A magnesium alloy coating agent and its preparation method, and metal surface treatment method

Abstract

The present invention belongs to the technical field of metal surface treatment, and discloses a magnesium alloy coating agent and a preparation method thereof, and a metal surface treatment method. The magnesium alloy coating agent includes component A, component B, and component C; component A, by weight, includes 5-15 parts of composite acid, 3-10 parts of fluorosilicone resin, 4-20 parts of hydroxy polydimethylsiloxane, 5-15 parts of silane coupling agent, 0.5-3 parts of nano niobium pentoxide, and 1-8 parts of auxiliary agent; component B includes water and ethanol; component C includes isocyanate; composite acid includes lauric acid, boric acid, tannic acid, and at least one of phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, and citric acid; the weight ratio of component A, component B, and component C is 10: (50-90): (0.5-3). The dense protective film formed by the magnesium alloy coating agent on the surface of the magnesium alloy has good barrier properties to acids, alkalis, and neutral substances in the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and particularly relates to a magnesium alloy coating agent and a preparation method thereof, and a metal surface treatment method. Background Art

[0002] Magnesium alloys are beautiful, light, and high in strength, and are widely used in various fields. However, magnesium alloys have active chemical properties. Under natural conditions, the oxide film formed on the surface of magnesium alloys cannot effectively protect the magnesium alloy matrix. Therefore, in order to make efficient use of magnesium alloys and obtain a longer service life, it is necessary to treat their surface to improve the corrosion resistance of magnesium alloys.

[0003] The surface anticorrosion treatment methods for magnesium alloys in the prior art include chemical reagent treatment or electrochemical treatment. The chemical reagents used in chemical reagent (such as film-forming agent) treatment often require the use of highly toxic hexavalent chromium ions, fluorozirconic acid or fluorotitanic acid. Moreover, the wastewater generated by using such chemical reagents containing toxic substances to treat the surface of magnesium alloys is often difficult to treat, causing great environmental pollution.

[0004] In the prior art, there are also chemical reagents that do not contain hexavalent chromium ions and are used to improve the corrosion resistance of magnesium alloys. However, their corrosion resistance to acid, alkalinity and neutrality is often weak, especially their tolerance to acid and alkalinity is poor.

[0005] Therefore, there is an urgent need to provide a new chemical reagent that does not contain hexavalent chromium ions, fluorozirconic acid or fluorotitanic acid, is environmentally friendly, and after treating the magnesium alloy, makes the magnesium alloy have good corrosion resistance to acidic, alkaline and neutral environments. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a magnesium alloy coating agent and a preparation method thereof, and a metal surface treatment method. The magnesium alloy coating agent of the present invention can form a protective layer on the surface of the magnesium alloy by treating the magnesium alloy, and significantly improve the corrosion resistance of the magnesium alloy to acidic, alkaline and neutral environments.

[0007] The inventive concept of the present invention is as follows: the magnesium alloy coating agent of the present invention comprises component A, component B and component C; the component A comprises, by weight, 5-15 parts of composite acid, 3-10 parts of fluorosilicone resin, 4-20 parts of hydroxy polydimethylsiloxane, 5-15 parts of silane coupling agent, 0.5-3 parts of nano niobium pentoxide and 1-8 parts of auxiliary agent; the component B comprises water and ethanol; the component C comprises isocyanate; the composite acid comprises lauric acid, boric acid, tannic acid, and at least one of phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid and citric acid. The present invention has good dispersibility for organic matter (such as hydroxy polydimethylsiloxane, lauric acid, tannic acid, and phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, citric acid) and inorganic matter (such as nano niobium pentoxide, boric acid) after hydrolysis of silane coupling agent in water. The composite acid of the present invention is composed of a specific type of acid, and the film formed after the reaction of the specific type of acid has high density. Isocyanate reacts with substances containing active hydroxyl groups (such as hydroxy polydimethylsiloxane, lauric acid, tannic acid, and phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, citric acid, etc.) to form a uniform dense film layer. The inorganic matter is also well dispersed in the film layer, so that the film layer finally formed not only has good adhesion to the magnesium alloy substrate, but also has better barrier properties for acids, alkalis, and neutral substances in the environment, and finally improves the protectiveness of the film layer to the magnesium alloy. The setting of the magnesium alloy film agent component of the present invention is conducive to the uniform dispersion of fluorosilicone resin, so that the anti-corrosion performance of fluorosilicone resin can be fully utilized.

[0008] A first aspect of the present invention provides a magnesium alloy coating agent.

[0009] Specifically, a magnesium alloy coating agent includes component A, component B, and component C;

[0010] The component A comprises, by weight, 5-15 parts of composite acid, 3-10 parts of fluorosilicone resin, 4-20 parts of hydroxy polydimethylsiloxane, 5-15 parts of silane coupling agent, 0.5-3 parts of nano niobium pentoxide, and 1-8 parts of auxiliary agent;

[0011] The B component includes water and ethanol;

[0012] The C component includes isocyanate;

[0013] The composite acid includes at least one of lauric acid, boric acid, tannic acid, phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, and citric acid;

[0014] The weight ratio of the component A, the component B and the component C is 10:(50-90):(0.5-3).

[0015] The auxiliary agent includes at least one of sodium lauryl sulfate, sodium benzoate, polydimethylsiloxane and polymethylphenylsiloxane.

[0016] Preferably, the weight ratio of component A, component B and component C is 10:(60-80):(0.8-1.8).

[0017] Preferably, the isocyanate is selected from at least one of hexamethylene diisocyanate (HDI) and diphenylmethane diisocyanate (MDI).

[0018] Preferably, in the B component, the volume ratio of water to ethanol is 100:(1-10), more preferably 100:(2-5).

[0019] Preferably, the weight ratio of the composite acid, lauric acid, boric acid, tannic acid, and at least one of phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, and citric acid is 1: (0.1-0.5): (0.1-0.6): (0.1-0.8); further preferably, the weight ratio is 1: (0.2-0.4): (0.2-0.5): (0.2-0.6).

[0020] Preferably, the composite acid consists of lauric acid, boric acid, tannic acid, and tartaric acid.

[0021] Further preferably, the composite acid is composed of lauric acid, boric acid, tannic acid, and tartaric acid in a weight ratio of 1: (0.1-0.3): (0.2-0.5): (0.3-0.5).

[0022] Preferably, the component A comprises, by weight, 6-12 parts of composite acid, 4-8 parts of fluorosilicone resin, 5-15 parts of hydroxypolydimethylsiloxane, 5-12 parts of silane coupling agent, 0.5-1.5 parts of nano niobium pentoxide, and 1-5 parts of auxiliary agent.

[0023] Preferably, the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. Further preferably, the silane coupling agent includes γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. That is, including these three silane coupling agents at the same time helps to improve the adhesion between the film layer and the magnesium alloy substrate.

[0024] Preferably, the A component further comprises nano yttrium oxide. Adding nano yttrium oxide to the A component makes the protective layer formed by the magnesium alloy coating agent have good tolerance to alkaline environment, thereby improving the alkaline corrosion resistance.

[0025] Preferably, the weight ratio of the nano yttrium oxide to the nano niobium pentoxide is (0.1-0.5):1.

[0026] A second aspect of the present invention provides a method for preparing a magnesium alloy coating agent.

[0027] Specifically, a method for preparing a magnesium alloy coating agent comprises the following steps:

[0028] The components contained in component A are weighed and mixed to obtain component A, the components contained in component B are weighed and mixed to obtain component B, and then component A is added to component B, mixed and dispersed to obtain a mixture; and component C is taken to form the magnesium alloy coating agent.

[0029] Preferably, the mixing and dispersing process is carried out under ultrasonic conditions. The mixing and dispersing is carried out under ultrasonic conditions so that the components are mixed evenly.

[0030] Preferably, the preparation method of the magnesium alloy coating agent comprises mixing water and ethanol, then adding a silane coupling agent, and then adding a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, and an additive to mix and disperse to obtain a mixture, and the mixture and the isocyanate constitute the magnesium alloy coating agent. That is, the silane coupling agent is first hydrolyzed, and then other components are added, so that the organic substance and the inorganic substance can be well dispersed.

[0031] Preferably, when nano niobium pentoxide is added, nano yttrium oxide is also added.

[0032] When the magnesium alloy coating agent is used, the mixture is first mixed with the C component and then used.

[0033] A third aspect of the present invention provides an application of a magnesium alloy coating agent.

[0034] A magnesium alloy comprises a magnesium alloy substrate and a protective layer on the surface of the magnesium alloy substrate, wherein the protective layer is formed by the magnesium alloy coating agent.

[0035] The application of the above-mentioned magnesium alloy coating agent in the field of magnesium alloy corrosion protection.

[0036] A metal surface treatment method comprises the following steps:

[0037] The metal is taken, polished, cleaned, then soaked in the magnesium alloy coating agent, and dried.

[0038] Preferably, the metal is a magnesium alloy.

[0039] Preferably, the soaking time is 8-20 minutes and the soaking temperature is 45-65°C.

[0040] Preferably, the drying temperature is 90-120° C., and the drying time is 30-60 minutes. Through the soaking treatment and drying treatment at a certain temperature, each component reacts fully, which helps to form a dense mesh protective film.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] (1) The magnesium alloy coating agent of the present invention comprises component A, component B and component C; the component A comprises, by weight, 5-15 parts of a composite acid, 3-10 parts of a fluorosilicone resin, 4-20 parts of a hydroxypolydimethylsiloxane, 5-15 parts of a silane coupling agent, 0.5-3 parts of nano-niobium pentoxide and 1-8 parts of an auxiliary agent; the component B comprises water and ethanol; the component C comprises isocyanate; the composite acid comprises lauric acid, boric acid, tannic acid, and at least one of phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid and citric acid. After the silane coupling agent is hydrolyzed in water, the present invention has good dispersibility for organic matter (such as hydroxy polydimethylsiloxane, lauric acid, tannic acid, phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, citric acid) and inorganic matter (such as nano niobium pentoxide, boric acid), and isocyanate reacts with substances containing active hydroxyl groups (such as hydroxy polydimethylsiloxane, lauric acid, tannic acid, phenylacetic acid, phenylpropionic acid, maleic acid, tartaric acid, citric acid, etc.) to form a uniform and dense film layer, and the inorganic matter is also well dispersed in the film layer, so that the finally formed film layer not only has good adhesion to the magnesium alloy substrate, but also has better barrier performance to acid, alkali and neutral substances in the environment, and finally improves the protectiveness of the film layer to the magnesium alloy.

[0043] (2) The A component also includes nano yttrium oxide. Adding nano yttrium oxide to the A component makes the protective layer formed by the magnesium alloy coating agent have good tolerance to alkaline environment, thereby improving the alkaline corrosion resistance. DETAILED DESCRIPTION

[0044] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0045] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0046] Example 1

[0047] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0048] Component A is composed of the following components by weight: 8 parts of composite acid, 5 parts of fluorosilicone resin, 7 parts of hydroxy polydimethylsiloxane, 12 parts of silane coupling agent (4 parts of γ-aminopropyl triethoxysilane, 4 parts of γ-aminopropyl trimethoxysilane, 4 parts of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane), 0.9 parts of nano niobium pentoxide, and 1.8 parts of additives (0.5 parts of sodium dodecyl sulfate, 0.8 parts of sodium benzoate, and 0.5 parts of polydimethylsiloxane);

[0049] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:2);

[0050] Component C is isocyanate (hexamethylene diisocyanate);

[0051] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and maleic acid in a weight ratio of 1:0.1:0.2:0.3;

[0052] The weight ratio of component A, component B and component C is 10:85:1.5.

[0053] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0054] Water and ethanol are mixed, and then a silane coupling agent is added (γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane are added first, and then N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is added), and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions for 40 minutes to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0055] Example 2

[0056] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0057] Component A is composed of the following components by weight: 7 parts of composite acid, 6 parts of fluorosilicone resin, 8 parts of hydroxy polydimethylsiloxane, 10 parts of silane coupling agent (3 parts of γ-aminopropyl triethoxysilane, 3 parts of γ-aminopropyl trimethoxysilane, 4 parts of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane), 1.3 parts of nano niobium pentoxide, and 2 parts of additives (0.5 parts of sodium dodecyl sulfate, 1.0 parts of sodium benzoate, and 0.5 parts of polydimethylsiloxane);

[0058] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:1);

[0059] Component C is isocyanate (diphenylmethane diisocyanate);

[0060] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and citric acid in a weight ratio of 1:0.2:0.3:0.3;

[0061] The weight ratio of component A, component B and component C is 10:90:1.8.

[0062] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0063] Water and ethanol are mixed, and then a silane coupling agent is added (γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane are added first, and then N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is added), and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions for 50 minutes to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0064] Example 3

[0065] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0066] Component A is composed of the following components by weight: 8 parts of composite acid, 5 parts of fluorosilicone resin, 7 parts of hydroxy polydimethylsiloxane, 12 parts of silane coupling agent (4 parts of γ-aminopropyl triethoxysilane, 4 parts of γ-aminopropyl trimethoxysilane, 4 parts of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane), 0.9 parts of nano niobium pentoxide, and 1.8 parts of additives (0.5 parts of sodium dodecyl sulfate, 0.8 parts of sodium benzoate, and 0.5 parts of polydimethylsiloxane);

[0067] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:2);

[0068] Component C is isocyanate (hexamethylene diisocyanate);

[0069] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and tartaric acid in a weight ratio of 1:0.1:0.2:0.3;

[0070] The weight ratio of component A, component B and component C is 10:85:1.5.

[0071] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0072] Water and ethanol are mixed, and then a silane coupling agent is added (γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane are added first, and then N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is added), and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions for 40 minutes to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0073] Example 4

[0074] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0075] Component A is composed of the following components by weight: 8 parts of composite acid, 5 parts of fluorosilicone resin, 7 parts of hydroxy polydimethylsiloxane, 12 parts of silane coupling agent (6 parts of γ-aminopropyl triethoxysilane, 6 parts of γ-aminopropyl trimethoxysilane), 0.9 parts of nano niobium pentoxide, and 1.0 parts of additives (0.5 parts of sodium dodecyl sulfate and 0.5 parts of polydimethylsiloxane);

[0076] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:2);

[0077] Component C is isocyanate (hexamethylene diisocyanate);

[0078] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and maleic acid in a weight ratio of 1:0.1:0.2:0.3;

[0079] The weight ratio of component A, component B and component C is 10:85:1.5.

[0080] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0081] Water and ethanol are mixed, and then a silane coupling agent is added, and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0082] Example 5

[0083] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0084] Component A is composed of the following components by weight: 8 parts of composite acid, 5 parts of fluorosilicone resin, 7 parts of hydroxy polydimethylsiloxane, 12 parts of silane coupling agent (4 parts of γ-aminopropyl triethoxysilane, 4 parts of γ-aminopropyl trimethoxysilane, 4 parts of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane), 0.9 parts of nano niobium pentoxide, and 1.0 parts of additives (0.5 parts of sodium dodecyl sulfate and 0.5 parts of polydimethylsiloxane);

[0085] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:2);

[0086] Component C is isocyanate (hexamethylene diisocyanate);

[0087] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and maleic acid in a weight ratio of 1:0.1:0.2:0.3;

[0088] The weight ratio of component A, component B and component C is 10:85:1.5.

[0089] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0090] Water and ethanol are mixed, and then a silane coupling agent is added (γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane are added first, and then N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is added), and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions for 40 minutes to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0091] Example 6

[0092] A magnesium alloy coating agent, consisting of component A, component B, and component C;

[0093] Component A is composed of the following components by weight: 8 parts of composite acid, 5 parts of fluorosilicone resin, 7 parts of hydroxy polydimethylsiloxane, 12 parts of silane coupling agent (4 parts of γ-aminopropyltriethoxysilane, 4 parts of γ-aminopropyltrimethoxysilane, 4 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane), 0.7 parts of nano niobium pentoxide, 0.2 parts of nano yttrium oxide, and 1.8 parts of additives (0.5 parts of sodium dodecyl sulfate, 0.8 parts of sodium benzoate, and 0.5 parts of polydimethylsiloxane);

[0094] Component B, consisting of the following components: water and ethanol (the volume ratio of water to ethanol is 100:2);

[0095] Component C is isocyanate (hexamethylene diisocyanate);

[0096] The composite acid is prepared by mixing lauric acid, boric acid, tannic acid and maleic acid in a weight ratio of 1:0.1:0.2:0.3;

[0097] The weight ratio of component A, component B and component C is 10:85:1.5.

[0098] A method for preparing a magnesium alloy coating agent comprises the following steps:

[0099] Water and ethanol are mixed, and then a silane coupling agent is added (γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane are added first, and then N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is added), and then a composite acid, a fluorosilicone resin, a hydroxy polydimethylsiloxane, nano niobium pentoxide, nano yttrium oxide, and an additive are added, and the mixture is mixed and dispersed under ultrasonic conditions for 40 minutes to obtain a mixture, and the mixture and isocyanate form a magnesium alloy coating agent.

[0100] Comparative Example 1

[0101] Compared with Example 1, the difference of Comparative Example 1 is that the maleic acid in Example 1 is replaced by an equal amount of acetic acid, and the rest of the composition and process are the same as those of Example 1.

[0102] Comparative Example 2

[0103] Compared with Example 1, the difference of Comparative Example 2 is that the boric acid in Example 1 is replaced by an equal amount of formic acid, and the rest of the composition and process are the same as those of Example 1.

[0104] Comparative Example 3

[0105] Compared with Example 1, the difference of Comparative Example 3 is that the tannic acid in Example 1 is replaced by an equal amount of oleic acid, and the rest of the composition and process are the same as those of Example 1.

[0106] Comparative Example 4

[0107] Compared with Example 1, the difference of Comparative Example 4 is that the nano-niobium pentoxide in Example 1 is replaced by an equal amount of nano-silicon dioxide, and the rest of the composition and process are the same as those of Example 1.

[0108] Comparative Example 5

[0109] Compared with Example 1, the difference of Comparative Example 5 is that hydroxy polydimethylsiloxane and isocyanate are not used, and the rest of the composition and process are the same as those of Example 1.

[0110] Product effect testing

[0111] A metal surface treatment method comprises the following steps: taking magnesium alloy AZ31B, grinding, ultrasonic cleaning for 30 minutes, and then soaking for 18 minutes with a magnesium alloy coating agent prepared in an embodiment or a comparative example, the soaking treatment temperature is 48° C., and then drying for 50 minutes at 110° C. to obtain a magnesium alloy with a protective film layer formed on the surface. Then, the adhesion and corrosion resistance of the protective film layer are tested.

[0112] 1. Adhesion test

[0113] The adhesion strength of the protective film layer formed on the surface of the magnesium alloy in Example 1, Example 3 and Example 4 was measured by conventional methods. The results are shown in Table 1.

[0114] Table 1

[0115] Example 1 Example 3 Example 4 Adhesion (ISO grade) 0 0 1

[0116] As can be seen from Table 1, compared with Example 1, in Example 4, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane was not used in the preparation process of the magnesium alloy coating agent, resulting in a weakened bonding strength between the formed protective film layer and the magnesium alloy substrate. It can be seen that the simultaneous use of three types of silane coupling agents in the present invention helps to improve the adhesion of the protective film layer.

[0117] 2. Corrosion resistance test

[0118] Referring to GB / T1771-2007 "Determination of Neutral Salt Spray Resistance of Paints and Varnishes", the magnesium alloy treated by the above-mentioned metal surface treatment method (the magnesium alloy coating agent prepared in Example 1, Example 3, Example 5, Example 6, and Comparative Examples 1-4 was used in the metal surface treatment process) was placed in a 5% NaCl solution and a salt spray box at a temperature of 35°C for a neutral salt spray resistance test. The results are shown in Table 2.

[0119] Table 2

[0120]

[0121] It can be seen from Table 2 that after the magnesium alloy is treated with the magnesium alloy coating agent prepared in the embodiment of the present invention, the time for the magnesium alloy to resist neutral salt spray is significantly longer than that of Comparative Examples 1-4, and the corresponding corrosion resistance of the embodiment is better. It can be seen from the results of Example 1 and Comparative Examples 1-4 that the composition of the composite acid has a direct impact on the corrosion resistance of the magnesium alloy coating agent.

[0122] The magnesium alloys treated with the magnesium alloy coating agent of Example 1, Example 6 and Comparative Example 5 were subjected to resistance to 10% by mass sodium hydroxide solution and 10% by mass hydrochloric acid, and the time when visible corrosion pits appeared on the surface of the magnesium alloy was recorded. The results are shown in Table 3.

[0123] Table 3

[0124]

[0125] It can be seen from Table 3 that, compared with Comparative Example 5, the magnesium alloy treated with the magnesium alloy coating agent in Example 1 and Example 6 has better acid and alkali resistance. It can be seen that when hydroxy polydimethylsiloxane and isocyanate are not used, the protective film layer formed is not dense enough and the protective effect on the magnesium alloy is poor. It can be seen from the corresponding results of Example 1 and Example 6 that the addition of nano yttrium oxide on the basis of nano niobium pentoxide improves the barrier properties of the protective film layer and can further improve the anti-corrosion performance of the protective film layer.

Claims

1. A magnesium alloy coating agent, characterized in that: It includes component A, component B and component C; The component A comprises, by weight, 5-15 parts of composite acid, 3-10 parts of fluorosilicone resin, 4-20 parts of hydroxy polydimethylsiloxane, 5-15 parts of silane coupling agent, 0.5-3 parts of nano niobium pentoxide, and 1-8 parts of auxiliary agent; The B component includes water and ethanol; The C component includes isocyanate; The weight ratio of component A, component B and component C is 10: (50-90): (0.5-3); The composite acid is composed of a mixture of lauric acid, boric acid, tannic acid and maleic acid or a mixture of lauric acid, boric acid, tannic acid and tartaric acid; The silane coupling agent is composed of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; The auxiliary agents include sodium lauryl sulfate, sodium benzoate and polydimethylsiloxane.

2. The magnesium alloy coating agent according to claim 1, characterized in that: In the composite acid, the weight ratio of lauric acid, boric acid, tannic acid, and one of maleic acid and tartaric acid is 1: (0.1-0.5): (0.1-0.6): (0.1-0.8).

3. The method for preparing the magnesium alloy coating agent according to any one of claims 1 to 2, characterized in that: The following steps are involved: The components contained in component A are weighed and mixed to obtain component A, the components contained in component B are weighed and mixed to obtain component B, and then component A is added to component B, mixed and dispersed to obtain a mixture; and component C is taken to form the magnesium alloy coating agent.

4. The preparation method according to claim 3, characterized in that: The method comprises the following steps: mixing water and ethanol, adding a silane coupling agent, and then adding a composite acid, fluorosilicone resin, hydroxy polydimethylsiloxane, nano niobium pentoxide, and an auxiliary agent for mixing and dispersing to obtain a mixture, wherein the mixture and isocyanate form the magnesium alloy coating agent.

5. The preparation method according to claim 4, characterized in that: When adding nano niobium pentoxide, nano yttrium oxide is also added.

6. A magnesium alloy, characterized in that: It comprises a magnesium alloy substrate and a protective layer on the surface of the magnesium alloy substrate, wherein the protective layer is formed by the magnesium alloy coating agent according to any one of claims 1 to 2.

7. A metal surface treatment method, characterized in that: The following steps are involved: The metal is taken, polished, cleaned, and then immersed in the magnesium alloy coating agent according to any one of claims 1 to 2, and dried.

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