Preparation method of water-based aluminum-rich matrix potential gradient carbon steel protective coating

Abstract

A method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating, relates to a method for preparing a carbon steel protective coating, and comprises the following raw materials by mass: 30 to 50 parts of spherical aluminum powder, 5 to 8 parts of passivator, 1 to 2 parts of oxidant, 20 to 45 parts of water-based resin, 8 to 20 parts of cosolvent, 0.1 to 0.5 parts of thickener, 0.1 to 0.5 parts of defoamer, 0.1 to 0.5 parts of leveling agent, 0.1 to 0.5 parts of emulsifier, 0.1 to 0.5 parts of dispersant, 0.1 to 0.5 parts of anti-settling agent, and 15 to 35 parts of deionized water. The invention reduces the use of organic solvents and effectively reduces the pollution of VOC to the environment. With aluminum powder that can be stored stably for a long time as the raw material, the protective effect of the aluminum coating on the carbon steel substrate is improved without affecting the protective system of the coating. The invention ensures that the potential difference between the aluminum powder and the carbon steel substrate exists continuously and stably, and has the characteristics of "high efficiency", "continuous" and "stable" for the protective effect of the carbon steel substrate.

Description

Technical Field

[0001] The invention relates to a method for preparing a carbon steel protective coating, in particular to a method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating. Background Art

[0002] Compared with traditional oil-soluble coatings, water-based coatings have the advantages of "green and environmentally friendly", "low carbon", and "high performance", and are booming in the field of corrosion protection. Since two water-based environmentally friendly coatings, water-based zinc-rich coatings and water-based zinc-aluminum coatings, have been developed and widely used in the field of water-based environmentally friendly corrosion protection coatings, the development of the two coatings has reached a plateau. Therefore, the present invention focuses on the development of high-performance corrosion protection coatings on the research and development of water-based aluminum-rich coatings.

[0003] During the preparation of water-based aluminum-rich coatings, aluminum powder will react chemically with water, making it difficult for aluminum powder to exist stably in the coating for a long time. Over the years, people have continuously improved the methods of surface modification of aluminum powder. Although the surface-modified aluminum powder has solved the problem of long-term storage, the potential of the modified aluminum powder has been significantly improved. It cannot be guaranteed that there will be an effective potential difference between the aluminum coating and the protected substrate iron during the application of the coating. Therefore, aluminum-rich coatings with long-term stable storage are difficult to achieve the expected protective effect.

[0004] The raw aluminum powder used in water-based aluminum-rich coatings has a problem that its potential is significantly increased after surface modification, making it difficult to play an effective protective role.

[0005] Due to its environmental protection requirements, the development of water-based aluminum-rich coatings is imminent, but the characteristics of aluminum powder limit its application. The storage stability of water-based aluminum coatings is solved by aluminum powder modification, but the potential difference between the coating and the substrate is reduced after modification, resulting in no significant improvement in the corrosion resistance of the coating. Therefore, a water-based aluminum-rich coating with good storage stability and excellent anti-corrosion performance needs to be developed to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating. Under the premise of not affecting the protective system of the coating, the present invention designs a passivation system for carbon steel in the coating, thereby passivating the protected carbon steel, ensuring that the potential difference between the aluminum-rich coating and the carbon steel is 0.1 to 0.2V, and improving the protective effect of the aluminum-rich coating on carbon steel. Under the premise of not destroying the coating system, by designing a passivation system for the carbon steel matrix in the coating system, the potential of the carbon steel is increased, ensuring that the potential difference between the aluminum coating and the carbon steel is 0.1 to 0.2V, so that the cathodic protection method of the sacrificial anode can be carried out "efficiently", "continuously" and "stably", greatly improving the protective effect of the water-based aluminum-rich coating on the carbon steel matrix.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating, the method comprising the following steps:

[0009] Step 1: Use spherical aluminum powder as the main raw material, the diameter of the spherical aluminum powder is 5-35um, weigh 150-200g of spherical aluminum powder, take 500ml of anhydrous ethanol solvent in a beaker, mix and stir at 40℃ for 20min at a speed of 800r / min, add 150ml of ethyl orthosilicate, react for 15min, add 241.5g of deionized water drop by drop, adjust the pH to 7-8 with triethanolamine, keep warm for 5h, and filter to obtain the surface-modified aluminum powder;

[0010] Step 2: The coating preparation process is as follows: First, weigh 1-3g of each of two or three of the passivators to prepare 100ml of passivation solution, add 0.5-1.5g of oxidant, then adjust the pH of the passivation solution to 8.0-10.0 with two or three of boric acid, molybdic acid, vanadic acid, phosphoric acid, and triethanolamine, then take 20-50g of the passivation solution to dissolve 8-20g of the water-based resin in the passivation solution, add 8-15g of the co-solvent and mix thoroughly for 30 minutes, and then add the surface-modified 20-35g of aluminum powder treated with water-based coating was stirred for 45min at a speed of 700-1700r / min, followed by adding 0.1-0.5g of thickener, 0.1-0.5g of defoamer, 0.1-0.5g of leveling agent, 0.1-0.5g of dispersant and 0.1-0.5g of anti-settling agent, and adjusting the pH to 8.0-10.0. The mixture was stirred for 50-70min at a speed of 700-1700r / min to obtain the final water-based aluminum-rich coating.

[0011] The method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating comprises the following raw materials in proportion by mass: 30 to 50 parts of spherical aluminum powder, 5 to 8 parts of passivator, 0.5 to 1.5 parts of oxidant, 20 to 45 parts of water-based resin, 8 to 20 parts of cosolvent, 0.1 to 0.5 parts of thickener, 0.1 to 0.5 parts of defoamer, 0.1 to 0.5 parts of leveling agent, 0.1 to 0.5 parts of emulsifier, 0.1 to 0.5 parts of dispersant, 0.1 to 0.5 parts of anti-settling agent, and 15 to 35 parts of deionized water.

[0012] The preparation method of the water-based aluminum-rich matrix potential gradient carbon steel protective coating, wherein the cosolvent is one or two of ethylene glycol monobutyl ether, dipropylene glycol butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, and propylene glycol. The thickener is one or two of organic bentonite, hydroxypropyl methylcellulose, methyl cellulose, hydroxyethyl cellulose, diatomaceous earth, and silicone gel. The defoamer is one or two of polydimethylsiloxane and polyether-modified polysiloxane. The leveling agent is one or two of alkyl-modified organic siloxane, terminal-modified organic silicon, and polyether polyester-modified organic siloxane. The dispersant is one or two of ethylene glycol, polyethylene glycol, and polyol. The anti-settling agent is one or two of castor oil derivatives, fumed silica, and polyolefin particles.

[0013] In the preparation method of the water-based aluminum-rich matrix potential gradient carbon steel protective coating, the passivating agent is two or three of sodium borate, potassium borate, sodium vanadate, potassium vanadate, sodium pyrosulfate, sodium phosphate, potassium phosphate, sodium molybdate, and potassium molybdate.

[0014] In the preparation method of the water-based aluminum-rich matrix potential gradient carbon steel protective coating, the oxidant is one or two of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium perchlorate, potassium perchlorate, and magnesium perchlorate.

[0015] The preparation method of the water-based aluminum-rich matrix potential gradient carbon steel protective coating, the water-based resin is one or two of water-based epoxy resin, water-based acrylic resin, water-based polyurethane resin, water-based silicone resin, and water-based alkyd resin.

[0016] The method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating, the pH of the aluminum-rich coating is 8.0-10.0; the pH adjusting substances used are two or three of boric acid, molybdic acid, vanadic acid, phosphoric acid, and triethanolamine.

[0017] The advantages and effects of the present invention are:

[0018] 1. The solvent used in the present invention is water, which greatly reduces the emission of VOCs and effectively avoids the environmental pollution caused by the volatilization of organic solvents. At the same time, the present invention aims at the problem of increased potential caused by the modification of the raw material aluminum powder used in the water-based aluminum-rich coating, selects green and environmentally friendly inorganic salts as passivators, designs an environmentally friendly passivation system in the coating, passivates the carbon steel substrate, increases the potential of the carbon steel substrate, ensures that the potential difference between the aluminum coating and the carbon steel substrate is 0.1-0.2V, and ensures the anti-corrosion effect of the water-based aluminum-rich coating on the carbon steel substrate.

[0019] 2. The present invention is green and environmentally friendly, has no environmental pollution, and does no harm to the health of production and construction personnel.

[0020] 3. Without destroying the coating system, the present invention designs an environmentally friendly composite passivation system for the carbon steel substrate in the coating to ensure that the potential difference between the aluminum coating and the carbon steel substrate is 0.1-0.2V, thereby significantly improving the protective effect of the coating and having excellent corrosion resistance.

[0021] 4. The present invention has low production cost, simple production process, and less waste liquid generated during the production process, and can be industrialized on a large scale. Implementation

[0022] The present invention is described in detail below with reference to the embodiments.

[0023] The processing technology of the present invention is as follows:

[0024] Step 1: Use spherical aluminum powder as the main raw material, the diameter of the spherical aluminum powder is 5-35um, weigh 150-200g of spherical aluminum powder, take 500ml of anhydrous ethanol solvent in a beaker, mix and stir at 40℃ for 20min at a speed of 800r / min, add 150ml of tetraethyl orthosilicate, react for 15min, add 241.5g of deionized water drop by drop, adjust the pH to 7-8 with triethanolamine, keep warm for 5h, and filter to obtain the surface-modified aluminum powder.

[0025] Step 2: The coating preparation process is as follows: First, weigh 1-3g of each of two or three of the passivators to prepare 100ml of passivation solution, add 0.5-1.5g of oxidant, then adjust the pH of the passivation solution to 8.0-10.0 with two or three of boric acid, molybdic acid, vanadic acid, phosphoric acid, and triethanolamine, then take 20-50g of the passivation solution to dissolve 8-20g of the water-based resin in the passivation solution, add 8-15g of the co-solvent and mix thoroughly for 30 minutes, and then add the surface-modified 20-35g of aluminum powder treated with water-based paint is stirred for 45 minutes at a speed of 700-1700r / min. Then 0.1-0.5g of thickener, 0.1-0.5g of defoamer, 0.1-0.5g of leveling agent, 0.1-0.5g of dispersant and 0.1-0.5g of anti-settling agent are added in sequence, and the pH value is adjusted to 8.0-10.0. Stir thoroughly for 50-70min at a speed of 700-1700r / min to obtain the final water-based aluminum-rich coating. Embodiment 1

[0026] 1. Prepare a passivation liquid system without aluminum powder and resin, weigh 3.0g of sodium borate, 1.0g of potassium molybdate, and 1.0g of sodium vanadate and dissolve them in 100ml of deionized water, add 0.2g of potassium hypochlorite and 0.3g of potassium perchlorate as oxidants, adjust the pH of the passivation liquid to 8.0 with boric acid, molybdic acid and triethanolamine, passivate the carbon steel in a 25℃ water bath for 2min, use 5% sodium chloride solution as the corrosion solution, measure the polarization curve of the carbon steel on an electrochemical workstation, and obtain the self-corrosion voltage of the carbon steel to be -0.49V.

[0027] 2. Dissolve 8.0g of water-based acrylic resin in 25.0g of the passivation solution prepared above, add 8.0g of ethylene glycol monobutyl ether, 1.0g of anhydrous ethanol and stir thoroughly for 30min, add 20.0g of modified aluminum powder, stir thoroughly for 45min, the speed is 700r / min, then add 0.1g of polydimethylsiloxane, 0.1g of silane-modified organosiloxane, 0.1g of organic bentonite, 0.1g of ethylene glycol, 0.1g of diatomaceous earth, 0.1g of castor oil derivative, and then add boric acid, molybdic acid and triethanolamine to adjust the pH to 8.0, mix and stir thoroughly for 50min, the speed is 700r / min, to obtain the final environmentally friendly water-based aluminum-rich coating.

[0028] 3. The environmentally friendly water-based aluminum-rich coating prepared above was sprayed on the steel plate and cured at 25°C for 24 hours. The spraying thickness was 30-50um and a 5% sodium chloride solution was used as the corrosive solution. The polarization curve was measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating was -0.61V. Embodiment 2

[0029] 1. Prepare a passivation liquid system without aluminum powder and resin, weigh 3.0g of sodium borate, 1.5g of sodium pyrosulfate, and 1.0g of potassium molybdate and dissolve them in 100ml of deionized water, add 0.4g of sodium hypochlorite and 0.4g of sodium perchlorate as oxidants, adjust the pH of the passivation liquid to 8.5 with boric acid, molybdic acid and triethanolamine, passivate the carbon steel in a water bath at 25℃ for 2min, use 5% sodium chloride solution as the corrosion liquid, measure the polarization curve of the carbon steel on the electrochemical workstation, and obtain the self-corrosion voltage of the carbon steel to be -0.47V.

[0030] 2. Dissolve 10.5g of waterborne polyurethane resin in 25.0g of the passivation solution prepared above, add 10.0g of dipropylene glycol monobutyl ether and 1.2g of anhydrous ethanol, stir thoroughly for 30min, add 24.0g of modified aluminum powder, stir thoroughly for 45min at a speed of 900r / min, then add 0.2g of polydimethylsiloxane, 0.2g of methyl cellulose, 0.2g of polyol, 0.2g of diatomaceous earth, and 0.2g of fumed silica in sequence, then add boric acid, molybdic acid and triethanolamine to adjust the pH to 8.5, mix and stir thoroughly for 55min at a speed of 900r / min to obtain the final environmentally friendly waterborne aluminum-rich coating.

[0031] 3. The environmentally friendly water-based aluminum-rich coating was sprayed on the steel plate and cured at 25°C for 24 hours. The spraying thickness was 30-50um. The polarization curve was measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating was -0.59V. Embodiment 3

[0032] 1. Prepare a passivation liquid system without aluminum powder and resin, weigh 2.0g of sodium borate, 1.5g of sodium pyrosulfate, and 2.5g of potassium phosphate and dissolve them in 100ml of deionized water, add 0.5g of oxidant magnesium hypochlorite and 0.5g of magnesium perchlorate, adjust the pH of the passivation liquid to 9.0 with boric acid, phosphoric acid and triethanolamine, passivate the carbon steel in a water bath at 25℃ for 2min, use 5% sodium chloride solution as the corrosion liquid, measure the polarization curve of the carbon steel on the electrochemical workstation, and obtain the self-corrosion voltage of the carbon steel as -0.45V.

[0033] 2. Dissolve 13.5g of water-based epoxy resin in 30.0g of the passivation solution prepared above, add 12.0g of dipropylene glycol monobutyl ether and 1.4g of anhydrous ethanol, stir thoroughly for 30min, add 28.0g of modified aluminum powder, stir thoroughly for 45min, the speed is 1100r / min, then add 0.3g of polydimethylsiloxane, 0.3g of hydroxyethyl cellulose, 0.3g of polyethylene glycol, 0.3g of castor oil derivative, and 0.3g of terminal oxane in turn, and then adjust the pH of the system to 9.0 with boric acid, phosphoric acid and triethanolamine, mix and stir thoroughly for 60min, and the speed is 1100r / min to obtain the final environmentally friendly water-based aluminum-rich coating.

[0034] 3. The prepared environmentally friendly water-based aluminum-rich coating was sprayed on the steel plate and cured at 25°C for 24 hours. The spraying thickness was 30-50um. A 5% by mass sodium chloride solution was used as the corrosive solution. The polarization curve was measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating was -0.65V. Embodiment 4

[0035] 1. Prepare a passivation liquid system without aluminum powder and resin, weigh 2.5g of sodium borate, 3.0g of sodium pyrosulfate, and 2.0g of potassium phosphate and dissolve them in 100ml of deionized water, add 1.1g of potassium perchlorate as an oxidant, adjust the pH of the passivation liquid to 9.5 with boric acid, phosphoric acid and triethanolamine, passivate the carbon steel in a 25℃ water bath for 2min, use 5% sodium chloride solution as the corrosion liquid, measure the polarization curve of the carbon steel on an electrochemical workstation, and obtain the self-corrosion voltage of the carbon steel to be -0.44V.

[0036] 2. Dissolve 9.5g of waterborne polyurethane resin and 6.5g of waterborne alkyd resin in 35.0g of the above-prepared passivation solution, add 15.0g of dipropylene glycol monobutyl ether and 1.8g of anhydrous ethanol, mix thoroughly for 30min, add 32.0g of modified aluminum powder, stir thoroughly for 45min, the speed is 1300r / min, stir thoroughly for 30min, then add 0.4g of polydimethylsiloxane, 0.4g of hydroxyethyl cellulose, 0.4g of polyethylene glycol, 0.4g of castor oil derivative, and 0.4g of terminal oxane in sequence, adjust the pH of the passivation solution to 9.5 with boric acid, phosphoric acid and triethanolamine, mix thoroughly and stir for 65min, the speed is 1300 / min, and the final environmentally friendly water-based aluminum-rich coating is obtained.

[0037] 3. The prepared environmentally friendly water-based aluminum-rich coating was sprayed on a steel plate and cured at 25°C for 24 hours. The spraying thickness was 30 to 50 um. The polarization curve was measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating was -0.58 V. Embodiment 5

[0038] 1. Prepare a passivation liquid system without aluminum powder and resin, weigh 1.8g of sodium borate, 2.2g of sodium pyrosulfate, and 3.0g of potassium phosphate and dissolve them in 100ml of deionized water, add 0.5g of calcium hypochlorite and 1.0g of calcium perchlorate as oxidants, adjust the pH of the passivation liquid to 10.0 with boric acid, phosphoric acid and triethanolamine, passivate the carbon steel in a water bath at 25℃ for 2min, use 5% sodium chloride solution as the corrosive solution, measure the polarization curve of carbon steel on an electrochemical workstation, and obtain the self-corrosion voltage of carbon steel to be -0.48V.

[0039] 2. Dissolve 15.0g of water-based acrylic resin and 5.0g of water-based silicone resin in 40g of the above-prepared passivation solution, add 16.0g of dipropylene glycol monobutyl ether and 2.0g of anhydrous ethanol, mix thoroughly for 30min, add 35.0g of modified aluminum powder, stir thoroughly for 45min, the speed is 1700r / min, stir thoroughly for 30min, finally add 0.5g of polydimethylsiloxane, 0.5g of hydroxyethyl cellulose, 0.5g of polyethylene glycol, 0.5g of castor oil derivative, 0.5g of terminal oxane, and adjust the pH of the passivation solution to 10.0 with boric acid and triethanolamine, mix thoroughly and stir for 70min, the speed is 1700 / min, to obtain the final environmentally friendly water-based aluminum-rich coating.

[0040] 3. The prepared environmentally friendly water-based aluminum-rich coating was sprayed on a steel plate and cured at 25°C for 30 hours with a spray thickness of 30 to 50 um. The polarization curve was measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating was -0.63 V.

[0041] Experimental Conclusion

[0042] Implementation Cases <![CDATA[E after passivation treatment of carbon steel corr (V)]]> <![CDATA[E of the aluminum-rich coating corr (V)]]> Potential difference between aluminum powder and carbon steel (V) one -0.49 -0.61 0.12 two -0.47 -0.59 0.12 three -0.45 -0.65 0.20 Four -0.44 -0.58 0.14 five -0.48 -0.63 0.15

Claims

1. A method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating, characterized in that: The method comprises the following steps: Step 1: Use spherical aluminum powder as the main raw material, the diameter of the spherical aluminum powder is 5-35 μm, weigh 150-200g of spherical aluminum powder, take 500ml of anhydrous ethanol solvent in a beaker, mix and stir at 40℃ for 20min at a speed of 800r / min, add 150ml of tetraethyl orthosilicate, react for 15min, add 241.5g of deionized water drop by drop, adjust the pH to 7-8 with triethanolamine, keep warm for 5h, and filter to obtain the surface-modified aluminum powder; Step 2, prepare a passivation liquid system without aluminum powder and resin, weigh 3.0g of sodium borate, 1.0g of potassium molybdate, and 1.0g of sodium vanadate and dissolve them in 100ml of deionized water, add 0.2g of potassium hypochlorite and 0.3g of potassium perchlorate as oxidants, adjust the pH of the passivation liquid to 8.0 with boric acid, molybdic acid and triethanolamine, passivate the carbon steel in a water bath at 25°C for 2min, use a sodium chloride solution with a mass fraction of 5% as the corrosion solution, measure the polarization curve of the carbon steel on an electrochemical workstation, and obtain a self-corrosion voltage of the carbon steel of -0.49V; Step three, dissolve 8.0g of water-based acrylic resin in 25.0g of the passivation solution prepared above, add 8.0g of ethylene glycol monobutyl ether, 1.0g of anhydrous ethanol and stir thoroughly for 30min, add 20.0g of surface-modified aluminum powder, stir thoroughly for 45min, the speed is 700r / min, then add 0.1g of polydimethylsiloxane, 0.1g of silane-modified organosiloxane, 0.1g of organic bentonite, 0.1g of ethylene glycol, 0.1g of diatomaceous earth, 0.1g of castor oil derivative, and then add boric acid, molybdic acid and triethanolamine to adjust the pH to 8.0, mix and stir thoroughly for 50min, the speed is 700r / min, and the final environmentally friendly water-based aluminum-rich coating is obtained; Step 4: Spray the prepared environmentally friendly water-based aluminum-rich coating on a carbon steel plate and cure it at 25°C for 24 hours. The spraying thickness is 30 to 50 μm. A 5% by mass sodium chloride solution is used as the corrosive solution. The polarization curve is measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating is -0.61V.

2. A method for preparing a water-based aluminum-rich matrix potential gradient carbon steel protective coating, characterized in that: The method comprises the following steps: Step 1: Use spherical aluminum powder as the main raw material, the diameter of the spherical aluminum powder is 5-35μm, weigh 150-200g of spherical aluminum powder, take 500ml of anhydrous ethanol solvent in a beaker, mix and stir at 40℃ for 20min at a speed of 800r / min, add 150ml of tetraethyl orthosilicate, react for 15min, add 241.5g of deionized water drop by drop, adjust the pH to 7-8 with triethanolamine, keep warm for 5h, and filter to obtain the surface-modified aluminum powder; Step 2, prepare a passivation liquid system without aluminum powder and resin, weigh 3.0g of sodium borate, 1.5g of sodium pyrosulfate, and 1.0g of potassium molybdate and dissolve them in 100ml of deionized water, add 0.4g of sodium hypochlorite and 0.4g of sodium perchlorate as oxidants, adjust the pH of the passivation liquid to 8.5 with boric acid, molybdic acid and triethanolamine, passivate the carbon steel in a water bath at 25°C for 2min, use a sodium chloride solution with a mass fraction of 5% as the corrosion solution, measure the polarization curve of the carbon steel on an electrochemical workstation, and obtain a self-corrosion voltage of the carbon steel of -0.47V; Step three, dissolve 10.5g of waterborne polyurethane resin in 25.0g of the passivation solution prepared above, add 10.0g of dipropylene glycol monobutyl ether and 1.2g of anhydrous ethanol, stir thoroughly for 30min, add 24.0g of surface-modified aluminum powder, stir thoroughly for 45min, the speed is 900r / min, then add 0.2g of polydimethylsiloxane, 0.2g of methylcellulose, 0.2g of polyol, 0.2g of diatomaceous earth, 0.2g of fumed silica, and then add boric acid, molybdic acid and triethanolamine to adjust the pH to 8.5, mix and stir thoroughly for 55min, the speed is 900r / min, and the final environmentally friendly waterborne aluminum-rich coating is obtained; Step 4: spray the prepared environmentally friendly water-based aluminum-rich coating on a carbon steel plate and cure it at 25°C for 24 hours. The spraying thickness is 30-50 μm. The polarization curve is measured on an electrochemical workstation, and the self-corrosion voltage of the aluminum-rich coating is -0.59V.