zinc-aluminum-magnesium coated steel plates with decorative effects. The technical scheme is simple, the production cost is low, the production efficiency is high, the decorative effect is good, and the corrosion resistance and friction resistance are good.

[0005] In order to achieve the above-mentioned invention object, the present invention provides a method for preparing a high-performance black zinc-aluminum-magnesium coated steel plate, which includes three processes: pretreatment, micro-arc oxidation, and sealing treatment. The specific steps are as follows:

[0006] ①Use anhydrous ethanol as the cleaning solution, ultrasonically clean the zinc-aluminum-magnesium coated steel plate for 10 minutes, and dry it with cold air.

[0007] ② Immerse the dried zinc-aluminum-magnesium coated steel plate in a hydrochloric acid solution with a mass fraction of 10% to 20% for pickling for 1 to 10 seconds, and then rinse it with water to improve the surface reaction activity of the zinc-aluminum-magnesium coating.

[0008] ③ Prepare the electrolyte and introduce high-purity oxygen into the bottom of the electrolyte for 10 to 30 minutes before micro-arc oxidation.

[0009] ④ Immersing the zinc-aluminum-magnesium coated steel plate activated in step ② into the prepared electrolyte for micro-arc oxidation in-situ coloring treatment; wherein the zinc-aluminum-magnesium coated steel plate is the anode, and the stainless steel or graphite is the cathode, and high-purity oxygen is continuously introduced throughout the micro-arc oxidation process to ensure that the oxygen content in the electrolyte is always in a supersaturated state; during the micro-arc oxidation process, ultrasonic waves are used to stir the solution, and the ultrasonic frequency is 50 to 100 kHz; after the micro-arc oxidation is completed, the solution is rinsed with distilled water for multiple times and dried with cold air to obtain a micro-arc oxidation coating on the zinc-aluminum-magnesium coated steel plate.

[0010] ⑤ Use a sealing agent to seal the micro-arc oxidation steel plate obtained in step ④ to further improve the corrosion resistance and anti-pollution performance of the zinc-aluminum-magnesium coated steel plate.

[0011] In the above technical solution, further, the electrolyte in step ③ is composed of a film-forming agent, a pH regulator, a modifier, an auxiliary film-forming agent and a tip discharge inhibitor.

[0012] Furthermore, the film-forming agent is sodium nitrate NaAlO with a concentration of 5 to 20 g / L. 2 ; The pH adjuster is potassium hydroxide or sodium hydroxide solution, and the pH value is 8-12.

[0013] Furthermore, the modifier is sodium molybdate NaMoO with a concentration of 5 to 10 g / L. 4 , nano graphite particles 5~20g / L.

[0014] Furthermore, the auxiliary film-forming agent is sodium fluoride with a concentration of 1 to 5 g / L; the tip discharge inhibitor is glycerol with a concentration of 5 to 15 g / L; the additive is oxalate, preferably 1 to 5 g / L sodium oxalate; the dispersant is sodium carboxymethyl cellulose with a concentration of 0.5 to 2 g / L; and the wetting agent is octylphenol polyoxyethylene ether OP-10 with a concentration of 0.5 to 2 g / L.

[0015] Furthermore, in step ④, the oxidation time of the micro-arc oxidation in-situ coloring treatment is 5 to 15 minutes, the voltage is 300 to 500 V, the duty cycle is 20% to 60%, the frequency is 400 to 500 Hz, and the electrolyte temperature is 30° C. to 60° C.

[0016] Furthermore, in step ④, the micro-arc oxidation coating has a nanoporous structure, a porosity of ≥30%, and a nanopore diameter of 20 to 100 nm; and the thickness of the micro-arc oxidation coating is about 10 to 20 μm.

[0017] Furthermore, in step ⑤, the sealing agent is a hydrolyzed solution of a silane coupling agent, and the sealing agent is preferably vinyl polysilane TC-P11, and the coating thickness is about 2 to 10 μm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a method for rapidly preparing a high-performance black zinc-aluminum-magnesium coated steel plate with a decorative effect. The black zinc-aluminum coated steel plate is prepared by a micro-arc oxidation method, and there is no need to carry out the process in a high-temperature and high-pressure sealed container. The preparation method is simple and the production is safer. The black zinc-aluminum coated steel plate prepared by this technical solution has low production cost, high production efficiency, short cycle, uniform blackening, good decorative effect, good corrosion resistance and friction resistance; it expands the application scenarios of zinc-aluminum-magnesium coated steel plates, can meet the green and low-carbon development concept of the steel industry, has very significant social and economic benefits, and has broad application prospects in the fields of construction, photovoltaics, home appliances, automobiles, etc. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0021] The preparation method of high-performance black zinc-aluminum-magnesium coated steel plate includes three processes: pretreatment, micro-arc oxidation, and sealing treatment. The specific steps are as follows:

[0022] ①Use anhydrous ethanol as the cleaning solution, ultrasonically clean the zinc-aluminum-magnesium coated steel plate for 10 minutes, and dry it with cold air;

[0023] ② Immerse the dried zinc-aluminum-magnesium coated steel plate in a 10% to 20% hydrochloric acid solution for pickling for 1 to 10 seconds, then rinse with water after taking it out;

[0024] ③ Prepare the electrolyte and introduce high-purity oxygen into the bottom of the electrolyte for 10 to 30 minutes before micro-arc oxidation;

[0025] ④ Immersing the zinc-aluminum-magnesium coated steel plate activated in step ② into the prepared electrolyte for micro-arc oxidation in-situ coloring treatment; wherein the zinc-aluminum-magnesium coated steel plate is the anode, and the stainless steel or graphite is the cathode, and high-purity oxygen is continuously introduced throughout the micro-arc oxidation process so that the oxygen content in the electrolyte is always in a supersaturated state; during the micro-arc oxidation process, ultrasonic waves are used to stir the solution, and the ultrasonic frequency is 50 to 100 kHz; after the micro-arc oxidation is completed, the steel plate is rinsed with distilled water for multiple times, and dried with cold air to obtain a micro-arc oxidation coating on the zinc-aluminum-magnesium coated steel plate;

[0026] ⑤ Using the hydrolyzed solution of silane coupling agent to seal the micro-arc oxidation steel plate obtained in step ④.

[0027] The matters not described in the following embodiments are the same as the description of the above specific implementation methods.

[0028] Example 1

[0029] The preparation method of high-performance black zinc-aluminum-magnesium coated steel plate, the specific process flow is:

[0030] The coating weight is about 270g / m 2 The Zn-11Al-3Mg-0.2Si coated steel plate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 minutes and then dried with cold air. The washed zinc-aluminum-magnesium coated steel plate was then immersed in a 10% hydrochloric acid solution for pickling for 10 seconds to improve the surface reaction activity of the coating, rinsed with distilled water, and dried for later use.

[0031] Prepare electrolyte: 10g / L NaAlO 2 , 5g / L NaMoO 4 , 5g / L nanographite particles, 5g / L sodium fluoride, 5g / L glycerol, 1g / L sodium oxalate, 1g / L sodium carboxymethyl cellulose, and 1g / L OP-10 were fully mixed, and potassium hydroxide was used to adjust the pH value of the electrolyte to 10. High-purity oxygen was continuously introduced into the bottom of the electrolyte for 30 minutes before micro-arc oxidation.

[0032] The activated zinc-aluminum-magnesium coated steel sheet is immersed in an electrolyte, wherein the zinc-aluminum-magnesium coated steel sheet is an anode and stainless steel or graphite is a cathode. The zinc-aluminum-magnesium coated steel sheet is subjected to micro-arc oxidation treatment using a multifunctional DC pulsed micro-arc oxidation power supply. The oxidation time is 5 min, the voltage is 300 V, the duty cycle is 20%, the frequency is 400 Hz, and the electrolyte temperature is 30 ° C. High-purity oxygen is continuously introduced throughout the micro-arc oxidation process to keep the oxygen content in the electrolyte in an oversaturated state. Ultrasonic waves are used to stir the solution during the micro-arc oxidation process, and the ultrasonic frequency is 100 kHz. After the micro-arc oxidation is completed, distilled water is taken out and rinsed several times, and then dried with cold air. The porosity of the micro-arc oxidation coating is about 50%, and the diameter of the nanopores is about 50 nm. The hydrolysis solution of the silane coupling agent is used to spray the zinc-aluminum-magnesium coating after micro-arc oxidation, and the coating thickness is about 5 μm. The properties of the obtained high-performance black zinc-aluminum-magnesium coated steel sheet are shown in Table 1.

[0033] Table 1 Performance comparison of zinc-aluminum-magnesium coated steel sheets

[0034]

[0035] Example 2

[0036] The preparation method of high-performance black zinc-aluminum-magnesium coated steel plate, the specific process flow is:

[0037] The coating weight is about 120g / m 2 The Zn-6Al-3Mg coated steel plate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 minutes and then dried with cold air. The cleaned zinc-aluminum-magnesium coated steel plate was then immersed in a 20% hydrochloric acid solution for pickling for 2 seconds to improve the surface reaction activity of the coating, rinsed with distilled water, and dried for later use.

[0038] Prepare electrolyte: 10g / L NaAlO 2 , 10g / L NaMoO 4 , 10g / L nanographite particles, 2g / L sodium fluoride, 10g / L glycerol, 3g / L sodium oxalate, 2g / L sodium carboxymethyl cellulose, and 2g / L OP-10 were fully mixed, and potassium hydroxide was used to adjust the pH value of the electrolyte to 12. High-purity oxygen was continuously introduced into the bottom of the electrolyte for 30 minutes before micro-arc oxidation.

[0039] The activated zinc-aluminum-magnesium coated steel sheet is immersed in an electrolyte, wherein the zinc-aluminum-magnesium coated steel sheet is an anode and stainless steel or graphite is a cathode. The zinc-aluminum-magnesium coated steel sheet is subjected to micro-arc oxidation treatment using a multifunctional DC pulsed micro-arc oxidation power supply. The oxidation time is 10 minutes, the voltage is 500V, the duty cycle is 60%, the frequency is 400Hz, and the electrolyte temperature is 50°C. High-purity oxygen is continuously introduced during the entire micro-arc oxidation process to keep the oxygen content in the electrolyte in an oversaturated state. Ultrasonic waves are used to stir the solution during the micro-arc oxidation process, and the ultrasonic frequency is 100kHz. After the micro-arc oxidation is completed, distilled water is taken out for multiple rinses and then dried with cold air. The porosity of the micro-arc oxidation coating is about 30%, and the diameter of the nanopores is about 20nm. The hydrolysis solution of the silane coupling agent is used to spray the zinc-aluminum-magnesium coating after micro-arc oxidation, and the coating thickness is about 8μm. The properties of the obtained high-performance black zinc-aluminum-magnesium coated steel sheet are shown in Table 2.

[0040] Table 2 Performance comparison of zinc-aluminum-magnesium coated steel sheets

[0041]

[0042] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a high-performance black zinc-aluminum-magnesium coated steel sheet, characterized in that: The preparation method includes three processes: pretreatment, micro-arc oxidation, and sealing treatment. The specific steps are as follows: ①Use anhydrous ethanol as the cleaning solution, ultrasonically clean the zinc-aluminum-magnesium coated steel plate for 10 minutes, and dry it with cold air; ② Immerse the dried zinc-aluminum-magnesium coated steel plate in a 10% to 20% hydrochloric acid solution for pickling for 1 to 10 seconds, then rinse with water after taking it out; ③ Prepare the electrolyte and introduce high-purity oxygen into the bottom of the electrolyte for 10 to 30 minutes before micro-arc oxidation; ④ Immersing the zinc-aluminum-magnesium coated steel plate activated in step ② into the prepared electrolyte for micro-arc oxidation in-situ coloring treatment; wherein the zinc-aluminum-magnesium coated steel plate is the anode, and the stainless steel or graphite is the cathode, and high-purity oxygen is continuously introduced throughout the micro-arc oxidation process so that the oxygen content in the electrolyte is always in a supersaturated state; during the micro-arc oxidation process, ultrasonic waves are used to stir the solution, and the ultrasonic frequency is 50 to 100 kHz; after the micro-arc oxidation is completed, the steel plate is rinsed with distilled water for multiple times, and dried with cold air to obtain a micro-arc oxidation coating on the zinc-aluminum-magnesium coated steel plate; ⑤ Use a sealing agent to seal the micro-arc oxidation steel plate obtained in step ④.

2. The preparation method according to claim 1, characterized in that: In step ③, the electrolyte is composed of a film-forming agent, a pH regulator, a modifier, an auxiliary film-forming agent and a tip discharge inhibitor.

3. The preparation method according to claim 2, characterized in that: The film-forming agent is sodium nitrate NaAlO2 with a concentration of 5 to 20 g / L; the pH value adjuster is potassium hydroxide or sodium hydroxide solution with a pH value of 8 to 12.

4. The preparation method according to claim 3, characterized in that: The modifier is sodium molybdate NaMoO4 with a concentration of 5 to 10 g / L and nano-graphite particles with a concentration of 5 to 20 g / L.

5. The preparation method according to claim 4, characterized in that: The auxiliary film-forming agent is sodium fluoride with a concentration of 1 to 5 g / L; the tip discharge inhibitor is glycerol with a concentration of 5 to 15 g / L; the additive is oxalate, preferably 1 to 5 g / L sodium oxalate; the dispersant is sodium carboxymethyl cellulose with a concentration of 0.5 to 2 g / L; and the wetting agent is octylphenol polyoxyethylene ether OP-10 with a concentration of 0.5 to 2 g / L.

6. The preparation method according to claim 5, characterized in that: The oxidation time of the micro-arc oxidation in-situ coloring treatment is 5 to 15 minutes, the voltage is 300 to 500 V, the duty cycle is 20% to 60%, the frequency is 400 to 500 Hz, and the electrolyte temperature is 30° C. to 60° C.

7. The preparation method according to claim 6, characterized in that: The micro-arc oxidation coating is a nano-pore structure, with a porosity of ≥30% and a nano-pore diameter of 20-100 nm; the thickness of the micro-arc oxidation coating is about 10-20 μm.

8. The preparation method according to claim 7, characterized in that: The sealing agent is a hydrolyzed solution of a silane coupling agent.

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