Chromium-free passivator for corrosion prevention of AZ31B magnesium alloy and production process of chromium-free passivator

Abstract

The invention relates to the technical field of passivating agents, and discloses a chromium-free passivating agent for corrosion prevention of an AZ31B magnesium alloy and a production process of the chromium-free passivating agent. Comprising the following raw materials: polyurethane acrylic resin, glycidyl methacrylate, anti-corrosion vinyl chloride-vinyl acetate resin, a self-repairing compound, 1-hydroxycyclohexyl phenyl ketone, propylene glycol methyl ether acetate, a flatting agent and a defoaming agent. The anti-corrosion vinyl chloride-vinyl acetate resin and the self-repairing compound participate in the preparation process of the passivator, so that the prepared passivator has excellent corrosion resistance, mechanical strength, adhesive force and self-repairing capacity, is not prone to falling off and scratching when acting on the magnesium alloy, can be used for repairing small cracks when the small cracks are generated, and has the advantages that the service life of the passivator is prolonged, and the service life of the passivator is prolonged. And the integrity of the anti-corrosion barrier effect is effectively kept, so that the magnesium alloy protective coating can play a more excellent and long-acting magnesium alloy protective effect.

Description

Technical Field

[0001] This invention relates to the field of passivating agent technology, specifically to a chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy and its production process. Background Technology

[0002] Magnesium alloys are among the lightest engineering metal structural materials, possessing extremely high specific strength and excellent electromagnetic shielding, casting, and machining properties. They have great application potential in aerospace, military, automotive, and electronic and biomedical implant fields. However, magnesium is chemically reactive, has a low standard electrode potential, and is highly susceptible to corrosion, forming a loose and porous hydroxide film with high corrosion sensitivity. This severely restricts the large-scale and long-term application of magnesium alloys.

[0003] In traditional magnesium alloy surface protection technologies, chromate conversion treatment is widely used for magnesium alloy protection because it is simple to operate, low in cost, and can form a dense chromium-containing passivation film on the surface, which can significantly improve the corrosion resistance of magnesium alloys. However, chromates are internationally recognized as strong carcinogens and mutagens. Their production, use, and waste liquid treatment pose a threat to the health of operators and cause persistent pollution to the ecological environment. Ordinary chromium-free passivators generally have problems such as weak adhesion, insufficient corrosion resistance, and easy cracking. They also lack self-healing ability. When used, they are not good at active protection and long-term durability of magnesium alloys, making it difficult to meet the needs of magnesium alloy protection in complex environments.

[0004] Patent CN107201514B discloses a chromium-free passivating agent for magnesium alloys and its application method. The passivating agent is prepared by combining titanium compounds and their derivatives, zirconium compounds and their derivatives, nanoparticles, thiourea, and coupling agents. It can not only solve the problem of large amounts of wastewater pollution caused by traditional chromium-based water washing, but also solve the problem that the corrosion protection performance and coating adhesion performance of chromium-free products cannot reach the effect of chromium-based products. However, this passivating agent does not have self-healing ability. When tiny cracks appear in the passivation film, it cannot repair them in time. The expansion of cracks will lead to the loss of protection for magnesium alloys and make it difficult to achieve a long-term protective effect. Summary of the Invention

[0005] The purpose of this invention is to provide a chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy and its production process, which solves the following technical problems: (1) the problem that ordinary passivating agents containing chromium elements have adverse effects on the environment and operators during construction; (2) the problem that ordinary passivating agents have weak bonding ability with magnesium alloy substrate and are easy to peel off and lose their protective effect; (3) the problem that ordinary passivating agents have weak corrosion resistance and are prone to cracking, affecting service life; (4) the problem that ordinary passivating agents do not have self-repairing ability and need to be replaced in time when small cracks are generated.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy comprises the following raw materials in parts by weight: 80-100 parts polyurethane acrylic resin, 15-20 parts glycidyl methacrylate, 10-12 parts corrosion-resistant chloroacetic acid resin, 6-8 parts self-healing compound, 2-4 parts 1-hydroxycyclohexylphenyl ketone, 80-100 parts propylene glycol methyl ether acetate, 0.5-1 parts leveling agent, and 1-2 parts defoamer; wherein the corrosion-resistant chloroacetic acid resin is prepared by reacting furfuryl-modified chloroacetic acid resin with vinylphosphonic acid; wherein the furfuryl-modified chloroacetic acid resin is prepared by reacting carboxyl chloroacetic acid resin with glycidyl furfuryl ether; wherein the self-healing compound is prepared by reacting modified polyetheramine with bis(2-hydroxyethyl) disulfide; and wherein the modified polyetheramine is prepared by reacting polyetheramine with norbornene adiene anhydride.

[0008] Furthermore, the leveling agent is any one of leveling agent RM-2020 and leveling agent BYK-378; the defoamer is any one of polyether modified polysiloxane defoamer and dimethyl silicone oil defoamer.

[0009] Furthermore, the preparation method of the corrosion-resistant chlorinated vinyl acetate resin includes the following steps:

[0010] S1: Place the carboxylated chloroacetic acid resin in toluene, mix and stir, then add glycidyl furfuryl ether and catalyst, heat to 80-90℃ and stir for 4-6 hours, collect the product after vacuum distillation, and obtain furfuryl-modified chloroacetic acid resin.

[0011] S2: Furfuryl-modified chloroacetic acid resin, vinylphosphonic acid, p-toluenesulfonic acid, and hydroquinone are placed in a mixed solvent of toluene and isopropanol, nitrogen gas is introduced, the mixture is stirred and refluxed, and after cooling to room temperature, the product is collected to obtain the anti-corrosion chloroacetic acid resin.

[0012] Through the above technical solution, under the action of a catalyst, the carboxyl group in the carboxyl chloride ester resin structure and the epoxy group in the glycidyl furfuryl ether structure undergo a ring-opening reaction to obtain furfuryl-modified chloride ester resin. Then, under the action of p-toluenesulfonic acid and hydroquinone, the hydroxyl group in the furfuryl-modified chloride ester resin structure and the phosphate group in the vinylphosphonic acid structure undergo an esterification reaction to obtain an anti-corrosion chloride ester resin. This anti-corrosion chloride ester resin uses chloride ester resin as a matrix, and the double bond introduced into its structure can participate in the preparation process of the passivating agent, effectively enhancing the compactness of the passivating agent. Moreover, the introduced furfuryl group has a rigid furan ring structure, which not only improves the mechanical strength of the passivating agent, but also has strong aromaticity and chemical stability, which can effectively enhance the passivating agent's resistance to corrosive media penetration. At the same time, the introduced phosphate group can form a dense and firm phosphate conversion film with the magnesium alloy matrix, improving adhesion and effectively inhibiting the erosion of corrosive media. It produces a synergistic anti-corrosion effect with the furfuryl group, greatly enhancing the corrosion resistance of the passivating agent.

[0013] Further, in step S1, the catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium hydroxide, and tetrabutylammonium chloride.

[0014] Furthermore, in step S2, the stirring and reflux reaction time is 10-12 hours.

[0015] Furthermore, the preparation method of the self-healing complex includes the following steps:

[0016] SS1: Polyetheramine and norbornene adipic anhydride are placed in xylene, heated to 80-85℃ and reacted for 3-5 hours. The solvent is removed by rotary evaporation and the product is collected to obtain modified polyetheramine.

[0017] SS2: Modified polyetheramine and bis(2-hydroxyethyl) disulfide were placed in N,N-dimethylformamide, thoroughly mixed and stirred, nitrogen gas was introduced, p-toluenesulfonic acid was added, the reaction was heated, and the product was collected by vacuum distillation to obtain the self-healing complex.

[0018] Through the above technical solution, the amino group in the polyetheramine structure and the anhydride group in the norbornene anhydride structure undergo a ring-opening reaction to obtain a modified polyetheramine. Then, under the action of p-toluenesulfonic acid, the carboxyl group in the modified polyetheramine structure undergoes an esterification reaction with the hydroxyl group in the bis(2-hydroxyethyl) disulfide structure to obtain a self-healing composite. The double bond in this self-healing composite structure can participate in the preparation process of the passivating agent, enhancing the density of its coating. Using the flexible segment of polyetheramine as the molecular skeleton, it can impart good internal stress and dissipation characteristics to the coating, effectively avoiding brittle cracking. The rigid structure of norbornene in its structure can effectively improve the mechanical strength of the passivating agent, and the introduction of dynamic disulfide bonds can endow the coating after the passivating agent is cured with self-healing function. When micro-cracks appear, it can effectively repair itself, restore the integrity of the barrier, and significantly extend the service life of the passivating agent coating.

[0019] Further, in step SS1, the amine value of the polyetheramine is 440-500 mg KOH / g.

[0020] Furthermore, in step SS2, the temperature of the heating reaction is 90-100℃, and the time is 3-5 hours.

[0021] A production process for a chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy includes the following steps:

[0022] Step 1: Thoroughly mix polyurethane acrylic resin, glycidyl methacrylate, anti-corrosion chloroacetic acid resin, self-healing compound, 1-hydroxycyclohexylphenyl ketone and propylene glycol methyl ether acetate to obtain a mixture.

[0023] Step 2: Add leveling agent and defoamer to the mixture, stir thoroughly at 200-300 rpm for 0.5-1 h, and let stand for 24-48 h to obtain passivating agent.

[0024] The beneficial effects of this invention are:

[0025] By incorporating the anti-corrosion chlorinated resin and self-healing compound into the preparation process of the passivating agent through the above technical solution, the prepared passivating agent has excellent corrosion resistance, mechanical strength, adhesion and self-healing ability. When applied to magnesium alloys, it is not easy to fall off or scratch, and it can repair micro-cracks, effectively maintaining the integrity of the anti-corrosion barrier and enabling it to play a more outstanding and long-lasting protective role for magnesium alloys.

[0026] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a production process flow diagram of the chromium-free passivating agent used for corrosion protection of AZ31B magnesium alloy according to the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The preparation methods of the anti-corrosion chlorinated vinyl resin and self-healing composite in the following embodiments and comparative examples of the present invention are as follows:

[0031] I. Preparation of Corrosion-Inhibiting Chlorinated Vinyl Acetate Resin

[0032] S1: Place 2g of carboxylated chloroacetic acid resin in 60ml of toluene, mix and stir, then add 1.2g of glycidyl furfuryl ether and 0.1g of tetrabutylammonium bromide, heat to 80℃ and stir for 4h, collect the product after vacuum distillation, and obtain furfuryl-modified chloroacetic acid resin.

[0033] S2: 2.5g of furfuryl-modified chloroacetic acid resin, 2g of vinylphosphonic acid, 0.05g of p-toluenesulfonic acid, and 0.02g of hydroquinone were placed in a mixed solvent of 30ml toluene and 10ml isopropanol. Nitrogen gas was introduced, and the mixture was stirred and refluxed for 10h. After cooling to room temperature, the product was collected to obtain the anti-corrosion chloroacetic acid resin.

[0034] II. Preparation of Self-Healing Complex

[0035] SS1: 3g of polyetheramine with an amine value of 460mgKOH / g and 2.6g of norbornene adipic anhydride were placed in 50ml of xylene, heated to 80℃ and reacted for 3h. The solvent was removed by rotary evaporation and the product was collected to obtain modified polyetheramine.

[0036] SS2: 3.5g of modified polyetheramine and 3g of bis(2-hydroxyethyl) disulfide were placed in 80ml of N,N-dimethylformamide, thoroughly mixed and stirred, nitrogen gas was introduced, 0.1g of p-toluenesulfonic acid was added, the temperature was raised to 90℃ and reacted for 3h, and the product was collected by vacuum distillation to obtain the self-healing complex.

[0037] Example 1

[0038] Preparation of passivating agent

[0039] Step 1: Thoroughly mix 80 parts of polyurethane acrylic resin, 15 parts of glycidyl methacrylate, 10 parts of anti-corrosion chloroacetic acid resin, 6 parts of self-healing compound, 2 parts of 1-hydroxycyclohexylphenyl ketone and 80 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0040] Step 2: Add 0.5 parts of leveling agent RM-2020 and 1 part of dimethyl silicone defoamer to the mixture, stir thoroughly at 200 rpm for 0.5 hours, and let stand for 24 hours to obtain the passivating agent.

[0041] Example 2

[0042] Preparation of passivating agent

[0043] Step 1: Thoroughly mix 90 parts of polyurethane acrylic resin, 18 parts of glycidyl methacrylate, 11 parts of anti-corrosion chloroacetic acid resin, 7 parts of self-healing compound, 3 parts of 1-hydroxycyclohexylphenyl ketone and 90 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0044] Step 2: Add 0.8 parts of leveling agent RM-2020 and 1.5 parts of polyether modified polysiloxane defoamer to the mixture, stir thoroughly at 250 rpm for 0.8 hours, and let stand for 32 hours to obtain the passivating agent.

[0045] Example 3

[0046] Preparation of passivating agent

[0047] Step 1: Thoroughly mix 100 parts of polyurethane acrylic resin, 20 parts of glycidyl methacrylate, 12 parts of anti-corrosion chloroacetic acid resin, 8 parts of self-healing compound, 4 parts of 1-hydroxycyclohexylphenyl ketone and 100 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0048] Step 2: Add 1 part leveling agent BYK378 and 2 parts dimethyl silicone defoamer to the mixture, stir thoroughly at 300 rpm for 1 hour, and let stand for 48 hours to obtain the passivating agent.

[0049] Comparative Example 1

[0050] Preparation of passivating agent

[0051] Step 1: Thoroughly mix 90 parts of polyurethane acrylic resin, 18 parts of glycidyl methacrylate, 7 parts of self-healing compound, 3 parts of 1-hydroxycyclohexylphenyl ketone and 90 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0052] Step 2: Add 0.8 parts of leveling agent RM-2020 and 1.5 parts of polyether modified polysiloxane defoamer to the mixture, stir thoroughly at 250 rpm for 0.8 hours, and let stand for 32 hours to obtain the passivating agent.

[0053] Comparative Example 2

[0054] Preparation of passivating agent

[0055] Step 1: Thoroughly mix 90 parts of polyurethane acrylic resin, 18 parts of glycidyl methacrylate, 11 parts of anti-corrosion chloroacetic acid resin, 3 parts of 1-hydroxycyclohexylphenyl ketone and 90 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0056] Step 2: Add 0.8 parts of leveling agent RM-2020 and 1.5 parts of polyether modified polysiloxane defoamer to the mixture, stir thoroughly at 250 rpm for 0.8 hours, and let stand for 32 hours to obtain the passivating agent.

[0057] Comparative Example 3

[0058] Preparation of passivating agent

[0059] Step 1: Thoroughly mix 90 parts of polyurethane acrylic resin, 18 parts of glycidyl methacrylate, 11 parts of furfuryl-modified chloroacetic acid resin, 7 parts of self-healing compound, 3 parts of 1-hydroxycyclohexylphenyl ketone and 90 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0060] Step 2: Add 0.8 parts of leveling agent RM-2020 and 1.5 parts of polyether modified polysiloxane defoamer to the mixture, stir thoroughly at 250 rpm for 0.8 hours, and let stand for 32 hours to obtain the passivating agent.

[0061] Comparative Example 4

[0062] Preparation of passivating agent

[0063] Step 1: Thoroughly mix 90 parts of polyurethane acrylic resin, 18 parts of glycidyl methacrylate, 11 parts of corrosion-resistant chloroacetic acid resin, 7 parts of modified polyetheramine, 3 parts of 1-hydroxycyclohexylphenyl ketone and 90 parts of propylene glycol methyl ether acetate to obtain a mixture.

[0064] Step 2: Add 0.8 parts of leveling agent RM-2020 and 1.5 parts of polyether modified polysiloxane defoamer to the mixture, stir thoroughly at 250 rpm for 0.8 hours, and let stand for 32 hours to obtain the passivating agent.

[0065] Performance testing

[0066] The passivating agents prepared in Examples 1-3 and Comparative Examples 1-4 were coated onto AZ31B magnesium alloy test pieces that had been polished, pickled, washed, and dried, with the film thickness controlled at 18-22 μm. After curing, these were used as samples. The adhesion of the samples was tested according to standard GB / T9286-2021. The salt spray resistance of the samples was tested according to standard GB / T10125-2021 to determine their corrosion resistance. Tensile strength tests were performed on the samples and on samples after a 3 mm long and 0.5 mm wide crack was made with a blade and then repaired at 150°C for 24 hours, according to standard GB / T1040-2006, to determine the mechanical properties of the samples and calculate the repair rate, calculated as (repaired tensile strength / initial tensile strength) × 100%. Finally, the samples were bent 180° around a Φ2 mm axis according to standard GB / T6742-2007, and the coating was observed for cracking or peeling to determine the sample's performance.

[0067] Adhesion rating Salt spray resistance / h Tensile strength / MPa Repair rate / % Coating properties Example 1 Level 0 1200 18.2 74% No cracking or peeling Example 2 Level 0 1300 18.9 76% No cracking or peeling Example 3 Level 0 1200 18.5 72% No cracking or peeling Comparative Example 1 Level 2 400 13.8 70% Cracks appeared after bending. Comparative Example 2 Level 0 600 13.7 0% Coating peels off after bending Comparative Example 3 Level 1 800 14.9 68% Tiny cracks appeared after bending. Comparative Example 4 Level 0 1000 18.1 0% No cracking or peeling

[0068] As shown in the table above, the samples prepared in Examples 1-3 all exhibit excellent adhesion, salt spray resistance, mechanical properties, flexibility, and self-healing effect. The sample prepared in Comparative Example 1 did not contain any anti-corrosion chloroacetic acid resin, resulting in poor adhesion and anti-corrosion ability. The sample prepared in Comparative Example 2 did not contain any self-healing compound, thus lacking self-healing ability, but exhibiting good adhesion and poor flexibility. The sample prepared in Comparative Example 3 directly used furfuryl-modified chloroacetic acid resin, resulting in good adhesion but inferior anti-corrosion ability compared to the examples. The sample prepared in Comparative Example 4 directly used modified polyetheramine, thus lacking self-healing ability.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy, characterized in that, The raw materials include the following parts by weight: 80-100 parts polyurethane acrylic resin, 15-20 parts glycidyl methacrylate, 10-12 parts anti-corrosion chloroacetic acid resin, 6-8 parts self-healing compound, 2-4 parts 1-hydroxycyclohexylphenyl ketone, 80-100 parts propylene glycol methyl ether acetate, 0.5-1 part leveling agent, and 1-2 parts defoamer; the anti-corrosion chloroacetic acid resin is prepared by reacting furfuryl-modified chloroacetic acid resin with vinylphosphonic acid; the furfuryl-modified chloroacetic acid resin is prepared by reacting carboxyl chloroacetic acid resin with glycidyl furfuryl ether; the self-healing compound is prepared by reacting modified polyetheramine with bis(2-hydroxyethyl) disulfide; and the modified polyetheramine is prepared by reacting polyetheramine with norbornene adiene anhydride.

2. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 1, characterized in that, The leveling agent is either RM-2020 or BYK-378; the defoamer is either polyether-modified polysiloxane defoamer or dimethyl silicone oil defoamer.

3. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 1, characterized in that, The preparation method of the corrosion-resistant chlorinated vinyl acetate resin includes the following steps: S1: Place the carboxylated chloroacetic acid resin in toluene, mix and stir, then add glycidyl furfuryl ether and catalyst, heat to 80-90℃ and stir for 4-6 hours, collect the product after vacuum distillation, and obtain furfuryl-modified chloroacetic acid resin. S2: Furfuryl-modified chloroacetic acid resin, vinylphosphonic acid, p-toluenesulfonic acid, and hydroquinone are placed in a mixed solvent of toluene and isopropanol, nitrogen gas is introduced, the mixture is stirred and refluxed, and after cooling to room temperature, the product is collected to obtain the anti-corrosion chloroacetic acid resin.

4. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 3, characterized in that, In step S1, the catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium hydroxide, and tetrabutylammonium chloride.

5. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 3, characterized in that, In step S2, the stirring and reflux reaction time is 10-12 hours.

6. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 1, characterized in that, The preparation method of the self-healing complex includes the following steps: SS1: Polyetheramine and norbornene adipic anhydride are placed in xylene, heated to 80-85℃ and reacted for 3-5 hours. The solvent is removed by rotary evaporation and the product is collected to obtain modified polyetheramine. SS2: Modified polyetheramine and bis(2-hydroxyethyl) disulfide were placed in N,N-dimethylformamide, thoroughly mixed and stirred, nitrogen gas was introduced, p-toluenesulfonic acid was added, the reaction was heated, and the product was collected by vacuum distillation to obtain the self-healing complex.

7. The chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 6, characterized in that, In step SS1, the amine value of the polyetheramine is 440-500 mg KOH / g.

8. A chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy according to claim 6, characterized in that, In step SS2, the temperature of the heating reaction is 90-100℃, and the time is 3-5 hours.

9. A production process for a chromium-free passivating agent for corrosion protection of AZ31B magnesium alloy as described in claim 1, characterized in that, Includes the following steps: Step 1: Thoroughly mix polyurethane acrylic resin, glycidyl methacrylate, anti-corrosion chloroacetic acid resin, self-healing compound, 1-hydroxycyclohexylphenyl ketone and propylene glycol methyl ether acetate to obtain a mixture. Step 2: Add leveling agent and defoamer to the mixture, stir thoroughly at 200-300 rpm for 0.5-1 h, and let stand for 24-48 h to obtain passivating agent.

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