CN113088966A

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Publication number: CN113088966A
Application number: CN202110347079.5A
Authority: CN
Inventors: 方晓祖; 杨晓禹; 杨亚璋; 顾明俊
Original assignee: China Weapon Science Academy Ningbo Branch
Current assignee: China Weapon Science Academy Ningbo Branch
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2021-07-09
Anticipated expiration: 2041-03-31
Also published as: CN113088966B

Abstract

The invention relates to a magnesium alloy composite coating, which is characterized by comprising the following components in sequence from inside to outside: the micro-arc oxidation layer is 10-50 mu m thick and is formed by micro-arc oxidation treatment of magnesium alloy in electrolyte; the epoxy resin transition layer is more than 0 and less than or equal to 50 mu m in thickness and is formed by coating epoxy resin on the outer surface of the micro-arc oxidation layer; and the polyurea layer is 1-3mm thick and is formed by coating polyurea on the outer surface of the epoxy resin transition layer. The application also discloses a preparation method of the magnesium alloy composite coating. Compared with the prior art, the magnesium alloy composite coating can improve corrosion resistance and reduce the risk of coating falling.

Description

Magnesium alloy composite coating and preparation method thereof

Technical Field

The invention belongs to the technical field of metal surface treatment, and particularly relates to a magnesium alloy composite coating and a preparation method thereof.

Background

The magnesium alloy has the advantages of light weight, high specific strength, good impact resistance and the like, and has good application prospect in the field of equipment manufacturing. However, due to the low electrode potential of magnesium, magnesium and its alloys are easily corroded by this property, and thus the applications of magnesium and its alloys are greatly limited.

In order to overcome the defects, an invention patent with a patent number of ZL201610313339.6, namely a preparation method of a magnesium alloy composite coating with a self-repairing function (an authorization publication number of CN105887084B), discloses a preparation method of a magnesium alloy composite coating, which comprises the following steps: polishing the surface of the magnesium alloy, and removing oil and degreasing; micro-arc oxidation electrolyte is used, a current or voltage method is controlled, the frequency and the duty ratio of a pulse power supply are adjusted, and the micro-arc oxidation time is 15-60 min; cleaning and drying the magnesium alloy subjected to micro-arc oxidation, and placing the magnesium alloy under the pressure of 7-8 multiplied by 10^-3In a vacuum coating chamber with the temperature of 100-200 ℃ and the pressure of argon gas adjusted to be 2-3 Pa, the duty ratio of pulse bias voltage is 20-30%, the bias voltage is 800-1000V, and the vacuum coating chamber is cleaned by discharging for 2-5 min; adopting pure aluminum or pure titanium target material, finishing argon ion bombardment until the pressure is 3-5 multiplied by 10^-1Pa, bias duty ratio of 40-50%, bias voltage of 500-1000V; the arc current is 60-120A, and the coating time is 10-60 min.

Also, as disclosed in the invention patent application with application number CN201910372634.2, microarc oxidation method for magnesium alloy and preparation method for microarc oxidation iron-containing electrolyte (application publication number CN110016707A), microarc oxidation of magnesium alloy comprises three steps of pretreatment, microarc oxidation and post-treatment, and microarc oxidation iron-containing electrolyte comprises the following components: 10-60g/L of phosphate, 1-6g/L of strong base, 2-10g/L of complexing agent and 5-20g/L of iron-containing electrolyte, wherein the complexing agent is potassium gluconate, triethanolamine or sorbitol, and the iron-containing electrolyte is potassium iron oxalate, ferric citrate or ferrous sulfate, so that the electrolyte has good stability, and the solution is still stable and does not generate precipitates in an alkaline environment.

The magnesium alloy surface after the micro-arc oxidation treatment can generate a coating which has corrosion resistance, so that the magnesium alloy is protected to prevent the corrosion of the magnesium alloy.

Disclosure of Invention

The first technical problem to be solved by the present invention is to provide a magnesium alloy composite coating capable of improving corrosion resistance in view of the current state of the prior art.

The second technical problem to be solved by the invention is to provide a magnesium alloy composite coating capable of reducing the risk of coating falling.

The third technical problem to be solved by the invention is to provide a preparation method of the magnesium alloy composite coating.

The technical scheme adopted by the invention for solving the first and second technical problems is as follows: the magnesium alloy composite coating is characterized by comprising the following components in sequence from inside to outside:

the micro-arc oxidation layer is 10-50 mu m thick and is formed by micro-arc oxidation treatment of magnesium alloy in electrolyte;

the epoxy resin transition layer is more than 0 and less than or equal to 50 mu m in thickness and is formed by coating epoxy resin on the outer surface of the micro-arc oxidation layer;

and the polyurea layer is 1-3mm in thickness and is formed by coating polyurea on the outer surface of the epoxy resin transition layer.

The polyurea coating further comprises a functional layer or a decorative layer arranged on the outer surface of the polyurea layer, and the thickness of the functional layer or the decorative layer is more than 0 and less than or equal to 200 mu m.

Preferably, the functional layer is a coating with a marine antifouling function or a stealth function, and the decorative layer is a coating with a camouflage pattern. The coating with the marine antifouling function can be coated by the existing marine antifouling paint, the main function of the marine antifouling paint is to prevent fouling of marine organisms by gradual seepage of an antifouling agent in a paint film, the existing commercial antifouling paint is mainly divided into two types, and the first type is an insecticide-containing antifouling paint, such as a water-combined self-polishing antifouling paint, a hydrolysis type self-polishing antifouling paint (such as an acrylic acid copper copolymer self-polishing antifouling paint, an acrylic acid zinc copolymer self-polishing antifouling paint, a silanized acrylic acid copolymer self-polishing antifouling paint) and a mixed self-polishing antifouling paint; and the other is an insecticide-free antifouling paint, such as an organosilicon low-surface-energy antifouling paint. The coating with the stealth function comprises the existing optical (including near infrared) stealth coating, laser stealth coating, radar stealth coating, infrared stealth coating and the like.

Preferably, the epoxy resin is bisphenol A type epoxy resin with the product trade name of E-51. The bisphenol A type epoxy resin with the product brand number of E-51 is solvent-free epoxy resin, small bubbles can be upwards released in the curing process of the solvent type epoxy resin, the bubbles can not pass through the composite coating with the multilayer structure after the surface of the composite coating is dried, and various performance defects such as paint film breakage or matrix falling can be generated by the accumulated bubbles. The product of the application, namely the bisphenol A type epoxy resin with the brand number of E-51, can overcome the defects.

Preferably, the polyurea is a two-component polyurea comprising a polyaspartate resin of type F-524 and an aliphatic polyisocyanate, which are manufactured by Zhuhai Feiyang chemical Co., Ltd, and the mass ratio of the polyaspartate resin to the aliphatic polyisocyanate is 1: 1.

The technical scheme adopted by the invention for solving the third technical problem is as follows: the preparation method of the magnesium alloy composite coating is characterized by comprising the following steps:

firstly, pretreating, polishing the surface of a magnesium alloy, then ultrasonically cleaning for 10-40 min, taking out, and immersing in chromic acid solution for 5-60 s, wherein the ultrasonic power is 50W, the ultrasonic frequency is 80KHz, and the chromic acid solution is prepared from the following components in percentage by weight: the chromic acid solution contains 200-300 g of CrO per liter₃50-100 g of HF with the mass concentration of 40%, taking out from a chromic acid solution, washing with deionized water for 5-10 min, then washing with a NaOH solution of 5-20g/L for 10-40 s, taking out, cleaning with deionized water, and drying;

secondly, preparing a micro-arc oxidation layer, immersing the pretreated magnesium alloy into electrolyte, performing micro-arc oxidation treatment by using a double-pulse power supply to obtain a sample with the micro-arc oxidation layer, and then cleaning and drying the sample; the positive voltage of the double-pulse power supply in a constant voltage mode is 250-550V, the negative voltage is 50-250V, the ratio of positive pulses to negative pulses is 1:1, the frequency is 300-1000 Hz, the duty ratios of the positive pulses to the negative pulses are the same and are 5-45%, the micro-arc oxidation time is 10-40 min, and the temperature of electrolyte is 5-30 ℃; the electrolyte comprises the following components:

the film forming agent component adopts one or two of 5-25 g/L silicate and 10-35 g/L phosphate;

the complexing agent is one or two of 5-25 g/L, EDTA-disodium 5-15 g/L sodium citrate;

the arc inhibitor is one or two of triethanolamine 5-15 ml/L and glycerol 5-15 ml/L;

other electrolytes are KF 5-30 g/L and nano Al with the grain diameter less than or equal to 30nm₂O₃ 0.5～3g/L；

The pH regulator is one or two of 0.5-5 g/L sodium hydroxide and 0.5-5 g/L potassium hydroxide;

the balance of water;

the pH value of the electrolyte is 8-12; during micro-arc oxidation treatment, the magnesium alloy is used as an anode and connected with the anode of a double-pulse power supply, the stainless steel is used as a cathode and connected with the cathode of the double-pulse power supply, and then the anode and the cathode are jointly placed into an electrolytic bath containing electrolyte for micro-arc oxidation treatment;

thirdly, preparing an epoxy resin transition layer, and coating the epoxy resin on the outer surface of the micro-arc oxidation layer within 6 hours after the micro-arc oxidation treatment is finished;

and fourthly, preparing a polyurea layer, and coating polyurea on the outer surface of the epoxy resin transition layer within 6 hours after the epoxy resin transition layer is prepared, so as to obtain the magnesium alloy composite coating.

Preferably, in the first step, the surface of the magnesium alloy is polished by 1000-mesh sand paper.

Preferably, the coating in the third step and the fourth step is carried out by spraying, brushing or dipping.

Preferably, the sample obtained after the micro-arc oxidation treatment in the second step is washed with deionized water for 10-30 min, dried in a drying oven at 100-120 ℃ for 10-20 min, taken out and placed to cool to below 30 ℃.

Compared with the prior art, the invention has the advantages that: the micro-arc oxidation layer, the epoxy resin transition layer and the polyurea layer with certain thickness are sequentially arranged on the outer surface of the magnesium alloy, and the micro-arc oxidation layer and the polyurea layer can effectively improve the corrosion resistance, the water resistance, the scratch resistance and the collision resistance of the magnesium alloy, so that the magnesium alloy can work in a harsh atmospheric environment and underwater for a long time. And the micro arc oxidation layer is the porous structure of the fine and close outer layer of inlayer in this application, the hole radius is less, for about 1 micron, the viscosity of polyurea is big, if polyurea direct coating is at the surface of micro arc oxidation layer, polyurea can not permeate into the hole of micro arc oxidation layer well, lead to polyurea relatively poor with the cohesion of micro arc oxidation layer, this application is through setting up the epoxy transition layer between micro arc oxidation layer and polyurea layer, epoxy transition layer and micro arc oxidation layer, all have good cohesion between the polyurea layer, and then improve the adhesive force of whole coating, reduce the coating because of receiving the scraping, the risk that the striking drops.

Drawings

FIG. 1 is a schematic structural diagram of a magnesium alloy composite coating according to a first embodiment of the present invention;

fig. 2 is a schematic structural diagram of a magnesium alloy composite coating in the second embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

The first embodiment is as follows:

as shown in fig. 1, a magnesium alloy composite coating and a first preferred embodiment of a preparation method thereof according to the present invention, the magnesium alloy composite coating includes a micro-arc oxidation layer, an epoxy resin transition layer and a polyurea layer, which are sequentially connected from inside to outside. Wherein the thickness of the micro-arc oxidation layer is 10 mu m, and the micro-arc oxidation layer is formed by micro-arc oxidation treatment of magnesium alloy in electrolyte. The thickness of the epoxy resin transition layer is 20 μm, and the epoxy resin transition layer is formed by coating the epoxy resin on the outer surface of the micro-arc oxidation layer. The thickness of the polyurea layer is 1mm, and the polyurea layer is formed by coating polyurea on the outer surface of the epoxy resin transition layer.

The epoxy resin in this example is bisphenol A epoxy resin with product designation E-51. The polyurea is a bi-component polyurea which comprises polyaspartic acid ester resin and aliphatic polyisocyanate, wherein the polyaspartic acid ester resin is produced by Zhuhai Feiyang chemical company Limited and is in a model of F-524, and the mass ratio of the polyaspartic acid ester resin to the aliphatic polyisocyanate is 1: 1.

The preparation method of the magnesium alloy composite coating comprises the following steps:

firstly, pretreatment, grinding the surface of the magnesium alloy by using 1000-mesh sand paper, then cleaning for 10min by adopting ultrasonic, taking out and immersing in chromic acid solution for 5s, wherein the ultrasonic power is 50W, the ultrasonic frequency is 80KHz, and the chromic acid solution is prepared by the following steps: the chromic acid solution contains 200g of CrO per liter₃And 50g of hydrogen fluoride HF with the mass concentration of 40%, taking out from the chromic acid solution, washing for 5min by using deionized water, then putting into 5g/L NaOH solution for washing for 10s, taking out, cleaning by using deionized water, and drying;

secondly, preparing a micro-arc oxidation layer, immersing the pretreated magnesium alloy into electrolyte, and performing micro-arc oxidation treatment by using a double-pulse power supply to obtain a sample with the micro-arc oxidation layer; the positive voltage of the double-pulse power supply in a constant voltage mode is 250V, the negative voltage is 50V, the ratio of positive to negative pulses is 1:1, the frequency is 300Hz, the duty ratios of the positive and negative pulses are the same and are all 5%, the micro-arc oxidation time is 10min, and the temperature of electrolyte is 5 ℃; the electrolyte comprises the following components:

the film forming agent component adopts silicate 25 g/L; the complexing agent is 5g/L, EDTA-disodium citrate 5 g/L; the electric arc inhibitor adopts 5ml/L triethanolamine and 5ml/L glycerol; the other electrolyte is KF 5g/L nano Al with the grain diameter less than or equal to 30nm₂O₃0.5 g/L; the pH regulator is 0.5g/L of sodium hydroxide and 0.5g/L of potassium hydroxide; the balance of deionized water; during micro-arc oxidation treatment, the magnesium alloy is used as an anode and connected with the anode of a double-pulse power supply, the stainless steel is used as a cathode and connected with the cathode of the double-pulse power supply, and then the anode and the cathode are placed togetherCarrying out micro-arc oxidation treatment in an electrolytic bath containing electrolyte; and after the micro-arc oxidation is finished, washing with deionized water for 10min, drying in a drying oven at 100 ℃ for 10min, taking out, and cooling to below 30 ℃.

Thirdly, preparing an epoxy resin transition layer, and coating the epoxy resin on the outer surface of the micro-arc oxidation layer in a spraying, brushing or dip-coating mode within 6 hours after the micro-arc oxidation treatment is finished; within 6 hours after the micro-arc oxidation treatment is finished, the surface of the micro-arc oxidation layer is dried, and the interior of the micro-arc oxidation layer is not dried;

fourthly, preparing a polyurea layer, namely coating polyurea on the outer surface of the epoxy resin transition layer within 6 hours after the epoxy resin transition layer is prepared, so as to obtain the magnesium alloy composite coating; within 6 hours after the preparation of the epoxy resin transition layer, the surface of the epoxy resin transition layer was dried and the inside was not dried.

The magnesium alloy composite coating prepared by the embodiment has the adhesive force of 7 MPa, salt spray resistance of 2000h and seawater immersion resistance of more than 1 year.

Example two:

as shown in fig. 2, a magnesium alloy composite coating and a preparation method thereof according to a second preferred embodiment of the present invention are substantially the same as the first embodiment, except that the magnesium alloy composite coating further includes a functional layer, the functional layer is disposed on an outer surface of the polyurea layer, the functional layer is a coating having a marine antifouling function or a stealth function, and a thickness of the functional layer is 100 μm.

The preparation method of the magnesium alloy composite coating of the embodiment is basically the same as the first embodiment, except that the embodiment further comprises the following steps: step five, preparing a functional layer, namely coating a functional coating on the outer surface of the polyurea layer within 6 hours after the polyurea layer is prepared, so as to obtain the functional layer; within 6 hours after the completion of the preparation of the polyurea layer, the surface of the polyurea layer was dried and the inside was not dried.

In this embodiment, the thickness of the micro-arc oxide layer is 30 μm, and the preparation method is as follows:

firstly, preprocessing, polishing the surface of the magnesium alloy, then cleaning for 20min by adopting ultrasonic, taking out and immersing in chromic acid solution for 20s, wherein the ultrasonic power is 50W, the ultrasonic frequency is 80KHz, and the chromic acid solution ratio is as follows: the chromic acid solution contained 250g of CrO per liter₃And 70g of HF with the mass concentration of 40%, taking out from the chromic acid solution, washing for 7min by using deionized water, then putting into 10g/L NaOH solution for washing for 20s, taking out, washing by using deionized water, and drying;

secondly, preparing a micro-arc oxidation layer, immersing the pretreated magnesium alloy into electrolyte, and performing micro-arc oxidation treatment by using a double-pulse power supply to obtain a sample with the micro-arc oxidation layer; the positive voltage of the double-pulse power supply in a constant voltage mode is 400V, the negative voltage is 100V, the ratio of positive to negative pulses is 1:1, the frequency is 800Hz, the duty ratios of the positive and negative pulses are the same and are 15%, the micro-arc oxidation time is 25min, and the temperature of electrolyte is 15 ℃; the electrolyte comprises the following components:

the film forming agent component adopts 35g/L of silicate; the complexing agent adopts 25g/L of sodium citrate; the electric arc inhibitor adopts 15ml/L triethanolamine; the other electrolyte is KF 15g/L and nano Al with the grain diameter less than or equal to 30nm₂O₃1.5 g/L; the pH regulator is 5g/L of sodium hydroxide; the balance of deionized water; during micro-arc oxidation treatment, the magnesium alloy is used as an anode and connected with the anode of a double-pulse power supply, the stainless steel is used as a cathode and connected with the cathode of the double-pulse power supply, and then the anode and the cathode are jointly placed into an electrolytic bath containing electrolyte for micro-arc oxidation treatment; and after the micro-arc oxidation is finished, washing with deionized water for 20min, drying in a drying oven at 100 ℃ for 15min, taking out, and cooling to below 30 ℃.

Example three:

the magnesium alloy composite coating and the preparation method thereof in this embodiment are basically the same as those in the second embodiment, except that the thickness of the micro-arc oxidation layer in this embodiment is 50 μm, the thickness of the epoxy resin transition layer is 30 μm, and the thickness of the polyurea layer is 3 mm. The magnesium alloy composite coating of the embodiment further comprises a decorative layer, the decorative layer replaces the functional layer, the decorative layer is a coating with camouflage patterns, and the thickness of the decorative layer is 200 microns.

The preparation method of the micro-arc oxidation layer in the embodiment is as follows:

the method comprises the following steps of firstly, preprocessing, polishing the surface of the magnesium alloy, then ultrasonically cleaning for 40min, taking out, immersing into chromic acid solution for 60s, wherein the ultrasonic power is 50W, the ultrasonic frequency is 80KHz, and the chromic acid solution is prepared from the following components in percentage by weight: the chromic acid solution contains 300g of CrO per liter₃100g of HF with the mass concentration of 40 percent is taken out of chromic acid solution, then is washed by deionized water for 10min, then is put into 20g/L NaOH solution for washing for 40s, and is taken out, washed by deionized water and dried;

step two, preparing a micro-arc oxidation layer, immersing the pretreated magnesium alloy into electrolyte, and performing micro-arc oxidation treatment by using a double-pulse power supply to obtain a sample with the micro-arc oxidation layer; the positive voltage of the double-pulse power supply in the constant voltage mode is 550V, the negative voltage is 250V, the ratio of positive to negative pulses is 1:1, the frequency is 1000Hz, the duty ratios of the positive and negative pulses are the same and are 45%, the micro-arc oxidation time is 40min, and the temperature of the electrolyte is 30 ℃; the electrolyte comprises the following components:

the film forming agent adopts 5g/L silicate and 10g/L phosphate; the complexing agent adopts 15g/L of EDTA-disodium; the electric arc inhibitor adopts 15ml/L of glycerin; the other electrolyte is KF 30g/L and nano Al with the grain diameter less than or equal to 30nm₂O₃3 g/L; the pH regulator is 5g/L of potassium hydroxide; the balance of deionized water; during micro-arc oxidation treatment, the magnesium alloy is used as an anode and connected with the anode of a double-pulse power supply, the stainless steel is used as a cathode and connected with the cathode of the double-pulse power supply, and then the anode and the cathode are jointly placed into an electrolytic bath containing electrolyte for micro-arc oxidation treatment; and after the micro-arc oxidation is finished, washing with deionized water for 30min, drying in a drying oven at 120 ℃ for 20min, taking out, and cooling to below 30 ℃.

Example four:

the magnesium alloy composite coating and the preparation method thereof in this embodiment are substantially the same as those in the first embodiment, except that the thickness of the epoxy resin transition layer is 50 μm, and the thickness of the polyurea layer is 2 mm.

Claims

1. The magnesium alloy composite coating is characterized by comprising the following components in sequence from inside to outside:

2. The magnesium alloy composite coating of claim 1, wherein: the polyurea layer is characterized by further comprising a functional layer or a decorative layer arranged on the outer surface of the polyurea layer, and the thickness of the functional layer or the decorative layer is more than 0 and less than or equal to 200 mu m.

3. The magnesium alloy composite coating of claim 2, wherein: the functional layer is a coating with a marine antifouling function or a stealth function, and the decorative layer is a coating with camouflage patterns.

4. The magnesium alloy composite coating of claim 1, wherein: the epoxy resin is bisphenol A type epoxy resin with the product brand number of E-51.

5. The magnesium alloy composite coating of claim 1, wherein: the polyurea is a bi-component polyurea, and comprises a polyaspartic acid ester resin and aliphatic polyisocyanate, wherein the polyaspartic acid ester resin is produced by Zhuhai Feiyang chemical Limited and is in a model of F-524, and the mass ratio of the polyaspartic acid ester resin to the aliphatic polyisocyanate is 1: 1.

6. A method for preparing a magnesium alloy composite coating according to any one of claims 1 to 5, characterized by comprising the steps of:

firstly, pretreating, polishing the surface of a magnesium alloy, then cleaning for 10-40 min by adopting ultrasonic, taking out, immersing in chromic acid solution for 5-60 s, wherein the ultrasonic power is 50W, the ultrasonic frequency is 80KHz, and the chromic acid solution is prepared from the following components in percentage by weight: the chromic acid solution contains 200-300 g of CrO per liter₃50-100 g of HF with the mass concentration of 40%, taking out from a chromic acid solution, washing with deionized water for 5-10 min, then washing with a NaOH solution of 5-20g/L for 10-40 s, taking out, cleaning with deionized water, and drying;

the balance of water;

7. The method of claim 6, wherein: in the first step, the surface of the magnesium alloy is polished by 1000-mesh sand paper.

8. The method of claim 6, wherein: and in the third step, the coating is carried out in a spraying, brushing or dipping mode.

9. The method of claim 6, wherein: and washing the sample obtained after the micro-arc oxidation treatment in the step two for 10-30 min by using deionized water, drying the sample in a drying box at the temperature of 100-120 ℃ for 10-20 min, taking out the sample, and cooling the sample to the temperature below 30 ℃.